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Nuclear Power in a Clean Energy System

About this report.

With nuclear power facing an uncertain future in many countries, the world risks a steep decline in its use in advanced economies that could result in billions of tonnes of additional carbon emissions. Some countries have opted out of nuclear power in light of concerns about safety and other issues. Many others, however, still see a role for nuclear in their energy transitions but are not doing enough to meet their goals.

The publication of the IEA's first report addressing nuclear power in nearly two decades brings this important topic back into the global energy debate.

Key findings

Nuclear power is the second-largest source of low-carbon electricity today.

Nuclear power is the second-largest source of low-carbon electricity today, with 452 operating reactors providing 2700 TWh of electricity in 2018, or 10% of global electricity supply.

In advanced economies, nuclear has long been the largest source of low-carbon electricity, providing 18% of supply in 2018. Yet nuclear is quickly losing ground. While 11.2 GW of new nuclear capacity was connected to power grids globally in 2018 – the highest total since 1990 – these additions were concentrated in China and Russia.

Global low-carbon power generation by source, 2018

Cumulative co2 emissions avoided by global nuclear power in selected countries, 1971-2018, an aging nuclear fleet.

In the absense of further lifetime extensions and new projects could result in an additional 4 billion tonnes of CO2 emissions, underlining the importance of the nuclear fleet to low-carbon energy transitions around the globe. In emerging and developing economies, particularly China, the nuclear fleet will provide low-carbon electricity for decades to come.

However the nuclear fleet in advanced economies is 35 years old on average and many plants are nearing the end of their designed lifetimes. Given their age, plants are beginning to close, with 25% of existing nuclear capacity in advanced economies expected to be shut down by 2025.

It is considerably cheaper to extend the life of a reactor than build a new plant, and costs of extensions are competitive with other clean energy options, including new solar PV and wind projects. Nevertheless they still represent a substantial capital investment. The estimated cost of extending the operational life of 1 GW of nuclear capacity for at least 10 years ranges from $500 million to just over $1 billion depending on the condition of the site.

However difficult market conditions are a barrier to lifetime extension investments. An extended period of low wholesale electricity prices in most advanced economies has sharply reduced or eliminated margins for many technologies, putting nuclear at risk of shutting down early if additional investments are needed. As such, the feasibility of extensions depends largely on domestic market conditions.

Age profile of nuclear power capacity in selected regions, 2019

United states, levelised cost of electricity in the united states, 2040, european union, levelised cost of electricity in the european union, 2040, levelised cost of electricity in japan, 2040, the nuclear fade case, nuclear capacity operating in selected advanced economies in the nuclear fade case, 2018-2040, wind and solar pv generation by scenario 2019-2040, policy recommendations.

In this context, countries that intend to retain the option of nuclear power should consider the following actions:

• Keep the option open:  Authorise lifetime extensions of existing nuclear plants for as long as safely possible. 
• Value dispatchability:  Design the electricity market in a way that properly values the system services needed to maintain electricity security, including capacity availability and frequency control services. Make sure that the providers of these services, including nuclear power plants, are compensated in a competitive and non-discriminatory manner.
• Value non-market benefits:  Establish a level playing field for nuclear power with other low-carbon energy sources in recognition of its environmental and energy security benefits and remunerate it accordingly.
• Update safety regulations:  Where necessary, update safety regulations in order to ensure the continued safe operation of nuclear plants. Where technically possible, this should include allowing flexible operation of nuclear power plants to supply ancillary services.
• Create a favourable financing framework:  Create risk management and financing frameworks that facilitate the mobilisation of capital for new and existing plants at an acceptable cost taking the risk profile and long time-horizons of nuclear projects into consideration.
• Support new construction:  Ensure that licensing processes do not lead to project delays and cost increases that are not justified by safety requirements.
• Support innovative new reactor designs:  Accelerate innovation in new reactor designs with lower capital costs and shorter lead times and technologies that improve the operating flexibility of nuclear power plants to facilitate the integration of growing wind and solar capacity into the electricity system.
• Maintain human capital:  Protect and develop the human capital and project management capabilities in nuclear engineering.

Executive summary

Nuclear power can play an important role in clean energy transitions.

Nuclear power today makes a significant contribution to electricity generation, providing 10% of global electricity supply in 2018.  In advanced economies 1 , nuclear power accounts for 18% of generation and is the largest low-carbon source of electricity. However, its share of global electricity supply has been declining in recent years. That has been driven by advanced economies, where nuclear fleets are ageing, additions of new capacity have dwindled to a trickle, and some plants built in the 1970s and 1980s have been retired. This has slowed the transition towards a clean electricity system. Despite the impressive growth of solar and wind power, the overall share of clean energy sources in total electricity supply in 2018, at 36%, was the same as it was 20 years earlier because of the decline in nuclear. Halting that slide will be vital to stepping up the pace of the decarbonisation of electricity supply.

A range of technologies, including nuclear power, will be needed for clean energy transitions around the world.  Global energy is increasingly based around electricity. That means the key to making energy systems clean is to turn the electricity sector from the largest producer of CO 2 emissions into a low-carbon source that reduces fossil fuel emissions in areas like transport, heating and industry. While renewables are expected to continue to lead, nuclear power can also play an important part along with fossil fuels using carbon capture, utilisation and storage. Countries envisaging a future role for nuclear account for the bulk of global energy demand and CO 2 emissions. But to achieve a trajectory consistent with sustainability targets – including international climate goals – the expansion of clean electricity would need to be three times faster than at present. It would require 85% of global electricity to come from clean sources by 2040, compared with just 36% today. Along with massive investments in efficiency and renewables, the trajectory would need an 80% increase in global nuclear power production by 2040.

Nuclear power plants contribute to electricity security in multiple ways.  Nuclear plants help to keep power grids stable. To a certain extent, they can adjust their operations to follow demand and supply shifts. As the share of variable renewables like wind and solar photovoltaics (PV) rises, the need for such services will increase. Nuclear plants can help to limit the impacts from seasonal fluctuations in output from renewables and bolster energy security by reducing dependence on imported fuels.

Lifetime extensions of nuclear power plants are crucial to getting the energy transition back on track

Policy and regulatory decisions remain critical to the fate of ageing reactors in advanced economies.  The average age of their nuclear fleets is 35 years. The European Union and the United States have the largest active nuclear fleets (over 100 gigawatts each), and they are also among the oldest: the average reactor is 35 years old in the European Union and 39 years old in the United States. The original design lifetime for operations was 40 years in most cases. Around one quarter of the current nuclear capacity in advanced economies is set to be shut down by 2025 – mainly because of policies to reduce nuclear’s role. The fate of the remaining capacity depends on decisions about lifetime extensions in the coming years. In the United States, for example, some 90 reactors have 60-year operating licenses, yet several have already been retired early and many more are at risk. In Europe, Japan and other advanced economies, extensions of plants’ lifetimes also face uncertain prospects.

Economic factors are also at play.  Lifetime extensions are considerably cheaper than new construction and are generally cost-competitive with other electricity generation technologies, including new wind and solar projects. However, they still need significant investment to replace and refurbish key components that enable plants to continue operating safely. Low wholesale electricity and carbon prices, together with new regulations on the use of water for cooling reactors, are making some plants in the United States financially unviable. In addition, markets and regulatory systems often penalise nuclear power by not pricing in its value as a clean energy source and its contribution to electricity security. As a result, most nuclear power plants in advanced economies are at risk of closing prematurely.

The hurdles to investment in new nuclear projects in advanced economies are daunting

What happens with plans to build new nuclear plants will significantly affect the chances of achieving clean energy transitions.  Preventing premature decommissioning and enabling longer extensions would reduce the need to ramp up renewables. But without new construction, nuclear power can only provide temporary support for the shift to cleaner energy systems. The biggest barrier to new nuclear construction is mobilising investment.  Plans to build new nuclear plants face concerns about competitiveness with other power generation technologies and the very large size of nuclear projects that require billions of dollars in upfront investment. Those doubts are especially strong in countries that have introduced competitive wholesale markets.

A number of challenges specific to the nature of nuclear power technology may prevent investment from going ahead.  The main obstacles relate to the sheer scale of investment and long lead times; the risk of construction problems, delays and cost overruns; and the possibility of future changes in policy or the electricity system itself. There have been long delays in completing advanced reactors that are still being built in Finland, France and the United States. They have turned out to cost far more than originally expected and dampened investor interest in new projects. For example, Korea has a much better record of completing construction of new projects on time and on budget, although the country plans to reduce its reliance on nuclear power.

Without nuclear investment, achieving a sustainable energy system will be much harder

A collapse in investment in existing and new nuclear plants in advanced economies would have implications for emissions, costs and energy security.  In the case where no further investments are made in advanced economies to extend the operating lifetime of existing nuclear power plants or to develop new projects, nuclear power capacity in those countries would decline by around two-thirds by 2040. Under the current policy ambitions of governments, while renewable investment would continue to grow, gas and, to a lesser extent, coal would play significant roles in replacing nuclear. This would further increase the importance of gas for countries’ electricity security. Cumulative CO 2 emissions would rise by 4 billion tonnes by 2040, adding to the already considerable difficulties of reaching emissions targets. Investment needs would increase by almost USD 340 billion as new power generation capacity and supporting grid infrastructure is built to offset retiring nuclear plants.

Achieving the clean energy transition with less nuclear power is possible but would require an extraordinary effort.  Policy makers and regulators would have to find ways to create the conditions to spur the necessary investment in other clean energy technologies. Advanced economies would face a sizeable shortfall of low-carbon electricity. Wind and solar PV would be the main sources called upon to replace nuclear, and their pace of growth would need to accelerate at an unprecedented rate. Over the past 20 years, wind and solar PV capacity has increased by about 580 GW in advanced economies. But in the next 20 years, nearly five times that much would need to be built to offset nuclear’s decline. For wind and solar PV to achieve that growth, various non-market barriers would need to be overcome such as public and social acceptance of the projects themselves and the associated expansion in network infrastructure. Nuclear power, meanwhile, can contribute to easing the technical difficulties of integrating renewables and lowering the cost of transforming the electricity system.

With nuclear power fading away, electricity systems become less flexible.  Options to offset this include new gas-fired power plants, increased storage (such as pumped storage, batteries or chemical technologies like hydrogen) and demand-side actions (in which consumers are encouraged to shift or lower their consumption in real time in response to price signals). Increasing interconnection with neighbouring systems would also provide additional flexibility, but its effectiveness diminishes when all systems in a region have very high shares of wind and solar PV.

Offsetting less nuclear power with more renewables would cost more

Taking nuclear out of the equation results in higher electricity prices for consumers.  A sharp decline in nuclear in advanced economies would mean a substantial increase in investment needs for other forms of power generation and the electricity network. Around USD 1.6 trillion in additional investment would be required in the electricity sector in advanced economies from 2018 to 2040. Despite recent declines in wind and solar costs, adding new renewable capacity requires considerably more capital investment than extending the lifetimes of existing nuclear reactors. The need to extend the transmission grid to connect new plants and upgrade existing lines to handle the extra power output also increases costs. The additional investment required in advanced economies would not be offset by savings in operational costs, as fuel costs for nuclear power are low, and operation and maintenance make up a minor portion of total electricity supply costs. Without widespread lifetime extensions or new projects, electricity supply costs would be close to USD 80 billion higher per year on average for advanced economies as a whole.

Strong policy support is needed to secure investment in existing and new nuclear plants

Countries that have kept the option of using nuclear power need to reform their policies to ensure competition on a level playing field.  They also need to address barriers to investment in lifetime extensions and new capacity. The focus should be on designing electricity markets in a way that values the clean energy and energy security attributes of low-carbon technologies, including nuclear power.

Securing investment in new nuclear plants would require more intrusive policy intervention given the very high cost of projects and unfavourable recent experiences in some countries.  Investment policies need to overcome financing barriers through a combination of long-term contracts, price guarantees and direct state investment.

Interest is rising in advanced nuclear technologies that suit private investment such as small modular reactors (SMRs).  This technology is still at the development stage. There is a case for governments to promote it through funding for research and development, public-private partnerships for venture capital and early deployment grants. Standardisation of reactor designs would be crucial to benefit from economies of scale in the manufacturing of SMRs.

Continued activity in the operation and development of nuclear technology is required to maintain skills and expertise.  The relatively slow pace of nuclear deployment in advanced economies in recent years means there is a risk of losing human capital and technical know-how. Maintaining human skills and industrial expertise should be a priority for countries that aim to continue relying on nuclear power.

The following recommendations are directed at countries that intend to retain the option of nuclear power. The IEA makes no recommendations to countries that have chosen not to use nuclear power in their clean energy transition and respects their choice to do so.

• Keep the option open:  Authorise lifetime extensions of existing nuclear plants for as long as safely possible.
• Value non-market benefits:  Establish a level playing field for nuclear power with other low carbon energy sources in recognition of its environmental and energy security benefits and remunerate it accordingly.
• Create an attractive financing framework:  Set up risk management and financing frameworks that can help mobilise capital for new and existing plants at an acceptable cost, taking the risk profile and long time horizons of nuclear projects into consideration.
• Support new construction:  Ensure that licensing processes do not lead to project delays and cost increases that are not justified by safety requirements. Support standardisation and enable learning-by-doing across the industry.
• Support innovative new reactor designs:  Accelerate innovation in new reactor designs, such as small modular reactors (SMRs), with lower capital costs and shorter lead times and technologies that improve the operating flexibility of nuclear power plants to facilitate the integration of growing wind and solar capacity into the electricity system.

Advanced economies consist of Australia, Canada, Chile, the 28 members of the European Union, Iceland, Israel, Japan, Korea, Mexico, New Zealand, Norway, Switzerland, Turkey and the United States.

Reference 1

Cite report.

IEA (2019), Nuclear Power in a Clean Energy System , IEA, Paris https://www.iea.org/reports/nuclear-power-in-a-clean-energy-system, Licence: CC BY 4.0

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The Controversy of the Bataan Nuclear Power Plant

Teo camacho may 24, 2017, submitted as coursework for ph241 , stanford university, winter 2017.

The Bataan Nuclear Power Plant (BNPP) is an interesting case study of nuclear energy. Completed back in 1980s and costing $2.2 billion, the BNPP currently stands in Morong, Bataan, atop Napot Point that overlooks the West Philippine Sea (as seen in Fig. 1). However, it never achieved its goal of generating 623 MW of electricity. The BNPP is currently the only nuclear power plant in the Philippines and more interestingly, was still the only nuclear plant in the Association of Southeast Asian Nations (ASEAN) as of 2014. [1]

Nuclear energy first came to the forefront of Philippine politics back in the 1950s when the U.S. gave the Philippines a nuclear fission reactor. [2] The government then formally established a nuclear program in 1958 under the Philippine Atomic Energy Commission (PAEC). The BNPP was then proposed in the 1960s and approved under the Marcos regime (1965 - 1986) in July of 1973. The final contract was given to Westinghouse Electric. The project was completed in 1984. [2]

Controversy

Before, during, and after the construction of the BNPP, this power plant was surrounded by controversy. From President Marcos's connection to Westinghouse, to the dispute of General Electric and Westinghouse, to issues of following protocol during and after construction, the BNPP faced many issues that led to criminal charges being brought against Westinghouse. The whole controversy was described in detail by Dumaine two years after the plant's completion. [3]

One of the biggest controversies was the Marcos connection with Westinghouse. First, Marcos requested that National Power Co. (the government owned electric utility) negotiate a deal to buy two nuclear reactors. Westinghouse used connections to Marcos to strike the deal. Already known to be more expensive than other options, the Westinghouse contract jumped from $650 million for only one reactor to $2.2 billion. Later, evidence of large sums of money going to President Marcos himself was found. Westinghouse denied corruption accusations. [3]

Another controversy was how Westinghouse was able to gain the contract over General Electric. It is documented that National Power was negotiating with General Electric before Westinghouse came into the picture. However, once the connections between Westinghouse and the Marcos regime were established by Hermino Disini, a friend of the president himself, General Electric appeared to be strung along, as thought they were still in contention even though they actually were not. There is documentation that contract negotiations began before General Electric could pitch its proposal to the government. [3]

Additionally, there were issues during and after the construction of how Ebasco Services (hired for safety testing) were observing protocol. Librado Ibe, Marcos' top nuclear expert questioned Ebasco's work of checking the siting. He is documented as saying that he was offered bribes to approve the site for construction and reluctantly did end up issuing the construction permit in 1979. [3] After the construction was completed in 1984, William Albert, an advisor from the International Atomic Energy Agency (IAEA), was brought in by new Aquino government to do inspections. Albert brought up issues of welding, working hours, base plates, pipe hangers, water values, and transmission cables. He attibuted all these shortcomings to quality control. Even though these issues were brought up to National Power, who had the final say whether the plant was to be operable or not, there is no evidence that the structural issues were dealt with appropriately. [3]

Current News

Currently, there are talks about the Philippines reviving the BNPP. This is mainly because of Philippine energy needs. [4] The talks about reopening the BNPP are being debated in the Senate, and there are voices on both sides of the issue. Proponents for reinstating the plant say that the energy source is cheap and that after the initial investment to upgraded the plant and it can help with the issue of the supply of electricity. However, opponents staunchly disagree saying that the revival of the plant is too expensive even to consider and that the money would be better spent on other electricity generation projects. [4]

Nevertheless, scientists are also still considering the plant's siting issues. There is still uncertainty about the eruption history of Mt. Natib, a volcano only a few miles away. Because of this problem and the proximity to active faults, seismologist are proposing to set up more sensors to do testing before reconsidering opening the BNPP to electric generation. [5] However, proponents of reinstating the plant as soon as possible point out the the BNPP was allegedly built to withstand earthquakes and tsunamis. [1] It is clear that the issue of the Bataan Nuclear Power Plant will be talked about in the Philippines for months and years to come as the country tries to deal with supplying electricity to a continually growing population.

© Teo Camacho. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

[1] J. P. Terry and J. R. Goff, Natural Hazards in the Asia-Pacific Region: Recent Advances and Emerging Concepts (Geological Society of London, 2012).

[2] A. Volentik et al. , "Aspects of Volcanic Hazard Assessment For the Bataan Nuclear Power Plant, Luzon Peninsula, Philippines," in Volcanic and Tectonic Hazard Assessment for Nuclear Facilities , ed. by C. B. Conner, N. A. Chapman and L. J. Conner (Cambridge University Press, 2009), pp. 229-256.

[3] B. Dumaine, " The $2.2 Billion Nuclear Fiasco ," Fortune, 1 Sep 86.

[4] D. L. Lucas, " Duterte Gives Nuke Plant Green Light ," Philippine Daily Inquirer, 12 Nov 16.

[5] J. R. Uy, " Scientists Want Faults, Volcano near Nuke Plant Studied ," Philipine Daily Inquirer, 2 Dec 16.

The case for nuclear power – despite the risks

Professor of Nuclear Engineering and Radiological Sciences, University of Michigan

Disclosure statement

Gary Was does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

University of Michigan provides funding as a founding partner of The Conversation US.

View all partners

This article is part of The Conversation’s worldwide series on the Future of Nuclear. You can read the rest of the series here , and a counterpoint to the views expressed in this article here .

Nuclear power is likely the least well-understood energy source in the United States. Just 99 nuclear power plants spread over 30 states provide one-fifth of America’s electricity. These plants have provided reliable, affordable and clean energy for decades. They also carry risk - to the public, to the environment and to the financial solvency of utilities.

Risk is the product of the probability of an occurrence and its consequence. The probability of dying in a car accident is actually quite high compared to other daily events, but such accidents usually claim few individuals at a time, and so the risk is low. The reason nuclear energy attracts so much attention is that while the probability of a catastrophic event is extremely low, the consequence is often perceived to be extremely high.

Nuclear power and public risk

In the US, commercial nuclear plants have been operating since the late 1960s. If you add up the plants’ years in operation, they average about 30 years each, totaling about 3,000 reactor years of operating experience. There have been no fatalities to any member of the public due to the operation of a commercial nuclear power plant in the US. Our risk in human terms is vanishingly low.

Nuclear power’s safety record is laudable, considering that nuclear plants are running full-tilt. The average capacity factor of these plants exceeds 90%; that means 99 plants are generating full power over 90% of the time.

If you compare that to any other energy form, there’s a huge gap. Coal is a mainstay of electricity generation in this country and has a capacity factor of around 65%. Gas is about the same; wind’s capacity factor is around is 30%, and solar is at 25%.

While the probability of a nuclear catastrophe is extremely low, it is only part of the risk calculation. The other part of risk is consequence. The world has been host to three major nuclear power generation accidents: Three Mile Island in 1979, Chernobyl in 1986 and Fukushima in 2011. To the best of our knowledge , Three Mile Island, while terribly frightening, resulted in no health consequences to the public.

Chernobyl was an unmitigated disaster in which the reactor vessel – the place where the nuclear fuel produces heat – was ruptured and the graphite moderator in the reactor ignited, causing an open-air fire and large releases of radioactive material. This reactor design would never have been licensed to operate in the Western world because it lacked a containment.

The scientific consensus on the effects of the disaster as developed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has identified 66 deaths from trauma, acute radiation poisoning and cases of thyroid cancer . Additional deaths may occur over time, as understanding the causes of death is a statistical rather than a deterministic process. Considering that the authorities didn’t alert the neighboring communities for many hours, the long-term health consequences of that reactor accident are surprisingly small.

And then there was Fukushima Daiichi. At least three of the reactors have sustained core damage, and there is potentially damage to the reactor vessel as well. At this time, no deaths have been attributed to radiation release at Fukushima, but an estimated 1,600 people died as a result of evacuation, and land contamination was widespread.

So if you look at these cases together, in Chernobyl, you had a reactor core on fire and open to the air; in Fukushima, three reactors lost all power during full operation and sustained major core damage, resulting in substantial radioactivity release in one of the most densely populated countries in the world.

These accidents had serious, lasting consequences that aren’t to be trivialized, but the consequences are nothing like what has been feared and glorified in movies over the past 50 years. What we’ve learned about public risk during that time is that the forecasted nightmares resulting from nuclear accidents, even in serious accidents, simply haven’t come to fruition. At the same time, as a society, we’ve come to accept - or at least look the other way from - thousands of traffic- or coal-related deaths every year in the US alone.

Waste containment: risk and storage

The production of energy in any form alters the environment. Coal and natural gas generate particulates, greenhouse gases and the like. In 2012, coal plants in the US generated 110 million tons of coal ash . Nuclear waste created by power generation is in solid form, and the volume is minuscule in comparison, but extremely toxic. Even the production of wind and solar energy generates waste.

Fuel for nuclear plants is in the form of fuel assemblies or bundles, each containing tubes of a zirconium alloy that hold hundreds of ceramic pellets of uranium oxide.

Each fuel assembly provides power for four to five years before it is removed. After removal, the fuel is considered to be waste and must be safely stored, as its radiotoxicity level is extremely high. Unprocessed, it takes about 300,000 years for the radiation level of the waste inside an assembly to return to background levels, at which point it is benign.

Due to the cancellation of the Yucca Mountain site in Nevada, there is no place designated for long-term nuclear waste storage in the US, and utilities have resorted to constructing on-site storage at their plants. These storage containers were not designed to be permanent, and the Nuclear Regulatory Commission (NRC) is now licensing these temporary facilities for up to 100 years.

Many cheered when the Yucca Mountain project was shuttered , but waste still must be stored, and clearly it is safer to store the waste in a single, permanent depository than in 99 separate and temporary structures.

Monitored, retrievable storage is the safest approach to nuclear waste storage. Waste sites could be centralized and continuously monitored, and built in such a way that waste canisters could be retrieved if, for example, storage technology improves, or if it becomes economical to reprocess the waste to recover the remaining uranium and plutonium created during operation.

If we are to keep using nuclear power even at the present rate, our risks related to waste will increase every year until storage is addressed thoughtfully and thoroughly.

Infrastructure: same plant, different century

At the dawn of commercial nuclear power, the prospect of cheap, plentiful energy produced forecasts that nuclear energy would be too cheap to meter - we’d all be ripping the meters off our houses. But as plant designs evolved, it became clear that ensuring safety would increase the cost of the energy produced.

Every accident taught us something, and with every accident the NRC unveiled a new set of regulations, resulting in a system of plants that are, from the perspective of a few decades ago, much safer. Such tight regulatory oversight, while needed, drives up cost and means that utilities undertake significant financial risk with each nuclear plant they build.

Decades ago, the idea that the NRC would be granting 20-year license extensions to power plants was unheard of. Today, 75% of plants have received them. Now there’s talk about a second round of license extensions, and the NRC, the US Department of Energy and the industry are engaged in talking about what it would take to get a third. We’re talking about 80 or even 100 years of operation, in which case a plant would outlive the Earth’s population at the time it was built.

In the shorter term, life extension makes sense. Most of the plants in the United States are Generation 2 plants, but Generation 3 is being built all over the world. Gen 2 plants are proving very robust, and existing plants are quite economical to operate. Gen 3 plants, like Vogtle now being built in Georgia, boast better safety systems, better structural components and better design.

Would I rather have one of those than the one I have now? Absolutely. The risk of operating such a facility is simply lower. At US$4.5 billion to $10 billion , Gen 3 plants are very expensive to build, but we must either accept that capital outlay or find another source of electricity that has all the benefits of nuclear energy.

How much risk do we accept?

As a society, we accepted over 32,000 traffic accident deaths in 2013, and no one stopped driving as a result.

I think most people would be surprised to know that in 2012, seven million people globally died from health complications due to air pollution and that an estimated 13,000 US deaths were directly attributable to fossil-fired plants.

US deaths from coal represent an annual catastrophe that exceeds that of all nuclear accidents over all time. In fact, nuclear power has prevented an estimated 1.84 million air-pollution related deaths worldwide. Natural gas plants, increasingly being constructed around the country, are highly subject to price volatility and, while cleaner than coal, they still account for 22% of carbon dioxide emissions from electricity generation in the US. This is not to mention the illogical use of this precious resource for electricity generation versus uses for which it is more uniquely suited, such as heating homes or powering vehicles.

And until the capacity factor for renewables increases dramatically, the cost drops and large-scale storage is developed, they are simply not equipped to handle the bulk of US energy needs nor to provide electricity on demand.

Through the NRC’s oversight and the work of researchers all over the world, we have applied lessons from every global nuclear event to every American nuclear plant. The risk inherent in nuclear plant operation will always be present, but it is one of the world’s most rigorously monitored activities, and its proven performance in delivering zero-carbon electricity is one that shouldn’t be dismissed out of fear.

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DAILY SCIENCE

Two studies make a strong case for nuclear power: less pollution, smaller footprint.

Let the best of Anthropocene come to you.

The Fukushima nuclear disaster in 2011 was a death knell for nuclear power. Rising fear and anxiety about nuclear power plants prompted many countries to phase out this form of clean energy completely.

But with climate disasters on the rise, and geopolitical tensions making fuel supplies unreliable, nuclear power is seeing a comeback. Nuclear power generation is now increasing again around the world. And even environmentalists have had a change in heart .

Two new studies now present a strong case for nuclear. Air pollution would increase if nuclear plants in the U.S. are shut down, as coal and natural gas plants would step up to fill the gap, according to one study published in Nature Energy . This would result in an additional 5,200 deaths in just one year. The other study, in Scientific Reports , finds that nuclear is the winner in terms of land use and related environmental impact compared to other carbon-free energy sources.

There are about 440 nuclear reactors around the world today providing 10 percent of the world’s electricity, according to the World Nuclear Association . In the U.S. that share is 20 percent. France, meanwhile, relies on nuclear for almost 70 percent of its electricity, and others like Belgium and Slovakia get about half from nuclear.

While it faces contention in many countries, nuclear is still the second-largest source of carbon-free electricity after hydropower. And even though solar and wind are racing to replace fossil fuels, nuclear power plants are easier to tie into the power grid.

Accidents at nuclear power plants, howeverm have raised valid safety and environmental concerns. But the closures of nuclear power plants, at least in Germany and the U.S. have led to increased use of fossil fuels to fill the gap in energy production.

So an MIT team decided to study the impacts of all nuclear power plants in the U.S. being shut down. They developed a grid dispatch model to estimate emissions of carbon dioxide, nitrogen oxides and sulfur dioxide from each coal and natural gas plant that would substitute for nuclear power at any given time. Then they fed these emissions into a chemical transport model to calculate the effects on ozone and fine particulate matter.

The increased pollution led to thousands of additional deaths in a single year. African American communities were exposed to the highest levels of pollution. Even more availability of wind and solar would still increase air pollution slightly in some parts of the country, they found, resulting in 260 extra pollution-related deaths over one year.

“We need to be thoughtful about how we’re retiring nuclear power plants if we are trying to think about them as part of an energy system,” said lead author Lyssa Freese in a press release .

Producing energy from any source, of course, requires land, which can impact surrounding ecosystems. To find out just how big that footprint is, researchers from the Norwegian University of Science and Technology analyzed 870 power plants worldwide, including solar, onshore and offshore wind, hydropower, nuclear, geothermal, and wave power. They calculated the energy produced by area, and also the land or sea area requirements to power the world.

Bioenergy was the worst, they found, needing almost 900 square kilometers of space to generate one terawatt-hours (TWh) of energy, enough or just over a quarter of New York City’s needs. Hydropower was the most energy-dense renewable resource, producing up to 1.67 TWh/km2. It was more energy-dense than solar, contrary to popular belief, needing less land to produce the same power.

Nuclear, which has a small material footprint comparable to renewables , was the clear winner here. It could supply the entire world with zero-emission energy from an area half the size of the state of Vermont.

“Just like the three crises—climate, nature and energy—arise together, they also need to be resolved together,” writes the paper’s lead author Jonas Kristiansen Nøland. “For many years, the focus has been on climate-smart solutions, while environmentally smart solutions have remained a little under the radar. Nuclear power is a clear winner in such a race.”

• Jonas Kristiansen Nøland et al, Spatial energy density of large-scale electricity generation from power sources worldwide, Scientific Reports , 2022.
• Lyssa Freese et al. Nuclear power generation phase-outs redistribute US air quality and climate-related mortality risk, Nature Energy , 2023.

Image by Wolfgang Stemme from Pixabay

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MIT Energy Initiative study reports on the future of nuclear energy

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How can the world achieve the deep carbon emissions reductions that are necessary to slow or reverse the impacts of climate change? The authors of a new MIT study say that unless nuclear energy is meaningfully incorporated into the global mix of low-carbon energy technologies, the challenge of climate change will be much more difficult and costly to solve. For nuclear energy to take its place as a major low-carbon energy source, however, issues of cost and policy need to be addressed.

In " The Future of Nuclear Energy in a Carbon-Constrained World ," released by the MIT Energy Initiative (MITEI) on Sept. 3, the authors analyze the reasons for the current global stall of nuclear energy capacity — which currently accounts for only 5 percent of global primary energy production — and discuss measures that could be taken to arrest and reverse that trend.

The study group, led by MIT researchers in collaboration with colleagues from Idaho National Laboratory and the University of Wisconsin at Madison, is presenting its findings and recommendations at events in London, Paris, and Brussels this week, followed by events on Sept. 25 in Washington, and on Oct. 9 in Tokyo. MIT graduate and undergraduate students and postdocs, as well as faculty from Harvard University and members of various think tanks, also contributed to the study as members of the research team.

“Our analysis demonstrates that realizing nuclear energy’s potential is essential to achieving a deeply decarbonized energy future in many regions of the world,” says study co-chair Jacopo Buongiorno, the TEPCO Professor and associate department head of the Department of Nuclear Science and Engineering at MIT. He adds, “Incorporating new policy and business models, as well as innovations in construction that may make deployment of cost-effective nuclear power plants more affordable, could enable nuclear energy to help meet the growing global demand for energy generation while decreasing emissions to address climate change.”

The study team notes that the electricity sector in particular is a prime candidate for deep decarbonization. Global electricity consumption is on track to grow 45 percent by 2040, and the team’s analysis shows that the exclusion of nuclear from low-carbon scenarios could cause the average cost of electricity to escalate dramatically.

“Understanding the opportunities and challenges facing the nuclear energy industry requires a comprehensive analysis of technical, commercial, and policy dimensions,” says Robert Armstrong, director of MITEI and the Chevron Professor of Chemical Engineering. “Over the past two years, this team has examined each issue, and the resulting report contains guidance policymakers and industry leaders may find valuable as they evaluate options for the future.”

The report discusses recommendations for nuclear plant construction, current and future reactor technologies, business models and policies, and reactor safety regulation and licensing. The researchers find that changes in reactor construction are needed to usher in an era of safer, more cost-effective reactors, including proven construction management practices that can keep nuclear projects on time and on budget.

“A shift towards serial manufacturing of standardized plants, including more aggressive use of fabrication in factories and shipyards, can be a viable cost-reduction strategy in countries where the productivity of the traditional construction sector is low,” says MIT visiting research scientist David Petti, study executive director and Laboratory Fellow at the Idaho National Laboratory. “Future projects should also incorporate reactor designs with inherent and passive safety features.”

These safety features could include core materials with high chemical and physical stability and engineered safety systems that require limited or no emergency AC power and minimal external intervention. Features like these can reduce the probability of severe accidents occurring and mitigate offsite consequences in the event of an incident. Such designs can also ease the licensing of new plants and accelerate their global deployment.

“The role of government will be critical if we are to take advantage of the economic opportunity and low-carbon potential that nuclear has to offer,” says John Parsons, study co-chair and senior lecturer at MIT’s Sloan School of Management. “If this future is to be realized, government officials must create new decarbonization policies that put all low-carbon energy technologies (i.e. renewables, nuclear, fossil fuels with carbon capture) on an equal footing, while also exploring options that spur private investment in nuclear advancement.”

The study lays out detailed options for government support of nuclear. For example, the authors recommend that policymakers should avoid premature closures of existing plants, which undermine efforts to reduce emissions and increase the cost of achieving emission reduction targets. One way to avoid these closures is the implementation of zero-emissions credits — payments made to electricity producers where electricity is generated without greenhouse gas emissions — which the researchers note are currently in place in New York, Illinois, and New Jersey.

Another suggestion from the study is that the government support development and demonstration of new nuclear technologies through the use of four “levers”: funding to share regulatory licensing costs; funding to share research and development costs; funding for the achievement of specific technical milestones; and funding for production credits to reward successful demonstration of new designs.

The study includes an examination of the current nuclear regulatory climate, both in the United States and internationally. While the authors note that significant social, political, and cultural differences may exist among many of the countries in the nuclear energy community, they say that the fundamental basis for assessing the safety of nuclear reactor programs is fairly uniform, and should be reflected in a series of basic aligned regulatory principles. They recommend regulatory requirements for advanced reactors be coordinated and aligned internationally to enable international deployment of commercial reactor designs, and to standardize and ensure a high level of safety worldwide.

The study concludes with an emphasis on the urgent need for both cost-cutting advancements and forward-thinking policymaking to make the future of nuclear energy a reality.

"The Future of Nuclear Energy in a Carbon-Constrained World" is the eighth in the "Future of…" series of studies that are intended to serve as guides to researchers, policymakers, and industry. Each report explores the role of technologies that might contribute at scale in meeting rapidly growing global energy demand in a carbon-constrained world. Nuclear power was the subject of the first of these interdisciplinary studies, with the 2003 "Future of Nuclear Power " report (an update was published in 2009). The series has also included a study on the future of the nuclear fuel cycle. Other reports in the series have focused on carbon dioxide sequestration, natural gas, the electric grid, and solar power. These comprehensive reports are written by multidisciplinary teams of researchers. The research is informed by a distinguished external advisory committee.

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Press mentions, national geographic.

Prof. Jacopo Buongiorno speaks with National Geographic reporter Lois Parshley about the future of nuclear energy in the U.S. and western Europe. “Our analysis shows a big share of nuclear, a big share of renewables, and some storage is the best mix that is low-carbon, reliable, and at the lowest cost,” says Buongiorno of an MIT report showing the most cost-efficient, reliable grid comes from an energy mix.  

Marketplace

Prof. Jacopo Buongiorno speaks with Marketplace reporter Sabri Ben-Achour about MITEI’s study showing the potential impact of nuclear power in addressing climate change. Buongiorno noted that if costs can be reduced and more supportive policies enacted, nuclear power has the “potential to decarbonize the power sector on a global scale.”

Forbes contributor Jeff McMahon writes that a new study by MIT researchers finds that nuclear reactors “cost so much in the West because of poor construction management practices.” The study’s authors suggest several ways to reduce the cost of constructing a nuclear plant, including standardizing multi-unit sites, seismic isolation, and modular construction.

A recent study from the MIT Energy Initiative finds that the cost of nuclear reactors can be twice as high in the U.S. and Europe compared to Asian countries. The researchers found that costs were “bundled up in the site preparation, the building construction, [and] the civil works,” rather than the reactor itself, writes Jeff McMahon for Forbes .

The Wall Street Journal

Wall Street Journal reporter Neanda Salvaterra writes about a new MITEI study showing how nuclear power can help reduce carbon emissions. Nuclear power, says MITEI Director Robert Armstrong, “has been demonstrated historically as capable of delivering energy on demand over decades with zero carbon footprint so it’s an option we need to keep in our quiver.”

Axios reporter Ben Geman writes that a MIT Energy Initiative study shows that while nuclear power is critical to cutting carbon emissions, expanding the industry will be difficult without supportive policies and project cost reductions. The report’s authors explain that the increasing cost of nuclear power undermines its "potential contribution and increases the cost of achieving deep decarbonization."

A new MIT Energy Initiative study details how nuclear power could help fight climate change, reports Jonathan Tirone for Bloomberg News. The study’s authors explain that U.S. policy makers could support the nuclear industry by putting a “price on emissions, either through direct taxation or carbon-trading markets. That would give atomic operators more room to compete against cheap gas, wind and solar.”

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Chernobyl Accident 1986

(Updated April 2024)

• The Chernobyl accident in 1986 was the result of a flawed reactor design that was operated with inadequately trained personnel.
• The resulting steam explosion and fires released at least 5% of the radioactive reactor core into the environment, with the deposition of radioactive materials in many parts of Europe.
• Two Chernobyl plant workers died due to the explosion on the night of the accident, and a further 28 people died within a few weeks as a result of acute radiation syndrome.
• The United Nations Scientific Committee on the Effects of Atomic Radiation has concluded that, apart from some 5000 thyroid cancers (resulting in 15 fatalities), "there is no evidence of a major public health impact attributable to radiation exposure 20 years after the accident."
• Some 350,000 people were evacuated as a result of the accident, but resettlement of areas from which people were relocated is ongoing.

The April 1986 disaster at the Chernobyl a nuclear power plant in Ukraine was the product of a flawed Soviet reactor design coupled with serious mistakes made by the plant operators b . It was a direct consequence of Cold War isolation and the resulting lack of any safety culture.

The accident destroyed the Chernobyl 4 reactor, killing 30 operators and firemen within three months and several further deaths later. One person was killed immediately and a second died in hospital soon after as a result of injuries received. Another person is reported to have died at the time from a coronary thrombosis c . Acute radiation syndrome (ARS) was originally diagnosed in 237 people onsite and involved with the clean-up and it was later confirmed in 134 cases. Of these, 28 people died as a result of ARS within a few weeks of the accident. Nineteen more workers subsequently died between 1987 and 2004, but their deaths cannot necessarily be attributed to radiation exposure d . Nobody offsite suffered from acute radiation effects although a significant, but uncertain, fraction of the thyroid cancers diagnosed since the accident in patients who were children at the time are likely to be due to intake of radioactive iodine fallout m , 9 . Furthermore, large areas of Belarus , Ukraine, Russia , and beyond were contaminated in varying degrees. See also sections below and  Chernobyl Accident Appendix 2: Health Impacts .

The Chernobyl disaster was a unique event and the only accident in the history of commercial nuclear power where radiation-related fatalities occurred e . The design of the reactor is unique and in that respect the accident is thus of little relevance to the rest of the nuclear industry outside the then Eastern Bloc. However, it led to major changes in safety culture and in industry cooperation, particularly between East and West before the end of the Soviet Union. Former President Gorbachev said that the Chernobyl accident was a more important factor in the fall of the Soviet Union than Perestroika – his program of liberal reform.

The Chernobyl site and plant

The Chernobyl Power Complex, lying about 130 km north of Kiev, Ukraine, and about 20 km south of the border with Belarus, consisted of four nuclear reactors of the RBMK-1000 design (see information page on RBMK Reactors ). Units 1 and 2 were constructed between 1970 and 1977, while units 3 and 4 of the same design were completed in 1983. Two more RBMK reactors were under construction at the site at the time of the accident. To the southeast of the plant, an artificial lake of some 22 square kilometres, situated beside the river Pripyat, a tributary of the Dniepr, was constructed to provide cooling water for the reactors.

This area of Ukraine is described as Belarussian-type woodland with a low population density. About 3 km away from the reactor, in the new city, Pripyat, there were 49,000 inhabitants. The old town of Chornobyl, which had a population of 12,500, is about 15 km to the southeast of the complex. Within a 30 km radius of the power plant, the total population was between 115,000 and 135,000 at the time of the accident.

Source: OECD NEA

The RBMK-1000 is a Soviet-designed and built graphite moderated pressure tube type reactor, using slightly enriched (2% U-235) uranium dioxide fuel. It is a boiling light water reactor, with two loops feeding steam directly to the turbines, without an intervening heat exchanger. Water pumped to the bottom of the fuel channels boils as it progresses up the pressure tubes, producing steam which feeds two 500 MWe turbines. The water acts as a coolant and also provides the steam used to drive the turbines. The vertical pressure tubes contain the zirconium alloy clad uranium dioxide fuel around which the cooling water flows. The extensions of the fuel channels penetrate the lower plate and the cover plate of the core and are welded to each. A specially designed refuelling machine allows fuel bundles to be changed without shutting down the reactor.

The moderator, the function of which is to slow down neutrons to make them more efficient in producing fission in the fuel, is graphite, surrounding the pressure tubes. A mixture of nitrogen and helium is circulated between the graphite blocks to prevent oxidation of the graphite and to improve the transmission of the heat produced by neutron interactions in the graphite to the fuel channel. The core itself is about 7 m high and about 12 m in diameter. In each of the two loops, there are four main coolant circulating pumps, one of which is always on standby. The reactivity or power of the reactor is controlled by raising or lowering 211 control rods, which, when lowered into the moderator, absorb neutrons and reduce the fission rate. The power output of this reactor is 3200 MW thermal, or 1000 MWe. Various safety systems, such as an emergency core cooling system, were incorporated into the reactor design.

One of the most important characteristics of the RBMK reactor is that it can possess a 'positive void coefficient', where an increase in steam bubbles ('voids') is accompanied by an increase in core reactivity (see information page on RBMK Reactors ). As steam production in the fuel channels increases, the neutrons that would have been absorbed by the denser water now produce increased fission in the fuel. There are other components that contribute to the overall power coefficient of reactivity, but the void coefficient is the dominant one in RBMK reactors. The void coefficient depends on the composition of the core – a new RBMK core will have a negative void coefficient. However, at the time of the accident at Chernobyl 4, the reactor's fuel burn-up, control rod configuration, and power level led to a positive void coefficient large enough to overwhelm all other influences on the power coefficient.

The 1986 Chernobyl accident

On 25 April, prior to a routine shutdown, the reactor crew at Chernobyl 4 began preparing for a test to determine how long turbines would spin and supply power to the main circulating pumps following a loss of main electrical power supply. This test had been carried out at Chernobyl the previous year, but the power from the turbine ran down too rapidly, so new voltage regulator designs were to be tested.

A series of operator actions, including the disabling of automatic shutdown mechanisms, preceded the attempted test early on 26 April. By the time that the operator moved to shut down the reactor, the reactor was in an extremely unstable condition. A peculiarity of the design of the control rods caused a dramatic power surge as they were inserted into the reactor (see Chernobyl Accident Appendix 1: Sequence of Events ).

The interaction of very hot fuel with the cooling water led to fuel fragmentation along with rapid steam production and an increase in pressure. The design characteristics of the reactor were such that substantial damage to even three or four fuel assemblies would – and did – result in the destruction of the reactor. The overpressure caused the 1000 t cover plate of the reactor to become partially detached, rupturing the fuel channels and jamming all the control rods, which by that time were only halfway down. Intense steam generation then spread throughout the whole core (fed by water dumped into the core due to the rupture of the emergency cooling circuit) causing a steam explosion and releasing fission products to the atmosphere. About two to three seconds later, a second explosion threw out fragments from the fuel channels and hot graphite. There is some dispute among experts about the character of this second explosion, but it is likely to have been caused by the production of hydrogen from zirconium-steam reactions.

Two workers died as a result of these explosions. The graphite (about a quarter of the 1200 tonnes of it was estimated to have been ejected) and fuel became incandescent and started a number of fires f , causing the main release of radioactivity into the environment. A total of about 14 EBq (14 x 10 18 Bq) of radioactivity was released, over half of it being from biologically-inert noble gases.*

* The figure of 5.2 EBq is also quoted, this being "iodine-131 equivalent" - 1.8 EBq iodine and 85 PBq Cs-137 multiplied by 40 due its longevity, and ignoring the 6.5 EBq xenon-33 and some minor or short-lived nuclides.

About 200-300 tonnes of water per hour was injected into the intact half of the reactor using the auxiliary feedwater pumps but this was stopped after half a day owing to the danger of it flowing into and flooding units 1 and 2. From the second to tenth day after the accident, some 5000 tonnes of boron, dolomite, sand, clay, and lead were dropped on to the burning core by helicopter in an effort to extinguish the blaze and limit the release of radioactive particles.

The damaged Chernobyl unit 4 reactor building

The 1991 report by the State Committee on the Supervision of Safety in Industry and Nuclear Power on the root cause of the accident looked past the operator actions. It said that while it was certainly true the operators placed their reactor in a dangerously unstable condition (in fact in a condition which virtually guaranteed an accident) it was also true that in doing so they had not in fact violated a number of vital operating policies and principles, since no such policies and principles had been articulated. Additionally, the operating organization had not been made aware either of the specific vital safety significance of maintaining a minimum operating reactivity margin, or the general reactivity characteristics of the RBMK which made low power operation extremely hazardous.

Immediate impact of the Chernobyl accident

The accident caused the largest uncontrolled radioactive release into the environment ever recorded for any civilian operation, and large quantities of radioactive substances were released into the air for about 10 days. This caused serious social and economic disruption for large populations in Belarus, Russia, and Ukraine. Two radionuclides, the short-lived iodine-131 and the long-lived caesium-137, were particularly significant for the radiation dose they delivered to members of the public.

It is estimated that all of the xenon gas, about half of the iodine and caesium, and at least 5% of the remaining radioactive material in the Chernobyl 4 reactor core (which had 192 tonnes of fuel) was released in the accident. Most of the released material was deposited close by as dust and debris, but the lighter material was carried by wind over Ukraine, Belarus, Russia, and to some extent over Scandinavia and Europe.

The casualties included firefighters who attended the initial fires on the roof of the turbine building. All these were put out in a few hours, but radiation doses on the first day caused 28 deaths – six of which were firemen – by the end of July 1986. The doses received by the firefighters and power plant workers were high enough to result in acute radiation syndrome (ARS), which occurs if a person is exposed to more than 700 milligrays (mGy) within a short time frame (usually minutes). Common ARS symptoms include gastrointestinal problems ( e.g. nausea, vomiting), headaches, burns and fever. Whole body doses between 4000 mGy and 5000 mGv within a short time frame would kill 50% of those exposed, with 8000-10,000 mGy universally fatal. The doses received by the firefighters who died were estimated to range up to 20,000 mGy.

The next task was cleaning up the radioactivity at the site so that the remaining three reactors could be restarted, and the damaged reactor shielded more permanently. About 200,000 people ('liquidators') from all over the Soviet Union were involved in the recovery and clean-up during 1986 and 1987. They received high doses of radiation, averaging around 100 millisieverts (mSv). Some 20,000 liquidators received about 250 mSv, with a few receiving approximately 500 mSv. Later, the number of liquidators swelled to over 600,000, but most of these received only low radiation doses. The highest doses were received by about 1000 emergency workers and onsite personnel during the first day of the accident.

According to the most up-to-date estimate provided by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) , the average radiation dose due to the accident received by inhabitants of 'strict radiation control' areas (population 216,000) in the years 1986 to 2005 was 31 mSv (over the 20-year period), and in the 'contaminated' areas (population 6.4 million) it averaged 9 mSv, a minor increase over the dose due to background radiation over the same period (about 50 mSv) 4 .

Initial radiation exposure in contaminated areas was due to short-lived iodine-131; later caesium-137 was the main hazard. (Both are fission products dispersed from the reactor core, with half lives of 8 days and 30 years, respectively. 1.8 EBq of I-131 and 0.085 EBq of Cs-137 were released.) About five million people lived in areas of Belarus, Russia and Ukraine contaminated (above 37 kBq/m 2 Cs-137 in soil) and about 400,000 lived in more contaminated areas of strict control by authorities (above 555 kBq/m 2 Cs-137). A total of 29,400 km 2 was contaminated above 180 kBq/m 2 .

The plant operators' town of Pripyat was evacuated on 27 April (45,000 residents). By 14 May, some 116,000 people that had been living within a 30-kilometre radius had been evacuated and later relocated. About 1000 of these returned unofficially to live within the contaminated zone. Most of those evacuated received radiation doses of less than 50 mSv, although a few received 100 mSv or more.

In the years following the accident, a further 220,000 people were resettled into less contaminated areas, and the initial 30 km radius exclusion zone (2800 km 2 ) was modified and extended to cover 4300 square kilometres. This resettlement was due to application of a criterion of 350 mSv projected lifetime radiation dose, though in fact radiation in most of the affected area (apart from half a square kilometre close to the reactor) fell rapidly so that average doses were less than 50% above normal background of 2.5 mSv/yr. See also following section on Resettlement of contaminated areas .

Long-term health effects of the Chernobyl accident

Several organizations have reported on the impacts of the Chernobyl accident, but all have had problems assessing the significance of their observations because of the lack of reliable public health information before 1986.

In 1989, the World Health Organization (WHO) first raised concerns that local medical scientists had incorrectly attributed various biological and health effects to radiation exposure g . Following this, the Government of the USSR requested the International Atomic Energy Agency (IAEA) to coordinate an international experts' assessment of accident's radiological, environmental and health consequences in selected towns of the most heavily contaminated areas in Belarus, Russia, and Ukraine. Between March 1990 and June 1991, a total of 50 field missions were conducted by 200 experts from 25 countries (including the USSR), seven organizations, and 11 laboratories 3 . In the absence of pre-1986 data, it compared a control population with those exposed to radiation. Significant health disorders were evident in both control and exposed groups, but, at that stage, none was radiation related.

Paths of radiation exposure h

In February 2003, the IAEA established the Chernobyl Forum, in cooperation with seven other UN organisations as well as the competent authorities of Belarus, the Russian Federation, and Ukraine. In April 2005, the reports prepared by two expert groups – "Environment", coordinated by the IAEA, and "Health", coordinated by WHO – were intensively discussed by the Forum and eventually approved by consensus. The conclusions of this 2005 Chernobyl Forum study (revised version published 2006 i ) are in line with earlier expert studies, notably the UNSCEAR 2000 report j   which said that "apart from this [thyroid cancer] increase, there is no evidence of a major public health impact attributable to radiation exposure 14 years after the accident. There is no scientific evidence of increases in overall cancer incidence or mortality or in non-malignant disorders that could be related to radiation exposure." There is little evidence of any increase in leukaemia, even among clean-up workers where it might be most expected. Radiation-induced leukemia has a latency period of 5-7 years, so any potential leukemia cases due to the accident would already have developed. A low number of the clean-up workers, who received the highest doses, may have a slightly increased risk of developing solid cancers in the long term. To date, however, there is no evidence of any such cancers having developed. Apart from these, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) said: "The great majority of the population is not likely to experience serious health consequences as a result of radiation from the Chernobyl accident. Many other health problems have been noted in the populations that are not related to radiation exposure."

The Chernobyl Forum report says that people in the area have suffered a paralysing fatalism due to myths and misperceptions about the threat of radiation, which has contributed to a culture of chronic dependency. Some "took on the role of invalids." Mental health coupled with smoking and alcohol abuse is a very much greater problem than radiation, but worst of all at the time was the underlying level of health and nutrition. Apart from the initial 116,000, relocations of people were very traumatic and did little to reduce radiation exposure, which was low anyway. Psycho-social effects among those affected by the accident are similar to those arising from other major disasters such as earthquakes, floods, and fires.

A particularly sad effect of the misconceptions surrounding the accident was that some physicians in Europe advised pregnant women to undergo abortions on account of radiation exposure, even though the levels concerned were vastly below those likely to have teratogenic effects. Robert Gale, a hematologist who treated radiation victims after the accident,  estimated  that more than 1 million abortions were undertaken in the Soviet Union and Europe as a result of incorrect advice from their doctors about radiation exposure and birth defects following the accident.

Some exaggerated figures have been published regarding the death toll attributable to the Chernobyl disaster, including a publication by the UN Office for the Coordination of Humanitarian Affairs (OCHA) 6 . However, the Chairman of UNSCEAR made it clear that "this report is full of unsubstantiated statements that have no support in scientific assessments" k , and the Chernobyl Forum report also repudiates these claims.

The number of deaths resulting from the accident are covered most fully in the account of health effects provided by an annex to the UNSCEAR 2008 report, released in 2011. The report concluded: "In summary, the effects of the Chernobyl accident are many and varied. Early deterministic effects can be attributed to radiation with a high degree of certainty, while for other medical conditions, radiation almost certainly was not the cause. In between, there was a wide spectrum of conditions. It is necessary to evaluate carefully each specific condition and the surrounding circumstances before attributing a cause." 5

According to an UNSCEAR report in 2018, about 20,000 cases of thyroid cancer were diagnosed 1991-2015 in patients who were 18 and under at the time of the accident. The report states that a quarter of the cases (5000 cases) were "probably" due to high doses of radiation, and that this fraction was likely to have been higher in earlier years, and lower in later years. However, it also states that the uncertainty around the attributed fraction is very significant – at least 0.07 to 0.5 – and that the influence of annual screenings and active follow-up make comparisons with the general population problematic. Thyroid cancer is usually not fatal if diagnosed and treated early; the report states that of the diagnoses made between 1991 and 2005, 15 proved to be fatal 9 .

Progressive closure of the Chernobyl plant

In the early 1990s, some $400 million was spent on improvements to the remaining reactors at Chernobyl, considerably enhancing their safety. Energy shortages necessitated the continued operation of one of them (unit 3) until December 2000. (Unit 2 was shut down after a turbine hall fire in 1991, and unit 1 at the end of 1997.) Almost 6000 people worked at the plant every day, and their radiation dose has been within internationally accepted limits. A small team of scientists works within the wrecked reactor building itself, inside the shelter l .

Workers and their families now live in a new town, Slavutich, 30 km from the plant. This was built following the evacuation of Pripyat, which was just 3 km away.

Ukraine depends upon, and is deeply in debt to, Russia for energy supplies, particularly oil and gas, but also nuclear fuel. Although this dependence is gradually being reduced, continued operation of nuclear power stations, which supply half of total electricity, is now even more important than in 1986.

When it was announced in 1995 that the two operating reactors at Chernobyl would be closed by 2000, a memorandum of understanding was signed by Ukraine and G7 nations to progress this, but its implementation was conspicuously delayed. Alternative generating capacity was needed, either gas-fired, which has ongoing fuel cost and supply implications, or nuclear, by completing Khmelnitski unit 2 and Rovno unit 4 ('K2R4') in Ukraine. Construction of these was halted in 1989 but then resumed, and both reactors came online late in 2004, financed by Ukraine rather than international grants as expected on the basis of Chernobyl's closure.

Chernobyl today

Russian military operation 2022.

On 24 February 2022, Russian forces took control of all facilities of the Chernobyl nuclear plant. Control levels of gamma radiation dose rates in the Chernobyl exclusion zone were exceeded. The SNRIU said that the rise in radiation levels was likely due to “disturbance of the top layer of soil from movement of a large number of heavy military machinery through the exclusion zone and increase of air pollution.” It added: “The condition of Chernobyl nuclear facilities and other facilities is unchanged." Radiation readings from the site were assessed by the IAEA to be low and in line with near background levels.

On 9 March at 11.22 the Chernobyl plant lost connection to the grid. The SNRIU said that backup diesel generators were running and had 48 hours of fuel. The IAEA stated that, based on the heat load of spent fuel in the ISF-1 storage pool, and the volume of cooling water it contained, there would be sufficient heat removal without electrical supply. It said that it saw no critical impact on safety as a result of the loss of power, but said that the loss of power would likely create additional stress for the about 210 staff who have not been able to rotate for the past two weeks.

Professor Geraldine Thomas, director of the Chernobyl Tissue Bank, said: "They [the used fuel bundles] will not be producing significant amounts of heat, making a release of radiation very unlikely. In the unlikely event of a release of any radiation, this would be only to the immediate local area, and therefore not pose any threat to western Europe – there would be no radioactive cloud."

On 13 March Energoatom reported that transmission system operator Ukrenergo had succeeded in repairing a power line needed to restore external electricity supplies to Chernobyl. The site was due to be reconnected to the grid a day later, but Ukrenergo reported in the morning of 14 March that the line had sustained further damage "by the occupying forces". Later on 14 March Ukrenergo said that external power had been restored at 13.10 local time, and at 16.45 the plant was reconnected to Ukraine's electricity grid.

On 31 March control of the site was returned to Ukrainian personnel.

For more detailed information, see page on  Russia-Ukraine War and Nuclear Energy .

Unit 4 containment

Chernobyl unit 4 was enclosed in a large concrete shelter which was erected quickly (by October 1986) to allow continuing operation of the other reactors at the plant. However, the structure is neither strong nor durable. The international Shelter Implementation Plan in the 1990s involved raising money for remedial work including removal of the fuel-containing materials. Some major work on the shelter was carried out in 1998 and 1999. About 200 tonnes of highly radioactive material remains deep within it, and this poses an environmental hazard until it is better contained.

The New Safe Confinement (NSC) structure was completed in 2017, having been built adjacent and then moved into place on rails. It is an arch 110 metres high, 165 metres long and spanning 260 metres, covering both unit 4 and the hastily-built 1986 structure. The arch frame is a lattice construction of tubular steel members, equipped with internal cranes. The design and construction contract for this was signed in 2007 with the Novarka consortium and preparatory work onsite was completed in 2010. Construction started in April 2012. The first half, weighing 12,800 tonnes, was moved 112 metres to a holding area in front of unit 4 in April 2014. The second half was completed by the end of 2014 and was joined to the first in July 2015. Cladding, cranes, and remote handling equipment were fitted in 2015. The entire 36,000 tonne structure was pushed 327 metres into position over the reactor building in November 2016, over two weeks, and the end walls completed. The NSC is the largest moveable land-based structure ever built.

The hermetically sealed building will allow engineers to remotely dismantle the 1986 structure that has shielded the remains of the reactor from the weather since the weeks after the accident. It will enable the eventual removal of the fuel-containing materials (FCM) in the bottom of the reactor building and accommodate their characterization, compaction, and packing for disposal. This task represents the most important step in eliminating nuclear hazard at the site – and the real start of dismantling. The NSC will facilitate remote handling of these dangerous materials, using as few personnel as possible. During peak construction of the NSC some 1200 workers were onsite. 

The Chernobyl Shelter Fund, set up in 1997, had received €864 million from international donors by early 2011 towards this project and previous work. It and the Nuclear Safety Account (NSA), set up in 1993, are managed by the European Bank for Reconstruction and Development (EBRD). The total cost of the new shelter was in 2011 estimated to be €1.5 billion. In November 2014 the EBRD said the overall €2.15 billion Shelter Implementation Plan including the NSC had received contributions from 43 governments but still had a funding shortfall of €615 million. The following month the EBRD made an additional contribution of €350 million in anticipation of a €165 million contribution by the G7/European Commission, which was confirmed in April 2015. This left a balance of €100 million to come from non-G7 donors, and €15 million of this was confirmed in April 2015.

Chernobyl New Safe Confinement under construction and before being moved into place (Image: EBRD)

Funding other Chernobyl work

The Nuclear Safety Account (NSA), had received €321 million by early 2011 for Chernobyl decommissioning and also for projects in other ex-Soviet countries. At Chernobyl it funds the construction of used fuel and waste storage (notably ISF-2, see below) and decommissioning units 1-3. In April 2016 the European Commission pledged €20 million to the NSA, the largest part of €45 million expected from the G7 and the European Commission. A further €40 million was expected from the EBRD in May 2016.

In total, the European Commission has committed around €730 million so far to Chernobyl projects in four ways. First, €550 million for assistance projects, out of which €470 million were channelled through international funds, and €80 million implemented directly by the European Commission. Secondly, power generation support of €65 million. Thirdly, €15 million for social projects. And finally, €100 million for research projects.

Chernobyl used fuel: ISF-1 & ISF-2

Used fuel from units 1-3 was stored in each unit's cooling pond, and in an interim spent fuel storage facility pond (ISF-1). A few damaged assemblies remained in units 1&2 in 2013, with the last of these removed in June 2016. ISF-1 now holds most of the spent fuel from units 1-3, allowing those reactors to be decommissioned under less restrictive licence conditions. Most of the fuel assemblies were straightforward to handle, but about 50 are damaged and required special handling.

In 1999, a contract was signed with Framatome (now Areva) for construction of the ISF-2 radioactive waste management facility to store 25,000 used fuel assemblies from units 1-3 and other operational waste long-term, as well as material from decommissioning units 1-3 (which are the first RBMK units decommissioned anywhere). However, after a significant part of the dry storage facility had been built, technical deficiencies in the concept emerged in 2003, and the contract was terminated amicably in 2007.

Holtec International became the contractor in September 2007 for the new interim spent nuclear fuel storage facility (ISF-2 or SNF SF-2) for the state-owned Chernobyl NPP. Design approval and funding from the NSA was confirmed in October 2010, and the final €87.5 million of €400 million cost was pledged in April 2016. Construction was completed in January 2020. Hot and cold tests took place during 2020, and the facility received an operating licence in April 2021.

ISF-2 is the world’s largest dry used fuel storage facility, accommodating 21,217 RBMK fuel assemblies in dry storage for at least a 100-year service life.

The project includes a processing facility, able to cut the RBMK fuel assemblies* and to put the material in double-walled canisters, which are then filled with inert gas and welded shut. They will then be transported to concrete dry storage vaults in which the fuel containers will be enclosed for up to 100 years. This facility, treating 2500 fuel assemblies per year, is the first of its kind for RBMK fuel.

* According to Holtec: “Unique features of the Chernobyl dry storage facility include the world's largest 'hot cell' for dismembering the conjugated RBMK fuel assembly and a (Holtec patented) forced gas dehydrator designed to run on nitrogen.”

Other Chernobyl radwaste

Industrial Complex for Radwaste Management (ICSRM): In April 2009, Nukem handed over this turnkey waste treatment centre for solid radioactive waste. In May 2010, the State Nuclear Regulatory Committee licensed the commissioning of this facility, where solid low- and intermediate-level wastes accumulated from the power plant operations and the decommissioning of reactor blocks 1-3 is conditioned. The wastes are processed in three steps. First, the solid radioactive wastes temporarily stored in bunkers is removed for treatment. In the next step, these wastes, as well as those from decommissioning reactor blocks 1-3, are processed into a form suitable for permanent safe disposal. Low- and intermediate-level wastes are separated into combustible, compactable, and non-compactable categories. These are then subject to incineration, high-force compaction, and cementation respectively. In addition, highly radioactive and long-lived solid waste is sorted out for temporary separate storage. In the third step, the conditioned solid waste materials are transferred to containers suitable for permanent safe storage.

As part of this project, at the end of 2007, Nukem handed over an Engineered Near Surface Disposal Facility for storage of short-lived radioactive waste after prior conditioning. It is 17 km away from the power plant, at the Vektor complex within the 30-km zone. The storage area is designed to hold 55,000 m 3 of treated waste which will be subject to radiological monitoring for 300 years, by when the radioactivity will have decayed to such an extent that monitoring is no longer required.

Another contract has been let for a Liquid Radioactive Waste Treatment Plant (LRTP), to handle some 35,000 cubic metres of low- and intermediate-level liquid wastes at the site. This will be solidified and eventually buried along with solid wastes on site. Construction of the plant has been completed and the start of operations was due late in 2015. LRTP is also funded through EBRD’s Nuclear Safety Account (NSA).

Non-Chernobyl used fuel

The Central Spent Fuel Storage Facility (CSFSF) Project for Ukraine’s VVER reactors is being built by Holtec International within the Chernobyl exclusion area, between the resettled villages Staraya Krasnitsa, Buryakovka, Chistogalovka, and Stechanka, southeast of Chernobyl and not far from ISF-2. This will not take any Chernobyl fuel, though it will become a part of the common spent nuclear fuel management complex of the state-owned company Chernobyl NPP.

Decommissioning units 1-3

After the last Chernobyl reactor shut down in December 2000, in mid-2001 a new enterprise, SSE ChNPP was set up to take over management of the site and decommissioning from Energoatom. (Its remit includes eventual decommissioning of all Ukraine nuclear plants.)

In January 2008, the Ukraine government announced a four-stage decommissioning plan which incorporated the above waste activities and progresses towards a cleared site.

In February 2014 a new stage of this was approved for units 1-3, involving dismantling some equipment and putting them into safstor condition by 2028. Then, to 2046, further equipment will be removed, and by 2064 they will be demolished.

See also official website .

Resettlement of contaminated areas

In the last two decades there has been some resettlement of the areas evacuated in 1986 and subsequently. Recently the main resettlement project has been in Belarus.

In July 2010, the Belarus government announced that it had decided to settle back thousands of people in the 'contaminated areas' covered by the Chernobyl fallout, from which 24 years ago they and their forbears were hastily relocated. Compared with the list of contaminated areas in 2005, some 211 villages and hamlets had been reclassified with fewer restrictions on resettlement. The decision by the Belarus Council of Ministers resulted in a new national program over 2011-15 and up to 2020 to alleviate the Chernobyl impact and return the areas to normal use with minimal restrictions. The focus of the project is on the development of economic and industrial potential of the Gomel and Mogilev regions from which 137,000 people were relocated.

The main priority is agriculture and forestry, together with attracting qualified people and housing them. Initial infrastructure requirements will mean the refurbishment of gas, potable water and power supplies, while the use of local wood will be banned. Schools and housing will be provided for specialist workers and their families ahead of wider socio-economic development. Overall, some 21,484 dwellings are slated for connection to gas networks in the period 2011-2015, while about 5600 contaminated or broken down buildings are demolished. Over 1300 kilometres of road will be laid, and ten new sewerage works and 15 pumping stations are planned. The cost of the work was put at BYR 6.6 trillion ($2.2 billion), split fairly evenly across the years 2011 to 2015 inclusive.

The feasibility of agriculture will be examined in areas where the presence of caesium-137 and strontium-90 is low, "to acquire new knowledge in the fields of radiobiology and radioecology in order to clarify the principles of safe life in the contaminated territories." Land found to have too high a concentration of radionuclides will be reforested and managed. A suite of protective measures was set up to allow a new forestry industry whose products would meet national and international safety standards. In April 2009, specialists in Belarus stressed that it is safe to eat all foods cultivated in the contaminated territories, though intake of some wild food was restricted.

Protective measures will be put in place for 498 settlements in the contaminated areas where average radiation dose may exceed 1 mSv per year. There were also 1904 villages with annual average effective doses from the pollution between 0.1 mSv and 1 mSv. The goal for these areas is to allow their re-use with minimal restrictions, although already radiation doses there from the caesium are lower than background levels anywhere in the world.

The Belarus government decision was an important political landmark in an ongoing process. Studies reviewed by UNSCEAR show that the Chernobyl disaster caused little risk for the general population. A UN Development Program report in 2002 said that much of the aid and effort applied to mitigate the effects of the Chernobyl accident did more harm than good, and it seems that this, along with the Chernobyl Forum report, finally persuaded the Belarus authorities. In 2004 President Lukashenko announced a priority to repopulate much of the Chernobyl-affected regions of Belarus, and then in 2009 he said that he “wants to repopulate Chernobyl’s zone quickly”.

In 2011 Chernobyl was officially declared a tourist attraction, with many visitors.

In 2015 the published results of a major scientific study showed that the mammal population of the exclusion zone (including the 2162 sq km Polessian State Radiation-Ecological Reserve – PSRER in Belarus) was thriving, despite land contamination. The “long-term empirical data showed no evidence of a negative influence of radiation on mammal abundance.” The data “represent unique evidence of wildlife's resilience in the face of chronic radiation stress.” ( Current Biology , Elsevier 8 ) . Other studies have concluded that the net environmental effect of the accident has been much greater biodiversity and abundance of species, with the exclusion zone having become a unique sanctuary for wildlife due to the absence of humans.

What has been learned from the Chernobyl disaster?

Leaving aside the verdict of history on its role in melting the Soviet 'Iron Curtain', some very tangible practical benefits have resulted from the Chernobyl accident. The main ones concern reactor safety, notably in eastern Europe. (The US Three Mile Island accident in 1979 had a significant effect on Western reactor design and operating procedures. While that reactor was destroyed, all radioactivity was contained – as designed – and there were no deaths or injuries.)

While no-one in the West was under any illusion about the safety of early Soviet reactor designs, some lessons learned have also been applicable to Western plants. Certainly the safety of all Soviet-designed reactors has improved vastly. This is due largely to the development of a culture of safety encouraged by increased collaboration between East and West, and substantial investment in improving the reactors.

Modifications have been made to overcome deficiencies in all the RBMK reactors still operating. In these, originally the nuclear chain reaction and power output could increase if cooling water were lost or turned to steam, in contrast to most Western designs. It was this effect which led to the uncontrolled power surge that led to the destruction of Chernobyl 4 (see Positive void coefficient section in the information page on RBMK Reactors ). All of the RBMK reactors have now been modified by changes in the control rods, adding neutron absorbers and consequently increasing the fuel enrichment from 1.8 to 2.4% U-235, making them very much more stable at low power (see Post accident changes to the RBMK section in the information page on RBMK Reactors ). Automatic shut-down mechanisms now operate faster, and other safety mechanisms have been improved. Automated inspection equipment has also been installed. A repetition of the 1986 Chernobyl accident is now virtually impossible, according to a German nuclear safety agency report 7 .

Since 1989, over 1000 nuclear engineers from the former Soviet Union have visited Western nuclear power plants and there have been many reciprocal visits. Over 50 twinning arrangements between East and West nuclear plants have been put in place. Most of this has been under the auspices of the World Association of Nuclear Operators (WANO), a body formed in 1989 which links 130 operators of nuclear power plants in more than 30 countries (see also information page on Cooperation in the Nuclear Power Industry ).

Many other international programmes were initiated following Chernobyl. The International Atomic Energy Agency (IAEA) safety review projects for each particular type of Soviet reactor are noteworthy, bringing together operators and Western engineers to focus on safety improvements. These initiatives are backed by funding arrangements. The Nuclear Safety Assistance Coordination Centre database lists Western aid totalling almost US$1 billion for more than 700 safety-related projects in former Eastern Bloc countries. The Convention on Nuclear Safety adopted in Vienna in June 1994 is another outcome.

The Chernobyl Forum report said that some seven million people are now receiving or eligible for benefits as 'Chernobyl victims', which means that resources are not targeting those most in need. Remedying this presents daunting political problems however.

Notes & references

a. Chernobyl is the well-known Russian name for the site; Chornobyl is preferred by Ukraine. [ Back ]

b. Much has been made of the role of the operators in the Chernobyl accident. The 1986 Summary Report on the Post-Accident Review Meeting on the Chernobyl Accident (INSAG-1) of the International Atomic Energy Agency's (IAEA's) International Nuclear Safety Advisory Group accepted the view of the Soviet experts that "the accident was caused by a remarkable range of human errors and violations of operating rules in combination with specific reactor features which compounded and amplified the effects of the errors and led to the reactivity excursion." In particular, according to the INSAG-1 report: "The operators deliberately and in violation of rules withdrew most control and safety rods from the core and switched off some important safety systems."

However, the IAEA's 1992 INSAG-7 report, The Chernobyl Accident: Updating of INSAG-1 , was less critical of the operators, with the emphasis shifted towards "the contributions of particular design features, including the design of the control rods and safety systems, and arrangements for presenting important safety information to the operators. The accident is now seen to have been the result of the concurrence of the following major factors: specific physical characteristics of the reactor; specific design features of the reactor control elements; and the fact that the reactor was brought to a state not specified by procedures or investigated by an independent safety body. Most importantly, the physical characteristics of the reactor made possible its unstable behaviour." But the report goes on to say that the International Nuclear Safety Advisory Group "remains of the opinion that critical actions of the operators were most ill judged. As pointed out in INSAG-1, the human factor has still to be considered as a major element in causing the accident."

It is certainly true that the operators placed the reactor in a dangerous condition, in particular by removing too many of the control rods, resulting in the lowering of the reactor's operating reactivity margin (ORM, see information page on RBMK Reactors ). However, the operating procedures did not emphasize the vital safety significance of the ORM but rather treated the ORM as a way of controlling reactor power. It could therefore be argued that the actions of the operators were more a symptom of the prevailing safety culture of the Soviet era rather than the result of recklessness or a lack of competence on the part of the operators.

In what is referred to as his Testament – which was published soon after his suicide two years after the accident – Valery Legasov, who had led the Soviet delegation to the IAEA Post-Accident Review Meeting, wrote: "After I had visited Chernobyl NPP I came to the conclusion that the accident was the inevitable apotheosis of the economic system which had been developed in the USSR over many decades. Neglect by the scientific management and the designers was everywhere with no attention being paid to the condition of instruments or of equipment... When one considers the chain of events leading up to the Chernobyl accident, why one person behaved in such a way and why another person behaved in another etc , it is impossible to find a single culprit, a single initiator of events, because it was like a closed circle." [ Back ]

c. The initial death toll was officially given as two initial deaths plus 28 from acute radiation syndrome. One further victim, due to coronary thrombosis, is widely reported, but does not appear on official lists of the initial deaths. The 2006 report of the UN Chernobyl Forum Expert Group "Health", Health Effects of the Chernobyl Accident and Special Health Care Programmes , states: "The Chernobyl accident caused the deaths of 30 power plant employees and firemen within a few days or weeks (including 28 deaths that were due to radiation exposure)." [ Back ]

d. Apart from the initial 31 deaths (two from the explosions, one reportedly from coronary thrombosis – see Note c above – and 28 firemen and plant personnel from acute radiation syndrome), the number of deaths resulting from the accident is unclear and a subject of considerable controversy. According to the 2006 report of the UN Chernobyl Forum's 'Health' Expert Group 1 : "The actual number of deaths caused by this accident is unlikely ever to be precisely known."

On the number of deaths due to acute radiation syndrome (ARS), the Expert Group report states: "Among the 134 emergency workers involved in the immediate mitigation of the Chernobyl accident, severely exposed workers and fireman during the first days, 28 persons died in 1986 due to ARS, and 19 more persons died in 1987-2004 from different causes. Among the general population affected by the Chernobyl radioactive fallout, the much lower exposures meant that ARS cases did not occur."

According to the report: "With the exception of thyroid cancer, direct radiation-epidemiological studies performed in Belarus, Russia and Ukraine since 1986 have not revealed any statistically significant increase in either cancer morbidity or mortality induced by radiation." The report does however attribute a large proportion of child thyroid cancer fatalities to radiation, with nine deaths being recorded during 1986-2002 as a result of progression of thyroid cancer. [ Back ]

e. There have been fatalities in military and research reactor contexts, e.g. Tokai-mura. [ Back ]

f. Although most reports on the Chernobyl accident refer to a number of graphite fires, it is highly unlikely that the graphite itself burned. Information on the General Atomics website (but now deleted) stated: "It is often incorrectly assumed that the combustion behavior of graphite is similar to that of charcoal and coal. Numerous tests and calculations have shown that it is virtually impossible to burn high-purity, nuclear-grade graphites." On Chernobyl, the same source stated: "Graphite played little or no role in the progression or consequences of the accident. The red glow observed during the Chernobyl accident was the expected color of luminescence for graphite at 700°C and not a large-scale graphite fire, as some have incorrectly assumed."

A 2006 Electric Power Research Institute Technical Report states that the International Atomic Energy Agency's INSAG-1 report is ...potentially misleading through the use of imprecise words in relation to graphite behaviour. The report discusses the fire-fighting activities and repeatedly refers to “burning graphite blocks” and “the graphite fire”. Most of the actual fires involving graphite which were approached by fire-fighters involved ejected material on bitumen-covered roofs, and the fires also involved the bitumen. It is stated: “The fire teams experienced no unusual problems in using their fire-fighting techniques, except that it took a considerable time to extinguish the graphite fire.” These descriptions are not consistent with the later considered opinions of senior Russian specialists... There is however no question that extremely hot graphite was ejected from the core and at a temperature sufficient to ignite adjacent combustible materials.

There are also several referrals to a graphite fire occurring during the October 1957 accident at Windscale Pile No. 1 in the UK. However, images obtained from inside the Pile several decades after the accident showed that the graphite was relatively undamaged. [ Back ]

g. The International Chernobyl Project, 1990-91 - Assessment of Radiological Consequences and Evaluation of Protective Measures, Summary Brochure, published by the International Atomic Energy Agency, reports that, in June 1989, the World Health Organization (WHO) sent a team of experts to help address the health impacts of radioactive contamination resulting from the accident. One of the conclusions from this mission was that "scientists who are not well versed in radiation effects have attributed various biological and health effects to radiation exposure. These changes cannot be attributed to radiation exposure, especially when the normal incidence is unknown, and are much more likely to be due to psychological factors and stress.Attributing these effects to radiation not only increases the psychological pressure in the population and provokes additional stress-related health problems, it also undermines confidence in the competence of the radiation specialists." [ Back ]

h. Image taken from page 31 of The International Chernobyl Project Technical Report , Assessment of Radiological Consequences and Evaluation of Protective Measures, Report by an International Advisory Committee , IAEA, 1991 (ISBN: 9201291914) [ Back ]

i. A 55-page summary version the revised report, Chernobyl’s Legacy: Health, Environmental and Socio-Economic Impacts and Recommendations to the Governments of Belarus, the Russian Federation and Ukraine, The Chernobyl Forum: 2003–2005, Second revised version , as well as the Report of the UN Chernobyl Forum Expert Group “Environment” and the Report of the UN Chernobyl Forum Expert Group “Health” are available through the IAEA's webpage on the Chernobyl accident ( https://www.iaea.org/topics/chornobyl ) [ Back ]

j. The United Nations Scientific Commission on the Effects of Atomic Radiation (UNSCEAR) is the UN body with a mandate from the General Assembly to assess and report levels and health effects of exposure to ionizing radiation. Exposures and effects of the Chernobyl accident , Annex J to Volume II of the 2000 United Nations Scientific Committee on the Effects of Atomic Radiation Report to the General Assembly, is available at the UNSCEAR 2000 Report Vol. II webpage (www.unscear.org/unscear/en/publications/2000_2.html). It is also available (along with other reports) on the webpage for UNSCEAR's assessments of the radiation effects of The Chernobyl accident (www.unscear.org/unscear/en/chernobyl.html). The conclusions from Annex J of the UNSCEAR 2000 report are in Chernobyl Accident Appendix: Health Impacts [ Back ]

k. The quoted comment comes from a 6 June 2000 letter from Lars-Erik Holm, Chairman of UNSCEAR and Director-General of the Swedish Radiation Protection Institute, to Kofi Annan, Secretary-General of the United Nations. [ Back ]

l. A reinforced concrete casing was built around the ruined reactor building over the seven months following the accident. This shelter – often referred to as the sarcophagus  – was intended to contain the remaining fuel and act as a radiation shield. As it was designed for a lifetime of around 20 to 30 years, as well as being hastily constructed, a second shelter – known as the New Safe Confinement – with a 100-year design lifetime is planned to be placed over the existing structure. See also ASE keeps the lid on Chernobyl , World Nuclear News (19 August 2008). [ Back ]

m. The UNSCEAR committee in 2018 9 estimated that the fraction of the incidence of thyroid cancer attributable to radiation exposure among non-evacuated residents of Belarus, Ukraine and the four most contaminated oblasts of the Russian Federation, who were under 18 at the time of the accident, is in the order of 0.25 . The committee states that the uncertainty range of the fraction is large, at least from 0.07 to 0.5. [ Back ]

1. Health Effects of the Chernobyl Accident and Special Health Care Programmes , Report of the UN Chernobyl Forum, Expert Group "Health", World Health Organization, 2006 (ISBN: 9789241594172) 2. Appendix D, Graphite Decommissioning: Options for Graphite Treatment, Recycling, or Disposal, including a discussion of Safety-Related Issues , EPRI, Palo Alto, CA, 1013091 (March 2006) 3. The International Chernobyl Project, 1990-91 - Assessment of Radiological Consequences and Evaluation of Protective Measures, Summary Brochure , International Atomic Energy Agency, IAEA/PI/A32E, 1991; The International Chernobyl Project, An Overview , Assessment of Radiological Consequences and Evaluation of Protective Measures, Report by an International Advisory Committee , IAEA, 1991 (ISBN: 9201290918); The International Chernobyl Project Technical Report , Assessment of Radiological Consequences and Evaluation of Protective Measures, Report by an International Advisory Committee , IAEA, 1991 (ISBN: 9201291914) [ Back ] 4. Mikhail Balonov, Malcolm Crick and Didier Louvat, Update of Impacts of the Chernobyl Accident: Assessments of the Chernobyl Forum (2003-2005) and UNSCEAR (2005-2008) , Proceedings of the Third European IRPA (International Radiation Protection Association) Congress held in Helsinki, Finland (14-18 June 2010) [ Back ] 5. UNSCEAR, 2011, Health Effects due to Radiation from the Chernobyl Accident ,  UNSCEAR 2008 Report, vol II, annex D (lead author: M. Balanov) [ Back ] 6. Chernobyl - A Continuing Catastrophe, United Nations Office for the Coordination of Humanitarian Affairs (OCHA), 2000 [ Back ] 7. The Accident and the Safety of RBMK-Reactors, Gesellschaft für Anlagen und Reaktorsicherheit (GRS) mbH, GRS-121 (February 1996) [ Back ] 8. Deryabina, T.G. et al. , Long-term census data reveal abundant wildlife populations at Chernobyl , Current Biology, Volume 25, Issue 19, pR824–R826, Elsevier (5 October 2015) [ Back ] 9. Evaluation of data on thyroid cancer in regions affected by the Chernobyl accident , UNSCEAR (2018) [ Back ]

General sources

INSAG-7, The Chernobyl Accident: Updating of INSAG-1, A report by the International Nuclear Safety Advisory Group, International Atomic Energy Agency, Safety Series No. 75-INSAG-7, 1992, (ISBN: 9201046928)

Chernobyl’s Legacy: Health, Environmental and Socio-Economic Impacts and Recommendations to the Governments of Belarus, the Russian Federation and Ukraine, The Chernobyl Forum: 2003–2005, Second revised version, International Atomic Energy Agency, IAEA/PI/A.87 Rev.2/06-09181 (April 2006)

Environmental Consequences of the Chernobyl Accident and their Remediation: Twenty Years of Experience, Report of the Chernobyl Forum Expert Group ‘Environment’, International Atomic Energy Agency, 2006 (ISBN 9201147058)

Health Effects of the Chernobyl Accident and Special Health Care Programmes, Report of the UN Chernobyl Forum Expert Group "Health", World Health Organization, 2006 (ISBN: 9789241594172)

The Chernobyl accident, UNSCEAR's assessments of the radiation effects on the UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) radiation website

Exposures and effects of the Chernobyl accident, Annex J of Sources and Effects of Ionizing Radiation , UNSCEAR 2000 Report to the General Assembly Vol. II

Ten Years after Chernobyl: what do we really know? (based on the proceedings of the IAEA/WHO/EC International Conference, Vienna, April 1996), International Atomic Energy Agency

Chernobyl: Assessment of Radiological and Health Impacts - 2002 Update of Chernobyl: Ten Years On, OECD Nuclear Energy Agency (2002).

Zbigniew Jaworowski, Lessons of Chernobyl with particular reference to thyroid cancer , Australasian Radiation Protection Society Newsletter No. 30 (April 2004). The same article appeared in Executive Intelligence Review (EIR), Volume 31, Number 18 (7 May 2004). An extended version of this paper was published as Radiation folly, Chapter 4 of Environment & Health: Myths & Realities, Edited by Kendra Okonski and Julian Morris, International Policy Press (a division of International Policy Network), June 2004 (ISBN 1905041004). See also Chernobyl Accident Appendix 2: Health Impacts

The chernobyl.info website www.chernobyl.info – out of date but some useful information

Chernobyl Forum information on IAEA website

Mikhail Balonov, The Chernobyl Forum: Major Findings and Recommendations, presented at the Public Information Materials Exchange meeting held in Vienna, Austria on 12-16 February 2006

GreenFacts webpage on Scientific Facts on the Chernobyl Nuclear Accident (www.greenfacts.org/en/chernobyl)

European Centre of Technological Safety's Chernobyl website (www.tesec-int.org/Chernobyl) and its webpage on Sarcophagus and Decommissioning of the Chernobyl NPP

Chernobyl Legacy website (www.chernobyllegacy.com)

David Mosey, Looking Beyond the Operator, Nuclear Engineering International, 26 Nov 2014

Chernobyl 25th anniversary, Frequently Asked Questions, World Health Organization (23 April 2011)

Environmental Consequences of the Chernobyl Accident and their Remediation: Twenty Years of Experience , Report of the UN Chernobyl Forum Expert Group "Environment", STI/PUB/1239, International Atomic Energy Agency (2006)

Chernobyl Accident - Appendix 1: Sequence of Events

Chernobyl accident - appendix 2: health impacts, related information, decommissioning nuclear facilities, early soviet reactors and eu accession, fukushima daiichi accident, nuclear energy and sustainable development, rbmk reactors, safety of nuclear power reactors, ukraine: russia-ukraine war and nuclear energy, you may also be interested in.

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The Fantasy of Reviving Nuclear Energy

By Stephanie Cooke

Ms. Cooke is a former editor of Nuclear Intelligence Weekly and the author of “In Mortal Hands: A Cautionary History of the Nuclear Age.”

World leaders are not unaware of the nuclear industry’s long history of failing to deliver on its promises or of its weakening vital signs. Yet many continue to act as if a nuclear renaissance could be around the corner, even though nuclear energy’s share of global electricity generation has fallen by almost half from its high of roughly 17 percent in 1996.

In search of that revival, representatives from more than 30 countries gathered in Brussels in March at a nuclear summit hosted by the International Atomic Energy Agency and the Belgian government. Thirty-four nations, including the United States and China, agreed “to work to fully unlock the potential of nuclear energy,” including extending the lifetimes of existing reactors, building nuclear power plants and deploying advanced reactors.

Yet even as they did so, there was an acknowledgment of the difficulty of their undertaking. “Nuclear technology can play an important role in the clean energy transition,” Ursula von der Leyen, the president of the European Commission, told summit attendees. But she added that “the reality today, in most markets, is a reality of a slow but steady decline in market share” for nuclear power.

The numbers underscore that downturn. Solar and wind power together began outperforming nuclear power globally in 2021, and that trend continues as nuclear staggers along. Solar alone added more than 400 gigawatts of capacity worldwide last year, two-thirds more than the previous year. That’s more than the roughly 375 gigawatts of combined capacity of the world’s 415 nuclear reactors, which remained relatively unchanged last year. At the same time, investment in energy storage technology is rapidly accelerating. In 2023, BloombergNEF reported that investors for the first time put more money into stationary energy storage than they did into nuclear.

Still, the drumbeat for nuclear power has become pronounced. At the United Nations climate conference in Dubai in December, the Biden administration persuaded two dozen countries to pledge to triple their nuclear energy capacity by 2050. Those countries included allies of the United States with troubled nuclear programs, most notably France , Britain , Japan and South Korea , whose nuclear bureaucracies will be propped up by the declaration as well as the domestic nuclear industries they are trying to save.

“We are not making the argument to anybody that this is absolutely going to be a sweeping alternative to every other energy source,” John Kerry, the Biden administration climate envoy at the time, said. “But we know because the science and the reality of facts and evidence tell us that you can’t get to net zero 2050 without some nuclear.”

That view has gained traction with energy planners in Eastern Europe who see nuclear as a means of replacing coal, and several countries — including Canada, Sweden, Britain and France — are pushing to extend the operating lifetimes of existing nuclear plants or build additional ones. Some see smaller or more advanced reactors as a means of providing electricity in remote areas or as a means of decarbonizing sectors such as heat, industry and transportation.

So far, most of this remains in early stages, with only three nuclear reactors under construction in Western Europe, two in Britain and one in France, each more than a decade behind schedule. Of the approximately 54 other reactors under construction worldwide as of March, 23 are in China, seven are in India, and three are in Russia, according to the International Atomic Energy Agency. The total is less than a quarter of the 234 reactors under construction in the peak year of 1979, although 48 of those were later suspended or abandoned.

Even if you agree with Mr. Kerry’s argument, and many energy experts do not, pledging to triple nuclear capacity by 2050 is a little like promising to win the lottery. For the United States, it would mean adding 200 gigawatts of nuclear operating capacity (almost double what the country has ever built) to the current 100 gigawatts or so, generated by more than 90 commercial reactors that have been running an average of 42 years. Globally it would mean tripling the existing capacity built over the past 70 years in less than half that time, in addition to replacing reactors that will shut down before 2050.

The Energy Department estimates the total cost of such an effort in the United States at roughly $700 billion. But David Schlissel , a director at the Institute for Energy Economics and Financial Analysis , has calculated that the two new reactors at the Vogtle plant in Georgia — the only new reactors built in the United States in a generation — on average, cost $21.2 billion per gigawatt in today’s dollars. Using that figure as a yardstick, the cost of building 200 gigawatts of new capacity would be far higher: at least $4 trillion, or $6 trillion if you count the additional cost of replacing existing reactors as they age out.

For much less money and in less time, the world could reduce greenhouse gas emissions through the use of renewables like solar, wind, hydropower and geothermal power and by transmitting, storing and using electricity more efficiently. A recent analysis by the German Environment Agency examined multiple global climate scenarios in which Paris climate agreement targets are met, and it found that renewable energy “is the crucial and primary driver.”

The logic of this approach was attested to at the climate meeting in Dubai, where more than 120 countries signed a more realistic commitment to triple renewable energy capacity by 2030.

There’s a certain inevitability about the U.S. Energy Department’s latest push for more nuclear energy. An agency predecessor, the Atomic Energy Commission, brought us Atoms for Peace under President Dwight Eisenhower in the 1950s in a bid to develop the peaceful side of the atom, hoping it would gain public acceptance of an expanding arsenal of nuclear weapons while supplying electricity too cheap to meter.

Fast-forward 70 years, and you hear a variation on the same theme. Most notably, Ernest Moniz, the energy secretary under President Barack Obama, argues that a vibrant commercial nuclear sector is necessary to sustain U.S. influence in nuclear weapons nonproliferation efforts and global strategic stability. As a policy driver, this argument might explain in part why the government continues to push nuclear power as a climate solution, despite its enormous cost and lengthy delivery time.

China and Russia are conspicuously absent from the list of signatories to the Dubai pledge to triple nuclear power, although China signed the declaration in Brussels. China’s nuclear program is growing faster than that of any other country, and Russia dominates the global export market for reactors with projects in countries new to commercial nuclear energy, such as Turkey, Egypt and Bangladesh, as well as Iran.

Pledges and declarations on a global stage allow world leaders a platform to be seen to be doing something to address climate change, even if, as is the case with nuclear, they lack the financing and infrastructure to succeed. But their support most likely means that substantial sums of money — much of it from taxpayers and ratepayers — will be wasted on perpetuating the fantasy that nuclear energy will make a difference in a meaningful time frame to slow global warming.

The U.S. government is already poised to spend billions of dollars building small modular and advanced reactors and keeping aging large ones running. But two such small reactor projects based on conventional technologies have already failed. Which raises the question: Will future projects based on far more complex technologies be more viable? Money for such projects — provided mainly under the Infrastructure Investment and Jobs Act and the Inflation Reduction Act — could be redirected in ways that do more for the climate and do it faster, particularly if planned new nuclear projects fail to materialize.

There is already enough potential generation capacity in the United States seeking access to the grid to come close to achieving President Biden’s 2035 goal of a zero-carbon electricity sector, and 95 percent of it is solar, battery storage and wind. But these projects face a hugely constrained transmission system, regulatory and financial roadblocks and entrenched utility interests, enough to prevent many of them from ever providing electricity, according to a report released last year by the Lawrence Berkeley National Laboratory.

Even so, existing transmission capacity can be doubled by retrofitting transmission lines with advanced conductors, which would offer at least a partial way out of the gridlock for renewables, in addition to storage, localized distribution and improved management of supply and demand.

What’s missing are leaders willing to buck their own powerful nuclear bureaucracies and choose paths that are far cheaper, less dangerous and quicker to deploy. Without them, we are doomed to more promises and wasteful spending by nuclear proponents who have repeatedly shown that they can talk but can’t deliver.

Stephanie Cooke is a former editor of Nuclear Intelligence Weekly and the author of “In Mortal Hands: A Cautionary History of the Nuclear Age.”

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The Bataan Nuclear Power Plant in the Philippines: A Nuclear Plant, and a Dream, Fizzles

Nuclear Power Plant Engineer. In my study at KEPCO International Nuclear Graduate School in which I specialized in Project Management in Nuclear Power Plant (NPP) Construction, my team and I...

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A case study conducted by Mark Gino Aliperio and Byeonghui Song.

In many ways, the Philippines is a good case study of the effect of public perception and response to the establishment of a nuclear power program. The country’s first and only attempt at nuclear power development was the 621-MW Philippine Nuclear Power Plant in August 1977. It was supposed to be the first of two nuclear plants to be built in the northern province of Bataan. It was also the first nuclear power plant in Southeast Asia, and deemed as a promising solution to the 1973 oil crisis that had adversely affected the global economy, including the Philippines.

Unexpectedly, the Chernobyl accident happened turning optimism quickly into skepticism. This was followed by political events rapidly unfolding in the Philippines and the 21-year rule of President Marcos, crumbled in the face of the People Power revolution that catapulted Mrs. Corazon Aquino to the presidency. Almost everything associated with Marcos was rejected, invariably including the completed and fully constructed and equipped Bataan Nuclear Power Plant (BNPP). Thus, 1986 saw the first nuclear power plant in the Philippines and in Southeast Asia mothballed, because of an unfortunate association with an unlamented regime overthrown by the people. From thereon, the power plant was placed on ‘preservation mode’. But then, clamor for the reopening of BNPP was revived during the power crisis in the 90s and the skyrocketing of oil prices in 2007.

During these periods, the Department of Energy (DOE) actually came close to reconsidering nuclear power as a potential energy source for the country. An Inter-Agency Core Group on Nuclear Energy composed of the Department of Energy, the Department of Science and Technology and the NPC Power was organized to do the evaluation. But then the Fukushima nuclear plant incident happened in 2011, creating global panic and concerns about the safety and integrity of nuclear plants. Meanwhile, in the Philippines, the incident virtually led to an undeclared moratorium on all plans to go nuclear for power generation. If these weren't enough, adding to these various setbacks, the emergence of natural gas, wind and solar energy pushed nuclear power deeper into dormancy.

As public perception of nuclear technology has been tainted as a result of few but sensational incidents, Government has a clear role in regaining public trust. Government plays a key role in ensuring public participation and involvement which is critical at every stage of a nuclear power program. This case study takes into account the failure of public involvement and acceptance towards BNPP as it faced allegations of corruption and anomaly. Moreover, two surveys conducted by the Inter-Agency Core Group regarding nuclear energy utilization and awareness were analyzed.

Controversy and Timeline of Construction

Two proposals were submitted by reputable energy companies — General Electric and Westinghouse Electric. General Electric submitted a proposal containing detailed specifications of the nuclear plant and estimated it to cost US$700 million. On the other hand, Westinghouse submitted a lower cost estimate of US$500 million, but the proposal did not contain any detail or specification.

The presidential committee tasked to oversee the project preferred General Electric's proposal, but this was overruled by Marcos in June 1974 who signed a letter of intent awarding the project to Westinghouse, despite the absence of any specifications on their proposal. By March 1975, Westinghouse's cost estimate ballooned to US$1.2 billion without much explanation. The National Power Corporation would later construct only one nuclear reactor plant for US$1.1 billion. It would soon be discovered that Westinghouse sold the similar technology to other countries for only a fraction of the project cost it billed the Philippines.

Construction on the Bataan Nuclear Power Plant began in 1976. Following the 1979 Three Mile Island accident in the United States, construction on the BNPP was stopped, and a subsequent safety inquiry into the plant revealed over 4,000 defects. Among the issues raised was that it was built near a major geological fault line and close to the then dormant Mount Pinatubo.

By 1984, when the BNPP was nearly complete, its cost had reached $US2.3 billion. Equipped with a Westinghouse light water reactor, it was designed to produce 621 megawatts of electricity. President Ferdinand Marcos was overthrown by the People Power Revolution in 1986. Days after the April 1986 Chernobyl disaster, the succeeding administration of President Corazon Aquino decided not to operate the plant. Among other considerations taken were the strong position from Bataan residents and Philippine citizens as well as concern over the integrity of the construction.

The government sued Westinghouse for alleged overpricing and bribery but was ultimately rejected by a United States court. Debt repayment on the plant became the country's biggest single obligation. While successive governments have looked at several proposals to convert the plant into an oil, coal, or gas-fired power station, these options have all been deemed less economically attractive in the long term than simply constructing new power stations.

Anti-Nuclear Movement in the Philippines

The anti-nuclear movement in the Philippines aimed to stop the construction of nuclear power facilities and terminate the presence of American military bases, which were believed to house nuclear weapons on Philippine soil. Anti-nuclear demonstrations were led by groups such as the Nuclear-Free Philippines Coalition and No Nukes Philippines. A focal point for protests in the late 1970s and 1980s was the proposed Bataan Nuclear Power Plant, which was built but never operated. The project was criticized for being a potential threat to public health, especially since the plant was located in an earthquake zone.

The demand of the anti-nuclear movement for the removal of military bases culminated in a 1991 Philippine Senate decision to stop extending the tenure of US facilities in the Philippines. Tons of toxic wastes were left behind after the US withdrawal and anti-nuclear and other groups worked to provide assistance for the bases' cleanup.

Observations

In 2010, the Inter-Agency Core Group, led by the Philippine Department of Energy, the Department of Science and Technology, and the National Power Corporation, conducted a public perception survey to gauge the public’s appreciation of, as well as apprehensions towards, nuclear energy. This was part of an overall information and education campaign mandated by the Philippine Energy Plan 2009-2030.

The results of the survey indicated that there was a largely positive view with regard to the use of nuclear energy in the Philippines. These favorable views towards nuclear power generation were attributed to the escalating electricity rates during the period. The survey also surfaced the need to further improve the public’s perception of the application of nuclear energy by highlighting the benefits of nuclear power plants, and by focusing on the safety requirements/ guidelines and management of nuclear power plants.

In 2011, the nationwide Household Energy Consumption Survey, for the first time, included questions related to nuclear power. The survey aimed at determining awareness and perception of households on major energy issues, including nuclear energy, surfaced the following:

• Regardless of whether a household is aware or unaware of nuclear energy, one in every three households expressed their willingness to support nuclear energy as a viable and long-term option for electricity generation. Almost half of the total households (47%) remained undecided on the question of harnessing nuclear energy.

On the other hand, the bulk of households (79 percent) that belonged to the highest income group were cognizant about nuclear energy and its uses. However, the proportion of households with knowledge about this particular energy source dropped to 22.3 percent at the lowest income group.

• The National Capital Region (NCR) was the only region where at least half of the total household population was aware of nuclear energy, while the rest of the regions registered lower percentages.
• The results imply that income had a positive effect on a household’s awareness of nuclear energy – since households with higher income tended to have more access to various sources of information about nuclear energy, such as those obtained online and from the internet.

But before any further plans of the Core Group could come to fruition, the Fukushima incident in 2011 again turned receptivity into skepticism. The incident was a game changer – creating widespread concern about nuclear power plants, and invariably leading to their undeclared moratorium in the Philippines. The political issues associated with the Bataan nuclear power plant, the external catastrophes involving nuclear power plants in other countries, juxtaposed against the availability of cheaper sources of energy, such as natural gas, and the generally favorable reputation of other forms of renewable energy for power generation, consequently put nuclear power in the back burner.

Analysis and Conclusion

Public perception of nuclear technology has been tainted as a result of few but sensational incidents. These have not only eroded trust in the technology, but also in the ability to balance the need for safety and the need for an economically viable operation of nuclear power plants. Once nuclear power plant lose the trust, it is difficult to regain the confidence. The public contemn government corruptions and are terrified at nuclear incidents. Chernobyl and Fukushima incidents erased utilization of nuclear technology energy from people in the Philippines. Even the public perception survey and household energy consumption survey indicated that there was a largely positive view with regard to the use of nuclear energy, the BNPP being unsafe sat close to inactive volcano Mt. Natib has been causing an incredibly serious problem which people mistrust nuclear technology.

With a view to re-establishing public relations, NPP stakeholders and government has to evaluate BNPP and inform the public of the results. Fukushima was designed for a seismic acceleration of 0.18g, while the Bataan plant had a higher threshold of 0.4g. On the basis of these technical information, NPP stakeholders have to build relationship and two-way communication channel to improve public perception and awareness.

Regaining pubic trust is a prerequisite for a successful energy program and it involves two major aspects. On the one hand, educating the stakeholders, whether the general public, NGOs or other involved parties, not just on the benefits of nuclear technologies, but also in the many ways that technology has progressed. From the vast improvements in safety mechanisms to what the latest generations of reactor types can bring to the table. Both in terms of safety and in terms of efficiency of operations, there is much to talk about. Given the complexities of increasing grid capacities in countries like the Philippines – consisting of about 7.700 islands – small modular reactors may be special interest. As a country that is afflicted by earthquakes at regular intervals, new passive safety features are definitely of interest as well. But it also the trust in the state that needs to be affirmed. All decisions, from the initial stages through siting, safety and environmental issues, require public input, not just education. The trust of the public in the institutions tasked with establishing a nuclear power program has to be earned.

This case study of the Philippine's unsuccessful communication and public acceptance in the nuclear power industry, has been conducted in partial fulfillment of the requirements of the course EA201 Stakeholder Management and Public Acceptance.

References:

[1] Valdez-Fabros, Corazon, "The continuing struggle for a nuclear-free Philippines". WISE News Communique. (1998-10-16); [2] Magno, Alex R., “Kasaysayan: The Story of the Filipino People” Asia Publishing Co. Vol. 9, ISBN 962-258-232, pp. 204–205 (1998); [3] ABS-CBN News. (2007). ABS-CBN Interactive Retrieved 2007-06-13.; [4] Lee Yok-shiu, Jeff So, Alvin Y., (October 1999). Asia's Environmental Movements: Comparative Perspectives (Asia and the Pacific). M E Sharpe Inc. ISBN 978-1-56324-909-9; [5] Goodno, James. (1993-07-24). Fossil fuel plans for nuclear station. New Scientist

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Regaining pubic trust is a prerequisite for a successful energy program and it involves two major aspects. On the one hand, educating the stakeholders, whether the general public, NGOs or other involved parties, not just on the benefits of nuclear technologies, but also in the many ways that technology has progressed. 

This seems to be a universal need when it comes to nuclear projects-- do any countries/regions come to mind as having been particularly successful in this regard? What are some best practices that might be learned from those successes (if they exist)?

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This is an excellent example of what has happened with nuclear.  The public is, on the one hand, often too fickle to make informed decisions which require the long term commitment that nuclear requires. On the other hand, cost escalations and nuclear disasters undermine any chance of achieving long term public trust. The "shifting sands" of successive authoritarian governments exacerbate the situation.

Is France the only exception? But, even there faith in nuclear is waning.

https://www.researchgate.net/publication/309228697_The_future_of_nuclear_power_in_France_an_analysis_of_the_costs_of_phasing-out

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New Ways to Reliable Back-up Power for Nuclear Power Plants

Case studies, considerations and conclusions

Gert Hoffmeister  Caterpillar® Germany, Nuclear Power Division

Nuclear power plants (NPP) need reliable emergency backup power in order to maintain a safe condition after external power failure and to meet related regulations. Comparing two real-life projects upgrades of the emergency backup power infrastructure, it is revealed just how important it is to at early stage possible consider all relevant parameters, including technical requirements, regulatory requirements and site installation conditions. This comparison demonstrates how modular power solutions, like the ones offered by Caterpillar, can shorten project duration, reduce investment cost and project risk.

This paper also introduces to the various levels of emergency power sources at nuclear power plants, their functions, technical requirements and safety classification that can all have an impact on the design and implementation of emergency backup power installations.

INTRODUCTION

Reliable backup power is critical to nuclear power plants. Post Fukushima stress analysis, aging installations and reactor service life extensions pose new challenges to the industry. Many site designs did not foresee the need for additional generator sets, changing requirements or modifications to installations, making it difficult to update outdated facilities and improve reliability of the backup power system. 

As outlined in the below case studies, NPPs around the world take different approaches to addressing these problems. And as NPPs continue to age, innovative solutions are needed to keep emergency backup power installations up to code and to provide the highest level of reliability.  

Depending on the required safety class as well as Owner and/or Safety Authority regulations, modular systems, built off site, can be very attractive solutions. Caterpillar and Zeppelin CZ developed the first modular backup power installation, overcoming restrictions imposed by the initial plant design and conventional ways of installing backup power sources. This design can bring a new level of flexibility to the industry while fully meeting operators and regulators requirements. Owners and operators receive the highest level of dependability, not only during operation, but during planning and project implementation. By using modular installations, the cost and schedule stay under control throughout the entire project timeline and nuclear power plant service life.

ROLE OF DIESEL GENERATOR SETS IN A NPP

Depending on the reactor type and its level of passive safety systems nuclear power plants rely on backup power immediately or after some time after connection to the main grid is lost and cannot be restored. When the power plant turbine generator fails, the reactor needs to be shut down, steam generation to be reduced as quickly as possible. This typically is achieved by fully inserting all control rods immediately. 

After such a reactor trip, residual heat needs to be removed continuously for some days until it is decreased to a low enough level where natural convection is sufficient. Lack of cooling could ultimately result into reactor core damage. Core damage is rated the highest on the accident scale as it destroys the reactor beyond repair and can eventually cause radioactive material to be released into the environment.

Plant auxiliary equipment, like pumps and other electrical drives and lights during normal operation are typically fed from two redundant consumer bus-bar systems using power from the main alternator driven by the steam turbine. In case this main generator set is shut down the operational source of power is lost.  

When the external backup power line is no longer available, most nuclear power plants depend on various levels of Diesel engine driven generator sets.

CASE STUDY 1 – SIZEWELL B 

At the Sizewell B nuclear power plant in the UK two battery charger generator sets needed to be updated after 30 years. The complete installation was replaced and more stringent requirements for flood protection were imposed on the facility. The new installation had to be installed into the existing building. Customer decided to contract the project to Finning UK using Caterpillar generator sets.

The project was broke down into the following phases: Engineering and planning, civil work on the building to remove the existing generator set, disconnecting the old generator sets from their infrastructure and removing it from site; removing all the related installations, such as piping, cabling, fuel tank, and other small tanks, in order to provide complete clearance and preparation for the new installation; transportation of components and material to the site and into the building; and installation of a new stack, starter batteries, battery chargers, flood protection elevation structure, generator set, fuel tank and interconnecting piping and cabling.

Besides the normal engineering, procurement, logistics, construction and installation services, there were a number of engineering and support challenges that needed to be overcome, including various nuclear and seismic qualifications, extensive testing and documentation. 

Each step of the otherwise normal procedure was subject to a multi stage approval process. Especially modifications to the existing structure required special attention and preparation. Any change resulting from conditions discovered during the work needed to go through the approval process again causing extra cost and schedule delay.

A significant new requirement was the anticipated flood level higher than before. To meet this requirement it was decided to install the generator set and the fuel tank one meter above the initial installation level on support structures. These structures had to be designed to the anticipated seismic levels. Seismic qualification of the tank and the generator set became more challenging. Introducing flood elevation structures left less space for the equipment in a given building. Only due to its increased power density versus the removed generator set it was possible to fit the generator sets into the existing building on flood protection structures. Otherwise a new building or more complex means of flood protection might have been necessary.

During the entire project period, the operator used rental generator sets at significant cost. These rental sets did not have any nuclear certification, so that for more than two years the nuclear power plant operated in an exceptional mode from a regulatory point of view.

From the start of the installation of the new equipment, the scheduled completion date started to move, resulting in a project duration of more than two and a half years and respective cost increases. 

CASE STUDY 2 – DUKOVANY & TEMELIN 

Dukovany and Temelin NPPs in the Czech Republic were designed and built in the 1970s and 1980s with Russian reactor types and plant design. Dukovany NPP has four VVER440 reactors, with 500 MW electrical output each. Temelin NPP is equipped with two reactors, type VVER1000 with 1080 MW each.

These plants originally had three emergency Diesel generators (EDGs) per reactor, level 2 (for definition, please refer to chapter 6) without any additional layer of safety. The post Fukushima stress analysis revealed weaknesses of this concept, and authorities mandated the addition of two generator sets per power plant. Each generator set was sized to replace one of the existing EDGs. Various safety related requirements included:

• Complete independence from any other equipment in the NPP, especially the existing Diesel generator sets
• 50 years of service life
• From start to 100% load in less than one minute
• Fuel tank for eight hours operation
• Battery starting
• 3200 kW output, 6.3 kV

The new installation also had to be designed to resist electromagnetic impact, explosion shock wave, extreme temperatures (both high and low), extreme wind speeds and precipitation, and impact from flying objects, such as debris carried by a hurricane or parts of the cooling towers that could drop during an earthquake.

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Figure 1: Modular Emergency Power Source

The installation also had to comply with the following standards:

• IEEE 344 - Seismic Qualification of Equipment for Nuclear Power Generating Stations. Seismic qualification was achieved through a shake table test, structural analysis and (exceeding the requirement) verification in a mobile application, via a mining truck test.
• KTA 3702, Emergency Power Generating Facilities with Diesel-Generator Units in Nuclear Power Plants. This includes design criteria and type test definitions.
• IEC 62003 - Instrumentation and Control Important To Safety. This includes requirements for electromagnetic compatibility testing.
• CZ 132/2008 Sb. - Decree on Quality Assurance System for activities related to the use of nuclear energy, radiation protection and quality assurance of selected equipment with respect to their safety classification.

CEZ, the nuclear power plant operator, evaluated various options to meet all of these criteria and the deadlines set by authorities, all while maintaining a reasonable project budget. Traditionally, a generator set installation of this size and requirements would have a solid concrete building with functional components mounted to the building or dedicated support structures inside. Instead, CEZ decided to have Zeppelin CZ design, build, deliver and install a modular fully integrated solution designed for their needs. 

This solution includes the generator set itself, the fuel tank, control panel and switchgear, and the cooling radiators. Its outer shell is hardened to withstand the mechanical impact design scenarios, and it is equipped with ingress protection modules to maintain sufficient clearance at the combustion air and cooling air inlet and outlet openings, and the exhaust gas outlet under any circumstances (Figure 1).

Other design requirements were met by using certified equipment, equipment sizing for performance at high ambient conditions and preheating devices sized for low temperatures.

Once all design details were approved, the modules were built in a controlled factory environment. Components were delivered to the nuclear power plants by truck and installed over the course of a few days on the foundation built by a CEZ contractor. The MV cable connection to the existing switchgear was the only interface with the existing installation. 

This project was completed in 12 months for both nuclear power plants due to the small amount of site work with very simple interfaces. All inspections and major tests were done at the manufacturer’s workshop, so that there were no modifications required on site. The project was on time and on budget without need for any temporary power supply. 

Comfortably meeting the deadline set by the authorities was particularly important in order to maintain the license to operate the reactors.

MAKING DESIGN LIFE A DESIGN CRITERIA

Keeping the above case studies in mind, nuclear power plant design can greatly affect future projects, safety requirements and maintenance cost. While a wide range of design criteria (see chapter 6) and technical designs are available to deal with these challenges, the effect of changing requirements and technical developments during the service life of a nuclear power plant is rarely considered, yet has significant impact. 

For most nuclear power plants periods of more than 70 years have to be considered: 

•  For service life extensions to existing plants:  A large number of today’s NPPs were designed in the 1960s and 1970s, initially for a design life of 30 to 40 years. However, toward the end of this initial design life, many plants received significant life extensions. In fact, 20 years of extra service life is not uncommon.
• For new projects:  Today, new NPPs are built for a 60 to 80 year design life right from the start. Taking into consideration that there is a decommissioning phase of six to 10 years, new NPPs can require more than 70 years of back-up power.

Just thinking of the evolution of a car, machine or any other technical device from the 1940s to today, it becomes obvious how significant technical changes are over such a period of time. A similar level of technical changes during the life of a nuclear power plant has to be anticipated.

In both project examples, the initial design of the nuclear power plant caused restrictions to the implementation of necessary changes to the emergency power systems. Sizewell B took advantage of the increased power density of generator sets available today to be able to implement the project in the existing structure, yet meeting additional requirements. The nuclear power plants in the Czech Republic did not replace but added generator sets, hence there was no existing structure available. What could be considered a restriction turned into an advantage, a green-field installation could be designed independently. By taking a creative and innovative approach, the project was exceptionally successful, both economically and from a project schedule point of view. 

BACKUP POWER REQUIREMENTS AT NPPS 

In an emergency shut-down, the control rods are inserted into the reactor stopping the fission reaction, consequently reducing its thermal power to the decay heat, continuously decreasing over time. 

The reactor becomes subcritical, and the reaction cannot restart under these conditions. The amount of decay heat directly following a shutdown still is around 6.5 percent of the previous core power. For a power plant block of 1300 MW electrical output the reactor produces around 4000 MW of heat at full output. Initial decay can be 260 MW (6.5 percent of 4000 MW). The decay heat decreases to 1.5 percent after one hour, down to 0.5 percent another 23 hours later and 0.2 percent after one week, around 8 MW. (1) This heat needs to be constantly removed during the initial hours after the shutdown by a flow of cooling water powered by pumps. 

Depending on the reactor design and local safety regulations, there are quite a variety of backup power strategies. In principle, there are four levels of backup power (Figure 2), although not all of them are used for all reactor types. While western European reactors were equipped with Level 1 through Level 3 backup power sources when they were built, Russian Pressure Water Reactor type, called Water-Water Energetic Reactors (VVER) originally were equipped with Emergency Diesel Generators (EDG) only, and some reactors also have mobile (Level 4) equipment.

Level 1 Backup Power  – from grid through separate feeder:  Each nuclear plant has its consumer bus-bars connected to the grid independently, so that power from the grid will feed the consumer bus-bars immediately and shutdown operation can continue without interruption using the standard operation equipment. 

Level 2 Backup Power  – LOOP:  When the grid is not available or fails during an emergency shutdown of the reactor the situation is called Loss-Of-Off-Site-Power (LOOP). There is no more external power available to the plant, and operation and safety rely on internal emergency power sources. 

The first sources of emergency power are typically EDGs. In European pressure water reactors, these are usually large medium speed Diesel generator sets, each sufficient to support the shutdown operation and to reach and maintain a controlled state using the reactors regular operating equipment. Between two and four of these sets are installed to provide redundancy. EDGs belong to the reactor operation equipment and are classified in the highest safety category of all backup power sources of a nuclear power plant (See chapter 7, section “Safety Related” or “1E”).

Level 3 Backup Power  – LOOP & loss of EDG:  In case the EDGs fail to start or cease to operate, the scenario is called Station Black Out (SBO). SBO units take over to shut down and maintain the reactor in a safe condition. These sets typically are smaller than the EDGs and are sized to drive dedicated emergency equipment only. In terms of nuclear safety classification, these units receive a lower category than EDGs. After post Fukushima stress test analysis, this level was introduced to some power plants that did not have it before. 

Level 4 Backup Power  – LOOP, loss of EDG & loss of SBO:  Based on post Fukushima stress test results, many authorities demanded the addition of Level 4 equipment (mobile sets or others). These are sized to support the most important emergency functions depending on the reactor design and are also used as crisis response equipment. They receive the lowest or no nuclear safety classification (“Non safety related” equipment, see ‘Considerations for Emergency Power at NPP.

Figure 2: Levels of Backup Power

CONSIDERATIONS FOR EMERGENCY POWER AT NPPS 

The following criteria influence sizing and design of emergency power sources and the selection of suitable equipment:

Regulatory Safety Classification

Major categories are: “Safety Related” and “Non-Safety Related”. Depending on the applicable regulation, Safety Related equipment can be further divided into subcategories. For example, International Atomic Energy Agency (IAEA) proposes the following definitions (original definition: (2)): 

Safety category 1:  Any function that is required to reach the controlled state after an operational occurrence or an accident and whose failure would result in consequences of high severity.

Safety category 2 includes three emergency power functions:

• Any function that is required to reach a controlled state and whose failure would result in consequences of medium severity; or
• Any function that is required to reach and maintain a long lasting safe state and whose failure would result in consequences of high severity; or
• Any backup of a function categorized in safety category 1.

Safety category 3 includes five emergency power functions: 

• Any function that is actuated in anticipation of an operational occurrence or design basis accident and whose failure would result in consequences of low severity; or
• Any function that is required to reach and maintain for a long lasting safe state and whose failure would result in consequences of medium severity; or
• Any function that is required to mitigate the consequences of design extension conditions, unless assigned to category 2, and whose failure would result in consequences of high severity; or
• Any function designed to reduce the actuation frequency of the reactor trip or engineered safety features in the event of a deviation from normal operation; or
• Any function relating to the monitoring needed to provide plant staff and off-site emergency services with a sufficient set of reliable information in the event of an accident as part of the emergency response plan, unless already in a higher category.

Redundancy is the number of equally sized, same type generator sets in an NPP. Considerations include physical separation to secure backup power under various external impact scenarios like fire, air-plane crash, terrorist attack or a beyond design accident. The redundancy concept also depends on the redundancy available from the plant bus-bar system and number of independent trains of plant operation or emergency auxiliaries and the anticipated probability of generator set failure or outage due to maintenance.

Generator set Sizing

Each generator set is sized to support a complete set of auxiliaries installed for its specific purpose. Total load of all such auxiliaries combined, including their starting inrush, determine the generator set capacity. Block loads of large motors and the equipment starting sequence need to be taken into consideration, as well as certain electrical failure scenarios that could lead to an unbalanced load.

Technological diversity is applied in order to reduce the risk of common cause failures (3). Common cause failure is based on the observation and statistical quantification that equipment commonalities (same technology, same manufacturer, same model, same design, same material, same production and test process, etc.) may result in certain failure patterns for the same inherent cause. 

Such causes might be material defects, design defects or imperfections in the production process that were not discovered by the inspections and tests performed after the manufacturer’s standard test and inspection program. It is also considered that identically designed equipment may fail in the same way due to any beyond design event like electromagnetic pulse, seismic accelerations, weather conditions, flooding or other unforeseen events.

To mitigate this risk, different types of equipment and even different manufacturers are used for the various levels of backup power.

Technical Requirements

Generator sets in NPPs need to meet certain technical requirements such as: 

Startup time 

This means the time from start signal to the generator set reaching nominal speed and being ready to accept load. At startup, the starting motor pinion will engage, beginning to crank the engine and the alternator. Larger medium speed engines are typically started by admitting air directly into the cylinders, controlled by a starting air distributer. Once the minimum firing speed of the engine is reached, fuel is injected, and the generator set accelerates by its internal combustion. Depending on the engine size and type of starting mechanism it should take between 12 and 20 seconds. 

Low load operation

Certain operating conditions of an NPP require generator sets to run at no or very low load for an extended period. When the reactor is shut down and main alternators are disconnected, the plant may only be connected to a single incoming line from the grid while decay heat still needs to be removed. For safety reasons, generator sets need to run without load, ready to take over all load in case the grid connection is lost. 

Block load acceptance

Large pump drives are the major electrical loads. To make these systems robust and simple, these pump motors are started direct on line without any soft start feature. At the same time, there are not to exceed values defined for voltage dip, speed drop and recovery time during the start of such motors. These values are a complex, highly interdependent function of the motor characteristics, mechanical block load capability of the engine, the engine governor, alternator size and voltage regulator characteristics. For both the Sizewell and Czech Republic NPPs, Caterpillar specialists were available to assist with the selection of the best generator set type and sizing of alternator. Design engineers used Cat® software “SpecSizer” to perform or verify their own calculations (4).

Climate conditions

Even though most nuclear power plants are located at relatively low elevations and in areas with moderate ambient temperatures, design conditions are often very stringent. Extreme ambient temperatures (high and low) are stated as a result of statistical calculations based on an occurrence frequency at the magnitude of 1/100,000 per year. High design ambient temperatures mainly result in larger size cooling system components and engine rating reduction, while low temperature ambient conditions may require combustion air pre-heating in addition to pre-heating the engine cooling water. 

Seismic loads 

One of the most important emergency scenarios considered for NPPs is the effect of a seismic event. A seismic event may disrupt the grid connection of the power plant and will also require the immediate shut down of the steam turbines in order to limit risk of damage by the accelerations caused by the earthquake. In any case, the reactor is shut down immediately, requiring continued cooling to remove the remaining decay heat. Magnitude of the design based seismic event is a result of statistical calculations based on extremely low occurrence frequency of 1/100,000 per year. Even for locations with very little seismic activity significant seismic loads have to be considered as a consequence.

Based on the emergency power application scenario, generator sets may be required to operate during and after a seismic event or after the event only.

There are three methods of seismically qualifying the emergency power equipment: by test, by calculation or by experience:

Qualification by test:  Many Caterpillar generator sets are qualified by shake table testing according to the International Building Code (IBC) at levels of 2.2 G’s (Figure 3). These sets can be used in nuclear power applications without project-specific qualification. A shake table test can also be performed for generator sets that have yet to be certified, non-standard configurations or if the project calls for higher acceleration levels. Caterpillar contracts a specialized institute to perform these tests and to provide an independent certificate. However, shake tables are limited by size. For example, the largest Cat® generator set ever tested on a shake table was a C175-20 at a weight of 37 t. Shake table facilities typically do not allow operation of the equipment during the test. This can be for technical reasons like availability of an external cooling system or fuel supply infrastructure, but it can also be a fire hazard or potentially cause contamination through oil or fuel leaks. 

Qualification by calculation:  A detailed structural analysis including Finite Element Method (FEM) is performed on all major generator set components, including generator sets that can’t undergo a shake table test. This analytical method typically is more economical than shake table test, depending on the equipment size. 

Figure 3: Seismic testing

Qualification by experience (well proven in use):  Qualification by experience was performed even though not required by the project and valid for the engine only. The Cat® C175-20 engine found in the generator sets used at Dukovany and Temelin are also used to drive large construction and mining machines, such as the Cat® 797 mining truck. This truck, for example, has a capacity of 400 tons of rock. It takes three trips for the loading machine to fill this truck, dumping 133 tons of rock on its back each time. The truck then travels on a dirt road for up to an hour before it dumps all 400 tons at once. After that, it travels back to be loaded again (Figure 4).

With this in mind, Caterpillar wanted to understand how the accelerations to the engines in such machines compare to seismic levels. To do this, acceleration sensors were equipped to the engine before it ran over a standardized machine test course.

Depending on the frequency, actual accelerations were found to be at relevant seismic levels and mostly well above the project requirements for NPPs (Figure 5). 

Figure 4: Caterpillar 797 Mining Application

Figure 5: Seismic comparison

While earthquakes typically only last between 4 to 8 seconds, thousands of Cat® mining machines work 24 hours a day for six to eight thousand hours per year for many years.

Mechanical impact protection

Typical considerations for mechanical impact protection include debris carried by tornados, projectiles shot at the installation and plane crashes. Mechanical impact resistance is mainly a feature demanded from the generator set building or its enclosure as a means to protect the equipment from such impacts. 

Flood protection

Tidal waves caused by earthquakes may flood the power plant site. Protecting the equipment from such events is a function of the building design, its elevation or the elevation of the equipment inside the building. Dikes or pile walls are other ways of flood protection. Best method depends on the local site conditions and whether flood protection is engineered into a new installation or shall be improved in an existing installation. At Sizewell, the flood protection was incorporated into the existing installation by raising the generator sets and fuel tank one meter higher than its original design. 

CONCLUSIONS 

In addition to all current requirements and considerations to Nuclear Power Plant design, planning for potential future changes is crucial. During its service life the operator can expect to see: 

• Service life extensions and/or capacity increases
• Obsolescence issues, when spare parts or Original Equipment Manufacturer (OEM) technical support is no longer available for the installed product
• Changes to the original technical requirements due to changing technology, changes in the regulatory environment, the need to adjust the protection philosophy
• Equipment failure that may drive the need for replacement

When due to one or more of these implications additional generator sets are needed, the modular design presented in this paper can result in significant advantages over installing power sources under conventional construction methods. Main benefits are drastically shorter construction time and lower budget.

In case there is a need to replace obsolete or damaged equipment it may be worthwhile considering installation of modular power sources. Existing installations could be left untouched during the project and eventually be removed later.

This avoids some of the complexities of a replacement project such as modifying certified structures or using temporary emergency power during the project. 

When planning a new power plant allowing for extra space, connection points and cable routing helps future modifications. Detailed 3-dimensional as-built documentation, including all possible interferences, would help expedite any modification work. Both are small investments compared to the time and money spent if not available when plant needs modification.

Even for new plants it may be sensible considering modular installations when possible from a regulatory point of view. Besides the benefits showcased in the Czech Republic case study, modular designs allow for the equipment to be ordered later in the overall schedule, helping the project cash flow and avoiding storage and preservation issues. This strategy will also limit the generator sets exposure to the construction environment, reducing the risk of damage. 

Taking into account the many emergency power considerations outlined in this paper, along with the challenges presented in the case studies, NPPs can benefit greatly from forethought and careful planning. 

Modular designs, such as the ones offered by Caterpillar, can be a viable solution to the problems posed by updating older NPPs, as well as a practical strategy for future projects.

REFERENCES 

• E. Shwageraus and E. Fridman, Department of Nuclear Engineering, Ben-Gurion University of the Negev Beer-Sheva 84105, Israel: “Decay Power Calculation for Safety Analysis of Innovative Reactor Systems”, September 2008
• Safety Classification of Structures, Systems and Components in Nuclear Power Plants, Specific Safety Guide, No. SSG-30 INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, ISBN 978–92 –0–115413–2
• Definition of “Common Cause Failure”: https://en.wikipedia.org/wiki/Common_cause_and_special_ cause_(statistics)
• SpecSizer: http://www.cat.com/en_US/articles/solutions/power-systems/electric-power-specsizer. html

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A Comparative Analysis of Text-to-Image Generative AI Models in Scientific Contexts: A Case Study on Nuclear Power

In this work, we propose and assess the potential of generative artificial intelligence (AI) to generate public engagement around potential clean energy sources. Such an application could increase energy literacy – an awareness of low-carbon energy sources among the public therefore leading to increased participation in decision-making about the future of energy systems. We explore the use of generative AI to communicate technical information about low-carbon energy sources to the general public, specifically in the realm of nuclear energy. We explored 20 AI-powered text-to-image generators and compared their individual performances on general and scientific nuclear-related prompts. Of these models, DALL-E, DreamStudio, and Craiyon demonstrated promising performance in generating relevant images from general-level text related to nuclear topics. However, these models fall short in three crucial ways: (1) they fail to accurately represent technical details of energy systems; (2) they reproduce existing biases surrounding gender and work in the energy sector; and (3) they fail to accurately represent indigenous landscapes – which have historically been sites of resource extraction and waste deposition for energy industries. This work is performed to motivate the development of specialized generative tools and their captions to improve energy literacy and effectively engage the public with low-carbon energy sources.

1 Introduction

There exists a growing global consensus on the need to orchestrate energy transitions to avert the worst effects of climate change. As a result, significant efforts are being made around the world to transform our energy systems, and, as part of this process, engage with communities to increase public awareness about various clean energy options faria2015new . These efforts have resulted in increased understanding, and acceptance of solar and wind energy technologies. [deleted what was previously here. Instead, insert a few sentences on energy literacy]

The emergence of state-of-the-art Text-to-Image Generative Artificial Intelligence (AI) Models, such as DALL-E, could potentially be used spread awareness of these systems by generating technical diagrams. This project explores the performance of generative AI models in creating realistic scientific images to motivate public engagement and increase public awareness of these unknown clean energy solutions. In this paper, Generative AI Models are defined to be ”models that create images from another and from different types of data including but not limited to text, scene, graph and object layout” elasri2022image .

In 2021, OpenAI’s Text-to-Image Generative AI Model DALL-E was made public. Since then, there has been a growing interest in exploring the potential of these models for creative and technical applications. However, the demand for generative AI models emerged before 2021 sapkota2023harnessing ; vartiainen2023using ; mccrum2008realistic_PANGU . Various motivations, like data augmentation, drove generative AI model development. Previous studies in this field have utilized generative AI models for educational purposes, such as clothing and accessory image generation for craft education, crop image generation in agriculture settings, in architecture and urban design, as well as novel art generation sapkota2023harnessing ; vartiainen2023using . In the fashion industry, generative AI models are used to improve designer efficiency; for example, Yan et al. 9693190 created a training data set of 115,584 pairs of fashionable items, which was used to test generative text-to-image AI performance.

In 2008, McCrum et al. mccrum2008realistic_PANGU used an generative AI models to create realistic images to simulate Martian exploration robots in the software Planet and Asteroid Natural Scene Generation Utility (PANGU). More recently, there has been a dynamic movement towards utilizing generative AI models to create images to improve the quantity and diversity of training data in predictive medical diagnostic programs akrout2023diffusion_skin . To tackle the challenges arising in acquiring massive data due to patient privacy concerns, Akrout et al akrout2023diffusion_skin employed such generative AI models for data augmentation. The commonality among the presented studies mccrum2008realistic_PANGU ; akrout2023diffusion_skin above is that, when data is relatively scarce, generative AI models can augment data to improve the performance of machine learning classification algorithms by reprocessing existing data. Generative AI models have been applied to areas beyond data augmentation. These areas include generation of novel artworks and the production of visual materials for communication paananen2023using_architecture ; seneviratne2022dalle . Recently, highly sophisticated and imaginative generative AI models have even been used in the field of architectural design. In Paananen et al. paananen2023using_architecture , students were tasked to design a culture center in a small island using generative AI models, namely DALL-E, StableDiffusion, and Midjourney. Figure 1 illustrates one of the standout works identified as the best in paananen2023using_architecture .

While the previously mentioned applications have employed generative AI models in a positive context, it is important to recognize that there are also negative implications and ethical concerns of AI image generators. A concern with generative AI images is copyright violations. Images are extracted from search engines, such as Google, to train a generative AI model. Since many of these images are protected by copyright, the resulting image produced by the generative AI models may breach copyright law as these images are trained without direct consent of the creators 10139768 . Generative AI models could also intentionally be used to generate images that portray a false representation of reality or contain disinformation. Such works like deepfakes could be used to damage reputations, blackmailing individuals’ for monetary benefits, inciting political or religious unrest by targeting politicians or religious scholars with fake videos/speeches dissemination, as well as spread disinformation about current events masood2023deepfakes . Additionally, images produced by generative AI could additionally reflect and perpetuate stereotypical, racist, discriminatory, and sexist ideologies. For example, Buolamwini and Gebru buolamwini2018gender reported that two facial generative AI training data sets, IJB-A and Adience, are composed of 79.6% and 86.2% lighter-skinned subjects, respectively, rather than darker-skinned subjects. It was also found that darker-skinned females are the most likely to be incorrectly classified, with a classification error rate of 34.7% buolamwini2018gender .

While there have been many studies highlighting the use of generative AI models in areas such as medical diagnostics, robotic motion planning, fashion, art, architecture and urban design, we discovered there are a lack of studies that utilize generative AI models to address climate change-related problems for most clean energy sources from a technical and policy perspective. Of the sources evaluated in our literature review, only one study qadri2023ai performed a community-centered study of cultural limitations of generative AI models. However, this study was specifically performed in the regime of the South Asian context to study the impact of global and regional power inequities. Another study wang2018public emphasized that there exists a need to incorporate visual images alongside written language to impact public perceptions of climate change. However, generative AI was not explicitly employed in the study. Due to this lack of prior investigation, our research team was interested in determining whether generative AI models can produce technically accurate image that reflects the given prompt even in specialized and technically sophisticated engineering-oriented image scenarios. Furthermore, previous studies primarily relied upon widely recognized tools, such as DALL-E, Stable Diffusion, and Midjourney. For example, Sapkota et al. sapkota2023harnessing used MidJourney and Vartiainen et al. vartiainen2023using used Dall-E 2. Recently, a plethora of models have been introduced beyond the three aforementioned models. Our research team has taken the initiative to directly engage with these models, evaluating their pros and cons in the process. In this paper, our team conducted a case study on generative AI models to test performance and accuracy related to nuclear energy prompts. We analyzed 20 different generative AI models, with an emphasis on the tools with an accessible Python API. We then selected the top 3 performing models among 20 models based on accessibility, image quality, accurate portrayal of prompts, process time, and cost. For this process, we selected prompts related to different nuclear power plant components and processes occurring within a power plant, ran these prompts through the top 3 generative AI tools, applied prompt engineering to enhance the generators ability to create images that reflect the given prompt as well as increase the technical accuracy of the images. Finally, we analyzed the performance of these tools in regard to their technical accuracy in depicting different nuclear engineering components such as radiation shielding of a nuclear reactor, the primary side of a pressurized water reactor, etc.

The work presented in this paper is novel for several reasons . First, the majority of these generative AI tools began their maturation process a few years ago, with a restricted amount of literature and analysis available regarding their technical accuracy in a scientific context. Second, our literature survey indicates a minimal application of generative AI for generating images to foster community engagement and enhance public perspectives on climate change. Third, this study assesses the robustness of current state-of-the-art generative AI models and assess the necessity of specialized generative AI tools within specific disciplines where models are trained on discipline-focused images and text captions. Such applications to nuclear energy include nuclear fuel rod fabrication, proper waste management images, and nuclear reactor designs.

This rest of this paper is organized as follows: Section 2 presents the concepts behind how generative AI models work and their primary features. In section 3 , we compare all testing generative AI models according to several factors by discussing their advantages and disadvantages. Section 4 presents the generative AI results for the top 3 generative AI models based on similar prompts. The conclusions of this work and the potential opportunities for future work are highlighted in section 5 .

2 Generative AI

2.1 generative ai concepts.

Generative text-to-image AI models are a subset of generative AI models that take text input and create an image based on the input description. Figure 2 illustrates images generated by various models using text as a basis. Figures 2 (a) and 2 (b) were generated using DALL-E, while Figure 2 (c) was produced through Midjourney. Generative AI models can create logical as well unusual images that would be difficult to find elsewhere, such as a turkey inside a nuclear cooling tower in Figure 2 .

As evident from Figure 2 , generative AI models process the captions provided by the user and reproduce corresponding images. Interestingly, both DALL-E and Midjourney generated images of cooling towers in response to the text ”nuclear power plant.” This suggests that these models have been pre-trained to associate the text ”nuclear power plant” with the concept of a cooling tower, likely because cooling towers are often the most visually prominent aspect of images of nuclear reactors. When generative AI models produce images of cooling towers, they are capturing an important feature of a nuclear plant but failing to depict other important features such as the reactor system itself. This is one of the gaps that we found in this work. The training process of text-to-image generative AI models is briefly described next:

Training Concept : Generative AI models use a pre-trained data set of images that link natural language to an image. A popular pre-trained deep learning model is Contrastive Language Image Pretraining (CLIP), developed by OpenAI; CLIP was trained on 400 million images with text schuhmann2021laion . CLIP learns the weight of how much a caption relates to a given image. CLIP follows this workflow: Images and text captions are passed through encoders, which map all objects to a m 𝑚 m italic_m -dimensional space radford2021learning . The cosine similarity is taken from the text caption and image. Ideally, we should maximize the cosine similarity between N 𝑁 N italic_N correct encoded image and text caption pairs, while minimizing the cosine similarity between N 2 − N superscript 𝑁 2 𝑁 N^{2}-N italic_N start_POSTSUPERSCRIPT 2 end_POSTSUPERSCRIPT - italic_N incorrect encoded image and text caption pairs radford2021learning . By comparison, other examples of models that use contrastive learning are ALIGN and CLOOB.

Decoding and Transformer Models : CLIP learns both an image and text encoding; Radford et al. radford2021learning used autoregressive models and diffusion models to perform the mapping of text caption encoding to image encoding for each image. The researchers found that both models produced similar results and diffusion models were computationally less intensive radford2021learning . Next, the diffusion model (also known as diffusion prior) is utilized to map the text caption encoding to image encoding, displayed in Figure 3 . After CLIP receives the encoded image and caption data, the generative AI tool (e.g., DALL-E) needs to reverse this to generate an image; it uses a diffusion model (also known as diffusion posterior) to decode the CLIP encoded data. Inspired by the principles of thermodynamics, diffusion models are text-to-image models that add Gaussian noise to data and then reverse the diffusion process to restore clarity to the Gaussian blurred images ho2020denoising . DALL-E uses GLIDE, a transformer model by Open-AI, to decode image and caption data from CLIP. For CLIP, it encodes the caption string into tokens, takes tokens and inputs that to transformer, generates output tokens, conditions the final token for embedding, and then combines projection of final token embedding to additional context nichol2021glide .

Figure 4 shows the format of how text-to-image generative AI works. A user inputs a text prompt, CLIP’s encoder maps this into m 𝑚 m italic_m -dimensional space, the diffusion prior maps the CLIP text encoding to the corresponding CLIP image encoding, then the GLIDE model will use reverse-Diffusion to map the CLIP text and image encoding to generate images based on the inputted text description nichol2021glide .

2.2 Generative AI Features

The prompt is the caption that creates an image; generative AI tools rely on a prompt to take the user’s intention to generate an image. Some generative AI tools such as Canva’s text-to-image generation service has a graphical user interface (GUI) that allows a user to input prompts, and generate an image based on that prompt. Other generative AI tools have either free or paid API access, where a user can input a prompt into a Python script. When employing generative AI through a GUI, while the usage is intuitive, it may not be optimal for generating a large volume of images using extensive prompts. Consequently, the most ideal scenario arises when both GUI and API are concurrently available.

In order to fully take advantage of text-to-image generative AI models, we looked for models that supported a text input prompt, inpainting, outpainting, model training, and image-to-image editing. Each of these terms are described below.

Inpainting is a tool used to take missing or unknown parts of an image and use AI to generate this unknown region zhang2022gan . Generative AI models are trained on an extensive set of images; inpainting takes its trained data set to replace specific parts of an image. Inpainting is most commonly used for the removal of unwanted objects, image restoration, and image editing doria2012filling . Figure 5 shows an example of inpainting from StableDiffusion.

Outpainting is the opposite of inpainting; outpainting is a tool used to extend the borders to add additional parts to the image using AI xiao2020image . Outpainting can be used to change the aspect ratio of an image and extend borders to an image. Figure 6 shows an example of outpainting using DALL-E model.

Image-to-image models take an image for an input, and allow specific edits to be made to yield a fine-tuned output brooks2023instructpix2pix . Commonly, image-to-image models will allow for style changes, altering resolution, and generation of high-quality images from low-quality images. Figure 7 shows a high-quality creation of an apple from a basic sketch performed using image-to-image technology in StableDiffusion.

”Model training feature” refers to the training of a machine learning model, usually a neural network, with a sample of image-caption pair. The generative AI will then use an input sample of the images for training data and output several images following a prompt kumari2022ensembling . For instance, to develop a specialized generative AI tailored to nuclear power, one can train the model using captions such as ”nuclear power plant” accompanied by a variety of images from different nuclear power plants. Ideally speaking, through this training, the AI becomes capable of producing more realistic and accurate images when prompted with content related to ”nuclear”.

3 Methodology

3.1 comparison of generative ai models.

We tested 20 total text-to-image generative AI tools, each with varying results shown in Table 1 for the tools with promising performance and in Table 2 for the tools with poor performance. In our initial evaluation, we first identified which tools had API access. Tools that did not have API access were then removed such as Nightafe, Fotor AI and Artbreeder. Additionally, tools such as DreamStudio that used the same API as another model (Stable Diffusion) were also removed. Then we narrowed down our tools based on the ability to generate images. Parti and Google Brain Images were eliminated because they are not available to the public. DeepAI was similarly eliminated due to the availability of only paid subscription services. Other text-to-image generative AI tools such as StackGan++ and CLIP required training data in order to generate images, and thus were also eliminated. Midjourney is a popular text-to-image generative AI model, but we decided against using Midjourney since a Discord account is required to access the API, and due to increased usage, the servers were generally unavailable. We then reviewed the commercial rights of these programs and found that Leonardo.Ai did not support commercial use and was thus removed. Starryai, Picsart, Kapwing, Writesonic additionally had poor technical image quality when tested on basic prompts including ”Display radioactive nuclear waste” and ”China and Nuclear.” These prompts were selected due to their simplicity; models were removed if provided poor technical details following a basic nuclear prompt (i.e. faces getting morphed in a nuclear setting, not displaying cooling towers). A summary of the basic prompts, along with prompt results are provided in Table 5 . Of the remaining systems, DALL-E 2 and Stable Diffusion both had paid subscriptions; however, they were chosen due to their capabilities of inpainting/outpainting, image-to-image editing, and good performance in image generation. In contrast, Canva and Craiyon both have free subscriptions but no inpainting/outpainting and image-to-image editing. However, Canva had a very long generation time for images, when compared to all of the other models and was thus removed.

3.2 Prompt Engineering

Prompt Engineering refers to optimizing the prompt (text input to models) for generating desired images from text-to-image generative AI models. Prompt Engineering can help in achieving the desired result from a pre-trained model, reducing the need of computational resources and knowledge to fine-tune these models for different tasks gu2023systematic . Apart from text-to-image models, this method has been applied to other generative models as well, like GPT-3 and ChatGPT, which are text-to-text generative AI models.

Prompt Engineering is an iterative process and helps in efficient interaction with the latent space of generative models. Researchers have identified and classified different type of keywords to produce images closer to desired results oppenlaender2022taxonomy . Certain types of keywords, such as ’hyperrealistic’ , ’oil on canvas’ , ’abstract painting’ , ’in the style of a cartoon’ , are especially useful in directing the style of the image, as displayed in Table 3 . Therefore, such keywords have been used in this study as well to generate images closer to real-life.

One of the main characteristics identified by the authors for images generated related to nuclear energy was that images should look realistic in order to avoid exaggeration. This exaggeration can occur in the images due to the artistic nature of these models (see for example sample results in Table 8 ). Further, the images should be detailed to capture the intricacies of different components, especially in case of technical designs. To ensure that these characteristics are reproduced in the images generated by the generative models, we decided to include style modifiers keywords and quality booster keywords in the prompts oppenlaender2022taxonomy , ensuring realistic flair and high detailing of the images. Further, to improve the image quality, an additional description of the theme regarding the visual appearance of the subject was appended to the prompt. Figure 8 displays the flowchart for prompt engineering we adopted in this study. The method is implemented in an iterative manner, changing keywords and descriptions associated with the prompt to get as realistic results as possible.

4 Results and Discussions

Of the 20 AI models explored, we narrowed our focus to three models based on access to API, cost, successful generation of images, and the accurate portrayal of prompts. As our focus in this study is generating high-quality images that accurately illustrate the prompts, we focused our attention on DALL-E, Craiyon, and DreamStudio. Despite the costly credit system of DALL-E and DreamStudio, the tool produces high-quality images in addition to inpainting, outpainting, and image-to-image editing. We also chose Craiyon for optional cost expenses but high-quality image generation.

4.1 Results for General Prompts

We tested the narrowed pool of 3 generative AI models with 10 prompts selected from initially 36 prompts to evaluate the quality of images, however, for brevity, we have demonstrated two samples in Table 4 . All the AI-powered generator models gave multiple image outputs for a single prompt, out of which the image which portrayed the prompt with highest technical accuracy was chosen.

In our first prompt, we asked DALL-E 2, DreamStudio, and Craiyon to produce a ”High quality image of bunnies in a field.” The prompt was selected to demonstrate a commonly viewed nature scene, where surroundings of grass and trees are similar to the surroundings of a nuclear reactor. This produced similar results among the three, each with grass and varying bunny colors. Each bunny appears to be accurate, correctly depicting the ears, head, and body shape. DALL-E 2 produced the most realistic image, and this appears to be a cottontail bunny. This generative AI tool produced extremely realistic grass; however, DALL-E 2 only produced one bunny, when asked to produce ”bunnies.” DreamStudio produced two bunnies that look realistic. The grass appears to be over-saturated and the bunnies’ coloring appears slightly off and looks a little “cartoonish” (as interpreted by members of the research team); however, still produced a technically accurate result of bunnies. Craiyon produced two bunnies that appear physically accurate. The grass is out-of-focus and does not look as realistic compared to DALL-E 2 and DreamStudio.

In our second prompt as shown on the Table 4 , we compared the three AI tools with the prompt “An oil painting of Michigan sand dunes.” When testing these models, we generated four image outputs for a single prompt, out of which the image which portrayed the prompt with highest technical accuracy was chosen. From these tests we observed that, DALL-E 2 created an image that most resembles an oil painting. It has an accurate depiction of sand, sky, and sea grass. This generative AI tool also does an excellent job at shadows. In comparison, DreamStudio did not necessarily create an oil painting, but did create an image resembling qualities of a painting, such as the appearance of brush strokes and watercolor themes. It correctly depicted sand dunes and sea grass. Craiyon produced a realistic image that we would not consider as an oil painting. The shadows appear to be consistent from a light source relative to the left side of the image. Craiyon accurately generated a large body of water in front of the sand dunes, presumably the great lakes. It accurately depicts sand dunes with a lot of sea grass by the water. Overall, it appears that these generative AI models produce accurate details for prompts describing the natural environment.

4.2 Results for Nuclear Power Prompts – Promising Performance

As indicated in Section 4.1 , the generative AI models have successfully generated accurate images in response to prompts related to the natural environment. Next, we examine the extent to which models are trained with prompts related to nuclear energy. We provide nuclear-related prompts to the models and analyze the outcomes to understand their proficiency in generating images in this specific domain.

In this exploration, we tested the 3 generative AI tools against four prompts, the results are shown in Table 5 . In our first prompt, we asked all 3 tools to produce an image of a “Person who works in the nuclear industry.” DALL-E 2 produced an image of a male with a mask working at a nuclear power plant, standing next to a single cooling tower. The image appears very detailed and realistic, though showing only a cooling tower and not a reactor building. Additionally, the image does not accurately depict the attire of nuclear plant workers. DreamStudio produced two male workers in work attire and hard hats inside a nuclear power plant. Craiyon created a male in a hard hat, in front of an electrical grid. It did not directly produce anything related to a nuclear power plant, but did display a power transformer. Interestingly, each model only depicted men as nuclear plant workers, thus reproducing existing gender imbalances. It is also notable that DALL-E 2 and DreamStudio generated images of workers who appear to be Caucasian, whereas Craiyon generated an image of an ethnically ambiguous worker.

The second prompt we tested was “Impact of Uranium mining on Indigenous Peoples’ traditional lands.” DALL-E 2 produced an image of dry desert land with a small pond of water nearby, with cut-down trees. This image does not appear to be a Uranium mine, but is a high-quality image. DreamStudio produced a more accurate image of a Uranium mine, depicting rock and dirt excavated at different levels. It also showed animals and tools at the bottom of the image, inferring that these are Indigenous tools. Craiyon produced a technically accurate image of a Uranium mining, depicting different mining levels in a desert environment. Craiyon produced an image that is more of a drawing/painting, and not an image. However, Craiyon generated nothing related to “Indigenous people”. We further improvised this prompt by specifying Navajo instead of indigenous people. Therefore, the prompt was changed to ”Impact of Uranium mining on Navajo traditional lands”; in this case, Craiyon and Dreamstudio could capture the landscape of Navajoland, indicating improvement in Craiyon performance as the prompt got more specific. Dreamstudio could also include a Uranium mine in the image. However, DALL-E produced an image of dry land, failing to generate both Uranium mine and Navajoland.

The fourth prompt we tested was “Wildlife near a nuclear plant.” DALL-E 2 produced two ducks on the dirt around grass, with two cooling towers in the background. The detail of the ducks and the cooling towers are accurate, and looks close to reality. StableDiffusion generated a deer next to a cooling tower in long grass; the image looks noisy and grainy. Some features of StableDiffusion’s generated image are not detailed, as the sky is not a palette of blues, there are no clouds or other background scenery, and the grass proportionally tall and one dimensional compared to the deer and cooling tower. However, this image still accurately represents the prompt. Next, Craiyon accurately produced two cooling towers; however, it attempted to generate an animal at the top of the smoke clouds. It is also worth noting that the steam exiting each cooling tower is in opposite directions; this is barely possible for steam to be carried in opposite directions by the wind. Despite this error, it was included in successful attempts, as it still accurately portrayed nuclear cooling towers and attempted to create an animal.

It seems that general nuclear energy prompts produce promising results; however, it was observed that nuclear prompts tend to almost always produce cooling towers. This could be due to the data sets used to train these generative models in that there is am availability of large number of cooling tower images on internet in comparison to images of other technical components. This suggests that all the explored models associate nuclear energy with cooling towers; however, it also suggests that these generative AI models do not have a thorough understanding of other components of nuclear power and nuclear power plants in areas outside of cooling towers.

In the next phase of this work, we went beyond image generation and explored image editing capabilities using inpainting and outpainting functionalities. With the image that DALL-E 2 generated to the prompt “Person works in the nuclear industry,” we used the inpainting prompt “Person Near a nuclear power plant in a hazmat suit.” The resulting images produced a man in a hazmat suit in Figure 9 .

Next, we used outpainting feature with the DALL-E 2 image from the prompt ”Wildlife near a nuclear plant.” This was used to expand the borders of the image on the left side of the image. The outpainting algorithm added additional ducks, while adding a third cooling tower. The resulting images are shown in Figure 10 .

4.3 Results for Nuclear Power Prompts – Poor Performance

In Section 4.2 , we examined successful cases of generative AI nuclear energy applications. However, models also occasionally generated poor images depending on the prompts as shown in Table 6 . The first unsuccessful prompt was “China and nuclear.” DALL-E 2 produced a flag similar in color and pattern to the Chinese flag, and included the atomic nuclear symbol on the flag. DreamStudio produced 2 extremely wide cooling towers, but there is nothing indicative of China in this picture. Craiyon produced another flag similar to the Chinese flag, but has an unusual blue stripe. There is nothing indicative about nuclear in this image. Text to image generative AI models struggled to link countries to nuclear.

Next, we tried the prompt “Display radioactive waste.” DALL-E 2 produced an image of a crate with what our researchers believed to be stones inside the box, with an atomic logo and incomprehensible text on a lid. DreamStudio has boxes with a pattern and text on a yellow background; however, this image did not appear to be related to the prompt. Craiyon has the closest depiction of nuclear waste (even though still very far), of an atomic logo being in a cylindrical container. None of these images are a correct depiction of nuclear waste.

Our third prompt was ”Create a functional diagram of a nuclear reactor core.” DALL-E 2 showed a nuclear reactor core from the top down and got the circle shape right. This image had text that is not English, and appears meaningless. The diagram is also not technically accurate. DreamStudio attempted to create a diagram of a reactor core; the words are not legible and the diagram is difficult to see; this is also not correct on a technological level. Craiyon did not create a diagram, and it created a blue light cylinder on a grey base. Overall, none of these images show a correct diagram of a nuclear reactor core.

While general nuclear prompts produced promising results, anything technical or requiring words produced meaningless results. In a failed attempt to create better results, we used Leonardo.AI’s model training with a small data set of 8 images to make a more accurate nuclear diagram. Figure 11 illustrates the training set as well as the diagrams produced. The diagrams generated by the trained model appeared plausible at first glance; however, upon closer examination numerous issues surfaced. Firstly, the characters displayed on the diagram remained intricate gibberish, and the nuclear fuel rods that should have been situated within the reactor core were absent. Though images containing such technical and specialized content prioritize precise information transmission over creativity, none of those tools satisfied the criteria. It seems that more extensive training and meticulous adjustments are necessary.

4.4 Results for Prompt Engineering

To test the efficacy of prompt engineering as indicated in Figure 8 , a set of 7 prompts related to nuclear engineering were collected from a set of subjects. Table 7 , Table 8 , and Table 9 display the prompt engineering results by DALLE-2, Craiyon, and Dreamstudio models, respectively. Each table contains the original prompt provided by the analyst, the image associated with the original prompt, the modified prompt by prompt engineering, and the modified image associated with that modified prompt.

In the case of DALL-E, Table 7 illustrates a combination of promising and unsatisfactory outcomes following prompt engineering. Notably, prompts 1, 2, and 4 related to the control room, spent fuel pool, and fission reaction exhibited considerable improvement, while the others remained inaccurate. Prompt 1, for instance, resulted in a modified image of the control room that closely resembled an actual nuclear control room, however it omitted the nuclear reactor core. Despite prompt 2 omitting nuclear waste and spent fuel, the modified version still portrayed a realistic image of the spent fuel pool, where nuclear waste is temporarily stored after being discharged from the reactor for cooling. Prompt 4, focusing on the fission reaction, displayed atoms splitting into smaller atoms, reflecting the process of fission. However, prompt 4’s results still contained unreadable wording and gibberish language. Prompts 3, 5, 6, and 7 remained considerably distant from reality. For instance, prompt 6 failed to depict the nuclear fuel pellet and nuclear fuel rod in the context of a birthday event.

Tables 8 and 9 depict the outcomes of Crayion and DreamStudio, revealing inferior performance compared to DALL-E across both original and modified prompts. The generated images from these models consistently exhibit unrealistic characteristics. Notably, the only instances of improvement are observed in prompt 1 for Crayion and DreamStudio, associated with the nuclear control room. Additionally, prompt 2 for DreamStudio yields somewhat realistic images of the spent fuel pool, with both the original and modified versions displaying a fair quality.

4.5 Discussion

The main goal of our research focuses on creating realistic and accurate images that could accurately depict nuclear energy in both technical and non-technical ways to reflect the reliability of generative AI models in a scientific context. Text-to-image systems appear to successfully depict only the cooling towers in a nuclear plant; they struggle with technical details related to nuclear power plants. For example, as shown in Figure 11 , all models could not produce a diagram of a nuclear reactor, even with some training data templates that depict real nuclear reactor cores. Additionally, we noticed that radioactive waste was portrayed incorrectly by DALL-E 2 and DreamStudio, and only Craiyon depicted a barrel, which is still far from how the radioactive wastes and their storage casks look like. Such outcomes indicate that models have not yet been adequately trained on data related to nuclear power. Such a conclusion might be also true for other scientific disciplines. Consequently, the development of a generative AI specialized in nuclear necessitates the acquisition of a greater volume of nuclear-energy-related data. Ensuring sufficient high-quality training data must undoubtedly be incorporated into future work.

Comparing all three models, DALLE-2 gave the best results with prompt engineering. It was also noticed that DALL-E 2 generated better images when only a few number of subjects are present in the prompt, otherwise, different objects interpolated into each other. For instance, in case of Prompt 2 at Table 7 , optimal results are obtained by removing nuclear fuel from the original prompt and instead describing about cooling pool in detail. Further, in case of prompt 1, optimal results could be obtained by removing nuclear reactor core from the prompt. This pattern was observed in all the three models. From the prompt engineering results, it can be observed that generative AI models give better results for the nuclear components that have a substantial number of images present on the internet, such as depicting cooling towers or nuclear reactor control rooms than the prompts referring to subjects which have comparatively less images (e.g., steam generator, reactor core, fuel rod). Further, the results can be improved by giving visual cues to the model in layman’s language, as in the case of cooling fuel in prompt 2 of Table 7 . However, all generative AI models are still not able to comprehend the technical terms, relying on the appearance description provided in most of the cases.

Additionally, it is important to note that all images presented in this paper are the initial images generated through generative AI. We have made this decision in light of concerns about cherry-picking results and potentially biasing performance by selecting the best images after multiple attempts. That said, we conducted a single execution for each model, and from the approximately 3 to 4 images obtained from that run, we selected the images that we deemed to be of the highest quality to include in this paper. It should be noted that among our multidisciplinary team of nuclear engineers, AI, and data scientists, the researchers who chose the prompt and verified its quality had a nuclear engineering background.

Through this study, we have also identified several common issues that models encounter during image generation. All generative AI tools struggled with accurately drawing human faces. This may be due to the numerous facial expressions and facial variations humans have, which would result in having an extremely large database of human faces in order to accurately portray the human face. As Table 5 ’s prompt 1 shows, one can recognize that they are humans, but the faces are off. The man’s right eye is malformed. For prompt 3 on the same table, eyes were completely overshadowed by the hat. The generative AI tools also perpetuate prevailing biases related to gender and employment within the nuclear energy sector and inadequately depict indigenous environments, which have traditionally served as locations for resource extraction and the disposal of nuclear waste by energy industries.

Furthermore, words were presented as nonsense. Despite entering an English prompt, the characters presented in the generated image were intricate symbols rather than alphabetic letters. There could be multiple reasons for this phenomenon, yet the most plausible explanation is the insufficient training of the model in depicting textual content directly as images. In other words, while the machine has acquired the capability to illustrate the entity referred to by the text “nuclear power reactor,” it has not been trained to produce the exact image representation of the text “nuclear power reactor” itself.

In summary, after this study’s exploration of various generative AI models with a specific focus towards nuclear engineering in both a technical and non-technical sense, we have found that a nuclear-specific generative AI model is needed as current models lack the technical expertise to accurately illustrate nuclear topics besides the stereotypes. Beyond that, we have found that for the generative AI models studied they struggle with producing images with readable words, and human faces despite slight improvements after applying prompt engineering. However, we should emphasize that the concerns we found here are specific to the models we tested even though the pool we tested is still large.

5 Conclusions

In the context of humanity, who must concurrently address energy crisis and climate change, communication between the general public and experts regarding green energy has become more crucial than ever. As stated by Veera et al. vimpari2023adapt , one of the current slogans in the field of artificial intelligence is ‘Adapt or Die.’ In this regard, energy experts should now harness generative AI to create synergistic effects in their communication with the public. In this study, we explored various generative AI models in search for ones that accurately depict scientific and nuclear energy prompts from both a technical and non-technical perspective. Among 20 tools, we narrowed our focus to DALL-E 2, Craiyon, and DreamStudio for their promising results on general nuclear prompts. Through our exploration, we found that all the models we studied struggle with creating images of technical nuclear objects such as “nuclear reactor core.” Specifically, we found that the models struggle with complex objects and technical terminologies in general. We noticed an overabundance of nuclear cooling towers during the research. While cooling towers are the most noticeable for the general public when it comes to nuclear energy, it does not accurately portray nuclear energy, which further suggests that a nuclear energy-specific generative AI is needed. This could also be true for other energy systems (e.g., renewable).

Prompt Engineering techniques were applied to further optimize the prompt and generate desired images. It was noticed that improved results can be obtained by giving highly specified prompts to the generative model, along with substantial descriptions regarding the visual appearance of the prompt subject. However, improvement was mostly seen in result of prompts having a large number of related images present on the internet or containing common more general terms, like deer grazing near a cooling tower. The model still was unable to comprehend the technical terms related to nuclear engineering or generate images when multiple nuclear objects are present in the prompt. Though these models are not satisfactory as of now, they may be significantly improved if they are trained on a large data set of nuclear-related images. Furthermore, when accompanied by efforts to optimize prompts, the model performance is likely to improve even further.

In light of these findings, our research team’s future works are as follows. It is evident that for a specialized text-to-image generative model for nuclear energy, a greater accumulation of pertinent training data is imperative. The variance in data volume across domains introduces substantial performance disparities. As demonstrated in our study, as shown in Table 4 , all three tools generated images of near-perfect quality for the text “Bunny.” In contrast, as evident from Table 6 , when it comes to nuclear expertise-related content, they produce perplexing images. Ultimately, increased exposure to certain texts during training allows for the refinement of image generation, indicating that the more exposure, the more accurate the imagery becomes. Consequently, our research team recognizes the necessity for nuclear-centered generative AI development and intends to pursue this as part of our future work. In addition, gender, race, and ethnicity inclusive set of images would reduce the bias these tools carry. Such a specialized tool will then be tested through social experiments with the public to obtain realistic prompts regarding public concerns about nuclear power and clean energy policy.

Acknowledgment

Our team is grateful to the Fastest Path to Zero at the University of Michigan for sponsoring this work under project number (G028455). Furthermore, we express our gratitude to the graduate students and researchers affiliated with the Artificial Intelligence and Multiphysics Simulations (AIMS) group at the University of Michigan. Meredith Eaheart, Kamal Abdulraheem, Leo Tunkle, Umme Nabila, and Omer Erdem have suggested sample prompts that aided in the testing of the tools and methods employed in this study.

CRediT Author Statement

Veda Joynt : Methodology, Software, Validation, Data Curation, Formal analysis, Visualization, Investigation, Writing - Original Draft.

Jacob Cooper : Methodology, Software, Validation, Data Curation, Formal analysis, Visualization, Investigation, Writing - Original Draft.

Naman Bhargava : Methodology, Software, Validation, Data Curation, Formal analysis, Visualization, Investigation, Writing - Original Draft.

Katie Vu : Methodology, Software, Validation, Data Curation, Formal analysis, Visualization, Investigation, Writing - Original Draft.

O Hwang Kwon : Methodology, Software, Validation, Data Curation, Formal analysis, Visualization, Investigation, Writing - Original Draft.

Todd R. Allen : Conceptualization, Funding acquisition, Project administration, Writing - Review and Edit.

Aditi Verma : Conceptualization, Methodology, Funding acquisition, Writing - Review and Edit.

Majdi I. Radaideh : Conceptualization, Methodology, Investigation, Funding acquisition, Supervision, Project administration, Writing - Review and Edit.

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PSA study of the effect of extreme snowfall on a floating nuclear power plant: case study in the Bohai Sea

• Published: 22 November 2023
• Volume 34 , article number  179 , ( 2023 )

Cite this article

• Lan-Xin Gong   ORCID: orcid.org/0000-0001-6417-6599 1 ,
• Qing-Zhu Liang 1 &
• Chang-Hong Peng   ORCID: orcid.org/0000-0003-0368-9301 1  

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This study presents a probabilistic safety analysis (PSA) method for the external event of extreme snowfall on a floating nuclear power plant (FNPP) deployed in the Bohai Sea. We utilized the Weibull and Gumbel extreme value distributions to fit the collected meteorological data and obtained a hazard curve for the event of an extreme snowfall where the FNPP is located, providing a basis for the frequency of extreme snowfall-initiating events. Our analysis indicates that extreme snowfall primarily affects the ventilation openings of the equipment, leading to the failure of devices such as the diesel generators. Additionally, extreme snowfall can result in a loss of off-site power (LOOP). Therefore, the developed extreme snowfall PSA model is mainly based on the LOOP event tree, considering responses such as snowfall removal by personnel. Our calculations indicate a core damage frequency (CDF) of 1.13 × 10 −10 owing to extreme snowfall, which is relatively low. The results of the cut-set analysis indicate that valve failures in the core makeup tank (CMT), passive residual heat removal system (PRS), and in-containment refueling water storage tank (IRWST) significantly contribute to the CDF.

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Development of Risk Assessment Methodology Against External Hazards for Sodium-Cooled Fast Reactors

Loss of offsite power (LOOP) accident analysis by integration of deterministic and probabilistic approaches in Bushehr-1 VVER-1000/V446 nuclear power plant

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Data availability.

The data that support the findings of this study are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.12003 and https://cstr.cn/31253.11.sciencedb.12003.

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Acknowledgements

This study received no specific grants from funding agencies in the public, commercial, or non-profit sectors.

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Lan-Xin Gong, Qing-Zhu Liang & Chang-Hong Peng

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All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by Lan-Xin Gong and Qing-Zhu Liang. The supervision and review of the manuscript were performed by Chang-Hong Peng. The first draft of the manuscript was written by Lan-Xin Gong, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

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Appendix A: K-S test

When the distribution of population X is unknown, hypothesis testing of the population distribution (goodness-of-fit test) can be performed using the Kolmogorov–Smirnov (K-S) test on samples from the population. The main steps involved are as follows:

Hypothesis formulation \(H_0\) : A hypothesis \(H_0\) regarding the population distribution is proposed, typically specifying the distribution type and relevant parameters. The cumulative distribution function of the population X is \(F(x;\theta _1,..., \theta _m)\) .

Sample data (with a sample size of n ) are used to estimate the distribution parameters \((\theta _1,..., \theta _m)\) through fitting methods such as least squares, maximum likelihood, and method of moments.

The value range of X is divided into k groups \([x_{i-1}, x_i] (i=1,..., k)\) .

A cumulative distribution function of the sample observations is calculated \(F_n(x) = n_x/n\) , where \(n_x\) represents the number of samples equal to or less than x .

Test statistics are built: \(D_n = \max {|F(x)-F_n(x)|}\) .

Based on the sample size n and significance level \(\alpha\) , the critical value \(D(n,\alpha )\) is obtained through a table lookup (see Table 9 ), and a rejection domain \(D_n > D(n, \alpha )\) is constructed.

If the test statistic falls into the rejection domain, the hypothesis \(H_0\) is rejected; otherwise, there is no sufficient reason to reject \(H_0\) based on the current sample.

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Gong, LX., Liang, QZ. & Peng, CH. PSA study of the effect of extreme snowfall on a floating nuclear power plant: case study in the Bohai Sea. NUCL SCI TECH 34 , 179 (2023). https://doi.org/10.1007/s41365-023-01335-8

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Published : 22 November 2023

DOI : https://doi.org/10.1007/s41365-023-01335-8

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