How Safe is Nuclear Energy?

January 2006

The Global Energy Situation

1. What is the situation regarding nuclear power reactors in the world?

2. What is the contribution of nuclear energy to mitigating the problems associated with green house gas emissions and consequent global warming?

3. How has privatisation and the opening of electricity markets affected the safety of the nuclear power plants?

4. A burdensome regulatory process could be difficult to maintain in a competitive business environment. How is this new environment affected the regulatory requirements? What is the impact on plant safety? Are utilities and operators pressing to lessen regulatory requirements? How can safety and competitiveness be balanced?

II. Safety of Nuclear Installations

5. Several countries around the world are building new nuclear power reactors. Is there some system to ensure that they all live up to a common, satisfactory level of safety?

6. Three Mile Island and Chernobyl were major nuclear disasters affecting thousands of people and contaminating large areas. Why haven´t plants of that type been shut down?

7. The Chernobyl accident in 1986 was the world’s worst nuclear accident. It killed dozens of people and contaminated a very large area around the plants. What is the risk that such accidents will happen again elsewhere?

8. More than 15 potentially dangerous RBMK reactors are still operating in Russia and Lithuania. What has been done to alter their design and operation to prevent similar nuclear disasters? What specific measures have been taken to ensure their safety?

9. What kind of safety assessment has the IAEA performed to assess the safety of WWER and RBMK reactors?

10. What kind of evaluation have the IAEA and other organizations conducted in plants that combine Eastern and Western technologies, such as Temelin in the Czech Republic?

11. Many nuclear power plants are reaching the end of their operational lifetimes. But many operators are getting extensions of their operating licenses. Isn´t this dangerous since the plants are too old?

12. The safe operation of any complicated equipment depends a lot on the people and how well they are trained. But levels of technical education and work discipline are low in some countries. Is anything being done to upgrade the quality of nuclear plant personnel to ensure better safety?

13. Power blackouts affected major cities in the USA, Canada and Europe in 2003. What has been the impact of these events on the operation of nuclear plants? Is their safe operation still ensured?

14. Some nuclear power plants are built on sites subject to natural phenomena such as earthquakes or tornados, which can pose a risk for any installation. What has been done to ensure the safety of these plants?

15. Some nuclear power plants are built on sites close to dangerous transportation routes or gas and oil pipelines. Others could be damaged by an airplane crash. Is there a way to protect these plants against such disasters?

16. What is the role of the IAEA in assessing plant safety and investigating abnormal events in nuclear power plants and other installations?

17. If a nuclear power plant does not have containment, how can one be sure that no radioactive material is released to the environment?

18. What has been done by the IAEA in the case of events involving nuclear plant safety reported by the press?

III. Security of Nuclear Installations

19. Are nuclear power plants and other nuclear facilities vulnerable to terrorist attacks? Is anything being done to protect them?

IV. Radiation Safety, Wastes and Transport

20. The spent fuel and high-level waste from nuclear plants is very dangerous, but no country has a complete plan for how to permanently deal with this waste. Shouldn´t this problem be addressed before any new nuclear plants are built?

21. Accidents involving radiation sources used in medicine or industry can occur in countries without the adequate infrastructure to cope with the consequences. What is being done to avoid these types of tragedies?

22. There is a large volume of radioactive material being transported in Europe and around the world. What are the risks for the other vehicles and the population that come close to these materials?

How Safe is Nuclear Energy?

22 Frequently Asked Questions:

I. The Global Energy Situation

1. What is the situation regarding nuclear power reactors in the world?

A1. Short Answer:
More than 50 years have passed since the operation of the first nuclear power plant in 1954, and during this time nuclear power has become a well established, mature technology. At the end of 2005, there were 443 civilian nuclear power reactors operating in 31 countries around the world. However the pace of constructing new nuclear plants has been slowed down in the past few decades – 26 reactors are in different stages of construction in 11 countries, most of them in Asia (Japan, China, Republic of Korea, Democratic Republic of Korea and India). Twenty-two of the last 31 reactors to be connected to the grid are also in the Far East and South Asia. By contrast, in Western Europe and North America, nuclear construction has been a frozen playing field – the last plant to be completed being Civaux-2 in France in 1999. However, site preparation began in Finland for the 1600 MW(e) Olkiluoto-3 plant. See IAEA data.

Explanation:
Nuclear energy supplies 16% of all electricity generated in the world. This percentage has been roughly stable since 1986, indicating that nuclear power has now grown at the same rate as total global electricity for 17 years.

According to the IAEA Power Reactor Information System (PRIS), in four countries (Lithuania, France, Slovakia, and Belgium), nuclear energy represents more than 50% of the installed capacity. In other 4 countries (Sweden, Ukraine, Slovenia and Republic of Korea), it represents more than 40% of the electric capacity.

There are 121 nuclear power plants in North America, most of them in the United States (104). Before the recent EU expansion nuclear energy was already the largest single source of electric energy in the European Community, ahead of coal and gas. In the newly expanded EU, 13 out of 25 countries operate 153 nuclear power reactors to generate electricity. In Latin America there are two operating plants in each of Argentina, Brazil and Mexico and one under construction in Argentina. There are two operating plants in South Africa.

Capacity is greatest in Japan, with 54 reactors in operation and two under construction. In the Republic of Korea, with 19 reactors in operation and one under construction, 40% of total electricity came from nuclear power in 2003. Elsewhere in Asia, nuclear power´s absolute and relative contributions are smaller, but China and India in particular plan significant expansion. India, with 14 operating reactors, gets only 3.3% of its electricity from nuclear power. But nine more reactors are under construction, including the 500 MW(e) prototype fast breeder reactor at Kalpakkam, and India´s goal is, by 2050, to supply 25% of its electricity from nuclear power. China, now with nine operating reactors, two under construction and but 2.2% of its electricity from nuclear power, plans expansion to 32-40 GW(e) by 2020 for 4-5% of the electricity supply. In 2004 China´s State Council formally approved at least 7 GW(e) of new capacity beyond that already under construction.

The majority of operating units (82%) are of the Light Water Reactor (LWR) type, 61% of those being of the Pressurized Water Reactor (PWR) type, and 21% being of the Boiling Water Reactor (BWR) type. Pressurized Heavy Water reactors (PHWR or CANDU) represent about 9% of the total. Different types of gas-cooled reactors represent 5%, while Light-water-cooled Graphite-moderated, water (RBMK) represent about 4% of the total amount.

Nuclear expansion, as well as near-term and long-term growth prospects, is centered in Asia. Nineteen out of 25 new plants will be located either in China, the Republic of Korea, Japan or India. Twenty-one of the last 30 reactors to have been connected to the grid are in the Far East and South Asia.

Given the limited amount of new construction, much of the increase in nuclear generating capacity over the past decade has been credited to increased availability – a change tied directly to improvements in global safety performance.

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2. What is the contribution of nuclear energy to mitigating the problems associated with greenhouse gas emissions and consequent global warming?

A2. Short Answer:
Nuclear power plants emit virtually no greenhouse gases. The complete nuclear power chain, from uranium mining to waste disposal, including reactor and facilities construction, emits only 2-6 grams of carbon per kilowatt-hour. Therefore, the operation of the world´s nuclear power reactors avoids the release of roughly 600 million tones of carbon, should the same energy have be generated by a proportionate mix of non-nuclear sources. Read more…

Explanation:
Studies have shown that, when the whole chain from mining to waste disposal is considered, nuclear power produces only 2-6 grams of carbon pre kilowatt-hour. This is about the same as wind or solar power, and less than 1% of the amount produced by coal, oil or even natural gas.

The 600 million tones of carbon avoided by the operation of the world´s 443 nuclear power reactors is approximately twice the total amount to be avoided by the Kyoto Protocol in 2010.

Both nuclear and other renewable sources of energy, such as wind, solar and geothermal plants could play a major role, as the reduction of carbon emissions becomes a higher priority. The problem is that no “renewable” source has been demonstrated to have the capacity to provide the “base-load” amounts of power needed to replace large fossil fuel plants. Wind power, for example, may be an excellent choice for sparsely populated rural economies, particularly if they lack modern electrical infrastructure; on the other hand, it seems unlikely that wind power will be able to support the electricity needs of tomorrow´s mega-cities.

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3. How has privatisation and the opening of electricity markets affected the safety of the nuclear power plants?

A3. Short Answer:
Privatisation has had a major impact on the electric power industry, and as such, the nuclear power industry in many countries. But the impact has been mainly on commercialisation and tariffs. The impact on plant safety has been minor, since no significant changes in regulatory requirements have occurred due to privatisation, and whoever owns and operates a nuclear power plant still has the ultimate responsibility for its safety. Read more…

Explanation:
The main impact of privatisation has been in the commercialization of the produced electric power. Of course, in a privatised environment operational costs are an important factor and efforts to cut costs become an ever important priority. However, a “safe plant is also a reliable plant”. This can be demonstrated by the examination of the list of “plant performance indicators” which are, in large part, common to the list of “safety indicators”.

The examination of both performance indicators and safety indicators in most plants shows that privatisation has not adversely affect plant safety. Even in exceptional cases, such as in Canada, where strong cost cutting measures have led to deterioration of plant performance to the point where several reactors have been temporarily shutdown, the regulatory body cited no safety reasons for ordering the plants to shutdown.

Since the accident at Chernobyl in 1986, the IAEA has established networks to conduct peer reviews, compare safety practices, and exchange vital operating information to improve safety performance. A more systematic analysis of risk was used to ensure that changes made were in areas that would bring the greatest safety return. Although the focus of this international effort was on improving safety, the secondary benefit has been a steady increase in nuclear plant availability and productivity. In 1990, nuclear plants on average were generating electricity 71% of the time. That figure had risen to 81% – an improvement in productivity equal to adding more than 34 new 1000 megawatt nuclear plants – all at relatively minimal cost.

The result is that existing well-run nuclear power plants have become increasingly valuable assets. Although the front-loaded cost structure of a nuclear plant is high, the operating costs have become relatively low and stable. While these improvements to safety and economics have not been well publicized – and have not yet had a significant impact on the public´s opinion of nuclear power – they have not escaped the notice of investors. They have been a strong factor in decisions to extend the licences of existing plants – for example, in the United States, where 19 plants have received 20 year licence extensions in the past 5 years. Regulatory bodies in countries where privatisation has taken place must continue to carefully monitor plant safety performance to ensure that cost reductions do not compromise the levels of safety.

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4. A burdensome regulatory process could be difficult to maintain in a competitive business environment. How is this new environment affected the regulatory requirements? What is the impact on plant safety? Are utilities and operators pressing to lessen regulatory requirements? How can safety and competitiveness be balanced?

A4. Short Answer:
Safety requirements have not been changed due to deregulation of the electric power market. The safety requirements and standards remain the same. And regulatory bodies have not, and will not, be willing to lessen them due to economic reasons. The utilities, on the other hand, now have additional requirements for competitiveness. These however must not compromise safety requirements. This is usually stated in the utilities safety policy statements. Read more…

Explanation:
Competitiveness is one of the key objectives of utilities in a deregulated electric power market. However, it is widely recognized that a well run, safe plant is also an economic, and thus a competitive, plant. The costs associated with unplanned or regulatory imposed outages can quickly exceed those associated with maintaining a safely built and safely operated facility.

The strategy of the industry is to demonstrate a good safety record and maintain high operational performance, and reduce the risks associated with insurance and liabilities. Optimisation of maintenance programs, based on predictive maintenance, instead of repair maintenance, has also contributed to high plant availability and therefore good safety and economic performance.

Lessons learned from recent events have demonstrated that operating a plant in an unsafe condition can be most costly in the long range.

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II. Safety of Nuclear Installations

5. Several countries around the world are building new nuclear power reactors. Is there some system to ensure that they all live up to a common, satisfactory level of safety?

A5. Short Answer:
Yes, a global safety regime has been instituted by the international community after the accident at Chernobyl to promote a common level of safety throughout the world. This “regime” includes binding safety conventions, internationally accepted safety standards, and a peer review system to promote compliance and assist countries in improving safety whenever necessary. Read more…

Explanation:
Nuclear safety has been always a matter of international concern. In the early 1970s, the IAEA developed a series of 5 Codes of Practice and 50 Safety Guides which were applied and/or adapted as regulation by developing countries entering into the nuclear power arena. Later, after the accident at Three Mile Island in 1979, the 5 Codes were revised as a set of international standards for all countries.

But it was after the accident at Chernobyl that a truly “international nuclear safety regime” was fully developed. This “regime” is based on:

1. Binding international conventions;
2. Internationally accepted safety standards; and
3. An extensive system of peer reviews.

Two conventions, one on the Early Notification of a Nuclear Accident and a second on Assistance in the Case of a Nuclear Accident or Radiological Emergency were developed just a few months after the Chernobyl accident. A Convention on Nuclear Safety was developed later, requiring the parties to: 1) report every 3 years on the safety status of their nuclear power plants according to detailed guidelines; 2) identify any known deficiencies; and 3) take the necessary actions to eliminate them. These reports are critically reviewed among the parties of the Convention and general recommendations are derived at a periodic review meeting every 3 years. Later, a similar Joint Convention on the Safety Management of Spent Nuclear Fuel and Nuclear Waste was developed with a similar reporting mechanism.

IAEA safety standards are periodically revised and updated to reflect the state of the art in nuclear safety, and to include new areas, such as the nuclear fuel cycle; modern techniques, such as human-machine interaction and assessment of the probability of occurrence of certain postulated accidents. These standards are now accepted worldwide, and, although not obligatory, have been adopted by several countries on a voluntary basis, and are used as the basis of national regulations in numerous other member States.

Evaluation of the safety status of nuclear programs is the third tier of the global safety regime. Operational safety reviews are been conducted by the WANO (World Association of Nuclear Operators) at almost every plant worldwide, and these services are scheduled to be repeated every 3 years. Additional plant reviews are conducted by the IAEA Operational Safety Review Teams (OSART), which are made up of experts from countries around the world. From a slightly different perspective, reviews of the national regulatory bodies, including their legal infrastructure and safety assessment activities, are carried out by the International Regulatory Review Team (IRRT) of the IAEA.

Altogether, these reviews confirm and keep current the information provided to the Conventions. They also provide assurance that an acceptable level of safety has been and continues to be achieved throughout the nuclear industry.

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6. Three Mile Island and Chernobyl were major nuclear disasters affecting thousands of people and contaminating large areas. Why haven´t plants of that type been shut down?

A6. Short answer:
Three Mile Island (Pennsylvania, USA) was a severe accident that occurred in 1979. The accident destroyed the power-producing core of the light water power reactor but led to no release of radioactivity to the environment and no personal injuries or contamination. The Chernobyl (Ukraine) accident, which occurred in 1986, was indeed the most devastating in the history of nuclear power. It resulted in 28 radiation-induced fatalities within few months after the accident, evacuation of hundreds of thousands of people and contamination of vast territories of Russia, Belarus and Ukraine. In both cases, the lessons learned from the accident were applied almost immediately by the world nuclear industry to modify similar plants, to improve personnel training and to improve operational management with the objective of avoid the repetition of similar a accident. These important steps led to considerable improvements in plant safety worldwide. Read more…

Explanation:
The accident at the American pressurized water reactor (PWR) at Three Mile Island was a loss of coolant due to a combination of design deficiencies and operators errors, leading to the uncovering and partial meltdown of the reactor core. The containment building around the reactor kept all of the contaminated water and any radioactive material confined to the plant. The only exception was the release of a minimal amount of radioactive gas released as a pressure control mechanism. This release had no significant impact on the environment, the plant personnel or the public.

The reaction from the nuclear industry and national regulators was a comprehensive investigation of the accident and its causes. This, in turn, led to several key design modifications to improve the safety of plants of the same type. The lessons learned from the TMI accident also resulted in significant changes to the overall approach to nuclear safety throughout the world, including new developments in the area of human factor engineering. It also led to the creation of the Institute of Nuclear Power Operation (INPO).

The Chernobyl accident occurred in a completely different type of reactor (Light water-cooled Graphite-moderated Reactor, RBMK), used only in the former Soviet Union. Acute radiation syndrome was diagnosed and confirmed for 134 persons (fire fighters and recovery operation workers). Among them, 28 persons died in 1986 due to acute radiation syndrome, and 17 died in 1987-2004 from various causes, not all linked to radiation. No cases of acute radiation syndrome have been recorded among the general population. About 600,000 persons have been recognised as liquidators (recovery operation workers). It was assessed that the average effective dose from external gamma radiation to recovery operation workers in the years 1986-1987 was on the order of 100 miliSieverts. In addition, 10 % of the 116,000 people that were evacuated from the “exclusion zone” may have received doses greater than 50mSv but fewer than 5% received more than 100 mSv. More than 18 years after the accident, the confirmed detectable radiation-induced human health effect of the accident has been a sharp increase of thyroid cancer among exposed children from the affected area. Since the accident, the number of patients having thyroid cancer (who were children and adolescents in 1986) reached 4 000 in Belarus, Russia and Ukraine. Since thyroid cancer can generally be successfully treated, only dozen patients among the diagnosed are known to have died from this cause.

The reaction from the nuclear industry to the Chernobyl accident was the wide recognition that “an accident anywhere is an accident everywhere.” An immediate international effort was launched to develop a truly “international nuclear safety regime” composed of binding safety conventions, internationally accepted safety standards and a peer review system to verify the safety level of all plants.

The reaction of utilities operating nuclear plants was the creation of the World Association of Nuclear Operators (WANO), in order to maximise the safety and reliability of the operation of nuclear power plants by exchanging information and encouraging communication, comparison and emulation amongst its members.
Several international initiatives have been conducted subsequently to improve the safety of Chernobyl-type reactors (RBMK). These have included hardware modifications, improved plant maintenance and in-service inspections, based on additional safety analysis, and the promulgation of a committed safety culture among the operators. The IAEA conducted a project on the safety of RBMK type reactors involving a complete review of plant design and operational aspects. The initiative resulted in a list of plant improvements that were implemented with international support from the European Community, European Bank for Reconstruction and Development (EBRD) and the World Bank. The other 3 reactors at the Chernobyl site were all later shut down. Both the International Atomic Energy Agency (IAEA) and the World Association of Nuclear Operators (WANO) have introduced periodic peer reviews of nuclear plants, worldwide, to assure that they are operated according to best international practices.

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7. The Chernobyl accident in 1986 was the world’s worst nuclear accident. It killed dozens of people and contaminated a very large area around the plants. What is the risk that such accidents will happen again elsewhere?

A7. Short answer:
The risk of a new accident of the same type of Chernobyl has been greatly reduced due to international and national efforts to improve substantially the safety of these plants. Read more…

Explanation:
The accident at Chernobyl was caused by a combination of design deficiencies and operator errors. Immediately after the Chernobyl accident, nuclear authorities of the former Soviet Union undertook several measures to avoid the repetition of a similar accident. These involved modifications to the reactor design and associated safety systems, as well as administrative measures to ensure proper actions by operators.

As a follow up, an Extra-Budgetary Project for the safety of RBMK Nuclear Power Plants was carried out by the IAEA during 1990-1997 with broad international support. This project carried out a comprehensive review of the design and operation of RBMK type plants and identified the main safety issues. Then, support from the international community was provided to improve the safety conditions at the RBMK reactors. At the conclusion of the Project, technical experts and scientists concluded that the likelihood of a similar accident was very low, could be discarded, although further safety improvements were encouraged.

Such improvements have continued in recent years. The National Reports of Russia and Lithuania (in Ukraine the 3 remaining RBMKs at Chernobyl have been shutdown) presented in the recent review meetings of the Convention on Nuclear Safety have demonstrated a significant upgrading of the level of safety of this type of plants. This has also been demonstrated by the reduction in the number of reported abnormal events as well by other safety indicators such as plant availability and dose reduction.

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8. More than 15 potentially dangerous RBMK reactors are still operating in Russia and Lithuania. What has been done to alter their design and operation to prevent similar nuclear disasters? What specific measures have been taken to ensure their safety?

A8. Short Answer:
After the Chernobyl accident, there was broad agreement that the original design of the RBMK reactor core and its shutdown system had severe deficiencies. Modifications carried on RBMK reactors between 1987 and 1991 addressed the most serious problems in these areas. Modifications introduced later, with the assistance of the international community, aimed at further improving overall safety to an (internationally) acceptable level. Some additional modifications are still underway in order to achieve even higher safety levels, as required by the Convention on Nuclear Safety. Read more…

To view reactors by type, see IAEA data. (Note: RBMKs are listed as LWGR types).

Explanation:
The immediate actions to avoid the repetition of the Chernobyl accident were carried out by the former Soviet Union itself. Later, in 1992, upon request of the former Soviet Union and later of Russia, the IAEA started a program on the safety of RBMK-type reactors which included a wide range of activities including review and assessment of the Smolensk and Ignalina plants that served as references for the program. Support from the international community, including EU, EBRD and WANO, were essential to the success of that five-year program.

At the conclusion of the IAEA program, it was generally agreed that results of the international assistance have increased the confidence that the known shortcomings and the requisite safety improvements of RBMK reactors have been identified and addressed. This includes both design and operational considerations. The plant specific status of the implementation of safety improvements have been reported in the National Reports to the Convention on Nuclear Safety. This demonstrates an ever increasing level of safety, which supports continuity of operation of these reactors, (except for the three additional units at Chernobyl, which have been shut down).

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9. What kind of safety assessment has the IAEA performed to assess the safety of WWER and RBMK reactors?

A9. Short Answer:
In 1990, the IAEA launched an international project on the safety of WWER 440/230. Later this project was expanded to include all WWER and RBMK – type reactors. This project evaluated the safety of the design and sponsored expert safety visits to the power plants to identify safety deficiencies and to make recommendations on how to solve them. The project grouped the deficiencies into so called “safety issues,” prioritised them and monitored their solutions through assistance provided by the EU, the World Bank, EBRD and bilateral agreements.

The project concluded in 1998 with the resolution of the main safety issues. But the enhancement of safety at WWER and RBMK reactors continues, with many of the additional low priority issues now being resolved as a result of follow-up assistance provided by the IAEA through its technical cooperation program. Read more…

Explanation:
The IAEA project on the Safety of WWER and RBMK Nuclear Power Plants was a major scientific and technical undertaking of IAEA, carried out with support of several Member Sates during the period of 1990 – 1998. Dozens of expert safety missions were conducted inside the plants, and 20 technical studies were conducted by the IAEA involving dozens of outside experts provided cost free by member States.

The final project report (IAEA-EBP-WWER-15) described and ranked all of the key safety issues, identified the issues that remained to be solved at that time, presented an overview of the remaining work to be done and specified the relevant IAEA assistance which was planned. The results and recommendations of the Project were intended only to assist the national decision makers who have the sole responsibility for the regulation and safe operation of their nuclear power plants.

Progress in the implementation of these additional safety improvements is further documented in the final report of the 2nd Review Meeting of the Convention of Nuclear Safety, where it is recognized the good progress achieved by all these plants to increase their level of safety.

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10. What kind of evaluation have the IAEA and other organizations conducted in plants that combine Eastern and Western technologies, such as Temelin in the Czech Republic?

A10. Short Answer:
The IAEA has been providing assistance in the safety evaluation of the Temelin nuclear plant since 1990. Indeed, it was the IAEA Temelin Design Review Mission, carried out in 1990, that prompted the decision to change the plant´s fuel design and instrumentation and control systems, which was provided by an America company. Additional IAEA assistance has been subsequently provided in the evaluation of safety issues and their solutions, and in the review of Probabilistic Safety Assessment (PSA), Quality Assurance (QA), and the application of Leak Before Break (LBB) concept. Fire protection and Operational Safety (OSART) missions have also been conducted at the Temelin plant. Read more…

Explanation:
Several international safety missions have been conducted at Temelin by the IAEA and other organizations. The initial missions focused on the design, but later they concentrated on the compatibility of Western technology with the original Russian design.

The most recent assessments were conducted by GRS – Germany, through a bilateral agreement, by the association of Western regulatory bodies (WENRA), and by the Atomic Question Group (AGQ) in relation to the acceptance of Czech Republic in the EU.

All of these recent assessments concluded that the design and operational safety of Temelin is in compliance with national requirements and international practices.

The work of the Czech regulatory body (SUJB) in licensing and controlling Temelin was also independently evaluated by two International Regulatory Review Team (IRRT) missions of the IAEA in January 2000 and June 2001, with positive results.

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11. Many nuclear power plants are reaching the end of their operational lifetimes. But many operators are getting extensions of their operating licenses. Isn´t this dangerous since the plants are too old?

A11. Short Answer:
The decision to extend the life of a nuclear power plant beyond the original “estimated life” is taken only after a careful evaluation of all safety implications, especially the actual condition of key components, such as the reactor vessel, (the steel vessel containing the reactor core) and its anticipated condition at the end of the extended life. Usually such extensions are accompanied by comprehensive upgrading of plant safety conditions, including replacement of obsolete components and the addition of new safety system and components according to the new standards and developments of technology. Read more…

Explanation:
The estimated “life time” for a nuclear power plant arises mainly from two requirements: 1) from the commercial point of view, one needs to estimate the period of operation in order to depreciate the capital cost and calculate tariffs; 2) from the technical viewpoint, one has to estimate the life time of the limiting component which cannot be easily replaced by maintenance, usually the reactor vessel.

Not all countries establish a fixed “life time” period for nuclear power plants at the initial licensing. Normally, however, the condition of all plant components are constantly monitored, and obsolete or worn out components are replaced during routine maintenance, as required. Since the “life” of components is estimated at the beginning using conservative operational conditions, the actual life may be longer than the initial estimate, thereby permitting the extension of plant life without compromising safety.

On the other hand, operating experience may show deterioration of components faster than estimates due to previously unknown phenomena. But modern technology has permitted the replacement of components which were planned to last for the “life of the plant”, as is typical the case of steam generators and reactor vessel heads of PWR. Even the radiation damage, which limits the life of reactor vessel can be overcome in some cases by the modern on-site “annealing” process.

At the end, the decision to extend the life of a plant is a commercial one, which balances the cost of the effort to refurbish the plant to maintain its safety, and the economic benefits of the additional electricity to be generated. This same balance has sometimes led to early plant retirements, showing that the nuclear industry is conscious of its responsibility for safety.

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12. The safe operation of any complicated equipment depends a lot on the people and how well they are trained. But levels of technical education and work discipline are low in some countries with nuclear plants. Is anything being done to upgrade the quality of personnel to ensure better safety?

A12. Short Answer:
New standards of qualification and training of operators have been developed with a recognition of the importance of the human factor in nuclear safety. The Systematic Approach to Training (SAT) has been used to ensure adequate training of plant operators across the nuclear industry. The creation of the World Association of Nuclear Operators (WANO) has contributed to the dissemination of this methodology, and WANO peer reviews have been used to demonstrate adequate levels of training, and to propose further improvements when necessary.

Staff training and qualifications is also an inherent module in IAEA nuclear plant safety review missions; additionally, training plant staff is a significant part of the safety assistance provided under the Agency´s technical cooperation programme. Read more…

Explanation:
The nuclear industry has always recognised the importance of the human factor in ensuring safety. Comprehensive training programs, including the use of plant simulators, have been part of nuclear industry from its inception.

But it was after the accident at Three Mile Island that the new discipline of “human factor engineering” (or man-machine interaction) was thoroughly developed. Additional requirements for the number of operators in the control room were established. The qualification and training of the operators were enhanced. The design of all control rooms were reviewed from the ergonomic point of view, and many modifications were introduced in order to assist the operators in the diagnosis of plant conditions, especially during emergency situations. Plant procedures were reviewed and revised in order to present the information in a more “operator friendly” way. The use of plant specific simulators, with greater simulation capabilities has been greatly extended.

The monitoring and evaluation of events caused by operator errors has been further developed and refined. These evaluations have demonstrated that, although still an important factor, operator errors have been consistently decreasing at most of nuclear plants around the world.

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13. Power blackouts affected major cities in the USA, Canada and Europe in 2003. What has been the impact of these events on the operation of nuclear plants? Is their safe operation still ensured?

A13. Short Answer:
Most nuclear power plants are designed to remain in operation even if they are not connected to the larger electrical grid. All nuclear power plants are equipped with multiple redundant emergency power supply (diesel generators) which can go into operation in few seconds in case of a total failure of power supply. In the meantime, redundant battery sets provide essential power to the instrumentation and controls that monitor plant status and activate the emergency power supply. The diesel generators sets are provided with independent fuel tanks and reserve fuel adequate for several days operation. In addition, administrative arrangements are in place for refilling these tanks in the improbable case of extended periods without re-establishing connection to the electric power grid. Read more…

Explanation:
The loss of external power supply is a “design basis accident” considered in all nuclear power plants. Multiple redundant emergency diesel generators are usually provided to cope with these events. This emergency power is used to operate the safety equipment necessary to maintain the cooling of the reactor core and other essential plant safety functions.

Calculations of the probability of occurrence of certain postulated accidents recognize that there is a remote probability that all diesel generators could fail due to a “common mode failure” (a common deficiency in the design or a common error in the maintenance of all units). This has led some plants to add a direct connection to a reliable alternate source (e.g., nearby hydro plants) or to use a “diverse” type of emergency, such as an electric generator driven by a small gas turbine.

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14. Some nuclear power plants are built on sites subject to natural phenomena such as earthquakes or tornados, which can pose a risk for any installation. What has been done to ensure the safety of these plants?

A14. Short answer:
Nuclear power plants are designed against natural phenomena according to detailed studies performed at the time of the selection of the site for the construction. These studies define the maximum threatening phenomena expected at the site, and include “design basis earthquakes, floods, etc.” Sites are constantly under re-evaluation during the entire life of the plant. Phenomena such as earthquakes are constantly monitored, and in the event that a lower level earthquake – the so called safe shutdown earthquake – occurs, the plant is shut down and a detailed investigation is carried out. Read more…

Explanation:
The pursuit of a nuclear project is only authorised after detailed studies are conducted to identify all important potential physical threats to a site. These include maximum meteorological conditions such as rain, wind, flood levels, and extreme natural phenomena such as tornados, earthquakes, hurricanes and tsunamis. Past data, as well as detailed analytical models, are used to define design basis parameters for the specific site.

The construction of the plant takes into account all these parameter when designing, fabricating and installing main components and essential safety equipment.

Site parameters are constantly re-evaluated and, in case of new information, design modifications can take place, such as the re-enforcement of structures or the replacement of equipment, as occurred in some WWER plants after a new earthquake design basis was defined.

Site parameters are constantly monitored and automatic actions or safety procedures are in place to put the plant in a safe condition if any of the parameters are exceeded. In certain situations, such as the approach of a hurricane, a precautionary shutdown may take place.

Extensive experience has shown that this philosophy of conservative design has been sufficient to cope with all of these types of natural phenomena at all nuclear power plants.

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15. Some nuclear power plants are built on sites close to dangerous transportation routes or gas and oil pipelines. Others could be damaged by an airplane crash. Is there a way to protect these plants against such disasters?

A15. Short Answer:
Site studies carried out before the construction of a nuclear power plant identifies all the potential threats due to human activities around the plant. Explosions of dangerous goods on nearby routes, in vulnerable pipelines or as a result of airplane crashes are either taken into account in the design. In some instances, they are excluded due to the low probability of such occurrences. In some cases, routes are redirected, pipelines are moved or air-space around the plant is controlled. Read more…

Explanation:
During the site selection for a nuclear power plant, all man-induced events which can be a threat to the plant are identified. Some of these may be decisive in excluding a given site from further consideration. Some may require remedial action, such as the re-location of roads, pipelines or air fields.

After identifying such possible events and considering their probability, a set of man-induced events is taken into consideration in the design and construction of the plant.

Plant buildings are usually designed and constructed to support the shock wave from a possible explosion of dangerous cargo on a nearby road, should it be relatively close to the plant. Dangerous ship cargo in a nearby river or sea are also considered.

Regarding airplane crashes, a detailed study of air routes is carried out, including the types of planes and the frequency of flights to determine the need for a specific protection against such events. In cases where an airplane crash is considered in the design, reinforcement of the containment building is required. In many countries, a “no fly zone” is established around the nuclear plant sites, where passage of commercial, military and civil airplanes is prohibited. Also the provision of redundant emergency systems, such as power supplied by stand-by diesel generators or more than one control room (spatially separated main and emergency control rooms) protect the plant from the simultaneous loss of both systems.

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16. What is the role of the IAEA in assessing plant safety and investigating abnormal events in nuclear power plants and other installations?

A16. Short Answer:
The assessment of nuclear power plant safety is the responsibility of national authorities of each country. The IAEA is only involved in the investigation of abnormal events or accidents if it is requested by a member State.

The IAEA regular programme puts considerable effort into developing standards for all safety thematic areas and for all types of nuclear installations (Safety Standards and Safety Guides). Tools and services to promote the exchange of information on abnormal events, such as the Incident Report System (IRS) and the Agency peer review services provide important opportunities to share lessons and learn from others. The Agency is also promoting self-sustaining networks within and between Member States based on strategic knowledge management to provide more opportunities to share safety information. Read more…

Explanation:
Assistance to Member Sates in the field of nuclear safety is in the Statutes of the IAEA. This assistance is always provided upon request of a member State and delivered as advice to the national authorities. It can be provided to review either design or operational considerations, or in case of abnormal events, to assist in the identification of root causes and the sharing of lessons throughout the world nuclear community.

In some cases, based on the provisions of the Convention for Assistance in Case of Nuclear or Radiological Accidents, the IAEA has also supported Member States in evaluating accident conditions, recovery activities and the mitigation of accident consequences.

Up to now, most of these cases have been related to radiological emergencies connected with loss of control of radiation sources. In these cases, the Agency has produced independent evaluation reports with a description of the events and the conclusions and recommendations related to the lessons learned.

Assistance has also been provided, on numerous occasions, to help with an independent assessment of events. Examples include events that have taken place at nuclear power plants in Spain, France and Hungary. In the case of Hungary, at the request of the Government of Hungary, the IAEA conducted an independent expert mission at the Hungarian Atomic Energy Authority and the Paks Nuclear Power Plant to assess the results of the national regulator´s investigation of the 10 April 2003 fuel cleaning incident at the Paks NPP.

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17. If a nuclear power plant does not have containment, how can one be sure that no radioactive material is released to the environment?

A17. Short Answer:
The containment is an additional safety barrier, included in the design of some nuclear power plants, but not necessarily in all plant designs. The acceptance of the design (and therefore, the license to construct) is only completed after the evaluation of a number of postulated accidents defined for each specific design. The ultimate goal is ensure that in the worst credible accident for a given design, the radiation dose to the public will not exceed the established national limits. This has been determined by some national regulatory authorities to be assured for certain designs without a containment building. Read more..

Explanation:
The authorization process to build a nuclear power plant requires the detailed analysis of postulated accident scenarios according to the plant design. These form the “design basis accidents” for a given design. Safety systems are designed to cope with these accidents, and the analyses must demonstrate, given conservative assumptions, that the doses to the public will not exceed the established safety limits.

For certain nuclear plants modular construction in the form of “multiple-channel” is used. Examples include Gas Cooled Reactors (Magnox and AGR type reactors) and Light-water-cooled Graphite-moderated Reactors (RBMK). In these cases, it has been demonstrated that under design basis accidents a containment building is not required to ensure that safety limits are not exceeded. There exists, however, a small possibility that an accident “beyond the design basis” may occur, such as was the case at Chernobyl. Recent evaluations show that in the case of Chernobyl, even if a containment building has been present, it would not have resisted the large steam explosion that occurred. Therefore, the current approach is to try to avoid “beyond design basis accidents,” or better, make their probability so low that they can be practically excluded.

Nowadays, more detailed safety analyses using probabilistic methods are carried out to identify possible sequences leading to “beyond design basis accidents”. Additional measures are now being taken into consideration to cope even with these remote possibilities.

Additionally, these accident scenarios are used for planning emergency preparedness measures, which could be used for ultimate protection of the population (through sheltering or evacuation) in the remote possibility of such an event.

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18. What has been done by the IAEA in the case of events involving nuclear plant safety reported by the press?

A18. Short Answer:
The IAEA´s Incident and Emergency Centre maintains a system of reporting of events related with nuclear energy, including both operational events at nuclear power plants and radiological incidents throughout Member States. The reporting system uses the International Nuclear Event Scale (INES) to convey to the public the significance of the event. The information is transferred to the INES contact point in all Member States, and also published on the IAEA website.

Later, more detailed information, the evaluation of the event and the lessons to be learned, are usually published as an entry in the Incident Reporting System (IRS). Read more…

Explanation:
The reporting of significant events – those graded level 2 or more, in the INES scale, or those attracting media attention – is a commitment of all Member Sates participating in the INES network. The dissemination of the initial information by the IAEA is a routine activity.

Through the Incident Reporting System (IRS), operated jointly with the OECD/NEA, feedback of international operating experience for nuclear power plants proper reporting and feedback of safety significant events for the international community is ensured, and its causes and the lessons learned can then be disseminated widely.

The detailed assessment of some events is carried out, depending on their significance for nuclear safety and their relevance for other organizations in the nuclear industry. In these cases, an IAEA mission is sometimes sent to the country to collect specific data, to review the facts and assess the actions taken. A report containing recommendations to the country – to the operators and/or regulatory body, depending on the situation – is prepared and presented to the country authorities. Lessons learned and recommendations to all related nuclear industries are also contained in the report.

Whenever several events present a common root cause or other commonalities, larger technical meetings are organized by the IAEA. These aim to produce deeper analyses, identify broader lessons from the collective series of events, develop additional guidelines, and possibly initiate new IAEA activities in the related field.

One recent example of this was a Workshop on Nuclear Management and Safety Culture: Lesson Learned from Recent Events organized in June 2003 to evaluate events that occurred in 4 power plants in Japan, Germany and the USA.

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III. Security of Nuclear Installations

19. Are nuclear power plants and other nuclear facilities vulnerable to terrorist attacks? Is anything being done to protect them?

A19. Short Answer:
Security has always been a vital consideration in nuclear plant design and operation, but since the terrorist attacks of 11 September 2001, security at nuclear plants has become a major focus for governments and concerned international organizations such as the IAEA. Good progress has been made in ensuring better nuclear security. While much remains to be done, nuclear installations around the world have strengthened security forces, added protective barriers, limited access to sensitive information and taken other measures commensurate with the current security risks. Read more…

Explanation:
Recent terrorist attacks in Tanzania, the USA, Saudi Arabia, Indonesia, Spain and other countries have led to a re-evaluation of security in every industrial sector, including nuclear power. Nuclear security activities have greatly expanded in scope and volume. New scenarios of security threats have been identified and the vulnerabilities are being reduced.

The risks of terror at nuclear power plants have been in the spotlight, but several features of nuclear power plants that protect them against external events, such as external explosions or airplane crashes, may also help to protect them against terrorist attacks.

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IV. Radiation Safety, Wastes and Transport

20. The spent fuel and high-level waste from nuclear plants is very dangerous, but no country has a complete plan for how to permanently deal with this waste. Shouldn´t this problem be addressed before any new nuclear plants are built?

A20. Short Answer:
The total amount of civilian high-level nuclear wastes is relatively small. Up to now, all of these wastes from the decades of operation of the more than 440 nuclear power plants are completely kept in intermediate repositories. There is a broad scientific consensus that deep geological disposal, using a system of engineering and natural barriers to isolate the wastes, is the preferred method for their permanent disposal.

However, up to now, no such system has been constructed. The technical means for final disposal of these wastes are readily available, and political factors have been the principal cause for delays in the implementation of such solutions.

In order to be able to fund the proper dispose of the wastes in the future, the cost of final disposal is taken into consideration in most countries as part of the cost of the electricity produced. However, this represents only a small fraction of the total cost. This approach demonstrates the responsible care being taken with respect to future generations, since environmental costs are being borne by those who enjoy the benefits of the operation of the nuclear power plants. Incorporation of external costs into the price of electricity is a unique feature of the nuclear industry. Read more…

Explanation:
There are two types of categories of radioactive wastes: Low and intermediate-level wastes (L/ILW); and High level wastes (HLW).

Low-level wastes are produced by numerous applications of nuclear activities in industry, medicine, research, and by nuclear power plants. Disposal of low-level wastes in near surface or shallow burial is used widely. Intermediate level wastes are produced by the operation of nuclear power plants. Such wastes may include resins from water cleanup or solidified chemical sludge as well as pieces of contaminated equipment. Disposal options are similar to those for low level wastes, but the radioactive content requires shielding during transportation and handling.

The high level waste arises from the reprocessing of spent fuel from nuclear power plants or the spent fuel itself in countries where no reprocessing is been carried out. They are placed in interim storage at plant sites or at reprocessing facilities, before an eventual final disposal in a geological repository. The liquid high-level wastes from reprocessing are immobilised in a stable matrix (e.g. borosilicate glass) before final disposal.

Several countries are evaluating the available options for final disposal. Finland has already taken a “decision in principle” to construct a geological repository in a site close to a nuclear power plant. The site is now into detailed evaluation and the detailed design is under development. Other countries, such as Sweden, France and United States, are at different stages of this process.

To better comprehend the magnitude of the waste issue one can note that the spent fuel produced from all the world´s reactors in a year, even without reprocessing, would fit in a structure the size of a soccer field with a depth of 1.5 m. When the actual amount of spent nuclear fuel produced globally every year (12 000 tonnes) is contrasted with the 25 billion tonnes of carbon waste released directly into the atmosphere every year from fossil fuels, the amount of nuclear waste seems relatively small.

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21. Accidents involving radiation sources used in medicine or industry can occur in countries without the adequate infrastructure to cope with the consequences. What is being done to avoid these types of tragedies?

A21. Short Answer:
The IAEA recommends that the appropriate infrastructure, both legal and technical, should be established in any country dealing with nuclear energy, even if only with small radiation sources. And the IAEA is assisting many developing countries in establishing such an infrastructure through its Technical Cooperation Program. In the event of a radiological emergency, the IAEA is ready to assist, upon request, and has assisted any country that is in urgent need. Read more…

Explanation:
The IAEA has established an Incident and Emergency Centre that receives requests and coordinates the provision of assistance to Member States in the case of a nuclear or radiological emergency.

These services have been used several times, in recent years, for events related to loss of radiation sources, finding of abandoned “orphaned” sources, and overexposures of individual workers and medical patients.

With the help of organizations and personnel from more developed countries, the IAEA has been able to coordinate such emergency assistance. This has included providing support in regaining control of the situation, evaluating the doses to affected personnel, evaluating the possible measures to be taken and providing medical treatment, when necessary.

Once an emergency is under control, an IAEA technical report has usually been prepared both to keep an historic account of the facts and to share the lessons learned with the international community. The final aim is to avoid similar events in the future.

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22. There is a large volume of radioactive material being transported in Europe and around the world. What are the risks for the other vehicles and the population that come close to these materials?

A22. Short Answer:
Experience has demonstrated that the risk involved in the transportation of radioactive material is very low; much lower than the risks associated with the transport of other dangerous goods. With more than twenty million shipments made every year, no major accident has occurred in which radiation was spread to the environment or posed some risk to the population or the workforce. The few cases of injuries were due to mechanical factors associated with the accident rather than from the radioactive nature of the shipment. Read more…

Explanation:
Transportation of radioactive materials is only a small fraction (less than 2%) of all dangerous goods transported every year. And those are already a minor fraction (less than 0.02%) of all shipments. Since 1961, the IAEA has developed Regulations for the Safety Transport of Radioactive Materials (Requirements-TS-R-1), which has been consistently revised and updated (2 year cycle). These regulations have been adopted, essentially, by all countries and by regional and international transport organisations. The adoption has been either directly or by reference, and therefore, became mandatory for all international shipments by rail, air or sea transportation.

These regulations, and the additional associated guidance material developed later, are based upon two principles: i) they formulate “what” is to be achieved, rather than “how” it has to be achieved. ii) the burden of safety is put, as far as practicable, upon the packing that contains the radioactive material by a safe design containing multiple barriers – and the limitation of the transported quantities, not on the carrier or their procedures.

The first principle relies on designers, fabricators and users to demonstrate that the packages satisfy the regulatory standards. The second principle minimises the contribution to safety by the carrier, but does not remove from the carrier or the transport workers the responsibility to treat radioactive material consignments with the requirements of the regulations.

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