The causes and consequences of the Chernobyl nuclear accident and implications for the regulation of U.S. nuclear power plants

As in the case of the TMI accident public concern around the world over nuclear safety has been aroused by the Chernobyl nuclear accident. Because of its severity and enormous impact on public opinion, it is important to study the accident and its implications carefully and to provide accurate information to the public.Since this was the first nuclear accident with large offsite releases of radionuclides, valuable insights are to be gained especially, for example, from Soviet actions to terminate the accident and mitigate its consequences, emergency preparedness and evacuation measures, medical treatment, protection against contaminated food and water supplies, and a variety of post-accident recovery measures.With the perspective of a year since the accident and a recent visit by the Author to Chernobyl with a U.S. nuclear safety delegation this paper reviews a number of new studies to draw conclusions about the causes of the Chernobyl accident, its health and environmental consequences and some of the implications for regulation of the safety of U.S. nuclear power plants.     

Contributing to the nuclear 3S's via a methodology aiming at enhancing the synergies between nuclear security and safety

Nuclear safety, nuclear security and nuclear safeguards regimes have not historically developed at the same pace and surely have not reached the same level of maturity. Nevertheless, these aspects are of special relevance in the current global nuclear energy context when considering the numerous countries that have and will have the legitimate ambition to start a nuclear energy production programme without any or scarce previous nuclear safety, security and safeguards cultures.The future development of nuclear energy exploitation will depend more and more on the convergence of decisions from governments, from the nuclear industry, from utilities, from private and institutional investors as well as from the level of acceptance by the public opinion.Following an in-depth state-of-the-art analysis and literature search, a methodological approach focussed on the safety and security connections is presented, as it seems a field where more commonalities and operational aspects could be possibly found and exploited.     

Inherently safe containments for nuclear power plants

Nuclear energy cannot be avoided in the near future. To regain public acceptance the safety of nuclear power plants has to be increased. Consequently, feasibility studies have been carried out for a containment proposal for future pressurized water reactors which will keep people unharmed even in the case of severe nuclear accidents under the assumption “all that can go wrong, will go wrong”. The main features of the design concept are a core melt cooling and retention device, a passively acting cooling system to remove the decay heat and a double-wall containment which is able to withstand high static and dynamic internal pressures due to hydrogen detonation. Internal structures are designed to resist extreme loadings resulting from various accident scenarios including in-vessel steam explosion and vessel failure under high system pressure.     

The impact of TMI upon the public acceptance of nuclear power

This paper discusses long-term trends in public attitudes toward nuclear power, focusing on the extent to which the accident at Three Mile Island appears to have affected public acceptance of nuclear energy. Public attitudes towards other energy production options also are considered, particularly in terms of changes that may be related to TMI. Finally, the relationships between attitudes toward nuclear power and perceptions of broader energy, environmental and social issues are examined. The data used in this analysis are from national surveys conducted by major national opinion research organizations from the early 1970s through 1981.

There is considerable evidence that TMI has had a significant impact on public acceptance of nuclear power, in the direction of increasing opposition to and decreasing support for construction of new nuclear power plants. TMI appears to have increased the rates of decline in support and rise in opposition to local construction of nuclear power plants, although a trend of decreasing public acceptance of such local construction had been in evidence since the mid-1970s, prior to TMI. In spite of this decline in public acceptance of new construction, there is substantial support for both completing nuclear power plants currently under construction and for the continued operation of existing plants.     

国外核潜艇反应堆系统事故浅析

本文针对国外已发生的核潜艇反应堆系统事故进行了梳理分析研究,发现国外核潜艇反应堆系统事故多发生于早期型号,近年各国在役及新一代核潜艇未出现反应堆系统发生事故的报道。此外,还发现各国已发生的核潜艇反应堆系统事故中,失水事故和反应性事故所占比例最大。本文研究表明,通过先进核安全方法及技术的采用、核安全文化的重视、核安全监管力度的加强,反应堆系统事故可不会给核潜艇带来额外的事故风险,核反应堆及核安全能够不成为制约核潜艇发展的主要因素。     

Use of PRA and safety goals in nuclear power plant regulation

Probabilistic risk assessments (PRAs) have been performed on a number of nuclear power plants, both by the NRC and industry. The NRC has used risk perspectives gained from PRAs, both in an absolute as well as a relative sense, as an aid in making decisions on plant-specific as well as generic safety issues. However, substantial uncertainties pervade present-day risk assessments, which makes the application of the results of such analyses difficult at best in the regulation of nuclear power. Nonetheless, the Commission approved in January 1983 a policy statement on safety goals for public comment and a two year evaluation period. These safety goals include quantitative design objectives which could serve in the future as risk benchmarks for use by the NRC as part of the decision making process on matters relating to nuclear safety. While the Commission's policy statement explicitly excludes the safety goals from use both in licensing cases and in regulation for the two year evaluation period, PRA will be used generically and on a plant-specific basis more and more to assess the importance of new safety issues, prioritize resources within the agency, and test the adequacy of (or in some instances the need for) NRC's regulations.     

Meeting the energy challenge for the environment: The role of safety

Nuclear power has an overwhelming potential to meet the demands of an energy hungry world while protecting the environment. However, the renaissance of nuclear energy will only become true when the public can be convinced that nuclear power plants are safe and that a strong safety culture exists around the globe. While the overall safety performance of the world's power plants had been steadily improved after the shock of Chernobyl, unfortunately, the overall plant availability has levelled off in the last few years. The main reason for this is found in a complacency toward nuclear safety issues which can be linked to the arrival of new CEOs in the nuclear industry who – all too often – have no nuclear background and who manage nuclear power plants in the same way they would manage any other industrial plants – being not at all aware of the necessity of a very special and very sensitive safety culture of nuclear installations.     

Post-chernobyl period at the Kursk Nuclear Power Plant: Advances and prospects

Conclusion The accident at the Chernobyl nuclear power plant reverberated throughout the world of nuclear power, mainly at nuclear power plants with RBMKs. We feel that this article in some measure will convince both specialists and nonspecialists to have a more objective few both of current safety levels and the prospects of future improvements. Kursk Nuclear Power Plant. Translated from Atomnaya énergiya, Vol. 83, No. 2, pp. 79–94, August, 1997. Journal version.     

日本提高核能公众接受度的工作研究

2011年3月,日本福岛核事故的发生在全世界引起了一场“反核”风暴。分析原因得知,公众对核电信任的丧失直接导致了对核能接受度的下降。相关信息的公开透明以及与民众展开积极的沟通、促进公众参与,已成为提高公众对核电信任的决定性因素。为了提高福岛核事故后公众的信任,日本做了很大的努力。调研了福岛核事故后,日本在信息公开、公众参与、公众沟通方面所做的工作,分析了我国在核能信息公开、公众参与的问题,并对我国如何提高核能公众接受度提出了建议。2011年3月,日本福岛核事故的发生在全世界引起了一场“反核”风暴。分析原因得知,公众对核电信任的丧失直接导致了对核能接受度的下降。相关信息的公开透明以及与民众展开积极的沟通、促进公众参与,已成为提高公众对核电信任的决定性因素。为了提高福岛核事故后公众的信任,日本做了很大的努力。调研了福岛核事故后,日本在信息公开、公众参与、公众沟通方面所做的工作,分析了我国在核能信息公开、公众参与的问题,并对我国如何提高核能公众接受度提出了建议。     

Regulatory policies and the future of nuclear power

This paper reviews some of the national policies and regulatory decisions that have the potential to affect the production of electricity from nuclear power. It is shown that many policies and regulatory initiatives are introduced to meet objectives other than determining the mix of electricity supply resources, such as reducing the cost of electricity or protecting public health and safety. Nevertheless, such policies and requirements can have a substantial effect on the competitiveness of present nuclear power plants, as well as on prospects for future nuclear power plants. Because electricity from nuclear power can substitute for electricity from fossil fuels, policies and regulations which affect the competitiveness of nuclear power can have an effect of the production of carbon emissions, and therefore can compete with, or complement, national environmental objectives.     

Safety experience on EDF's PWRs

Following a brief presentation of the safety organization in France and of the safety implications of the standardization policy adopted for the PWRs programme, the paper will review the safety experience acquired in France on this programme.The prevention of severe accidents following Three Mile Island in 1979 was considered a first priority in the French safety approach. EDF has developed an ultimate procedure based on the characterization of every possible cooling state of the core which allows the operators to prevent severe core degradation. Ultimate safety features, such as filtered-venting of the containment's atmosphere, aim at mitigating the consequences for the environment of any core melt accident.Today our first objective is to keep the highest possible level of safety in operation. The first issue is personnel training. Due to the complexity of nuclear power plants, the human factor plays a significant role in all incidents and accidents. We have learnt the importance of specific training for accidental situations, making use of sophisticated simulators. The second issue is operational experience feedback. The system set up by EDF will be described.Although not all data relative to the Chernobyl accident are known, the lessons learnt from that very important event will be described, as used to improve the safety of French nuclear power plants, especially on radioactive accidents' management.     

Basic ideas of a philosophy to protect nuclear plants against shock waves related to chemical reactions

There is an increasing trend to build nuclear plants, especially nuclear power plants, within the vicinity of industry (particularly chemical plants), transport ways (streets, railroads, river) and cities. This is linked to the danger for the population in this region due to an accident in connection with explosive material. Such accidents can influence the safety of the nuclear power plant, too. To avoid risks, even in cases in which such risks are not evident at the moment, appropriate safeguarding provisions have to be taken. With respect to future developments, on one side this can be done by designing the installations to withstand the loading which is caused by explosions, on the other side this can be done by defining exclusion regions around nuclear power plants within which no storage of explosive materials or transportation that is connected with high risk is allowed.The gaseous hydrocarbons (under normal conditions) - stored in a fluid state by means of pressure or deep cooling - are considered as being particularly dangerous. By theoretical considerations a load-function has been derived to describe the effect of an imaginable accident. This pressure-time diagram was deduced from the assumption that an explosion of a gas cloud would occur only in the form of a deflagration. In the case of saturated hydrocarbons this assumption is correct with a high degree of probability. On the other side, it is possible to get higher loadings after accidents in connection with unsaturated hydrocarbons. Owing to the present lack of knowledge, it is very difficult, or nearly impossible, to evaluate a pressure-time diagram for this case.A conservative and therefore safe assessment is possible if the detonation as thinkable form of an explosion is taken into account. The possibility of this form of reaction has been shown in experiments, though there have been idealized conditions, as homogeneous stoichiometric mixture in spherical shells and detonative ignition. Quasi-static pressures up to 20 bar have been measured in these experiments. It seems unrealistic to design buildings of nuclear power plants to withstand such loadings. Therefore, distances from the nuclear power plant have been calculated, in which a detonation may occur without generating a higher loading than that evaluated for the deflagration of a gas cloud. The assumptions and models to evaluate the pressure-time function in the case of deflagration and the safety distances in the case of detonation will be discussed.     

Consequence analysis for nuclear reactors,Yongbyon

Since the Fukushima nuclear power plant accidents in 2011, there have been an increased public anxiety about the safety of nuclear power plants in Korea. The lack of safeguards and facility aging issues at the Yongbyon nuclear facilities have increased doubts. In this study, the consequence analysis for the 5-MWe graphite-moderated reactor in North Korea was performed. Various accident scenarios including accidents at the interim spent fuel pool in the 5-MWe reactor have been developed and evaluated quantitatively. Since data on the design and safety system of nuclear facilities are currently insufficient, the release fractions were set by applying the alternative source terms made for utilization in the analysis of a severe accident by integrating the results of studies of severe accidents occurred before. The calculation results show the early fatality zero deaths and latent cancer fatality about only 13 deaths in Seoul. Thus, actual impacts of a radiological release will be psychological in terms of downwind perceptions and anxiety on the part of potentially exposed populations. Even considering the simultaneous accident occurrence in both 5-MWe graphite-moderated reactor and 100-MWt light water reactor, the consequence analysis using the MACCS2 code shows no significant damage to people in South Korea.     

On the application of probabilistic risk assessment to reactors with inherently safe features

In this paper, it is shown that because of the public perception of the risk of nuclear power and the likelihood that in the event of a severe core damage accident in a reactor claimed to have a high degree of inherent safety, it is necessary to reconsider the basis for establishing safety objectives. It is shown that, if there were a large program of inherently safe reactors, the safety objectives would be determined more by investment risk than by the public health risk. These considerations lead to an objective on the order of 1 × 10⁻⁷ per r.yr (reactor year) for the probabability of a severe core damage accident. It is also shown that the introduction of inherently safe features leads to a considerable change in the allocation of the safety goal between the major safety functions. For these reactors, a major portion of the allocation shifts from the decay heat removal function to the scram function, with emphasis on insuring the integrity of critical structures.     

核电站严重事故后果概率安全评价方法研究

核电站严重事故后果概率安全评价(PSA)是采用概率论的方法对核电站放射性后果进行分析,并定量给出放射性物质对核电站周围公众的健康效应影响。以国内某压水堆核电站为参考厂址,建立合适的场外后果分析模型。采用分层抽样方法对参考厂址1a的气象数据进行抽样,源项和释放特征等数据取自二级PSA的研究结果。利用事故后果评价程序对核电站严重事故后果进行计算,并用概率论方法对结果进行评估。通过计算将各事故和事故谱的场外个人剂量表示为CCDF曲线和总频率-剂量曲线,再用概率论方法得到不同距离处个人剂量超过指定剂量的条件概率;也可用此方法对确定烟羽应急计划区的安全准则中所描述的"大多数严重事故序列"进行量化。     

Advancing US public acceptance of spent fuel storage and transport: proposed outreach services for ionising radiation education support

Abstract

Expansion of commercial nuclear energy could be one of the future US sources for clean, safe, reliable and economic electricity. However, no federal policy has effectively achieved wide acceptance of nuclear energy, with such policies having fallen victim to the politics of public radiation fears from nuclear energy usage and from spent fuel storage and transport. Many experts have described the foundation of public fear as not so much nuclear technology, but the ionising radiation to which people fear they might be exposed, and this issue has been talked and written about, yet gone substantially unaddressed with respect to public education for more than three decades. In the USA, the Blue Ribbon Commission Final Report is just the latest of clear statements where such an educational need is firmly asserted. The lamentable fact is that no one has made that substantive and concerted effort to do anything about it. Indeed, the only effort seems to have been talk about ‘better communication’, with a focus on risk based communication. Any rejuvenation of public acceptance of commercial nuclear energy in the USA, including spent fuel storage and transport, can only be sustained using a different strategy from that of earlier decades. This paper highlights professional opinion on the radiation fear issue and why current industry efforts in risk based information for and communication with the public have not achieved the desired success. Education to expand the public’s understanding of comparative radiation sources and exposures while ameliorating concern about radiation from nuclear energy is the proposed alternative. In addition, here, the clear linkage between education supporting nuclear energy and facilitating necessary spent fuel storage and transport is unmistakable. The paper summarises a concept for outreach services for ionising radiation education support for application in the US, as well as key elements of such a process: its basis for success, its education content and potential implementation approaches. Comparative radiation education of the public can prove effective using current research, which has been effective in other industries. Additionally, while this discussion addresses the US situation, much of the content is likely applicable to many of the world’s nuclear energy producing countries.     

Loose-parts monitoring: Present status of the technology, its implementation in U.S. reactors, and some recommendations for achieving improved performance

At the request of the U.S. Nuclear Regulatory Commission (NRC), an assessment of the technical development status of loose-parts monitoring systems (LPMS) and their performance record to date in commercial light-water-cooled nuclear reactor plants was made during the spring of 1977, using an on-site personal interview and equipment demonstration approach. Our study revealed that while presently demonstrated LPMS technology does indeed provide a capability for detecting the presence of those relatively massive loose parts that would likely constitute a serious operational or safety hazard to the plant, it unfortunately affords little information useful to the determination of the parts' safety significance and has not yet attained the levels of sophistication and reliability ordinarily associated with safety systems. We also found a definite need for specification of the functional requirements for LPMS, in the form of a clear and comprehensive statement of NRC policy regarding the formulation and implementation of safety-oriented, yet operationally practicable, loose-parts monitoring programs for both existing and future nuclear generating stations so that overall objectives of both the utilities and the regulatory agency might be satisfied simultaneously.

While it is our best technical judgment that loose-parts monitoring programs providing reliable detection (but not characterization) capabilities could be implemented with today's technology, the path on which the nuclear utility industry should proceed in order to meet NRC expectations is not completely clear. A Regulatory Guide entitled “Loose Part Detection Program for the Primary System of Light-Water-Cooled Reactors,” soon to be issued for public comment, constitutes a first step towards satisfying this need for guidance and goal establishment.     

Author index to volume 60

This paper summarizes the main findings of a comprehensive study of the underground siting of nuclear power plants carried out at the Swiss Federal Institute for Reactor Research. Main aim of the investigations made was to identify suitable siting variants and to evaluate the feasibility, the safety potential and the cost of the concept. Two of the layouts developed for the main siting alternatives — the rock cavity alternative and the pit siting — are briefly described. In these designs an accident mitigation system based on the pressure relief concept, meant to reduce the consequences for the public and the environment in the case of extreme hypothetical events, has been proposed and an evaluation of its performances has been made to quantify the achievable risk reduction. The safety potential — especially under accident conditions — of this type of siting and the possibility that an underground plant may be exposed to new accident initiating events have been evaluated.From the technical point of view, an underground nuclear power plant is considered feasible while the economic penalty associated with the underground siting lies between 11 and 15%, according to the considered alternative.     

严重事故下设备可用性论证要求

核动力厂应针对某些极不可能发生的严重事故进行设计已逐步成为共识,对在严重事故工况下需要保持安全功能的设备的质量要求也随之成为焦点问题,故进一步明确严重事故下设备质量要求及其验证方法和准则是落实核安全监管要求的重要组成部分。本文回顾了国内外关于核动力厂严重事故对策的发展历程,并解读了不同阶段对严重事故下所用设备的质量要求的内在含义。从我国相关核安全法规要求出发,结合我国核安全规划及远景目标,提出了严重事故下设备可用性论证的相关建议。