Lessons Learnt after the Chernobyl Accident 25 Years Later

Transcription

1 Lessons Learnt after the Chernobyl Accident 25 Years Later Helena Janžekovič Slovenian Nuclear Safety Administration P.O. Box 5759, Železna cesta 16 SI-1001, Ljubljana, Slovenia ABSTRACT The Chernobyl accident in 1986 provided numerous lessons learnt regarding emergency preparedness on and off the nuclear sites as well as regarding the international cooperation in the nuclear or radiological accident. Many initiatives were started including the Convention on Early Notification of a Nuclear Accident and the Convention on Assistance in the Case of Nuclear Accident or Radiological Emergency. On the European and IAEA levels 24-hour onduty services are available in order to exchange information in case of an emergency. Safety standards were set for nuclear industry and for regulators. In many countries the role of the regulators was strengthened after the accident, in others it was established as a consequence of lessons learnt from the Chernobyl accident. Furthermore, the accident influenced many areas of nuclear industry including the re-evaluation of design of some systems in NPPs as well as operational exchange programmes. Specific research programmes started in connection to emergency preparedness and the evaluation of design and operation of nuclear facilities. Nevertheless, the Fukushima accident in 2011 revealed that many more lessons are going to be learnt by international organisations, nuclear industry, nuclear safety regulators, research institutions, technical support organisations and others involved in nuclear safety. The main lessons learnt are related to low probability of events beyond design basis accidents, e.g. flooding, severe accident management for single or more units, emergency preparedness including monitoring capabilities during severe accidents, availability of capable staff during such an accident, international cooperation regarding knowledge management and capabilities of personnel and equipment in case of a severe accident. In addition, the Fukushima accident also revealed that regulatory control as required by the IAEA standards is one of the cornerstones of nuclear safety. 1 INTRODUCTION The most severe nuclear accident before 2011 was the accident in Chernobyl that occurred in April 1986 at the Chernobyl NPP Unit 4 in Ukraine, at that time the Ukrainian SSR. The releases from the RMBK NPP, where the nuclear reactor was destroyed by an explosion lasted for 10 days. The legacy of the Chernobyl accident is still a subject of intensive studies. The accident resulted in around 50 deaths till 2011 due to workers direct involvement in the accident or in recovery operations. Around 6000 thyroid child cancers were diagnosed. In addition, the international organisations estimated that around 4000 people would die due to cancer caused by the discharges from the Chernobyl accident. Furthermore, the accident also resulted in contamination of land, especially on the territory of Ukraine, 108.1

2 108.2 Belarus and Russia. Owing to today s scientific and technical development, some parts of that area will have restricted use for more than ten thousand years. As a result around 0.5 million of people were resettled in the years that followed. The accident not only affected people in the above-mentioned states, but also influenced daily living in other countries, especially in Europe. For example people in Poland had to undergo iodine prophylaxes and the contamination of Europe influenced strict control or even prohibition of some food and drinking water in the first days after the accidents. Control of contamination of some food was in place for decades, even today. Other parts of the world, e.g. Asia, were not affected. The accident did not initiate only contamination control of people and the environment related to discharges, and required comprehensive remediation actions, but also influenced other domains, mainly the development of different fields of nuclear safety. The Chernobyl accident also resulted in some drastic changes in the implementation of nuclear technology. Some countries decided not to implement this technology in the energy sector. The lessons learnt from the Chernobyl accident are connected with many stakeholders, e.g. designers of NPPs, operators and subcontractors, licensing and inspection bodies, technical support organisations and research institutions, training centres, electrical companies and distributors, emergency preparedness units, emergency teams, recovery operation teams, monitoring units, waste management units and international bodies. The accident also resulted in the establishment of close collaboration among countries in order to use a harmonised approach in nuclear accidents. For example bilateral agreements between countries were signed, systematic monitoring of contamination of environment started and future accidents directives in the European Union (EU) were published. Nevertheless, it should be emphasised that the accident also played a role in political changes in the USSR and some European countries that followed a few years after the Chernobyl accident. After the Fukushima accident which started on March 11, 2011 it is not possible to analyse the effect of the Chernobyl accident on nuclear safety in isolation of events, which are still going on in Japan at the time of writing. Nevertheless, the Chernobyl and the Three Mile Island (TMI) accidents were one of the milestones in developing nuclear safety standards. Figure 1 presents the selected milestones related to the development of nuclear industry as well as the main milestones in the development of nuclear safety standards after World War II, starting with the operation of the first NPP, namely the Obninsk NPP. Namely, three international organisations were established in the sixties, i.e. EURATOM, IAEA and OECD NEA all of them with different missions, but with an aim to better understanding of challenges posed by safe use of nuclear power and technologies. a USSR b UK

3 108.3 Figure 1: Selected milestones related to the development of nuclear industry as well as the main nuclear accidents. 2 LESSONS LEARNT The fundamental changes based on the lessons learnt regarding nuclear safety can be categorised based on the roles of four stakeholders, i.e. 1. nuclear industry all over the word 2. international organisations dealing with nuclear safety 3. national regulators of nuclear safety 4. USSR where the accident took place. 2.1 Chernobyl Accident Lessons Learnt and Nuclear Industry After the Chernobyl accident nuclear industry did not expand as expected before the accident. Namely, some countries prohibited the operation of NPPs as for example Italy, some stopped the announced nuclear projects, e.g. Poland, USA. Nevertheless, nuclear industry which is based on fundamental nuclear research was considered only partly global industry at the time of the Chernobyl accident. Actually, also nuclear research was still very much linked to the limited interests of states or group of states. As a result, very different lessons learnt from the accident were taken by nuclear industry and nuclear research. Namely, in Europe, America and Africa the majority of countries decided to re-evaluate the need for nuclear energy and as a result such re-evaluation very strongly inhibited prosperity of nuclear industry and nuclear research as a whole. This re-evaluation had in some states a fundamental impact on the nuclear research management, which was actually in many countries very supported by governments before the accident, e.g. research institutions acted as technical support organisations. As a result nuclear industry was also influenced by the shrinkage of the state support. In the last years, just before the Fukushima accident, changes were evident in the part of the world mentioned before. The so-called nuclear renaissance took place by starting new builds in that part of the world, e.g. in Finland and France, while some countries announced building new NPPs, e.g. Turkey. At that time the IAEA also reported that a lot of countries, i.e. around 30 countries announced their plans on building an NPP for the first time. On the other hand, countries very distant from the Chernobyl site, i.e. countries in Asia, were not influenced by contamination of Chernobyl releases meaning that nuclear industry and nuclear research did not suffer from substantial negative effects. As a result they continue building their nuclear infrastructure, e.g. Japan. Simultaneously nuclear industry which encountered substantial obstacles in Europe and America did not face substantial changes in countries far away from the Chernobyl site. The countries involved also tried to develope independence from other parts of the world, e.g. South Korea. Nevertheless, nuclear industry all over the world carefully studied the lessons from the Chernobyl and the TMI accidents. The improvements comprised the: 1. design of NPP systems 2. operation of a NPPs including emergency preparedness. The lessons learnt are related to three major directions regarding the design of NPPs, namely: a. simplification of the design and using passive systems for safety related systems as for example given in[1] b. multiplication of safety systems or related systems given for example in [2] c. small modular reactors which pose limited risk [3].

4 108.4 Concerning lessons learnt taken by operators ona of the major step forward was the establishment of the WANO [4]. The organisation enabled NPP operators to communicate on experiences related to the operation of NPPs, including appraisals of operation of an NPP conducted by WANO experts. The open data regarding WANO activities linked to particular NPP are scarce. Nevertheless, its role to improve of safety in NPPs is not challenged. At present there are no systematic open data on influence of waste management and decommissioning activities taken after the Chernobyl accident on nuclear industry. 2.2 International Organisations after the Chernobyl Accident The Chernobyl accident influenced very much the activities of IAEA, OECD/NEA and EU as well as other international organisations, e.g. ICRP, UNSCEAR, WHO, mainly related to the following four areas: a. harmonisation of emergency preparedness and safety standards to protect people and the environment in case of nuclear or radiological emergency b. enhancement of regulatory control based on national regulatory authorities c. supporting fundamental research and knowledge management needed to support nuclear safety d. harmonisation of safety standards used by all stakeholder in nuclear activities. The international organisations promptly identified a lack of cooperation regarding the information exchange during nuclear and radiological emergency. As a result many activities took place in the emergency preparedness area in the decades following the accident. Table 1 shows a list of selected initiatives related to emergency preparedness, which were initiated by the IAEA or OECD/NEA. One of the first initiatives was the Convention on Early Notification of a Nuclear Accident from September 1986, based on the experiences from the Chernobyl accident. It was followed by the Convention on Assistance in the Case of Nuclear Accident or Radiological Emergency two months later. The IAEA also established the International Nuclear and Radiological Event Scale (INES) in order to communicate to the general public in case of nuclear emergency. For completeness selected initiatives within the EU are also given in Table 1. Some important nuclear safety initiatives in the last years should be mentioned, e.g. publication of the nuclear safety directive from 2009 or radioactive waste and spent fuel management directive from 2011 are not added, because the Chernobyl accident was not the main cause for the preparation of such initiatives within the EU. It should be stressed that many other organisations started the programmes related to lessons learnt after the Chernobyl accident. For example the UNSCEAR regularly publishes documents related to contamination after the Chernobyl accident and risks associated with it as for example given in [5]. The ICRP also published a set of documents regarding emergency preparedness including stakeholder s involvement in areas where long term contamination is expected [6]. The OECD/NEA conducts INEX exercises [7].

5 108.5 Table 1: Selected international actions and activities of the IAEA and the EU taken after the Chernobyl accident IAEA a Action Convention on Early Notification of a Nuclear Accident Convention on Assistance in the Case of Nuclear Accident or Radiological Emergency Conventions Convention on Nuclear Safety Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management Convention on Supplementary Compensation for Nuclear Damage Operational Safety Review Team (OSART) Reviews Emergency Preparedness Review (EPREV) Integrated Regulatory Review Service (IRRS) Response and Assistance Network (RANET) IAEA Unified System for Incidents and Emergencies (USIE) b Services Inter-Agency Committee on Radiological and Nuclear Emergencies databases (IACRNE) actions Nuclear Events Web-based System (NEWS) International Nuclear and Radiological Event Scale (INES) International Reporting System for Operating Experience (IRS) Convention Exercise (ConvEx) EU Action Council Directive 89/618 on informing the general public about heath protection measures to be applied and steps to be taken in the event of radiological emergency (1989) Council Decision of 14 December 1987 on Community arrangements for the early exchange of information in the event of a radiological EU emergency emergency legislation Post-Chernobyl legislation related to a contamination of agriculture products originated from the accident c Future accident legislation, also called sleeping legislation containing maximum levels of radioactive contamination of foodstuffs and of feedingstuffs d Basic Safety Standard Directive 96/29/EURATOM, Title IX Intervention Research and other European approach to nuclear and radiological emergency programmes and the management and rehabilitation strategies (EURANOS) results Medical Effectiveness of Iodine Prophylaxis in a Nuclear Emergency Situation and Overview of European Practices European Community Urgent Radiological Information Exchange (ECURIE) Services European Radiological Data Exchange (EURDEP) European Clearing House for NPP Operational Safety Feedback (2010) a IAEA together with other organisations e.g. OECD/NEA, WHO, WMO, ICAO. b The system replaced ENAC in c Control will expire on 31 March d Legislation was put in force in a course of the Fukushima accident in 2011.

6 108.6 Analysing the activities taken it is evident that international organisations very soon after the Chernobyl accident learnt that information exchange in the course of an accident requires specific services in due time. In addition, they also learnt that emergency preparedness requires not only information exchange but all countermeasures and standards, e.g. reference levels for contamination of food, used in case of emergency, should be known in advance. In addition, exercises are necessary in order to be able to act in an emergency situation and to assure capable and available teams on and off site of a nuclear facility during and after the course of an accident. Furthermore, the exercises should include the general public. Informing the population at risk in the vicinity of a nuclear facility well before an accident has occurred is necessary. Furthermore, the accident revealed that safety standards for all phases of the design and operation of nuclear facility should be prepared taking into account: - strict design requirements and defence in depth - probability for beyond design basis accident - human errors. 2.3 Nuclear Safety Regulations after the Chernobyl Accident The Chernobyl accident initiated the establishment of many national regulators, especially in countries with NPPs. Taking into account that nuclear safety is an interdisciplinary field and considering the regulatory framework of different countries, based also on historical ground, no harmonised approach is used. Nevertheless, two fundamental characteristics are given in the IAEA documents as a prerequisite for an effective and efficient work. Namely, independence and knowledge of staff performing a job. 2.4 Influence of the Chernobyl Accident on the USSR No international agreed document regarding the overall influence of the accident on the USSR and nuclear industry of the USSR is available, although many authors were challenged as for example [8]. While the influence of the accident on political changes is not a subject of this article, it can be concluded that the accident initiated many changes regarding nuclear safety in the state. At least five main lessons learnt are identified. 1. Re-evaluation of RMBK safety issues took place and many improvements were initiated regarding its safety. 2. The operator as well as nuclear industry realised that this industry is always a global industry. 3. The state realised that the implementation of international standards is necessary. These standards are related to actions of the nuclear industry and to activities performed within regulatory bodies. 4. The state also realized that cooperation of nuclear and regulatory stakeholders with international community is necessary. 5. The operators and regulators identified that stakeholders involvement before, during and after the emergency phase is crucial for nuclear safety. 3 CONCLUSIONS The Chernobyl accident meant a huge initiative for the development of nuclear safety. Different institutions involved took many lessons learnt from the accident in the decades that followed. Different nuclear safety areas were developed based on the understanding of the course of the accident. Nevertheless taking into account the results of the IAEA Ministerial Conference on Nuclear Safety in June 2011 [9] many more lessons are going to be learnt by

7 108.7 international organisation, nuclear industry, nuclear safety regulators, research institutions, technical support organisations and others involved in nuclear safety. The main lessons learnt are related to: - improvement of knowledge about low probability beyond design basis accidents, e.g. flooding - severe accident management for single or more units, - emergency preparedness including monitoring capabilities during severe accidents and availability of capable staff during such accidents, - international cooperation regarding knowledge management and capabilities of personnel and equipment in case of a severe accident - appropriate regulatory control. REFERENCES [1] W.E. Cummins, M.M. Corletti, T.L. Schulz, Westinghouse AP1000 Advanced Passive Plant, Int. Conf. ICAPP, Cordoba, Spain, May 4-7, 2003, available at eactor.pdf. [2] AREVA, official web site available at [3] A. Lokhov, R. Cameron, V, Kuznetsov, Current Status and Economics of Small Nuclear Reactors, NEA New, No. 29.1, OECD/NEA, Paris, 2011, pp [4] WANO, official web site available at, [5] United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Effects of Ionising Radiation, UNSCEAR 2008, Vol. II, Annex D, UN, New York, [6] International Commission on Radiological Protection, Annals of the ICRP 111, Application of the Commission s Recommendations to the Protection of People Living in Long-term contaminated Areas after a Nuclear Accident or a Radiation Emergency, ICRP Publication 111, ICRP, Elsevier, [7] OECD/NEA, official web site available at INEX [8] Z. Medvedev, The Legacy of Chernobyl, W.W. Norton, Company, New York, London, [9] IAEA, Chairperson s Summaries, Ministerial Conference on Nuclear Safety, Vienna, Austria, June 20-24, 2011, IAEA, available at