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
[email protected]
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,
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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
b
USSR
UK
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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].
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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].
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108.5
Table 1: Selected international actions and activities of the IAEA and the EU taken after
the Chernobyl accident
IAEAa
Conventions
Reviews
Services
databases
actions
EU emergency
legislation
Research and other
programmes and the
results
Services
Action
Convention on Early Notification of a Nuclear Accident
Convention on Assistance in the Case of Nuclear Accident or
Radiological Emergency
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)
Emergency Preparedness Review (EPREV)
Integrated Regulatory Review Service (IRRS)
Response and Assistance Network (RANET)
IAEA Unified System for Incidents and Emergencies (USIE)b
Inter-Agency Committee on Radiological and Nuclear Emergencies
(IACRNE)
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
emergency
“Post-Chernobyl” legislation related to a contamination of agriculture
products originated from the accidentc
“Future accident” legislation, also called “sleeping legislation”
containing maximum levels of radioactive contamination of
foodstuffs and of feedingstuffsd
Basic Safety Standard Directive 96/29/EURATOM, Title IX
Intervention
European approach to nuclear and radiological emergency
management and rehabilitation strategies (EURANOS)
Medical Effectiveness of Iodine Prophylaxis in a Nuclear Emergency
Situation and Overview of European Practices
European Community Urgent Radiological Information Exchange
(ECURIE)
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.
The system replaced ENAC in 2011.
c
Control will expire on 31 March 2020.
d
Legislation was put in force in a course of the Fukushima accident in 2011.
b
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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
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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.
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Proceedings of the International Conference Nuclear Energy for New Europe, Bovec, Slovenia, Sept. 12-15, 2011