The accident did not affect each country in the same way and a different emphasis was placed on various aspects of the accident with particular reference to the circumstances of that country. Thus, countries remote from the accident, with no domestic nuclear power programmes or neighbouring reactors, tended to emphasise food control and information exchange as their major thrust for improvement. Whereas those countries which were contaminated by the accident, and had their own nuclear power programmes and/or reactors in neighbouring countries, drew extensive lessons from the way the accident developed and was treated. For these reasons, not all the lessons learnt were applied universally with the same emphasis.
The Chernobyl accident was one of a kind, and, although it highlighted deficiencies in emergency preparedness and radiation protection, it should not be seen as the reference accident for future emergency planning purposes (Bu91).
It was very clear from the initial reactions of the competent national authorities that they were unprepared for an accident of such magnitude and they had to make decisions, as the accident evolved, on criteria that could have been established beforehand. This also meant that too many organisations were involved in the decision making, as no clear-cut demarcations had been agreed and established. Areas of overlapping responsibility and jurisdiction needed to be clearly established prior to any accident. A permanent infrastructure needed also to be in place and maintained for any efficient implementation of protective measures. Such an infrastructure had to include rapid communications systems, intervention teams and monitoring networks. Mobile ground monitoring teams were required, as was aerial monitoring and tracking of the plume. Many countries responded to this need by establishing such monitoring networks and reorganising their emergency response.
Logistic problems associated with intervention plans, such as stable iodine distribution (Sc94, NE95a) and evacuation obviously needed to be in place and rehearsed long before the accident, as they are too complex and time-consuming to be implemented during the short time available during the evolution of the accident. Intervention actions and the levels at which they should be introduced needed to be agreed, preferably internationally, and incorporated into the emergency plans so that they could be immediately and efficiently implemented.
The accident also demonstrated the need to include the possibility of transboundary implications in the emergency plans, as it had been shown that the radionuclide release would be elevated and the dispersion of contamination more widespread. The concern, raised by the experience of Chernobyl, that any country could be affected not only by nuclear accidents occurring on its territory but also by the consequences of accidents happening abroad, stimulated the establishment of national emergency plans in several countries.
The transboundary nature of the contamination prompted the inter-national organisations to promote international cooperation and com-munication, to harmonise actions (NE88, IA94, IC90, IC92, NE93, NE89, NE90, NE89b, WH88, WH87, IA89b, IA92, IA91a, IA89c, IA87a, IA94a, EC89a, EC89b) and to develop international emergency exercises such as those organised by the NEA in its INEX Programme (NE95). A major accomplishment of the international community were the agreements reached on early notification in the event of a radiological accident and on assistance in radiological emergencies through international Conventions in the frame of the IAEA and the EC (EC87, IA86b, IA86c). In 1987, two Conventions came into effect, namely the Convention on Early Notification of a Nuclear Accident ("Early Notification Convention") and the Convention on Assistance in the Case of a Nuclear or Radiological Emergency ("Assistance Convention"). At present, 83 States are Party to the Early Notification Convention, and 79 States Parties to the Assistance Convention. In addition, the Food and Agriculture Organisation of the United Nations (FAO), the World Meteorological Organisation (WMO) and the World Health Organisation (WHO) are parties to both conventions.
Based on these two conventions, the International Atomic Energy Agency (IAEA) established a system for notification and information exchange in case of a nuclear or radiological emergency, as well as a network to provide assistance, on request, to affected countries.
The Council Decision 87/600/EURATOM of 14 December 1987 stipulated the European Community arrangements for the early exchange of information in the event of a radiological emergency. Based on this council decision, the European Commission established the European Community Urgent Radiological Information System (ECURIE) through which the EU Member States are required to notify the Commission on radiological emergencies and to promptly provide available information relevant to minimising the foreseen radiological information. The system focuses on communication and information and data exchange in case of a nuclear or radiological emergency.
Furthermore, in order to facilitate communication with the public on the severity of nuclear accidents, the International Nuclear Event Scale INES was developed by the IAEA and the NEA and is currently adopted by a large umber of countries.
The accident provided the stimulus for international agreement on food contamination moving in trade, promoted by the WHO/FAO, as there is a need to import at least some food in most countries, and governments recognised the need to assure their citizens that the food that they eat is safe. Monitoring imported food was one of the first control measures instituted and continues to be performed (FA91, EC89c, EC93a).
This event also clearly showed that all national governments, even those without nuclear power programmes, needed to develop emergency plans to address the problem of transboundary dispersion of radionuclides. Of necessity these plans had to be international in nature, involving the free and rapid exchange of information between countries.
It is essential that emergency plans are flexible. It would be foolish to plan for another accident similar to Chernobyl without any flexibility, as the only fact that one can be sure of is that the next severe accident will be different. Emergency planners need to distil the general principles applicable to various accidents and incorporate these into a generic plan.
The accident emphasised the need for public information and public pressure at the time clearly demonstrated this need. A large number of persons who are knowledgeable about techniques in providing information are needed to establish a credible source of information to the public before an accident, so that clear and simple reports can be disseminated continuously in a timely and accurate form (EC89).
Emergency plans also need to include a process by which large numbers of people could have their exposure assessed, and those with high exposures differentiated. The accident also highlighted the need for the prior identification of central specialised medical facilities with adequate transportation to treat the more highly exposed individuals.
Refinement and clarification of international advice was needed (Pa88). The recommendations for intervention in an accident contained in ICRP Publication 40 were not clearly understood when they came to be applied, and the Commission reviewed this advice in Publication 63 (IC92). This guide placed emphasis on the averted dose as the parameter against which an intervention measure should be assessed. It was also made clear that an intervention had to be "justified" in as far as it produced more good than harm, and that where a choice existed between different protection options, "optimisation" was the mechanism to determine the choice. Emphasis was also placed on the need to integrate all protective actions in an emergency plan, and not to assess each one in isolation, as one may well influence the efficacy of another.
Prior to the accident, it was felt that the flora and fauna of the environment were relatively radio-resistant and this was supported by the fact that no lethal radioecological injuries were noted after the accident except in pine forests (600 ha) and small areas of birch close to the reactor. A cumulative dose of less than 5 Gy has no gross effect even in the most sensitive flora of ecological systems, but there are still ecological lessons to be learnt especially on the siting of nuclear power reactors (Al93).
Plant foliar and root uptake is being studied, as are resuspension and weathering. The transfer coefficients at all stages of the pathways to human exposure are being refined. Following the accident, an assessment of the models used at thirteen sites to predict the movement of 131I and 137Cs from the atmosphere to food chains (Ho91) indicated that models commonly used tended to overpredict by anything up to a factor of ten. The extensive whole-body monitoring of radioactivity in persons undertaken in conjunction with the measurement of ground and food contamination allowed refinement of the accuracy of the models for human dose assessment from the exposure through different pathways. The methods and techniques to handle contamination of food, equipment and soil have been improved.
Meteorological aspects, such as the relationship between deposition and precipitation and greater deposition over high ground and mountains, have been shown to be important especially in the development of more realistic models (NE96a). The importance of synoptic scale weather patterns used in predictions was established, and different models have been developed to predict deposition patterns under a wide variety of weather conditions. The chemico-physical changes in the radioactive gases and aerosols transported through the atmosphere are being studied to improve the accuracy of transport models.
Other impacts of the accident on model refinement include the improvement in understanding the movement of radionuclides in soil and biota, pathways and transfer factors; the effect of rainstorms and the influence of mountains and the alignment of valleys on deposition patterns; particulate re-suspension; long range pollution transport mechanisms; and the factors which influence deposition velocities (NE89a, NE96).
Uniform methods and standards were developed for the measurement of contaminating radionuclides in environmental samples.
In the case of high exposures, the importance of symptomatic and prophylactic medical and nursing procedures, such as antibiotics, anti-fungal and anti-viral agents, parenteral feeding, air sterilisation and barrier nursing was demonstrated, as were the disappointing results of bone-marrow transplantation.
In addition, the accident led to an expansion of research in nuclear safety and the management of severe nuclear accidents.
On the other hand, there is a need to set up sound epidemiological studies to investigate potential health effects, both acute and chronic. In the Chernobyl case, the lack of routinely collected data, such as reliable and complete cancer registry data, led to difficulty in organising appropriate epidemiological investigations in timely manner. There appears to be a need for developing and maintaining a routine health surveillance system within and around nuclear facilities.
In Russia, the government has decided to create a national system for the handling of information on all aspects of crisis management. This system will be operational at national level, but also at regional level. The database will be managed by the IBRAE Russian Institute.
The OECD Nuclear Energy Agency (NEA), as a result of interest by its member countries, has been actively involved in emergency planning, preparedness and management for nuclear accidents, and created, in 1990, the Expert Group on Emergency Exercises, which became later the standing NEA Working Party on Nuclear Emergency Matters. This Working Party focuses on innovative ideas and new approaches to improve existing procedures in place for response to nuclear emergencies. In order to most efficiently achieve an improvements, the group creates, as needed, temporary sub-groups with well defined tasks, time lines and products, employing the most appropriate experts from NEA Member countries, but also from non-NEA members. In addition, the Working Party initiates the organisation of workshops and discussion groups, the launching of questionnaires on specific topics, or the organisation of international exercise series.
To explore, for the first time in an international context, the transboundary aspects of nuclear accidents, the NEA initiated the preparation and conduct of the first international nuclear emergency exercise INEX 1, performed in 1993. With this table-top exercise, the international community could for the first time test procedures and mechanisms in place to manage a nuclear or radiological emergency, leading to a wealth of lessons learnt and to an improvement in nuclear emergency management. Three INEX 1 related workshops allowed the exchange of experience in the implementation of short-term countermeasures after a nuclear accident, in agricultural aspects of nuclear and/or radiological emergency situations, and in nuclear emergency data management.
The INEX 2 exercise series, also initiated by the NEA and performed between 1996 and 1999, was more ambitious than the INEX 1 exercise, seeking to improve actual emergency response procedures and existing "hardware" through a truly international command post exercise. This experience established for the first time an international nuclear emergency "exercise culture" leading to a clear improvement of the international aspects of nuclear emergency preparedness and management. The INEX 2 series offered a wealth of lessons learnt with respect to emergency planning and management, particularly in the areas of communication and information exchange, public and media information, and decision making based on limited and uncertain information. The identified deficiencies in the area of communication and information exchange led to the most prominent outcome of INEX 2 and a major step forward in nuclear emergency management: the development of a new communication and information exchange strategy Monitoring and Data Management Strategies for Nuclear Emergencies, which is currently implemented by various NEA member countries as well as by the international community.
Regarding the role of international organisations, the INEX 2 series contributed to better understanding who are the relevant international organisations, what obligations and responsibilities each has, and how to co-ordinate and harmonise their response in case of a nuclear emergency. The relevant international organisations used the experience to establish a mechanism for co-operation and collaboration through an Inter-Agency Committee on the Response to Nuclear Accidents (IACRNA), for which the IAEA serves as Secretariat.
On a national level, many countries participating in INEX 1 and INEX 2 exercises used the experiences and lessons learnt to modify and improve national procedures for nuclear emergency preparedness and management. Countries also used the outcome of the exercises to update bilateral agreements.
In 2001, the INEX 2000 exercise was organised, similar to the four INEX 2 exercises, as a command-post real-time notification and communication exercise, dealing with the first hours of a nuclear emergency. In addition, the INEX 2000 exercise included for the first time a second major objective, to test compensation and third party liability issues after a nuclear accident, performed as a NEA workshop in November 2001 focusing on decision-making mechanisms in later phases of a nuclear emergency. This exercise, therefore, served as a bridging exercise between the INEX 2 series and the next generation of international nuclear emergency exercise programmes. On one hand, early notification and communication exercises will be institutionalised by the IAEA in collaboration and co-operation with other international organisations, and repeated periodically. On the other hand, a new innovative INEX 3 programme was initiated by the NEA to investigate post-accident management of contaminated sites and regions.
In summary, the Chernobyl accident triggered the start of many national and international programmes, which led to a considerable improvement of national and international procedures for nuclear emergency management and preparedness, especially in the areas of international communication and information exchange, and in harmonisation of response. However, there still remains room for improvement, for example in the field of co-ordinating and harmonising the response to nuclear accidents, as well as in the area of decision making in later phases after an accident. The work programmes of various international organisations are focusing on these aspects.
ETHOS is a European project that is looking at new methodologies for sustainable rehabilitation of living conditions for inhabitants of contaminated areas. It is a new approach to strategic co-expertise, and includes experts from different fields of activities. The project also vigorously involves the local population in the evaluation and the management of risk, in collaboration with the local authorities and experts, (Lo99, He99) thus helping to restore their confidence in experts and authorities.
The ETHOS methodology and practical approach were used in the first stage (1996-1999), in the village of Olmany, which is located in the Stolyn district of Belarus. This village, in the south east portion of Belarus, is located 200 km from Chernobyl. Great improvement in living conditions, especially in the area of radiological protection and private farm production, was achieved thanks to the strong involvement of the village people. A group of mothers became involved in activities to improve the radiological protection of their children. New pedagogic modules from this radiological protection culture were later introduced in the village school.
While it is too early to draw final conclusions about the long term impact of the actions implemented, it is interesting to note that during the project's three years, a profound change with regard to radiological protection took place and several lessons have been learnt. The first concerns the negative role played by regulatory limits when they are interpreted as a boundary between safe and unsafe. This was seen as a strong blocking factor, discouraging those confronted by higher levels, and destroying any potential initiative an ALARA attitude. The process followed by the mothers illustrates how it is possible to develop a framework for setting protection targets, where limits lose their previous status and are considered merely as a point of reference to guide action.
On a village scale, the ETHOS project also has been successful at improving the radiological quality of the food produced by the villagers. This has improved the local economic and radiological situations in a "hand-in-hand" fashion. The Bielorussian authorities, in agreement with European Union, launched in 1999 a similar project at a district scale, the Stolyn district (90 500 inhabitants). The aim of this second stage is to demonstrate that the ETHOS process could be implemented in everyday activity by locals such as physicians, nurses, head of collective farms, teachers and a radioactivity measurement specialist to improve radiological and economic conditions. All these activities are based on voluntary service.
Murphy and Allen (Mu99) have studied the factors that determine personal parameters guiding individuals to respect, or not, regulations regarding forest used and forest product consumption. The gathering of mushrooms and berries is, for these populations, a tradition and also a social and leisure activity. Behavioural compliance, with forest and forest food restrictions, was largely predicted by factors relating to behaviour itself: lifestyle factors. Factors concerning radiation had little or no impact. This suggests that people's decisions about whether or not to go to the forest and consume forest produce are largely based on whether they want or need to, and whether other people they know are engaging in the behaviour. Concerns over radiation appear to play little part in these behaviours.
However, more than sixteen years after the accident, these populations that did not respect the measures of protection are not ignoring the radiation situation, they are still aware of and concerned about the threat of radiation to their health. This concern may manifest itself in the increased risk of stress-related health problems.
In another study, Mays et al. (Ma99) have shown through the consumption of contaminated milk in rural settlements that it is necessary for the radiation protection experts to widen consideration of risk and impacts, beyond radioactive dose, to social and psychological costs of both the nuclear accident and countermeasures programmes.
In conclusion these studies clearly show the necessity to take in account the socio-psychological factors for acceptance by the public of the radiological protection measures taken by the national authorities.
Besides providing new impetus to nuclear safety research, especially on the management of severe nuclear accidents, the Chernobyl accident stimulated national authorities and experts to a radical review of their understanding of, and attitude to radiation protection and nuclear emergency issues.
This led to an expansion of knowledge of radiation effects and their treatment, and to a revitalisation of radioecological research and monitoring programmes, emergency procedures, and criteria and methods for the information of the public.
Moreover, a substantial role in these improvements was played by multiple international co-operation initiatives, including revision and ratio-nalisation of radiation protection criteria for the management of accident consequences, as well as reinforcement or creation of international communication and assistance mechanisms to cope with the transboundary implications of potential nuclear accidents.
More than sixteen years after the accident, we can observe that its consequences have not been completely addressed. Some pathologies have appeared, the amplitude of these being not directly correlated with the real impact of the accident.
But, one of the more spectacular lesson learnt after the Chernobyl accident is probably the change of government attitudes with regard to technological catastrophes. The change includes the recognition of the need for some common action at the international level, the admittance that a large accident is possible, and the necessity to organize national and transboundary exercises. In this field we can note the major role played by the NEA/CRPPH in the INEX exercises, and the significant maturing of mentalities. This can be measured by the fact that it was necessary to create artificial countries (Acciland and Neighbourland) in the INEX 1 exercise, whereas subsequent exercises have used real plants in real countries. These exercises are well appreciated by national and local authorities, who do not hesitate to invite local media for celebration of these exercises.
This important effort is now materialized in the form of an international document, the Joint radiation emergency management plan of the international organizations, jointly sponsored by Food and Agriculture Organization of the United Nations, International Atomic Energy Agency, Nuclear Energy Agency of the Organisation for Economic Co-operation and Development, United Nations Office for the Co-ordination of Humanitarian affairs, World Health Organization and the World Meteorological Organization (IA00).
* With the contribution of Stefan Mundigl (NEA).
The international radiological protection community performed a major status review of the situation around the damaged Chernobyl reactor on the 10-year anniversary of the accident. Since then, studies of the accident site and the contaminated territories continue to be undertaken, which have yielded new scientific results and highlighted important social and health aspects. This report is a complete update of the NEA's earlier publication, Chernobyl: Ten Years On. In particular, it offers the reader the most recent information on the significant new experience gained in the areas of emergency management, long-term environmental behaviour of radioactive materials and health effects.