The 1986 disaster at Chernobyl is the worst accident experienced by the civil nuclear power industry. The international efforts to assist the affected countries in addressing the consequences of the accident are similarly unprecedented in the nuclear field.
The IAEA’s involvement in providing support began within days of the accident and has continued ever since. Early in May 1986, the then IAEA Director General Hans Blix and two senior colleagues visited Moscow and the Chernobyl area, where they were briefed on what was known about the accident at the time. By the end of May 1986, a special session of the IAEA’s Board of Governors had agreed a programme of action that would lead to, inter alia, the development of the Conventions on Early Notification of a Nuclear Accident and on Assistance in the Case of a Nuclear Accident or Radiological Emergency and a thorough review of the IAEA’s nuclear safety and radiation protection programmes and its nuclear safety standards.
Another action agreed that May, 1986, was the organization with the Soviet Union of the first international review of the consequences of the Chernobyl accident. The Post-Accident Review Meeting held in August examined the causes of the accident and presented the preliminary Soviet assessment of the source term. It also provided a limited but significant early account of the radiological consequences. This included the observation that, although doses to thyroids were estimated to be mostly below 300 mSv, some children may have received thyroid doses as high as 2.5 Sv.
Two years later, in May 1988, the International Scientific Conference on the Medical Aspects of the Accident at the Chernobyl Nuclear Power Plant was held by the Soviet authorities in co-operation with the IAEA in Kiev. Information presented at the Kiev Conference included reporting of the cases of clinically diagnosed radiation injuries and estimates of surface contamination and contamination of milk.
In October 1989, the USSR formally requested the IAEA to co-ordinate an international expert assessment of the concept which the Soviet authorities had evolved to enable the population to live safely in contaminated areas, and an evaluation of the effectiveness of the steps taken in these areas to safeguard the health of the population. The International Chernobyl Project (ICP) was launched in early 1990, sponsored by the IAEA and six other organizations1 . About 200 experts from 23 countries and seven international organizations participated, and 50 scientific missions visited the USSR. The ICP focused on four key issues of concern to the population and policy makers: the extent of the existing contamination in the inhabited areas; the projected radiation exposure of the population; the current and potential health effects; and the adequacy of measures being taken to protect the public. Conclusions and recommendations were presented to an international conference in Vienna in May 1991.
One of the achievements of the ICP was the international corroboration of maps showing surface contamination levels. The ICP was also among the first international studies to highlight significant psychological disturbances in the population which were related to the accident but not to radiation exposure. Subsequent studies have given further insight into the importance and prevalence of these social and psychological effects, which relate to the lack of information immediately after the accident, the stress and trauma of relocation, the breaking of social ties, and the fear of radiation. It is very difficult, however, to distinguish the psychological effects of the Chernobyl accident from effects of economic hardship and the dissolution of the USSR.
In the early 1990s there were many international initiatives addressing a wide range of issues. I will just mention three projects in which the IAEA played a particular role.
In nuclear safety, the lessons learned from the accident were a significant driving force behind a decade of Agency assistance to the countries of central and eastern Europe and the former Soviet Union. This was conducted initially through an eight-year extrabudgetary programme, which included of the order of 150 expert missions of various types, and more recently through regional Technical Co-operation projects. Much of the work has focused on identifying the weaknesses in and improving the design safety of WWER and RBMK reactors, particularly the older models. A major achievement has been the identification and prioritization of generic and plant specific design safety issues. These so-called Safety Issue Books have been accepted and used internationally as a basis for planning safety improvement and modernization programmes. Just as important as the design safety work has been the focus on operational safety and on systems of regulatory oversight. The progress made in this area has been demonstrated at a number of international meetings in the past few years, such as the International Conference on Strengthening Nuclear Safety in Eastern Europe and the first Review Meeting of the Convention on Nuclear Safety, both in 1999.
Secondly, and on a much smaller scale, the "Prussian Blue Project", sponsored by FAO and the IAEA, aimed to reduce caesium contamination in milk and meat using a technique involving the use of Prussian Blue in ruminants’ foodstuffs. The essence of the technique is that the caesium binds preferentially to the Prussian Blue and is excreted with it, rather than being taken up in the animal’s bloodstream. It was mainly funded by the IAEA and by Norway, whose specialists developed the technique. This project has proved to be the most cost effective of all post-ICP follow up projects. An annual investment by Belarus of US$ 50 000 saved around US$ 30 million worth of milk and meat production annually.
And thirdly, following a request by Belarus at the 1994 IAEA General Conference, the IAEA organized a mainly environmental project on "prospects for the contaminated area", supported by the Institut de protection et de sûreté nucléaire (IPSN), France. Referring to the forest ecosystems that had reportedly suffered most from the Chernobyl accident, the project concluded that the radioactive contamination affected mainly pine forests: the death of the pine plantations, although severe in the immediate vicinity of the plant, amounted to less than 0.5% of the forested area of the exclusion zone.
In April 1996 the main international organizations involved in assessing the Chernobyl accident’s consequences, namely the IAEA, WHO and EC, co-sponsored the International Conference on One Decade After Chernobyl - Summing up the Accident’s Consequences. The 1996 Conference brought to the attention of a global audience the emerging evidence of a dramatic increase in thyroid cancer incidence among residents of Belarus and northern Ukraine who were infants in 1986. By 1996 there had been more than 800 such cases and, although almost all of these were non-fatal, they represent a huge increase over the normal incidence of this rare type of cancer. The 1996 Conference concluded that the increase was largely the result of intakes of radioactive iodine in the weeks after the accident, particularly the ingestion of milk contaminated with iodine. UNSCEAR’s 2000 Report to the UN General Assembly stated that the number of cases had risen to about 1800, and further cases can be expected for years to come. However, UNSCEAR found no scientific evidence of increases to date in the incidence of any other health effects that could be related to radiation exposure.
One group that continues to confound earlier predictions is the liquidators. Taking into account the relatively high doses reported in this group, some increased incidence of long-term effects — particularly leukaemia — might have been expected by now. For reasons that are not yet clear, studies to date have not found such an increase. Extensive epidemiological studies are in progress which should eventually help to clarify the matter.
Since the 1996 Conference, the Agency has continued to provide assistance in dealing with the long term consequences of the accident, and I will briefly mention a few examples. A primary concern is the rehabilitation of the contaminated areas.
One of the achievements of an ongoing project in Belarus on Rehabilitation of Chernobyl Affected Territories has been to demonstrate methods for decontaminating private dwellings that can reduce dose rates by more than half. The techniques demonstrated in this national project have been taken up by the regional project on Reducing External Exposure Doses in Contaminated Villages. In addition to the obvious radiological benefit, the reduction in exposure also seems to have had a positive psychological effect on inhabitants.
Another Agency Technical Co-operation project in Ukraine on Reduction of Radionuclides in Human Food and Environment has given particular attention to reducing concentrations of caesium and strontium radionuclides in milk products, especially those intended for infants. In November 1997, a milk decontamination plant was commissioned at the Ovruch Dairy in Ukraine, designed and constructed under a trilateral agreement initiated by the IAEA and financed by the US Government, and capable of reducing caesium levels by up to 80%. A radiological and radiochemical laboratory was also established at the plant to monitor the levels of radionuclides in milk.
However, the problems of the contaminated areas are not just related to reducing radiation exposure, but also to restoring economic life. A Technical Co-operation project in Belarus focused on the production of rapeseed on contaminated land. Suitably chosen varieties of rapeseed can be grown on moderately or even highly contaminated soils with minimal uptake of radionuclides. The seed can then be used for economically valuable end products such as biolubricants or high protein cattle feed. More than 50 000 hectares of contaminated land in the Gomel and Mogilev regions have been planted with rapeseed.
Another problem has been finding export markets for ‘traditional’ commodities from the affected areas, such as wood from the forests of Belarus. Some criteria exist for international trade in foodstuffs, but there are no corresponding criteria for other materials affected by radioactive contamination. At the request of its General Conference, the IAEA has recently established a programme of work aimed at reaching international agreement on such criteria.
Looking to the future, as the current IAEA Director General, Mohammed ElBaradei indicated when he visited Chernobyl last August, the Agency is also providing support to Ukraine for the decommissioning phase. This will include a new Technical Co-operation project to provide engineering and managerial advice for the planning and implementation of the decommissioning of units 1, 2 and 3. It will also include continued assistance in relation to the unit 4 shelter. Between 1995 and 1999, the Agency provided expert services and supplied spectrometry and computer equipment to assist in the assessment of the radiological integrity of the shelter. The project led to significant advances in knowledge of the chemistry of the water percolating through the shelter and its interaction with the fuel-containing materials, and in modelling the transport of radionuclides in the water. A new Agency project will assist in the characterization, management and physical protection of radioactive material from the shelter.
I have already mentioned some of the work aimed at preventing future accidents, but another important area of follow-up effort is improving preparedness for any accidents that might still occur. The regional Technical Co-operation programme in Europe includes several large projects on these topics, such as Medical Education for Nuclear Accident Preparedness and Harmonization of Regional Nuclear Accident Preparedness. Within the former project, seven training courses were conducted by the IAEA in the last three years. Three of them were hosted by Ukraine. These courses provided advanced training in radiation medicine and medical preparedness to radiation accidents to over 400 emergency and medical specialists from these and their neighbouring countries.
Of course, the consequences of the Chernobyl accident were not confined to direct effects at the plant and in the surrounding areas. I have already mentioned the Early Notification and Assistance Conventions, which were a direct response to the accident and have been central to international response to emergencies ever since, and the programmes to improve nuclear safety throughout the region. The establishment of the Convention on Nuclear Safety was also at least partly a consequence of the accident. I could quote many other examples, but suffice it to say the Chernobyl accident has probably been the biggest single influence on the IAEA’s programme of work on safety issues since 1986.
In conclusion, I would reiterate that the IAEA’s efforts have been only one part of an extraordinary international effort to support the national efforts of countries affected by this tragedy. A great deal has been achieved, but there is clearly a long road still ahead. We, the international community, must continue to improve our understanding of the consequences of the accident, whether they be radiological, social, economic or psychological, and to provide help where it is needed.