20 Years after Chornobyl Catastrophe. Future Outlook. National Report of Ukraine (English Edition)

The scale of the Chornobyl catastrophe – the most severe man made nuclear accident in the history of mankind – is well known to both scientists and politicians worldwide. About 3% of the radionuclides that had accumulated in the ChNPP Unit 4 at the time of the accident were released into environment. That was about 300 MCi, or 1.2⋅1019 Bq of radionuclides [1] and [2]. The accident contaminated over 145,000 km2 of the territory in Ukraine, the Republic of Belarus, and the Russian Federation with a density of contamination by 137Cs and 90Sr exceeding 37 kBq/m2. As a result of the Chornobyl accident, about 5 million people were affected; and about 5,000 inhabited settlements in the Republic of Belarus, Ukraine and the Russian Federation were contaminated with radionuclides. In Ukraine alone, 2293 villages and towns with a population of about 2.6 million were contaminated. Besides the three countries most affected above, the Chornobyl accident also affected many other countries, notably Sweden, Norway, Poland, the United Kingdom, Austria, Germany, Finland and Switzerland. The accident occurred when tests on utilising turbo generator rundown to ensure in-house power demand during complete de-energising of the NPP were conducted. The objective of the tests was to check the electrical equipment. The impact of such an experiment on the reactor was not analysed in details. The tests were proposed by the Chief Designer of the Reactor Plant (Scientific research constructional institute of power technic (RDDEEI), Moscow). It is now clear that such experiments should have been classified as integrated unit tests, and their program discussed in details and coordinated with the General Planner, General Designer, and Scientific Supervisor of the NPP RNBK reactors project (I. V. Kurchatov Institute for Atomic Energy (IAE), Moscow) and the State Supervisory Board. This was not done. Moreover, the regulations in effect in the USSR at that time did not require that the management of NPPs coordinate such programs with the above organisations. From the present standpoint, conducting such tests was an illegal action. The basic causes of the catastrophe were as follows: 1. Conduction an incompletely and incorrectly prepared electrical experiment. 2. The low professional level of operators, and of the NPP management and the officials of the Ministry of Electrification as a whole in the area of NPP safety. 3. Insufficient safety level of the graphite-uranium reactor RBMK-1000. 4. Constructive falts RBMK-1000. 5. Personnel mistakes. The world community is aware of these facts. However, many other related issues remain unknown not only to the global community, but also (in several cases) to the public of the countries affected. Such issues include the overall scope and extent of activities that had to be performed after the catastrophe; the role of science in addressing the radiation accident problem; the effect of interaction between the government, scientists and political forces during catastrophe recovery work; and the impact of social and psychological factors. The report describes and reviews the actions of the governments of the USSR, Ukraine, and the Verkhovna Rada of Ukraine; the activities of scientists in elimination of the accident consequences; and elimination of the additional experience gained over the past years. Mistakes made during these activities are highlighted.