Decision support techniques used in Hungary in cases of nuclear emergencies

Decisions concerning the implementation of countermeasures following nuclear accidents have to be based on quick and reliable predictions of the possible environmental effects. In Hungary, decisions are supported by three main sources. Whenever the site of the accident is the Paks NPP, the emergency is detected and declared by the shift supervisor. Radiation conditions in and around the plant are detected on a real-time system. The plant transfers these data to the emergency centres of both the Governmental Committee for Nuclear Emergency Preparedness and of the Hungarian Atomic Energy Authority. The Centre of Emergency Response Training and Analysis (CERTA) of the Hungarian Atomic Energy Authority is primarily meant for making analysis of a nuclear emergency situation, based on data obtained from the power plant or from the international nuclear community. The most important results of the analysis are the source term estimates and the forecast of the possible on-site consequences. The computer program system CERTA VITA collects, processes and displays the data for further analysis and reporting. The source term estimation is performed by using two alternative tools. A simple but rough estimate is obtained from the InterRAS program. A more detailed analysis is given by the SESAME code. The environmental consequences are evaluated by the program NACOS. Atmospheric dispersion, plume depletion, doses, dose commitments, early and late health effects are computed. Effects of the introduction of countermeasures are taken into account. The program works as a simulator, various scenarios can be specified and results obtained by these scenarios can directly be compared to each other. The user can execute two parallel runs - with and without countermeasures - and compare the consequences. Results (path of the plume, contaminated area, doses, health effects) are displayed on maps with spectacular symbols, and/or in tables showing the computed values. These tools have been successfully applied during the INEX2-HUN exercise. (author)