Station Blackout Severe Accident Calculation Using MELCOR 1.8.3 Computer Code

The overall objective of reactor safety is to protect the public and the environment against dangerous releases of radioactive materials from nuclear power plants. A nuclear power plant is designed to cope with a set of events including normal conditions, anticipated operational occurrences, external events and accidents. Station blackout is a severe accident that might produce core melt and major releases of fission products from the reactor core. This paper shows the results of station blackout (SBO) analysis of NPP Krsko model, by using MELCOR, a computer code that models the progression of severe accidents in LWR nuclear power plants. MELCOR was developed by Sandia National Laboratories for US Nuclear Regulatory Commission as a successor to the Source term code package. Calculations were realized at Faculty of Electrical Engineering and Computer Science, Department of Power Systems. The main goal of this analysis was to investigate the possibilities and the operation of MELCOR and to develop a model of NPP Krsko for further calculations. Therefore, at this stage, modeling is rather simplified and requires more detailed study of code packages and code itself. The results of SBO analysis show that, depending on initial conditions, SBO accident is a serious threat to safety barrier''s integrity and in this case leads to the damage of containment building, but they also show that MELCOR enables detailed calculations of long-term accident progression. (author)