Application of RELAP/SCDAPSIM and COCOSYS Codes for Severe Accident Analysis in RBMK-1500 Reactor

Regardless low probability of occurrence the severe accident phenomena are investigated for all types of nuclear reactors in the world because the consequences of such accident could be catastrophic. Most of research is performed for the prevailing vessel-type light water reactors like PWRs and BWRs. Less research is performed for the channel-type reactors like CANDUs and RBMKs as they are operated just in a few countries. Up to now the phenomena that could occur in case of a severe accident in RBMK reactors were not analysed in detail and little literature is available on this topic. The paper presents one of the first integrated analyses of severe accident in RBMK-1500 reactor. RELAP/SCDAPSIM code is used to simulate the phenomena in the reactor core and reactor cooling system and COCOSYS code is used to simulate the confinement phenomena during the same accident scenario. The performed analysis provided information regarding code acceptability for the severe accident analysis in RBMK reactor and assessment of the timing of the key events, i.e. core uncover, fuel cladding rupture, etc, and provided assessment regarding hydrogen distribution in confinement. (authors)