Sensitivity Analysis of Improved Reactor Building Parameters Using MAAP-ISAAC 4.03 Code

The reactor building is primarily designed to prevent or mitigate the uncontrolled release of radioactive materials to the environment in operational states and in accident conditions. The main purpose of this paper is to evaluate the effect of the improved variables related to reactor building on behavior of containment pressure and radiological transport during severe accident initiated by the station blackout (SBO) and the small loss of coolant accident (SBLOCA) in the Wolsong plants which are a typical CANDU-6 type using MAAPISAAC 4.03 (Modular Accident Analysis Program - Integrated Severe Accident Analysis Code for CANDU Plant)1 computer program. The parameters relevant to reactor building of MAAP-ISAAC 4.03 which is the severe accident analysis code were improved and their effects were evaluated. As a representative accident, the station blackout (SBO) and the small loss of coolant accident (SBLOCA) in the Wolsong plant were selected. As a result of the analysis, it was confirmed that distributed heat sinks were the greatest influence of the input variables related to reactor building. In the analysis case of using modified parameter file (Mod- Total RB parameters), the progress of the severe accident was delayed and mitigated. In other words, the times of airlock seal failure, reactor building failure, and calandria tank failure were delayed and the mass release fractions of CsI were sharply reduced than cases of using existing parameters (Reference). Therefore, it may be necessary to improve the parameters relevant to reactor building. The analysis result that reflects the modification of the input parameters can be applied to the improvements such as the Level 2 PSA or the severe accident management guidance (SAMG) which use the result of the severe accident analysis.