Uncertainty analysis of source term and off-site consequence for WH600 using MELCOR and WinMACCS

Abstract

In PSA, uncertainty analysis is required to assess the reliability of the safety assessment results. Uncertainties related to severe accidents have been reported in previous studies. But existing uncertainty analysis has been focused on such severe accident phenomena, as changes in pressure and temperature of the containment building and hydrogen production. However, in order to conduct uncertainty analysis of off-site risk, it is necessary to analyse the uncertainty related to the information of radioactive material released, not just the phenomenon. In this study, the source term uncertainty is evaluated using MELCOR and off-site consequence uncertainty analysis using MACCS are performed. And WH600 has been selected as a reference plant. The variables related with these result are selected. The values are adjusted taking into consideration the characteristics and environmental conditions of an actual NPP. The LHS method is used for sampling the random variables. In off-site consequence analysis, early fatality and cancer fatality are uses as measures. As a result of MELCOR uncertainty analysis source term information has significant uncertainty that affects the off-site consequence. Also in case of off-site consequence, risk band is so wide that risk has to be determined.