Development of the safety analysis method based on the 3-D core kinetics coupled with thermal-hydraulics code

In the present Non-LOCA safety analysis of the Pressurized Water Reactor (PWR), plant transient, core response and fuel behavior are independently calculated by different analysis codes to estimate the plant safety. Therefore these results often involve large un-quantified conservativeness due to additional safety margins for initial/boundary conditions of each calculation and simplistic approximations for complicated interactions between the core neutronics and plant thermal-hydraulics during the transient. Recently, best estimate 3-D core transient analysis codes have been widely developed in the area of nuclear reactor accident analysis to understand actual physical phenomena and quantification of conservativeness in the current safety analysis. Evaluating safety margins appropriately contributes to the more safety of the plant design and the efficiency of the plant operation. Mitsubishi Heavy Industries (MHI) has developed the 3-D core kinetics coupled with the thermal-hydraulics code SPARKLE, and has a plan to apply it for the commercial licensing in the near future. This paper presents the feature of the SPARKLE code and the results of the application to representative accident events. (author)