Validation and verification for the multi physics models in JUPITER code

Chai, P.; Yamashita, Susumu   

Study on core degradation process during severe accident have been attracting attention since Fukushima Daiichi Accident. Numerical analysis was considered as an applicable way since the on-site investigation is very difficult. However, previous Severe Accident (SA) analysis code does not have good performance on detailed estimating about the molten debris relocation. Therefore, to obtain precise understanding of molten material behavior inside RPV and to improve the accuracy of the SA code, a new computational fluid dynamics (CFD) code with multi-phase, multi-physics models was developed, which is called JUPITER. It optimized the algorithms of the multi-phase calculation. Besides, the chemical reactions are also modeled carefully in the code so that the melting process could be treated precisely. A series of verification and validation studies are conducted, which show good agreement with analytical solutions and previous experiments. The fuel bundles melting and subsequent relocation process is simulated and shows good agreement with experimental results. The capabilities of the multi-physics models in JUPITER code provide us another useful tool to investigate the molten material behaviors in the relevant severe accident scenario.