Abstract
Advanced small modular reactors (SMRs) such as the integrated pressurized water reactor (IPWR) IP200 use different design in the systems, structures, components from large reactors for achieving a high level of safety and reliability. Relap5 / SCDAP/MOD3.4 code is used to model and analyze the severe accident of IP200 reactor caused by SBLOCA superimposed by the emergency power failure. Based on the steady state calculation, which agrees well with designed values, the SBLOCA accident for transient calculation started. First, the SBLOCA accident without the passive core cooling system (PXS) was calculated, and the dynamic process of core degradation in the reactor pressure vessel (RPV) during this process is calculated and analyzed, including transient state response, cooling capacity and thermal hydraulic characteristics. Then the accident situation of different break areas in the small break water loss accident was calculated, and the results were compared and analyzed. The results show that the size of the break area does not affect the sequence of the accident sequence, but only the time and the accident process of the accident sequence. In general, the larger the violation area, the faster the severe accident process. Finally, at the beginning of the exposure in the core, the passive core cooling system (PXS) working can effectively reduce the accident process and protect the integrity of the core and the pressure vessel within the calculation time. Therefore, we can have more time to deal with accidents and effectively prevent the core from melting.
