Research on Severe Accident Management Strategies for CPR1000 NPP Under Refueling Cooling Mode

Abstract

There are six standard operating modes in CPR1000 NPP [1], containing Reactor in Power mode (RP), Normal Shutdown on Steam Generators mode (NS/SG), Normal Shutdown on RRA connected mode (NS/RRA), Maintenance Cold Shutdown mode (MCS), Refueling Cold Shutdown mode (RCS), Reactor Completely Discharged mode (RCD), and most severe accident management only focused on Reactor in Power and Normal Shutdown mode. However, the Fukushima Daiichi nuclear accident indicates that risk still exists in long-term SBO situation in RCS mode which used to be considered safe enough. To enhance the capability of SAMG [2], several scenarios are analyzed in this paper to find out the most effective strategies using the severe accident analysis code MAAP5. According to the results, there is little risk in first 24 h, but water makeup or cooling is needed in the following 2 to 3 days; furthermore, containment spray or depressurization is indispensable in long-term SBO situation. To assess the effectiveness for these strategies, the results are compared with analysis without these strategies. The comparisons showed that correct actions of these strategies would effectively prevent the accident process of CPR1000 power plant, which would help to develop SAMG in RCS mode.