Abstract
In the large advanced passive PWR nuclear power plant, the long term core cooling (LTCC) following loss of coolant accidents (LOCA) is provided by passive safety system. The purpose of this paper is to study whether the factors that could affect LTCC challenge the safety margin. According to the preliminary PIRT (Phenomena Identification and Ranking Table) of the large advanced passive PWR nuclear power plant, the following factors have been selected: the timing of the recirculation initiation ahead, the swing check valves in the safety injection lines partially opened, core inlet blockage due to debris, the resistances of automatic depressurization system ADS valves, the containment water flooding inventory, the containment pressure and the recirculation temperature. The cases of LTCC following a double-ended direct vessel injection (DEDVI) line break are analyzed. The effects of the increase of ADS valves resistances, the decrease of containment pressure and the increase of recirculation temperature are calculated respectively. It's found that the containment pressure and the containment sump temperature may also play important roles during LTCC. A limiting case combined with all of these factors is performed finally, which the results demonstrates that the passive systems of the large advanced passive PWR nuclear power plant will provide adequate core cooling performance during LTCC.
