Study on Influence of Material Physical Properties Change on Containment Performance under Severe Accident

As the last barrier of PWR nuclear power plant, the integrity of containment in severe accident condition depends not only on the occurrence of severe accident phenomenon, but also on the performance characteristics of containment. At present, in the performance analysis of HPR1000, only the physical characteristics of materials at normal temperature are considered, which cannot reflect the influence of temperature rise and pressure rise of the containment itself under severe accidents. In this paper, according to the response of containment under severe accident and considering the change of material properties under accident, the influence of material properties on containment performance under accident high temperature is analyzed, and the difference of containment performance between normal temperature and accident high temperature is compared. The difference of severe accident risk at different temperatures is analyzed, and the influence on early massive radioactive release frequency, massive radioactive release frequency and severe accident management is evaluated. The analysis results show that the performance of the containment decreases with the increase of the temperature in severe accidents, but the vulnerability of containment is the equipment hatch as before. Compared with the two curves of the containment failure probability distribution at normal temperature and high temperature, due to the large free volume of HPR1000 containment, the loads generated by DCH and AICC will not threaten the integrity of the containment. The original operation setpoint of containment filtration and exhaust system is not challenged.