Sensitivity Analysis for Passive Residual Heat Removal System of AP1000 Based on Grey Correlation Degree

To analyze the behavior of passive residual heat removal system（PRHRS） of AP1000 under loss of main feedwater accident, a thermal hydraulic model is built by RELAP5. Based on the results of RELAP5, the grey correlation degree is used to analyze the importance degree of influence factors. The results show that when the resolution is 0.1, the influence factors of reactor coolant outlet and fuel cladding maximum temperature can be well distinguished. Reactor coolant outlet maximum temperature directly affects the fuel cladding maximum temperature. The correlation coefficient between them is great. The initial reactor power has greatest effect on the reactor coolant outlet maximum temperature and the fuel cladding maximum temperature. And the sequences of influence factors are temperature of IRWST, height of ascending pipe and initial pressure. Correspondingly, the diameter and resistance coefficient of PRHRS-HX have less effect.