Abstract: Using the best estimate computer code RELAP5/SCDAPSIM/MOD3.2, the detailed calculation models of US Surry nuclear power plant(NPP) unit 2 were established and core melt accident induced by total loss of feed water(TLFW) was analyzed. In order to predict the in-vessel core melt progression accurately and provide probabilistic safety assessment(PSA) level 2 with the reliable initialization conditions, the creep rupture failure of primary loops pressure boundary was taken into account in code calculation. Core melt progression and accident results with operator action were evaluated. The calculated results suggest that severe accident induced by TLEU will not lead to high pressure core melt and the failure position of reactor pressure vessel lower head is in the side piece but the bottom and the accident progression will be greatly delayed by opening the pressurizer power-operated relief valve.