As one of the lessons-learned of the Fukushima accident, long term station blackout (SBO) and subsequent loss of ultimate heat sinks have widely aroused discussion in the nuclear industry. The SBO sequences for Westinghouse three-loop pressurized water reactor (PWR) has been under investigation for a long period. To cope with the long term SBO issue, many nuclear power plants have decided to replace the reactor coolant pump (RCP) seal by the new passive thermal shutdown seal (PSDS). The PSDS is a fail-safe protection device that will significantly reduce the leakage from RCP seal in case of loss of cooling. This makes the Seal Loss of Coolant Accident (SLOCA) no longer a risk significant event and the relevant PRA models need to be modified to reflect the associated plant change. The PRA model of a Westinghouse PWR plant has been reviewed and two relevant initiating events, i.e. the loss of component cooling water (CCW) and loss of offsite power (LOOP), are revised for their sequences. According to Westinghouse analysis, the PSDS temperature must be maintained below 104°C and the operators have to control the RCP speed. In this paper, those factors are incorporated into the event tree structure revision of the loss of CCW event (TC). Compared with past TC event tree, RCP speed slowdown is introduced into the PSDS mode. The relevant part in the PRA model is subject to review and modification. The risk effectiveness of the PSDS will be further studied and explained.