QUANTIFICATION OF A3 LOOPS WESTINGHOUSE PWR OUTAGE KEY SAFETY FUNCTIONS USING PROBABILISTIC SAFETY ASSESSMENT

摘要

The developed methodology provides a guidance of the systematic of using Probabilistic Safety Assessment (PSA) for the evaluation of guides or procedures which ensure the compliment of the Outage Key Safety Functions (OKSF) in nuclear power plants. As a pilot experience, the methodology has been applied to the 3th and 13th Operational Plant State (OPS), always within the operational mode 4 of a 3 loops Westinghouse Pressurized Water Reactor. The analyzed procedure requires the operability of just one charge pump as boric acid supply source. PSA gives a Core Damage Frequency increase (ΔCDF) of 1.19·10~(-6) year~(-1) for the pump in standby, consequently, an exposure time T= 53.6 hours. Given an average time for the OPS of 40 hours, it is concluded the correct treatment of the procedure. However, it could be improved with the inclusion of an additional inventory replacement function. This would limit the charge pump unavailability. On the other hand, the availability of the external electrical sources is ratified. The procedure requires the operability of both supplies during the OPS. The unavailability of one of them (transformer fail) involves a ACDF equal to 1.64·10~(-5) year~(-1) and a T= 3.89 hours. Then, it is considered appropriate the treatment of the procedure from the PSA point of view.