Shutdown PRA

The APIOOO Level 1 shutdown PRA has estimated the CDF to be 1.23x10 events/year, see Table 5. 4.3-1. This CDF is conservative because credit is not taken forthe design enhancement in using diverse squib valves in the recirculation lines. If credit is taken forthe diverse squib valves in the recirculation lines of the APIOOO plant, the estimated CDF of the Level 1 shutdown PRA would be the 1.04x 10 per year. 

The insights drawn from the shutdown PRA core damage frequency analysis are as follows ... 

The accident sequence corresponding to the loss of the Residual Heat Removal System in Operating Mode 4 (OM 4) during cool down operations has been studied (Table 1). The analysis of this sequence is framed within the Low Power Shutdown PRA (LPRA) of a typical Pressurized Water Reactor (PWR). 

---