Transient Analysis of Station Blackout While Shutdown for OPR1000 Nuclear Power Plant

Some studies have been performed to support and provide useful insights for operator guidelines to maintain critical safety functions during a Station Blackout (SBO) or ELAP event for shutdown modes. Shutdown SBO Guideline has been issued to provide instructions for responding to a SBO, including an ELAP, while shutdown with SIAS (Safety Injection Actuation Signal) blocked and fuel in the reactor vessel. The thermal-hydraulic transient analysis using RELAP5/Mod3.3 code was performed to provide insights for shutdown SBO for OPR1000 NPP. It will be helpful for developing a strategy to cope with shutdown SBO for OPR1000 NPP. The thermal-hydraulic transient analysis was performed to provide insights for shutdown SBO. For Shutdown State A, if SG ADV is opened by operator manual action within 4,000 sec, then 6 hour is available to avoid core uncovery and damage. 6 hour is sufficient time for operator to prepare the secondary external injection. For Shutdown State C, if RWST gravity feed is provided by operator manual action within 4,000 sec, then 24 hour is available to avoid core uncovery and damage. 24 hour is sufficient time for operator to prepare the primary external injection or refill RWST. This calculation results can be directly applied to the development of Plant Specific Technical Guide (PSTG) for OPR1000 NPP