Abstract
The ultimate response guideline (URG) is developed by Taiwan Power Company to cope with the station blackout which loss of designed AC power and water supply. The URG is operated by the DlVing plan, (1) depressurize the reactor, (2) inject any available water into reactor by any available power supply if this critical status cannot be restored in time. (3) vent the containment if necessary to maintain containment integrity URG relies on the use and operation of auxiliary feedwater system, depressunzation of steam generators, and line-up the alternate water sources such as sea water when regular systems arc not available. The simulations start from normal operation at 100% power then an earthquake is assumed to happen, then tsunami strike the site 20 minutes later. The turbine-dnven auxiliary feedwater system is assumed to be unavailable as conservative condition, and a seal leakage of 21 jepm (0.079 m 3 min) on each reactor coolant pump (RCP) is also modeled. Simulation results show that the case of SBO without URG strategy, the core water level drops to top of active fuel (TAF) in hours as a SBO happens. But the case of that with URG strategy, the fuels could be fully covered by coolant for 70 hours. The applying of URG strategy during SBO is to secure reactor core water courage and fuel integrity as long as possible, and the results show that it can extend the time for core fuels to be uncovered for various hours in different situations. Funhermore, the duration gained by URG is possibly for building up AC power sources and long-term cooling system.