Abstract
Taiwan Power Company has proposed a set of Ultimate Response Guideline (URG), in addition to existing EOP, to tackle with such extended SBO situation. There are three main operations in the URG, two-step depressurization, water injection, and containment venting. There are three initiating conditions and either one will enter into URG. The main purpose of URG is to maintain the cooling capability and the containment integrity. In this study, the URG effectiveness of Chinshan NPP will be discussed. Depending on the success of each of three operations, there are six cases under considerations in this study. The basic case assumed an earthquake occurred at 300 seconds which resulted in reactor scram and MSIV closure. At 2100 seconds, a tsunami hit the plant and finally a total EDG failure, and hence SBO, occurred at 3905 seconds. RCIC was assumed to last for only one hour and the low pressure alternate water was injected into the core at 6700 seconds. Other cases include failure to perform complete two-step depressurization, and with or without water injection. Current results showed that the two-step depressurization could extend the time available to cope with the lineup of the alternate water