The establishment of MELCOR/SNAP model of Chinshan nuclear power plant for Ultimate Response Guideline

- The establishment of a MELCOR/SNAP model of Chinshan (BWR/4).
- MELCOR/SNAP model was used to estimate the effectiveness of URG for Chinshan.
- The MELCOR results were compared to MAAP, TRACE and PCTRAN.
- URG is a new method to prevent a Fukushima-like accident.
- The low raw water (150 GPM) can make the cladding temperature below 1088.7 K.

After Fukushima Daiichi disaster, the safety analysis of severe accidents became one of the safety concerns in Taiwan. The Emergency Operating Procedure (EOP) cannot cope with a multiple system failure situation under a severe accident since it is a “Symptom-basis” procedure. To deal with that, Taiwan Power Company built up a new strategy for Fukushima-like accident called Ultimate Response Guideline (URG). It is a simple strategy with three main conditions: loss of regular motor driven injection system, loss of all AC power and tsunami/earthquake warning. If two of three happen, the operating procedure will change from EOP to URG and start the main works by following the strategy. There are three main works in URG: controlled-depressurization, line up low pressure injection water and prepare containment venting. In this study, MELCOR2.1 was used to calculate the cases of URG and checked the goal of the strategy that prevents the accident or not. There were three steps in this research. First, a model of Chinshan nuclear power plant (NPP) was built. Second, one was the case with URG and the other was not by using the above MELCOR model. The results were compared to MAAP5.0, TRACE and PCTRAN. Finally, some sensitivity studies of depressurization and water injection rate were done.