MELCOR를 이용한 공기에 완전 노출된 사용후연료 저장조에 대한 중대사고 해석

Abstract

Following Fukushima Daiichi nuclear power plant accident, spent fuel pool (SFP) accident studies have being undertaken to improve SFP safety even further. This study is provided of simulation result of severe accident for the SFP under the condition of complete drainage in typical PWR. We used the MECORE 1.8.6 code to compute the variation of the fuel cladding temperature after a complete loss of the cooling water in the spent fuel pool. Since we could not obtain detailed design data of the SFP for a domestic nuclear power plant, the SFP model and fuel assembly model used in this study were taken from a study conducted by Sandia National Laboratory(SNL). Important factors such as Zr oxidation by air, air natural circulation and thermal radiation were considered for complete drainage accidents without mitigation measures. The simulation result shows that the cladding temperature exceeds the rupture temperature in most of the fuel rods and some part of the fuel rods suffers melting of the cladding. Since the sudden rise and drop of the cladding temperature well coincides with those of the oxygen concentration, the oxidation of Zr seems to be a governing factor affecting the melting of cladding. For sensitivity analysis, the effects of emergency ventilation and decay heat, hole size, open door were analyzed. The analysis results, we have developed a minimum ventilation capacity table of suppressing fuel damage. Based on this Study, it was confirmed that needed additional models in the SFP modeling.