Study On The Loss Of Coolant Accident For Spent Fuel Pool Using MELCOR

Before shipped away for intermed iate storage or reprocessing,the spent fuels will be put into spent fuel pools(SFP) for transitional and temporary storage. The loss of SFP cooling flow or ineffectiveness of SFP heat sink can make the capacity of cooling invalid, and result in heat up and boiling off of SFP coolant inventory. Subsequently, due to the uncovery of the active fuel assemblies, the fuel elements heat up. Once temperature reaches the thresho ld temperature(about 1100K), the oxidation reaction could occur in a steam or air c ircumstance with strongly exothermic, eventually result in the fuels damage and the release of radioactive fission products if no effective mitigation was taken. In this paper, to simulate the accident response of the SFP of a typical nuc lear power plant, the MELCOR 1.8.6 for severe accident analysis was employed, with the hypothesis that no any water recovery system was availab le. There are 4408 fuel assemblies in this SFP. The total decay power was approximately 2.85 MW. The division of assemblies by groups or the rings in the MELCOR nodalization corresponds to SFP configuration. The results show that, with the initial water level of roughly 7.5 meter above fuels storage racks, it would take approximately 246.4 hours(10.3 days) for the pool level to drop below the top of fuel racks. The time for the fuel temperature to reach the oxidation thresho ld temperature(about 1100 K) was 308.9 hours(12.9 days). It would take approximately 315.2 hours(13.1 days) for the peak clad temperature to reach the maximum value of 2200 K, and the total hydrogen can be produced is about 4707 kg.