| Summary: | 碩士 === 國立清華大學 === 核子工程與科學研究所 === 103 === Spent fuel pool works as a temporary storage for fuel discharged from core, and relys on Spent Fuel Cooling System (SFPCS) to remove decay heat. When a loss of cooling event happens, the decay power of fuel can’t be removed from pool. The water level drops due to evaporation, and leads to fuel uncovery. After fuel is uncovered, the cladding temperature elevates due to deterioration of heat transfer. The oxidation of Zircaloy by the steam generated hydrogen and heat.
This work aims to analyze a loss of cooling event of spent fuel pool of Chinshan Nuclear Power Station. In the present study, RELAP/MOD3 and MAAP5.02 are used to simulate the event. Chinshan Nuclear Power Station is operated by Taiwan Power Company, which employs BWR IV reactor and Mark I containment.
The spent fuel pool of Chinshan Nuclear Power Station is divided into 14 storage region, and the hottest region is J region. This study uses ASB 9-2 formula to calculate decay power of spent fuels. The radiation heat transfer model and partial length fuel rods are built.
The results of J region RELAP simulation indicate that spent fuel is uncovered at 6.75 days after event takes place. The spent fuel is uncoverd at 19.33 days in the whole pool simulation of RELAP5 simulation. The results of former simulation is too conservative. The results simulated by MAAP are closed to RELAP5’s results. It takes 19.25 days for fuel to uncover in MAAP simulation. Moreover, the fuel uncovers at 17.78 days after event happens by simple energy balance calculation.
As predicted by RELAP5 core, the cladding temperature reaches 2200℉ at 22.92 days after event occurs. However, the corresponding time is 33.56 days in the MAAP5 simulation.
Due to inconsistency in MAAP5 numerical calculation after fuel uncovery, the hydrogen generation rate doesn’t predict correctly. Therefore, cladding temperature after fuel uncover is not correct.
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