Loss of Cooling Thermal Analysis for the Spent Fuel Pool of the Chinshan Nuclear Power Plant

The Chinshan Nuclear Power Plant owned and operated by the Taiwan Power Company is a twin-unit BWR-4 plant. Unit 1 and unit 2 began their commercial operation in 1978 and 1979, respectively. Since commercial operation, all the fuels discharged from reactor core at each cycle are stored in the spent fuel pool (SFP). An engineering analysis is performed to predict the SFP water temperature and pool water level during a postulated loss of forced cooling accident. A full-core discharged loading is considered, and the fuel assemblies are moved to the SFP just after 7 days of cooling. The pool temperature and level are calculated using lumped energy and mass balances. Calculation results show that the water temperature reaches the saturation temperature at 9.4 hours after the onset of the accident, and the pool level drops to the top of the active fuels at 76.8 hours. After the pool level drops to the top of the active fuels, the cladding temperature increases dramatically because the convective heat transfer of steam is much weaker than that of liquid water. The peak cladding temperature after fuel uncovery is calculated by detailed CFD simulations, and the results show that the peak cladding temperature reaches 600°C in 3 hours and 1200°C in 9.5 hours after the fuels are uncovered. Additionally, the check-board arrangement for fuels is also investigated. Through enhanced the radiation heat transfer, the check-board fuel arrangement can have slower heating rate for the fuels. For the Chinshan SFP, extra 2.5 hours can be gained by employing such an arrangement for necessary actions.Copyright © 2013 by ASME