Abstract
The Intermediate Break - Loss of Coolant Accident (IB-LOCA) is the most challenging design basis condition event in advanced pressurized water reactor due to high integrity components techniques. In the radiological consequence analysis for loss of coolant accident, it is obviously too conservative to assume that 100% of the fuel cladding failed. In this paper, the fuel damage fraction of IB-LOCA is studied to support source term optimization. Firstly, the fuel failure model under loss of coolant accident is studied. The main modes of fuel failure in IB-LOCA accident are due to cladding burst and Departure from Nucleate Boiling (DNB). Then, transient analysis, break spectrum and burn-up sensitivity analysis are carried out. The analysis results show that the overheating of fuel pellet is not significant, and the fuel is safe during the IB-LOCA accident. There is no cladding burst during the IBLOCA accident. The minimum Departure from Nucleate Boiling Ratio (DNBR) occurred near reactor trip time during the accident. The maximum amount of fuel rods experiencing DNB is about 27%, and the correspondent break size is 28.4 cm. As it is conservatively assumed that DNB occurrence means fuel failure, the fuel damage fraction for IB-LOCA accident is estimated at about 27%. The work results can provide support for safety analysis of nuclear power plants and provide reference for optimization of accident source terms.
