Multiphysics Analysis of Fuel Performance and Tritium Migration in FeCrAl and Cr-Coated Zircalloy Cladding Under PWR Normal Operating and Transient Conditions

Abstract

Due to the fact that the Cr-coated Zircalloy and the FeCrAl alloy have excellent high-temperature oxidation resistance, corrosion resistance, they are considered to be potential replacement materials for PWR cladding. However, it is also reported that the poor tritium resistance of FeCrAl alloy will accelerate the penetration of tritium throughout the cladding and increase the treatment cost. In this work, the physical models and tritium migration models of Cr-coated Zircalloy cladding and FeCrAl claddingare reviewed firstly. Then, based on the developed fuel performance analysis code CAMPUS, the fuel performance models of Cr-coated Zircalloy cladding and FeCrAl cladding are implemented, and a new model of the tritium migration in different claddings is implemented too. Finally, the performances of three fuel cladding combinations (UO2 pellets and Zircalloy cladding, Cr-coated Zircalloy cladding and FeCrAl cladding) under normal and LOCA conditions are simulated and discussed. And the tritium resistance performance of different fuel cladding combinations is further calculated and analyzed with the new tritium migration model. The calculation results show that under normal and LOCA conditions, compared with Zircalloy cladding, the application of FeCrAl cladding can reduce the overall temperature of fuel and improve fuel safety margin. And the application of Cr-coated Zircalloy cladding and FeCrAl cladding can effectively delay the failure time of cladding under LOCA condition; In terms of tritium penetration, the Cr-coated Zircalloy is found to have better tritium resistance effect than FeCrAl alloy, which greatly reduces the pollution treatment cost of reactor operation.