Zircaloy Clad Failure Simulation in Rod Bundles Under LOCA Conditions

Abstract

A methodology is presented to determine transient temperature distributions and simulate zircaloy-clad failure behavior in nuclear fuel rod bundles during a loss-of-coolant accident (LOCA). An efficient variational technique is used to solve the transient radial-azimuthal heat conduction problem in conjunction with a "modified view factor" technique to model radiative heat transfer between the rods. Results from the CARATE study are used to correlate clad temperature distributions to clad burst strains for all the rods in the bundle. The methodology is demonstrated through its application to a 4 x 4 boiling water reactor (BWR) subassembly. The most important advantage of this methodology is that it allows the determination of accurate temperature distributions with minimum computing times and in readily usable form for zircaloy-clad failure simulation.