Fuel fragmentation and relocation (FFR) model in SPACE code PART 1: Development and verification

Abstract

Ballooning of cladding, which can happen during a loss of coolant accident (LOCA), causes relocation of fragmented fuel. Recently, consideration of fuel fragmentation, relocation, and dispersal (FFRD) phenomena for safety analyses has been requested by a regulatory body. Therefore, new models related to the fuel fragmentation, relocation, and dispersal (FFRD) in SPACE code have been developed. In this study, the FFR model, excluding dispersal, will be discussed. The fuel fragmentation and relocation models, which were developed by Quantum Technology (QT), are modified and developed in SPACE code. In particular, the fuel relocation limitation threshold parameter and the fuel power distribution during relocation are newly developed. The FFR models are also verified with simple known problems. The newly developed and implemented FFR models in SPACE are validated with calculations using Halden IFA-650 test data. The newly developed FFR model in SPACE can reasonably predict the fuel relocation and axial rod temperature distribution due to fuel mass redistribution. However, intensive validation tests including various conditions are necessary to validate the new FFR model in SPACE code.