Development of a cladding burst model under the loss-of-coolant accident conditions in a spent fuel pool

Abstract

ABSTRACT The behavior of spent fuel rods under loss-of-coolant accident (LOCA) conditions in a spent fuel pool (SFP) is not fully understood. Prediction of the cladding burst is important because it results in the release of fission gas into the environment. The objective of this study is to develop a simulation model to predict cladding bursts under SFP-LOCA conditions. In the developed model, assuming that the profiles of temperature and internal rod pressure are known, the cladding hoop stress is evaluated sequentially until the hoop stress exceeds the threshold value. To improve the prediction accuracy of the creep strain, different correlations of the reported creep strain rates for Zircaloy-4 (Zry-4) and Zircaloy-2 (Zry-2) were used, depending on the range of temperature and hoop stress. The hoop stress criterion for a burst was correlated as a function of temperature by interpolating the burst stress measured in an out-of-pile degradation facility, DEGREE. The newly developed model was applied to simulate experimental bursting tests during heating and isothermal holding, and the bursting timing was successfully predicted. Developed model was also used to simulate the cladding burst under DBA-LOCA conditions and its applicability was confirmed.