Thermo-mechanical response of SiCf/SiC composite cladding: Effect of loss-of-coolant accident duration

Abstract

SiC_f/SiC composite is one of the candidate materials for fuel cladding in Generation IV advanced nuclear reactors. However, there are still few risks under accident conditions, such as large physical property changes and poor thermal conductivity, the performance of the cladding remains to be studied especially in extreme accident conditions (loss-of-coolant accident, LOCA and reactivity-insertion accident, RIA). In this study, the thermo-mechanical responses of SiC_f/SiC composite cladding under different LOCA durations were investigated by a meso-macroscopic coupling finite element simulation method. At mesoscopic scale, we present a mathematical model between the longitudinal tensile ultimate strength and temperature (200K∼2000K), which enables us to define the failure of macroscopic cladding. At macroscopic scale, the established mathematical model was applied to the failure analysis of macroscopic cladding, then the temperature and hoop stress of the inner and outer surfaces of the cladding were studied under different LOCA durations of 200s, 300s and 400s. The results showed that under LOCA condition, the hoop stress difference between the inner and external surfaces of the SiC_f/SiC composite cladding increases about 200% compared with that under normal service conditions. Meanwhile, the hoop stress difference increases slowly with the increase of LOCA duration, and the maximum increment can reach about 2.8%. In addition, the peak temperature increases with the increase of LOCA duration, which the maximum increment can reach about 5.6%, while the peak temperature difference between the inner and external surfaces increases slowly with the increase of LOCA duration, and the maximum increment can reach about 5.1%.