Investigation on irradiated-thermal-mechanical coupling performance and failure behaviors of TRISO particle fuel for space reactor applications

Abstract

TRISO particles, recognized for their excellent ability to retain fission products and maintain structural integrity, are crucial candidates for space reactor applications. However, current studies primarily focus on conventional reactor conditions, leaving gaps in understanding their performance under the more demanding conditions of space reactors. This study aims to address these gaps by developing a thermal-mechanical coupling simulation for TRISO particles using the finite element method, incorporating comprehensive material properties, irradiation behaviors and fission gas release. The model was validated through tangential stress comparison in IAEA CRP-6 Case 8 and further verified with TRISO particle calculation results from the BISON code, demonstrating the reliability of the simulation and the accuracy of the model. Under space reactor conditions, the higher kernel power, prolonged fuel lifetime, and increased fission gas pressure significantly elevate the tensile stress in the CVD-SiC layer, raising its failure probability at the later stages of burnup. While the SiC layer remains highly reliable under conventional HTGR conditions, its failure probability under space reactor conditions may become substantial. Sensitivity analysis was conducted by varying five key parameters. The results revealed that higher temperatures, greater fission rates, and extended operation times significantly increase the buffer-IPyC gas pressure, posing the greatest challenge to TRISO particle performance in space reactors. These findings reveal the greatest challenges for TRISO particles in space reactors compared to conventional reactors and underscore the necessity of enhancing their designs to ensure reliability and structural integrity in space reactor applications.