A structural model for multi-layered ceramic cylinders and its application to silicon carbide cladding of light water reactor fuel

A thermo-mechanical model for stress distribution and Weibull statistical fracture of a multi-layered SiC cladding for LWR fuel is developed. The model is validated by comparing its results to those of the Finite Element Analysis (FEA) code ANSYS. In steady-state operation, the temperature sensitive swelling may lead to undesirable tensile stresses which is anticipated to challenge the structural integrity of the fission-gas retaining inner layer of CVD-SiC monolith in a triple layer design with the composite being the middle layer. The stress distribution is sensitive to potential differences in the swelling of the monolith from that of the composite layer. The sensitivity is discussed in this work. A double-layered SiC cladding that employs the inner SiCf/SiC composite layer, and the outer CVD-SiC layer has also been analyzed. This SiC cladding design significantly reduces failure probability as it appropriately allocates peak tensile stresses in the inner composite while significantly reducing tensile stress levels of the CVD-SiC monolith.