Development of a thermo-mechanical coupling code based on an annular fuel sub-channel code

To simulate the thermal hydraulic performance of the annular fuel more accurately, some mechanical models have been incorporated into the sub-channel code SACAF, including pellet displacement model, gap heat transfer model, fission gas release model and fuel-cladding mechanical interaction model. The results calculated by the developed code are in good agreement with that by FROBA-ANNULAR. The developed code can consider the change of the heat transfer coefficient of the inner and outer gaps, the release of the fission gas release, the inner pressure of the fuel, the stress and strain of the cladding, which cannot be calculated by the conventional sub-channel code. Based on the calculation results, a great change is found in the gap heat transfer coefficient and MDNBR during the operation, which implies that the coupling of the sub-channel code and the mechanical performance models is necessary.