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To simulate the thermal–mechanical performance of a Supercritical CO2-cooled reactor fuel during the long-term normal operation, material models and new thermal and mechanical models are implemented in FROBA code to develop FROBA-SCO2. By calculation results comparison of the new models and ABAQUS, KAIST code and FRAPCON code, the reliability of new models were validated. The results show that with the effects of densification and burnup, the size and the temperature drop of the gas gap firstly increase and then decrease. The stress and the train of the cladding are affected by the pressure drop from both sides and change slightly. The fission gas release fraction is at a low level and the gas pressure increases slightly. The cladding corrosion behavior increases with the increment of temperature. The result indicated that the fuel element was safe enough during most time of the normal operation. The models established in this article calculates the fuel rod behaviors efficiently.

Most of the researches on supercritical CO2-cooled reactors focus on the design of core performance parameters world widely, but few on the detailed thermal hydraulic analysis. To supplement the lack of research in this area, in this study, the supercritical CO2-cooled reactor designed by the Nuclear Institute of China is taken as the resect. A complete solution method based on the thermal hydraulic model is established. And the sub-channel code SACOS-SCO2 is developed. The results of SACOS-SCO2 are compared with experimental results of SCUOL and code results of KAIST, and the good agreement fully illustrates the calculation ability of SACOS-SCO2. Based on the above models and codes, the thermal hydraulic characteristics of supercritical CO2-cooled reactor designed by the Nuclear Institute of China are analyzed under the conditions of reactivity introduction accident and the loss of flow accident. Through theoretical modeling and self-developed codes, the sub-channel thermal hydraulic characteristics of supercritical CO2-cooled reactor are studied, which can provide a powerful reference for the design and safety analysis of supercritical CO2-cooled reactor.