Abstract
Using the finite element multiphysics modeling method, the performance of the thorium-based fuel with Cr-coated SiC/SiC composite cladding under both normal operating and accident conditions was investigated in this work. First, the material properties of SiC/SiC composite and chromium were reviewed. Then, the implemented model was simulated, and the results were compared with those of the FRAPTRAN code to verify the correctness of the model used in this work. Finally, the fuel performance of the Th0.923U0.077O2 fuel, Th0.923Pu0.077O2 fuel, and UO2 fuel combined with the Cr-coated SiC/SiC composite cladding and Zircaloy cladding, respectively, was investigated and compared under both normal operating and accident conditions. Compared with the UO2 fuel, the Th0.923U0.077O2 and Th0.923Pu0.077O2 fuels were found to increase the fuel centerline temperature under both normal operating and reactivity-initiated accident (RIA) conditions, but decrease the fuel centerline temperature under loss-of-coolant accident (LOCA) condition. Moreover, compared to the UO2 fuel with the Zircaloy cladding, thorium-based fuels with Cr-coated SiC/SiC composite cladding were found to show better mechanical performance such as delaying the failure time by about 3 s of the Cr-coated SiC/SiC composite cladding under LOCA condition, and reducing the plenum pressure by about 0.4 MPa at the peak value in the fuel rod and the hoop strain of the cladding by about 16% under RIA condition.
Highlights
Thorium was considered as a potential alternative fuel since the beginning of nuclear energy development, and it is found to have potential to stretch nuclear fuel reserves due to its natural abundance and because it is possible to breed the 232Th isotope into a fissile fuel (233U) (Ade et al, 2016)
The temperature of the UO2 fuel with Cr-coated silicon carbide fiber–reinforced silicon carbide matrix (SiC/SiC) composite cladding is found to be the highest, and the temperature of the UO2 fuel with Zircaloy cladding is found to be the lowest, which is due to the fact that the thermal conductivity of the SiC/SiC composite cladding is lower than that of the Zircaloy cladding at the same temperature
It is noticed that the centerline temperature of thorium-based fuels is found to be lower than that of the UO2 fuel with the same cladding, and the average temperature of the Th0.923U0.077O2 fuel is found to be about 100 K lower than that of the UO2 fuel with the same cladding, FIGURE 14 | Gap size evolutions for the UO2 fuel with Zircaloy cladding, the Th0.923Pu0.077O2 fuel, and Th0.923U0.077O2 fuel with Cr-coated SiC/SiC composite cladding under the normal operating condition
Summary
Thorium was considered as a potential alternative fuel since the beginning of nuclear energy development, and it is found to have potential to stretch nuclear fuel reserves due to its natural abundance and because it is possible to breed the 232Th isotope into a fissile fuel (233U) (Ade et al, 2016). Inspired by the work of Liu et al (2020), in this work, UO2 fuel with the Zircaloy cladding and thorium-based fuels (including Th0.923U0.077O2 and Th0.923Pu0.077O2) with the Cr-coated SiC/ SiC composite cladding are selected to be investigated and compared under both normal operating and accident conditions by the CAMPUS code. Details of the Model In this work, accident conditions including LOCA and RIA are investigated by the CAMPUS code, based on the existing CAMPUS code under the normal operating condition (Liu et al, 2016), which applied a multiphysics coupled method for calculation. The plenum pressure is found to decrease after the rapid increase due to the increase of gap FIGURE 8 | Plenum pressure evolutions of the UO2 fuel with Zircaloy cladding calculated by the FRAPTRAN and CAMPUS codes under the RIA condition. From the calculation results presented above, it can be observed that results calculated by the CAMPUS code are found to be consistent with the results calculated by the FRAPTRAN code, which verify the correctness of the CAMPUS code under accident conditions
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