Performance analysis of UO2-SiC fuel under normal conditions

Abstract

This study aims to investigate a fuel mixture of silicon carbide (SiC) and uranium dioxide (UO2) and analyze performance when this fuel applies to light-water reactors (LWRs). Utilization of the licensing code, FRAPCON, with UO2 helped to determine the fuel response under normal conditions initially. High thermal conductivity could permit the use of UO2-10 vol% SiC fuel, showing thermal conductivity values that are far superior to the UO2 alone, exceeding 50% at 900 °C. Ultimately, the formulation should reduce gaseous fission products, avoid fuel cracking, and improve safety margins. SiC has excellent physical properties such as chemical stability, a cross-section with low absorption, irradiation resistance, and a higher melting point. There are some benefits for fuels that use carbon composites such as UO2-carbon nanotube (CNT), and UO2-diamonds. The pellets containing fractions of the carbon limit the amount of fissile U-235 and require additional enrichment to produce the same energy. In the past, there have been various attempts to increase the thermal conductivity of UO2. High conductivity is present in uranium nitride (UN), uranium carbide (UC), and UO2 mixed with beryllium oxide (BeO). The production method of UO2-SiC fuels should include the spark plasma sintering (SPS) technique. Advantages of SPS include a lower manufacturing temperature of 1050°C, better results, and reduced processing time of 30 s. SPS can help produce more tolerant fuels, such as UO2-SiC, UO2-carbon nanotube, and diamond powder dispersion in the UO2 matrix. The thermal conductivity of SiC can decrease substantially under irradiation. UO2-diamond has some drawbacks because of graphitization phenomena.