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Uranium disilicide is an inorganic chemical compound of uranium in oxidation state +4. It is a silicide of uranium.There has been recent interest in using uranium disilicide as an alternative to uranium dioxide forfuel in nuclear reactors. Advantages are higherpercentage of uranium and higher thermal conductivity. A direct replacement of UO2 with U3Si2should enable a reactor to generate more energy from a set of fuel rods and also provide more "coping time" in the case of a LOCA.
The development of uranium disilicide, uranium nitride, or other high thermal conductivity uranium compound may be critical for the performance of "Accident Tolerant Fuel", adevelopment effort mandated by the US Department of Energy. This is due to zircalloy having a higher thermalconductivity than all replacement materials being developed. In particular, SIC-SiC CMC , which has several superior material properties to zircalloy for this application, has about five times lower thermal conductivity than zircalloy.. The lower thermal conductivity means that a reactor using fuel rods with SiC-SiC CMC cladding and conventional UO2 fuel will have to either: 1] Run at a lower power output to keep the fuel the same temperature, or 2] Run with the same power, with the fuel hotter, which means the reactor has less coping time. The alternative, enabled by U3Si2 which has about five times better thermal conductivity than UO2 , is expected to be a fuel rod capable of equal power output, slightly better energy output, and longer coping time.