Uranium nitride and silicide composite fuels used to reduce fuel oxidation

Abstract

In the 1960s, the space nuclear program started reactor propulsion designs, sparking interest in uranium mononitride (UN) as a fuel. Since then, UN has become attractive due to its higher thermal conductivity and elevated uranium density compared with standard UO2. Reactors using sodium and lead as liquid coolants show a long experience with UN fuel. Recently, uranium UN mixed with uranium silicide (U3Si2) has been an option as a more tolerant fuel for power units. However, a few silicide compounds exist, such as USi, USi2, USi3, U3Si, U3Si2, and U3Si5. Thus, nitride-silicide composites like UN-U3Si5 took the place of UN-U3Si2 in order to reduce the energetic interaction with steam and shield the nitride phase from water reactions. Ther is increasing interest in UN-U3Si5 fuel, which has a secondary fissile phase with an elevated uranium density. This way, we compare UN-U3Si2 and UN-U3Si5 using Kanthal APMT as cladding.