Thermal and irradiation induced intermixing of uranium suicide reactor fuels with the aluminum cladding is an important consideration in understanding their fission gas and fuel swelling behavior. We have used Rutherford backscattering to follow the behavior of an Al thin film on U3Si and U3Si2 during 1.5 MeV Kr ion irradiation at temperatures of 30 and 350°C. After an initial dose during which no intermixing occurs, the Al mixes quickly into U3Si. The threshold dose is believed to be associated with an oxide layer between the Al and the uranium suicide. At 300°C and doses greater than threshold, rates of mixing and aluminide phase growth are extracted.