[en] The growth behavior of reaction layers and heat generation during the reaction between U-Mo fuel powder and the Al matrix in U-Mo/Al dispersion fuels were investigated. Annealing of 10vol.% U-10Mo/Al dispersion fuels at temperatures from 500 .deg. C to 550 .deg. C was carried out for 10 min. to 100 hrs to measure the growth rate and activation energy of diffusion in the reaction layer. The heat generation of U-Mo/Al dispersion fuels with 10∼50vol.% of U-Mo fuel during the thermal cycle from room temperature to 700 .deg. C was measured employing differential scanning calorimetry. Exothermic heat from the reaction between U-Mo fuel and the Al matrix is the largest when the volume fraction of U-Mo fuel is about 30vol%. The unreacted fraction of U-Mo fuel increases as the volume fraction of U-Mo fuel increases from 30vol% to 50vol%, while an endothermic reaction is also generated due to the melting of the Al matrix when the volume fraction of U-Mo fuel is less than 30%