During irradiation of dispersion U–Mo/Al fuel, along with the formation of the (U,Mo)Alx interaction layer, the formation of pores containing gaseous fission products also takes place. Gas pores are formed in the fuel particles, in the (U,Mo)Alx layer and in the aluminum matrix near the (U,Mo)Alx layer. Usually, the structure of pores is analyzed using optical and scanning electron microscopy, which makes it possible to study only very large pores, those with sizes from tenths of a micron or more. In the present paper, the effect of burnup and isochronous annealing in the 150–580°C temperature range on the change in the substructural characteristics of dispersion U–Mo/Al fuel is established. The values of the characteristics are determined on the basis of experimental data on small-angle neutron scattering. This made it possible to study the substructural characteristics of the fuel in the range of 1 to 50 nanometers.