Nuclear fuel element

Purpose: To suppress the progress of corrosion at the inner surface of fuel cans in the Cs accumulation portions and also suppress the formation of cesium uranate in fuel pins for use in FBR type reactors. Constitution: Blanket pellets with low O/M ratio (M represents the sum of the numbers of atoms for U and rear earth metal elements) and of stable composition from mixed oxides comprising a composition of uranium U and one or several of rare earth elements such as cerium Ce, yttrium Y, lanthanum La, etc. They are used as blanket pellets in the region in adjacent with the effective heat generation portion where Cs accumulation occurs. This can reduce the required amount of oxygen supplied for progressing the corrosion to obtain suitable pellets to insuring integrity upon irradiation in the reactor core during long period of time. (Takahashi, M.)