Fabrication method for mixed oxide fuel

A mixed oxide fuel fabrication method is described which uses a starting material of an oxide of one fuel in the form of spherical particles of two size fractions, fine and coarse, sintering the fine fraction to full density, sintering the coarse fraction to a predetermined density, impregnating the coarse fraction with a salt of a second fuel material and treating this fraction to convert the impregnating material to an oxide, and then loading both fractions into a fuel element. In the preferred process three size fractions are used, i.e. fine, medium, and coarse, with only the coarse fraction being subject to the impregnation step. (LL)