Method of manufacturing nuclear fuel pellet

Purpose: To effectively absorb the swelling at the central portion of a pellet, as well as obtain a sufficient creep velocity and reduce the release of gaseous fission products in fuel pellets for use in BWR type reactors. Method: A pellet is divided into a central region and outer peripheral region. The crystal grain size and the porosity in the central region are made greater than those in the outer peripheral region. In the central region, the O/U ratio for the UO2 powder is set to 2.10 - 2.30, material for increasing crystal grain size (TiO2, Nb2O5, Cr2O3, etc.) is mixed as additives and the specific surface area is made to 3 - 8 g/cm3. Further, in the outer peripheral region, O/U ratio for the UO2 powder is set to 2.00 - 2.100, and material for increasing sintering density (Al(OH)3, Al, etc.) is mixed as additives and the specific surface area is set to 3 g/cm3. Thus, the increase in the inner pressure and the elevation of temperature for the fuel can in the fuel rod can effectively be suppressed to prevent stress corrosion cracking in the fuel can. (Ikeda, J.)