Nuclear fuel pellet and its manufacturing method

Nuclear fuel pellets are each divided into an axial central region and an outer circumferential region in which the crystal grain size in the outer circumferential region is made smaller than the axial central region. Further, amorphous SiO2-Al2O3 is caused to deposit at the crystal boundary of the outer circumferential region. Thus, since the crystal grain size in the central portion of the nuclear fuel particle pellets is large, it takes a much time for gaseous nuclear fission products generated to reach the grain boundary, thereby enabling to reduce the amount released to the outside of the pellets. Further, since the crystal grain size is smaller and SiO2-Al2O3 is deposited in the outer circumferential portion, creep rate can be increased due to grain boundary slip. (Y.Y.)