NUCLEAR FUEL PELLET Russian patent published in 2021 - IPC G21C3/62 

FIELD: reactor fuel cells.

SUBSTANCE: invention relates to design of pelletised fuel for fuel elements of light water reactors, for example, VVER reactors, and can be used for fuel elements of reactors operating in long fuel cycles, as well as modes of maneuvering by reactor power. Tablet structure is made in the form of cylinder with external chamfers and with central hole along longitudinal axis, with external chamfer at angle of 20–30° to surface plane of end platform, with ratio of chamfer width to diameter of tablet from 0.02 to 0.15, wherein the size of single defects of the tablet appearance is not more than 1.3 % of the surface area of the tablet for end surface defects, not more than 1.0 % of the surface area of the tablet for defects of the lateral cylindrical surface and not more than 0.7 % of the surface area of the tablet for defects adjacent to the external border of the chamfer. Average size of uranium dioxide grains ranges from 6 to 35 mcm. Tablet may additionally contain aluminum – from 0.002 to 0.020 wt% and silicon – from 0.001 to 0.010 wt% in the form of oxides distributed uniformly throughout the tablet volume. Tablet can additionally contain gadolinium oxide – from 0.3 to 10.0 wt%, which in the form of a solid solution with uranium dioxide is uniformly distributed throughout the volume of the tablet, or erbium oxide – from 0.3 to 2.5 wt%, which in the form of a solid solution with uranium dioxide is uniformly distributed throughout the volume of the tablet.

EFFECT: reduced tensile stresses in the shell of fuel elements due to reduced size of single defects of the appearance of the tablet, as well as reduced output of gaseous fission products due to introduction of additives increasing grain size.

4 cl, 3 dwg