nuclear fuel pellets

Abstract

The invention relates to the nuclear technologies, and to the 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 degrees 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 mu m. 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. The object of the invention is nuclear fuel pellet design development, which should ensure safe operation of fuel elements in normal operating mode, interruption of normal operation and maneuvering mode of reactor operation and increase fuel combustion. The technical result consists in reducing the tensile circumferential stress in the fuel element cladding by reducing the size of unidirectional defects in the pellet appearance and in reducing the yield of gaseous fission products due to the addition of additives that can increase the particle size.

Description

technical field [0001] The invention belongs to the nuclear technology, that is, the fuel pellet structure of the fuel element of the light water reactor, such as the water-water type power reactor, the fuel element of the reactor which can use the long fuel cycle and the maneuvering state of the reactor power. [0002] Nuclear fuel requirements for atomic reactors are currently limited on an ongoing basis. In particular, the fuel should ensure safe operation of the reactor during long fuel cycles, maneuvering states of reactor power and maintain performance during high burnout operations. Background technique [0003] Known pellets (RU 2 376 665, IPC G21C 3 / 62, issued 2009) comprise oxides of aluminum and silicon, equivalent to uranium, distributed uniformly throughout the pellet volume, with an aluminum content of 0.005 to 0.03% by mass, Silicon content - 0.003 to 0.02% by mass, aluminum to silicon mass ratio of 1.5 to 4, uranium dioxide particle size of 20 to 45 μm. [...

AI Technical Summary

Problems solved by technology

[0012] Disadvantages of known pellets are reduced uranium capacity due to tapered projections and recesses and increased circumferential stresses inside the fuel element casing due to enlarged chamfer overall height and pellet projections at the pellet contact in the fuel rod

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