Method of making sintered nuclear fuel pellets, in particular consisting of uranium dioxide

摘要

Uranium oxide may be formed into fuel rods, with intergranular structure, i.e. having cavities or pores between the grains but substantially no pores within the grains, by adjusting the shaping pressure, the powder fineness and the rate of increase of temperature during sintering. In general increase of pressure, increase of powder fineness and increase of the rate of temperature rise facilitates the formation of the intergranular structure. The formed elements usually have a density from 88-96% of the theoretical density of N0 2 . Intergranular structure is defined as a microstructure essentially comprising ports distributed in the form of recesses at the grain joints and practically without communication with the outside, therefore of closed porosity. Fig. 4 shows intragranular structure, i.e. pores in communication, Fig. 5 shows intergranular structure. These were both formed under similar conditions except that the shaping pressure of Fig. 4 was 4 tons/cm.2 whereas the shaping pressure of Fig. 5 was 6 tons/cm.2.