Improvements in or relating to the production of nuclear fuel

A process is described for the production of dense U-Pu oxide fuel having a low oxygen to metal ratio. Such fuel has usually been produced by reduction with pure H2, but the use of undiluted H2 in a Pu facility is hazardous and explosions may occur, with serious consequences. In the improved process described the U-Pu oxide powder is mixed with C, granulated with a binder, formed into the required fuel bodies, and the latter heated to remove binder. Finally the fuel bodies are sintered in a neutral or reducing atmosphere, with production of CO. The presence of elemental C in fuel pellets before sintering does not appear to affect the density of the sintered pellets significantly compared with pellets without C, unless the binder is omitted. As regards the effect of C on the oxygen/metal ratio, this appears to depend directly on the amount of C present in a pellet after removal of the binder; the effect also appears to depend to some extent on the type of C added, and its particle size. The lowest limit of the oxygen/metal atomic ratio that can be obtained depends on the U/Pu ratio since only the Pu becomes hypostoichiometric. With 30% Pu [(Usub(0.7) Pusub(0.3) oxide] the 3-valent state has been reached for the Pu, and the same Pu state should be achievable with other percentages of Pu. A factor that should be taken into consideration is radiolytic decomposition of the binder. Some examples of application of the process is described. (U.K.)