Patent Number: 040455262
Section: summary

This invention relates to a process for the preparation of graphite-clad or graphite-coated nuclear fuel rods. More particularly, the invention relates to a process for the preparation of excellent integrated graphite-coated nuclear fuel rods for high temperature gas-cooled reactors, the graphite-coated rods being prepared by integrally molding a material for the nuclear fuel rod and a material for the graphite coat or sheath for the nuclear fuel rod and baking the integrally molded mass. Conventional rod-type, for example, cylindrically-shaped nuclear fuel compacts or rods, comprising coated particulate nuclear fuel, have heretofore been prepared by charging a mixture of the coated nuclear fuel particles, graphite powder and a binder therefor into a metallic molding die, compressing the mixture in its axial direction to obtain a molding thereof and baking the molding. Such conventional methods are impossible to thereby prepare fuel rods which are very large in length as compared with their diameter; moreover, these rods when each housed in a graphite sleeve for use in atomic reactors will constitute resistance to heat transfer in gaps between the rods and sleeves, and they will therefore be caused to be heated to excessively high temperatures when in use. This invention eliminates such drawbacks. The graphite-sheathed nuclear fuel rods, which are final products, of this invention consist essentially of a nuclear fuel rod and a graphite sheath (or coat) therefor which have been integrated by the use of specific integrally molding and subsequently baking techniques according to this invention. The integration of the fuel rod and graphite sheath in the final product of this invention when using the final product in the reactor, will be conducive to ensuring a decreased heat resistance at the portion between the rod and sheath and also to ensuring a less difference in irradiation shrinkability between the rod and sheath thereby preventing them from peeling from each other with the result that the final products have satisfactory heat characteristics and a high capability of specific heat dissipation. The integral structure of the final products of this invention gives the advantages and effects as detailed below. It enables the final products not only to exchange heat directly with a cooling gas when they are used but also to obtain high densification thereon whereby they have an increased strength and heat conductivity. It also enables the final products to be mechanically processed safely without exposing the nuclear fuel particles of the rod because the rod is covered with the graphite coat, that is the graphite-clad one.