Metal fuel for reactor

The present invention concerns nuclear metal fuels suitable to FBR type reactors and the object of the invention is to prevent partial reduction of melting point due to the re-distribution of the ZR ingredient in the metal fuels comprising U-Pu-Zr system alloy or U-Zr system alloy. That is, at a radial intermediate portion in a radial cross section of a cylindrical metal fuel comprising U-Pu-Zr system alloy or U-Zr system, a region with higher Zr content than that in the U-Pu-Zr system alloy or U-Zr system alloy is disposed. In conventional metal fuels of this type, the content at the radial intermediate portion of the cylinder is reduced accompanying the advance of burning and re-distributed such that the content ratio between the central region and the outer circumferential region is increased. On the other hand, in the fuels having the feature of the present invention, the higher Zr content region constitutes a source for the Zr ingredient even if the re-distribution of the alloy ingredient occurs, thereby enabling to prevent the reduction of the Zr ingredient. (I.S.)