Composite nuclear fuel assemblage - comprises upper and lower bundles of fuel rods with fewer rods but of larger dia. in lower bundle, increasing efficiency

摘要

A composite nuclear fuel assemblage comprising a number of structures of nuclear fuel rods and a number of lattice structures arranged around the rod structures and spaced, so as to support them in individuall cells, has fuel rod structures comprising upper and lower bundles of fuel rods spaced axially at a predetermined distance from one another. There are fewer fuel rods in the lower bundle than in the upper bundle, but the dia. of those in the lower bundle is large than those in the upper bundel. The periphery of the lattice structures of the lower bundle is practically equal to that of the lattice structure of the upper bundle. The assemblage is advantageously adaptable to the use of a mixed oxide fuel in the lower rods and uranium-based fuel in the upper rods. A nuclear fuel assemblage which reduces the temp. and the limitations on efficacy present in existing assemblages and which is compatible with the use of mixed oxide fuels, is produced.