Patent Number: 055240330
Section: abstract

Gadolinium is provided which is adapted for nuclear fuel as a burnable poison, having a plurality of isotopes in an isotopic composition such that the content of at least one even mass numbered isotope is smaller than the content of the same isotope in natural gadolinium. A fuel assembly is also provided having a plurality of nuclear fuel rods arrayed as a lattice in which at least one of the fuel rods contains the gadolinium burnable poison of the present invention. Also, a fuel assembly is described which has a plurality of nuclear fuel rods arrayed as a lattice which includes at least a first group and a second group of nuclear fuel rods containing gadolinium. The content of Gd-157 in the gadolinium is larger than that found in natural gadolinium. Further, the gadolinium concentrations in the first and second groups are different from each other.