| abstract |
Among fuel rods (13, 14, 15, 16, 17, 18, 19) which constitute a fuel assembly, low-gadolinia-added fuel rods (16, 17, 18) each of which contains an oxide of uranium having a condensation degree of more than 5% contain a Gd composite oxide. The Gd composite oxide is an oxide containing gadolinium and a rare earth element A other than gadolinium and represented by the chemical formula A 1-X Gd X O 2-0.5X or A 1-X Gd X O 1.5 . The rare earth element A may be cerium (Ce), lanthanum (La), erbium (Er) or the like. |