Fuel assembly

Purpose: To flatten the power distribution in fuel assemblies and decrease the burning residue of fissile nuclides in BWR type reactors. Constitution: In conventional fuel assemblies, since non-boiling water is present to the outside of a channel box, neutron decelerating effect is increased at the periphery of the fuel assembly and the burn-up proceeds remarkably to possibly impare the mechanical and thermal integrity of fuel rods. In this invention, fuel rods disposed in adjacent with the channel box are wholly or partially formed with nuclear fuel materials containing thermal neutron absorbent at the axial center portion. Thus, since the local power peaking coefficient is not worsened at the periphery of the fuel assembly, fuel burning is proceeded at a flat power distribution and, accordingly, mechanical and thermal integrity of the fuel rods can be secured. (Kamimura, M.)