FUEL ASSEMBLY

摘要

PURPOSE:To enable reactor stop even if the concentration of fuel is made high as a partial length fuel rod whose effective whole stack length is shortened and enhance axial output distribution by lowering the concentration of fissionable nuclide at the axial part on a part of fuel rods. CONSTITUTION:The concentration of fissionable nuclide is substantially lowered at the axial part where subcritical degree is shallow in the time of reactor stop in a part of many fuel rods 33 in which nuclear fuel substances are filled in the inside of coating tubes made of metal and partial length fuel rods (P fuel rod) 45 whose effective whole stack length is shortened are made. The P-fuel rods 45 are arranged at the position sandwiched by thick water rods 44 (A, B) arranged in the diagonal direction of a fuel assembly. Since a non-fuel part of the P fuel rod 45 is positioned as about three quarters of the height of a reactor core at which reactor stop margin is strict is included and the wide non-fuel area of the P fuel rods 45 is formed from the thick water rod A to the thick water rod B at this position of the height, reactor stop margin is improved.