Fuel assembly for PWR type reactor

An axial blank is constituted by adding 237Np (neptunium) as the upper and the lower end for all of the fuel rods constituting a fuel assembly. Then length of the 237Np-containing blanket is made about 10% of the effective length of the fuel rod. This increases the conversion ratio into the fissile material at the upper and the lower end of the fuel rod and neutron leakage can be compensated to improve the neutron economy. Further, 237Np is added homogeneously over the entire effective length of the fuel rod. This can improve the conversion ratio, as well as reduce the excess reactivity without increasing the power peaking coefficient., thereby enabling to utilize 237Np as a burnable absorbent. 237Np is contained in the spent fuel rods and effective utilization of reprocessing products can be attained. (I.N.)