Patent ID: 8422617

Claim:
A core of a light water reactor having a plurality of fuel assemblies, which are loaded in said core, having nuclear fuel material containing a plurality of isotopes of transuranium nuclides, an upper blanket zone, a lower blanket zone, and a fissile zone, in which said transuranium nuclides are contained, disposed between said upper blanket zone and said lower blanket zone; wherein a ratio of Pu-239 in all said transuranium nuclides contained in said loaded fuel assembly is in a range of 40 to 60% when burnup of said fuel assembly is 0; a sum of an axial length of said lower blanket zone and an axial length of said upper blanket zone is in a range of 250 to 600 mm; and the axial length of said lower blanket zone is in a range of 1.6 to 12 times the axial length of said upper blanket zone.