Core of a boiling water reactor

摘要

Fuel assemblies (5) composing a core (10) of a boiling water reactor include a plurality of fuel rods (6A, 6B, 6C, 6D, 6E) including uranium but not including gadolinium and a plurality of fuel rods (6F, 6G, 6H) including uranium and gadolinium. A mean thickness of a channel box (7) surrounding these fuel rods (6) is 2.6 mm and a ratio of an inner width of the channel box (7) to a width of a fuel assembly lattice (15) is 0.863. A mean uranium enrichment of the fuel assemblies (5) in a transverse section is 4.73 wt%. An uranium weight included in a unit volume of the core region is 2.4 kg/l. The reactor power can be improved from that of a current BWR/5 by 20 %. The core of a boiling water reactor can be realized the increase power output by keeping a thermal margin on the same level as that of a BWR in operation at present and make cooling of each of fuel rods in fuel assemblies during increase power output more uniform.