BOILING WATER THERMAL NEUTRON REACTOR

摘要

PROBLEM TO BE SOLVED: To provide a boiling water thermal neutron reactor capable of increasing shutdown margin and thermal margin and increasing the reactor power per unit core volume. SOLUTION: The core of the boiling water thermal reactor installed with a plurality of fuel assemblies having water rods in the inside surrounded by a channel box is constituted to have a relation between a total cross sectional area A of non-boiling region including a water gap region formed around the channel box and a region in the water rods and a cross sectional area B of boiling region formed outside the fuel rods and the water rods in the channel box, fulfilling B/(A+B)>=0.75.