Fuel assemblies for BWR type reactors

Purpose: To improve the core spray effect upon loss of coolant accidents in fuel assemblies for BWR type reactors by providing a specific spacer arrangement. Constitution: A plurality of spacers for supporting fuel rods are arranged at higher density at the middle portion of fuel rods with higher power distribution in accordance with the longitudinal power distribution in the fuel. Spray water scattered upon loss of coolant accidents is accumulated above each of the spacers by the upward vapor streams and, since a plurality of spacers are arranged at the portions of higher power density, most parts of the spray water are accumulated in those portions of the fuels that are liable to be failed, whereby satisfactory cooling for the fuel rods can be secured. (Ikeda, J.)