Channel flowrate control type fuel assembly

Fuel elements, a flow rate control element and flow rate suppression rods are incorporated in a wrapper tube. The flow rate suppression rod is made of stainless steel, and disposed to a space formed by the inner wall of the wrapper tube and fuel elements in adjacent with the inner side thereof. The flow rate of coolants in a channel between the wrapper tube and the fuel rods is suppressed. As a result, the highest temperature of a cladding tube is lowered, or the temperature of coolants at the exit of the assembly is elevated. The flow rate control element is a cylindrical tube made of stainless steel, and has a coolant inlet hole in a lower portion and a coolant exit hole in an upper portion. The inlet hole is disposed in the vicinity of a lower end of a reactor core and the exit hole is disposed lower than the upper end of the reactor core. New channels are disposed to the assembly by the flow rate control element, to change the distribution of the coolant flow rate in the assembly. This can flatten the temperature distribution of the coolants in the fuel assembly. (I.N.)