Patent Number: 047537744
Section: abstract

A BWR fuel assembly has a bundle of spaced fuel rods, an outer tubular flow channel surrounding the fuel rods so as to direct flow of coolant/moderator fluid along the fuel rods, and a hollow central water cross with opposed walls, a lower flow inlet end, an opposite upper flow outlet end, and an open inner cruciform flow channel for subcooled moderator fluid flow through the fuel assembly. The water cross extends through the outer flow channel and is interconnected with the outer channel so as to divide it into separate compartments and the bundle of fuel rods into a plurality of mini-bundles thereof. Also, a pair of upper and lower tie plates are connected to the opposite ends of the fuel rods in each mini-bundle thereof so as to provide a separate fuel rod subassembly in each of the compartments. The tie plates have flow openings defined therethrough for allowing the flow of the coolant/ moderator fluid into and from the separate fuel rod subsasembly. The BWR includes an improvement which allows selected flow into said water cross and cross flow of fluid between the lower ends of the respective fuel rod mini-bundles of the separate fuel rod subassemblies and in such manner minimizes maldistribution of flow between the mini-bundles. The improvement comprises cross flow inlet means in the form of opposed holes located in the opposed walls of the water cross above the lower tie plates of the mini-bundles.