Patent Number: 047160110
Section: abstract

A BWR fuel assembly includes a bundle of elongated fuel rods disposed in side-by-side relationship so as to form an array 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 bottom and top nozzles mounted at opposite ends of the flow channel and having an inlet and outlet respectively for allowing entry and exit of coolant fluid into and from the flow channel and along the fuel rods contained therein. The BWR fuel assembly includes an improvement in the form of a coolant flow direction control device mounted in the bottom nozzle of the fuel assembly and being operable to open the inlet thereof to flow of coolant fluid in an inflow direction into the flow channel through the bottom nozzle inlet but close the inlet to flow of coolant fluid from the channel through the bottom nozzle inlet upon reversal of coolant liquid flow from the inflow direction. In an exemplary form, the coolant flow direction control device is a one-way or unidirectional flow check valve positioned across the inlet of the fuel assembly bottom nozzle for sensing the direction of coolant flow and automatically opening when the flow direction sensed is into the bottom nozzle and closing when the flow direction sensed is out of the bottom nozzle.