Upper tie plate for boiling water nuclear reactor

Abstract

An improved upper tie plate is disclosed in a fuel bundle for a boiling water nuclear reactor. The tie plate resides in a fuel bundle including an upper tie plate, a lower tie plate, a matrix of sealed fuel rods supported therebetween, and a surrounding channel. Both the lower tie plate and the improved upper tie plate have two functions; they support the fuel rods in vertical upstanding relation between the tie plates and interior of the channel and permit the passage of moderating coolant through the channel from the bottom of the channel to the top of the channel. This moderating coolant enters through the lower tie plate in the liquid form, passes into the matrix of upstanding fuel rods where steam is generated and exits outwardly through the improved upper tie plate as a water steam mixture at the top of the fuel bundle. The improvement includes the support of the channel directly from the fuel bundle lifting bail for transmission of load directly to the bail instead of a cantilevered support through the tie plate. This direct support enables cutting away a portion of the matrix overlying the fuel rods for reduction of pressure drop in the escaping steam/water phase from the fuel bundle. Additionally, this alignment enables raising of the points of tie plate support for longer fuel rod length. Improved fuel bundle performance results.