Patent Number: 048715093
Section: abstract

A spring retainer is disclosed for use in retaining fuel pellets in a fuel rod both during fabrication and shipment to prevent the fuel pellets from being moved from their design location before installation within a reactor. The cylindrical and solid nuclear pellets containing the reactor fuel are placed within the fuel rods (or cladding) and have an outside diameter slightly less than the inside diameter of the fuel rod. Once the pellets are in place, a two-part spring holder is inserted into the end of the fuel rod. A first compression spring part of the coil spring holder is a conventional coil spring which, acting in compression, bears against the fuel pellets with a preselected force typically forcing the pellets when in the horizontal position into a compacted disposition when the fuel rod is horizontal. This conventional coil spring has a diameter which is less than the inside diameter of the fuel rod. A second locking spring part of the coil spring holder is a coil spring having a diameter which exceeds the inside diameter of the fuel rod. This helical locking spring is spirally wound down to an outside diameter less than that of the inside diameter of the fuel rod for insertion into the rod and released to key to the inside diameter of the rod. Winding occurs through a special tool which attaches to the respective ends of the coil spring.