Abstract: A burnable absorber cluster assembly includes a support plate, a plurality of burnable absorber rods, and an improved attachment joint for detachably connecting an upper end of each of the absorber rods to the support plate. The attachment joint includes a plug insert defined on the end of each of the rods, a hollow annular wall extending outwardly from each plug insert, holes defined through the support plate for receiving the plug inserts, and recesses formed in the support plate and connected with the holes therein. Each recess is conical-shaped and extends in flared fashion outwardly from one hole to a maximum diameter greater than the diameter of the hole. The annular wall on each plug insert is deformed into conformity with the shape of one of the recesses for providing an interengaging connection between the insert plug and the support plate in which the plug insert is disposed within the support plate hole.

Abstract: An improved arrangement for attaching and reattaching a top nozzle of a reconstitutable fuel assembly includes a sleeve member associated with each guide thimble of the fuel assembly and complementary elements for attaching the sleeve member and the upper end portion of the guide thimble together. The sleeve member includes an inner tubular alignment sleeve portion which receives the guide thimble upper end portion and extends between the upper hold-down and lower adapter plates of the top nozzle. The sleeve member also includes an outer tubular shroud portion having a lower annular flange which underlies a coil spring surrounding the sleeve portion and interconnects the shroud portion and the sleeve portion. The outer shroud portion extends upwardly about a portion of the coil spring for protecting the spring from damage by coolant cross flow from adjacent fuel assemblies.

Abstract: A modular in-core flow filter for capturing potentially harmful debris during cold hydrostatic and hot functional testing of a nuclear reactor. Since testing is carried out before fuel assemblies are placed in the reactor, multiple filters, each being of the same size and configuration, are temporarily installed on the reactor lower core plate. They fill the space which later is occupied by fuel assemblies when the assemblies are installed in an operating position. Each filter includes a square metal base having a single axial opening which desirably covers four holes in the core plate. Fine mesh and coarse mesh screens are secured in the axial opening and the unit is removably attached to the core plate by brackets which extend through the metal base and engage the underside of the core plate but are actuated into position from the upper side of the core plate. When functional flow testing of the primary coolant system has been completed, the filters are removed for subsequent use in other reactors.