Abstract: Disclosed is a grid structure for supporting fuel rods in a nuclear reactor. The grid structure is formed of a plurality of interconnected thin metal grid straps that are welded or brazed together to provide a structural network of interconnected open grid cells, similar to an "egg crate divider". The grid straps are provided at regular intervals, corresponding to the width of a grid cell, with pairs of spaced, substantially horizontal, slotted spring-like projections and a substantially X-shaped spring-like projection vertically intermediate the horizontal projections. The spring-like projections are designed to support and hold the fuel rods within the grid cells under both balanced and unbalanced forces acting on the fuel rod assembly while it is in service, surrounded by coolant in the nuclear reactor.

Abstract: An adjustable powder flow gate for a rotary pellet press has a movable gate wherein one dimensional motion of the gate across an opening in a powder flow feed frame on the rotating turret of the press is effected with a rotatable shaft having a screw connection to a member attached to the gate. The shaft is maintained in a selected rotational position with a bias member that is movable between an engaged and a disengaged position. The bias member is adapted to engage a selected detent on a member attached to the shaft having several circumferentially spaced detents when the bias member is in the engaged position. The shaft can freely rotate when the bias member is in the disengaged position. An operator can easily adjust the size of the opening by first disengaging the bias member from the selected detent, turning the shaft to move the gate to the desired position, and then engaging the bias member into a newly selected detent.

Abstract: An apparatus for forming a pellet is disclosed that includes at least one punch that is reciprocably movable through an opening in a die for compressing a granular material, such as uranium dioxide, into a pellet such as the fuel pellets used in the fuel assemblies that generate power in nuclear reactors. The punch is advantageously formed from an alloy consisting essentially of tungsten carbide having a grain size of less than one micron which is embedded in a matrix of cobalt which constitutes between 16.5 and 17.5% by weight of the alloy. The alloy is preferably hot isostatically pressed to achieve zero porosity and a density of approximately 14.0 gm/cc.sup.3. Additionally, essentially pure ingredients are preferably used to avoid interfaces in the resulting alloy which could provide situs for chipping. The resulting alloy has a Rockwell scale A hardness of 89.

Abstract: A fuel pellet for a nuclear reactor fuel rod is fabricated with smooth and gently sloping surfaces having no sharp edges or areas of high stress concentration. The bearing surfaces of the fuel pellets are contoured so that the pellets are easily stacked within a fuel rod and permit pivoting action between the fuel pellets. The fuel pellets are stacked end to end in a fuel rod which is incorporated into a fuel assembly for a nuclear reactor.

Abstract: A grid of improved design for a nuclear reactor fuel assembly which includes a multiplicity of interleaved straps enclosed in a peripheral frame which forms a grid of egg-crate configuration. Each cell formed by the grid straps, except those containing control rod guide tubes, supports a fuel rod which is held in place by springs projecting laterally inwardly into each cell from the grid straps. The springs extend parallel to the fuel rods and are spaced at 90.degree. intervals around the rod. Further, each of two adjacent springs contact a fuel rod at two points along its length and each of the other two adjacent springs contact the fuel rod at one point thus imparting strength and flexibility to the fuel assembly containing such grids.