Abstract: An advanced gray rod control assembly (GRCA) for a nuclear reactor. The GRCA provides controlled insertion of gray rod assemblies into the reactor, thereby controlling the rate of power produced by the reactor and providing reactivity control at full power. Each gray rod assembly includes an elongated tubular member, a primary neutron-absorber disposed within the tubular member said neutron-absorber comprising an absorber material, preferably tungsten, having a 2200 m/s neutron absorption microscopic capture cross-section of from 10 to 30 barns. An internal support tube can be positioned between the primary absorber and the tubular member as a secondary absorber to enhance neutron absorption, absorber depletion, assembly weight, and assembly heat transfer characteristics.

Abstract: A bracket assembly for mounting a reed switch and associated magnet on an overhead opening door includes first and second interlocking pieces, both of which are stamped from sheet metal that is, preferably, non-ferromagnetic. Each of the pieces incorporates an opening sized to slidably receive a locking door bolt fabricated from a ferromagnetic material such as mild or hardened steel. For a currently preferred embodiment of the invention, both pieces of the bracket assembly are stamped from sheet aluminum. Both the reed switch and its associated magnet mount may mount on either piece, so long as they are on opposite sides of the opening. The assembly incorporates an opening that is sized to receive a slidable, locking bolt fabricated from a ferromagnetic material such as mild or hardened steel. When the bolt is withdrawn from the opening, the reed switch is activated, thereby generating a signal which can be input to a security system.

Abstract: Hybrid nuclear reactor grey rods are described, wherein geometric combinations of relatively weak neutron absorber materials such as stainless steel, zirconium or INCONEL, and relatively strong neutron absorber materials, such as hafnium, silver-indium cadmium and boron carbide, are used to obtain the reactivity worths required to reach zero boron change load follow. One embodiment includes a grey rod which has combinations of weak and strong neutron absorber pellets in a stainless steel cladding. The respective pellets can be of differing heights. A second embodiment includes a grey rod with a relatively thick stainless steel cladding receiving relatively strong neutron absorber pellets only. A third embodiment includes annular relatively weak netron absorber pellets with a smaller diameter pellet of relatively strong absorber material contained within the aperture of each relatively weak absorber pellet.

Abstract: A mechanical spectral shift reactor comprises apparatus for inserting and withdrawing water displacer elements having differing neutron absorbing capabilities for selectively changing the water-moderator volume in the core thereby changing the reactivity of the core. The displacer elements may comprise substantially hollow cylindrical low neutron absorbing rods and substantially hollow cylindrical thick walled stainless rods. Since the stainless steel displacer rod have greater neutron absorbing capability, they can effect greater reactivity change per rod. However, by arranging fewer stainless steel displacer rods in a cluster, the reactivity worth of the stainless steel displacer rod cluster can be less than a low neutron absorbing displacer rod cluster.

Abstract: A modular component nuclear fuel assembly design in which sub-assembly fuel modules are joined together to form an integral fuel assembly. The invention permits a defective or damaged fuel assembly to be reconstituted from new sub-assembly fuel modules thereby facilitating quick repair. By using sub-assembly fuel modules, the invention allows for modular enrichment and/or burnup variations within a fuel assembly and permits tailoring of reactivity and/or fuel burnup within the core thereby enhancing fuel management and utilization and enabling peaking factors to be reduced. The sub-assembly fuel module design permits easy access to interior fuel rods thereby affording an increased fuel rod surveillance capability and further permits advanced fuel design to be incorporated into a reactor core with a minimum of risk.

Abstract: A mechanical spectral shift reactor comprises apparatus for inserting and withdrawing water displacer elements having differing neutron absorbing capabilities for selectively changing the water-moderator volume in the core thereby changing the reactivity of the core. The displacer elements may comprise substantially hollow cylindrical low neutron absorbing rods and substantially hollow cylindrical thick walled stainless rods. Since the stainless steel displacer rods have greater neutron absorbing capability, they can effect greater reactivity change per rod. However, by arranging fewer stainless steel displacer rods in a cluster, the reactivity worth of the stainless steel displacer rod cluster can be less than a low neutron absorbing displacer rod cluster.

Abstract: A fuel assembly includes top and bottom nozzles, elongated hollow control rod guide thimbles extending longitudinally between and rigidly interconnecting the top and bottom nozzles such that together they form a rigid structural skeleton of the fuel assembly, transverse grids being supported on the guide thimbles at axially spaced locations therealong between the top and bottom nozzles, fuel rods extending through and being supported by the grids between the top and bottom nozzles so as to extend in generally side-by-side spaced relation to one another and to the guide thimbles, and elongated solid tie rods extending longitudinally between the top and bottom nozzles and through and rigidly interconnected with the grids so as to extend in generally side-by-side spaced relation to one another, to the fuel rods and to the guide thimbles so as to bolster the stiffness of the structural skeleton of the fuel assembly.

Abstract: A tiltable terminal clamp assembly including a screw having a circular protrusion on the underhead surface and a clamp plate of generally rectangular configuration having a central aperture dimensioned to loosely receive the shank of the screw and four angularly spaced raised embossments projecting above the upper surface of the clamp plate and extending outwardly from the central aperture toward the four corners of the clamp plate for engagement with the circular protrusion on the head of the screw. The raised embossments have a maximum height and width adjacent the aperture and decrease in height and width in a direction outwardly of the aperture in the clamp plate.

Abstract: A bracket assembly for mounting a reed switch and associated magnet on an overhead opening door includes first and second interlocking pieces, both of which are stamped from sheet metal that is, preferably, non-ferromagnetic. Each of the pieces incorporates an opening sized to slidably receive a locking door bolt fabricated from a ferromagnetic material such as mild or hardened steel. For a currently preferred embodiment of the invention, both pieces of the bracket assembly are stamped from sheet aluminum. Both the reed switch and its associated magnet mount may mount on either piece, so long as they are on opposite sides of the opening. The assembly incorporates an opening that is sized to receive a slidable, locking bolt fabricated from a ferromagnetic material such as mild or hardened steel. When the bolt is withdrawn from the opening, the reed switch is activated, thereby generating a signal which can be input to a security system.