Abstract: A nuclear fuel element and a method of manufacturing the element. The fuel element is comprised of a metal primary container and a fuel pellet which is located inside it and which is often fragmented. The primary container is subjected to elevated pressure and temperature to deform the container such that the container conforms to the fuel pellet, that is, such that the container is in substantial contact with the surface of the pellet. This conformance eliminates clearances which permit rubbing together of fuel pellet fragments and rubbing of fuel pellet fragments against the container, thus reducing the amount of dust inside the fuel container and the amount of dust which may escape in the event of container breach. Also, as a result of the inventive method, fuel pellet fragments tend to adhere to one another to form a coherent non-fragmented mass; this reduces the tendency of a fragment to pierce the container in the event of impact.

Abstract: A fuel rod for a nuclear reactor fuel assembly includes a metal cladding tube having two closed ends. A column of nuclear fuel pellets is disposed in the cladding tube. A compression spring has helical coils and is coaxial with the column of pellets within one of the ends of the cladding tube. A shim has two sides and is disposed between the column of pellets and the helical spring. A pair of leaf springs on one of the sides of the shim is locked to and biased against the coils of the helical spring.

Abstract: An improved nuclear fuel element for service in power generating, water cooled nuclear reactors, comprising a fuel cladding container of an alloy of zirconium provided with a barrier lining of unalloyed zirconium metal metallurgically bonded to the container's inner surface, and enclosed therein fissionable nuclear fuel including an additive of aluminum silicate.

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.

Abstract: A cluster of standardized reduced length burnable absorber rods include a plurality of middle rod sections having a multiplicity of different axial lengths and containing burnable absorber material in sealed chambers therein, a plurality of upper end spacer sections having a multiplicity of different axial lengths and each defining an empty space, and a plurality of lower end spacer sections having a multiplicity of different axial lengths and each defining an empty space. Each of the rods is formed of one middle rod section tandemly arranged between and interconnecting one upper end spacer section and one lower end spacer section. The three interconnected sections which form each rod being selected so as to provide the same standard combined axial length for each of the rods in the cluster thereof although the axial lengths of the middle rod sections can vary from rod to rod and thereby the axial location of the burnable absorber material along the rod can also vary from rod to rod.

Abstract: A nuclear fuel rod has a sheath closed by end plugs and a stack of fuel pellets in the sheath. The stack is retained in abutment against one of the end plugs during handling of the fuel rod by a radially expandable element having a cross-sectional area in rest condition such as it frictionally engages an internal surface of said sheath. When the fuel rod is brought to the reactor operating temperature, the radially expandable element is contracted clear of frictional contact by temperature responsive means of a shape memory alloy operatively associated with said radially expandable element and having a transformation temperature above atmospheric temperature.

Abstract: Fuel and fertile rod for a nuclear reactor. It comprises a can, a column of fissile and/or fertile pellets within the can and end plugs welded to the two ends of the can. The column of pellets is held in place by two tubular spacers of limited thickness and with rounded edges abutting against the two ends of the fuel column and set with a fixed dimension to the can. The column of fissile and fertile pellets can also be held in place by a supplementary positioning setting of the fertile pellet column.

Abstract: The present invention relates to a nuclear fuel pellet having two sections: a cylindrical inner pellet inside of an annular outer pellet. The inner pellet is composed of gadolinia and natural or depleted uranium as UO.sub.2. The outer pellet contains enriched uranium as UO.sub.2 but without gadolinia.

Abstract: Substantially isotropic spherical fuel and absorber elements for high temperature reactors are produced by molding corresponding fuel particles and graphite molding compositions. There is used as graphite molding powder a mixture of graphitized granules of coke and a hardenable resin binder. There are first produced in steel dies at 80.degree. to 120.degree. C. half shells and a nucleus with a pressed density of 1.0 to 1.4 g/cm.sup.3 followed by molding in a further steel die to the final format.

Abstract: A soluble burnable absorber rod for a nuclear reactor fuel assembly has a tubular body with a pair of end plugs sealing the opposite ends thereof and defining a chamber within the body. A neutron absorber material in liquid form, preferably boric acid with an enhanced concentration of boron isotope B-10, is contained within the chamber. The tubular body has reinforcing convolutions formed therein for strengthening the body to withstand external pressure acting thereon. Also, one of the end plugs acts as a hydride sink and a hydrogen getter material is disposed adjacent the other end plug.

Abstract: Cask-like steel container for one-site storage, later-shipment and permanent disposal of low-level-radiation nuclear waste material. Container has configuration of a hollow cylinder with heavy walls. Bottom portion of container is affixed to cylindrical sides with a double weld. Steel top member has an annular recess as does the top portion of the cylindrical sides, with hermetic, radiation-resistant gasket material included therebetween, and the container top and sides are bolted together. The top member has spaced heavy eyelet-like members affixed thereto for handling the container.

Abstract: A tubular sheath for particulate nuclear fuel has microporous retaining elements formed by winding metal strip about a central pin and pushing the resulting spiral into the sheath ends. The metal strip has transverse grooves formed by a photo-etching process which form axial gas passages narrow enough to prevent passage of fuel particles. Suitable materials for the strip include molybdenum and tungsten. A stainless steel strip can be used if a molybdenum or tungsten disc is placed between it and the fuel.

Abstract: The invention discloses a metal-actinide mononitride composition with dimensional stability in extended nuclear reactor operations, with a method of operation at surface temperatures in excess of 1700.degree. C. The preferred embodiment and operating method uses a mononitride of uranium and a metal selected from the group consisting of titanium or yttrium. Parameters for determination of the metal element to stabilize the fuel are disclosed.

Abstract: A nuclear fuel element suitable for use in fast breeder. The fuel element has a clad tube and a wire spacer wound round the clad tube. The clad tube of the fuel element is composed of a first clad tube and a second clad tube which are connected to each other through an intermediate plug. The first clad tube extends upwardly from the intermediate plug. The upper end of the first clad tube is closed by an upper end plug, while the lower end of the second clad tube is closed by a lower end plug. The first clad tube is charged with a multiplicity of fuel pellets, while the second clad tube defines a gas plenum therein. The spaces inside the first and second clad tubes are communicated with each other through vent holes formed in the intermediate plug. The wire spacer is wound round the first clad tube and is fixed at its one end to the end plug attached to the first clad tube and at its other end to the intermediate plug.

Abstract: An array of rods is assembled to form a fuel element for a pressurized water reactor, the rods comprising zirconium alloy sheathed nuclear fuel pellets and containing helium.The helium gas pressure is selected for each rod so that it differs substantially from the helium gas pressure in its closest neighbors. In a preferred arrangement the rods are arranged in a square lattice and the helium gas pressure alternates between a relatively high value and a relatively low value so that each rod has as its closest neighbors up to four rods containing helium gas at the other pressure value.

Abstract: A device for shutting down a nuclear reactor during an undercooling or overpower event, whether or not the reactor's scram system operates properly. This is accomplished by double-clad fuel safety rods positioned at various locations throughout the reactor core, wherein melting of a secondary internal cladding of the rod allows the fuel column therein to shift from the reactor core to place the reactor in a subcritical condition.

Abstract: A fuel assembly for a liquid metal fast breeder reactor having an upper axial blanket region disposed in a plurality of zones within the fuel assembly. The characterization of a zone is dependent on the height of the axial blanket region with respect to the active fuel region. The net effect of having a plurality of zones is to establish a dispersal flow path for the molten materials resulting during a core meltdown accident. Upward flowing molten material can escape from the core region and/or fuel assembly without solidifying on the surface of fuel rods due to the heat sink represented by blanket region pellets.

Abstract: A burnable poison rod for use in a nuclear reactor fuel assembly which includes concentrically disposed rods having an annular space therebetween which extends the full length of the rods. The inner rod is hollow to permit circulation of coolant therethrough. Annular burnable poison pellets are positioned in the annular space which is closed at both ends by plugs. A spring clip is located in the plenum space above the pellet stack in the rods. The spring clip is of cylindrical configuration having a gap in the material which provides two ends adapted to be squeezed toward each other. A cross section of the clip shows that its ends contain alternating flat and round edges, the round edges conforming to the outer rod inner surface to provide a retentive force which is releasably applied to the pellet stack as it grows during operation in a reactor.