Abstract: A method for making a varistor disc with increased high temperature stability. The method includes the steps of formulating a mixture for the varistor disc, compacting the mixture to form a disc, sintering the disc at a first preselected temperature and cooling the disc at a predetermined linear rate. The predetermined linear rate and preselected temperature are selected to reduce nonequilibrium conditions which become "frozen-in" as said disc is cooled.

Abstract: Annular pellets of burnable poison specifically boron carbide, B.sub.4 C, in a matrix of a refractory material, specifically aluminum oxide, Al.sub.2 O.sub.3, are produced. The pellets are of small wall thickness. Powders of the Al.sub.2 O.sub.3 and the B.sub.4 C are milled in a ball mill in water in which a wetting agent, a surfactant and a deflocculant are included to produce a slurry. Organic binders and plasticizers are added. Then the slurry is spray dried in a centrifugal separator. The resulting powder is poured into a mold and a turbular green body is formed by isostatic pressure. The tube may be sintered to size as a whole and then cut into lengths; i.e., pellets, or the green body may be cut into green-body pellets which are then sintered.

Abstract: A process provides a method for attaching a turbine blade to a blade support such as a rotor or rotor disc of a turbine. The root portion of the blade is formed to a shape approximately that of a groove in the surface of the rotor or rotor disc and the root portion of the blade is inserted within the groove. A composition comprising a particulate compound selected from the group consisting of a ceramic, graphite metal, metal alloy and mixtures thereof is positioned between the root portion of the blade and steeples, located one on either side of the groove.

Abstract: A burnable absorber-containing glaze is formed on nuclear fuel pellets by applying a finely divided mixture of a boron-containing burnable absorber and a boron-containing glass to the pellet surface as a coating and firing the coated pellets at 900.degree.-1100.degree. C., for about 5 to 15 minutes, to melt the boron-containing glass and encapsulate the boron-containing burnable absorber. The coating is of a thickness of 1 mil or less and contains an amount of B.sup.10 sufficient to provide desired absorption of neutrons during reactor operation. The resultant pellets exhibit good adhesion of the coating and excellent resistance to moisture adsorption.

Abstract: A burnable absorber coated nuclear fuel. A fissionable material nuclear fuel substrate is at least partially covered by a burnable absorber layer. A hydrophobic material overcoat layer generally covers the burnable absorber layer and is bonded directly to it.

Abstract: A method for coating a nuclear fuel with a burnable poison and a burnable poison coated nuclear fuel made by the method. The nuclear fuel is surface cleaned, and then a burnable poison layer is sputtered thereon. A sputtering deposition rate is picked that preferably will heat the nuclear fuel surface between 200.degree. C. and 600.degree. C. For deposition rates that result in heating the nuclear fuel surface to less than 200.degree. C., external heat is applied to heat the nuclear fuel surface between 200.degree. C. and 600.degree. C. To make the burnable poison layer less hygroscopic, an overcoat layer of a hydrophobic material is sputtered on the burnable poison layer.

Abstract: A neutron-absorber body for use in burnable poison rods in a nuclear reactor. The body is composed of a matrix of Al.sub.2 O.sub.3 containing B.sub.4 C, the neutron absorber. Areas of high density polycrystalline Al.sub.2 O.sub.3 particles are predominantly encircled by pores in some of which there are B.sub.4 C particles. This body is produced by initially spray drying a slurry of Al.sub.2 O.sub.3 powder to which a binder has been added. The powder of agglomerated spheres of the Al.sub.2 O.sub.3 with the binder are dry mixed with B.sub.4 C powder. The mixed powder is formed into a green body by isostatic pressure and the green body is sintered. The sintered body is processed to form the neutron-absorber body. In this case the B.sub.4 C particles are separate from the spheres resulting from the spray drying instead of being embedded in the sphere.

Abstract: Apparatus for depositing a coating (such as a burnable absorber) on nuclear fuel pellets. Pallets 16 hold a single layer of fuel pellets 22 between lower and upper screened parts 18 and 20. A rotating drum 14 holds the pallets 16 on its circumference. A chamber 12 encloses the drum 14. A sputtering machine 24 has stationary, sputter-frangible, upper and lower targets (such as zirconium diboride) 26 and 28. The stationary upper targets 26 are placed inside the drum's circumference above its longitudinal axis and are pointed facing generally upward and radially outward. The stationary lower targets 28 are placed outside the drum's circumference below its longitudinal axis and are pointed facing generally upward and radially inward. The target material is sputtered onto the fuel pellets 22 as the pallets 16 on the drum 14 rotate past.

Abstract: A method of applying a burnable absorber coating on a nuclear fuel pellet comprising the step of exposing the nuclear fuel pellet to a gas stream of boron trichloride and anhydrous ammonia at a temperature of from about 600.degree.-800.degree. C. A coating of boron nitride is formed as a reaction product of boron trichloride with anhydrous ammonia on the fuel pellet.

Abstract: Method of making a burnable neutron absorber of boron carbide in a matrix of aluminum oxide. In the practice of this method, boron-carbide particles are coated with a pore former and then they are mixed in a slurry with aluminum oxide powder. When the slurry is subsequently dried and sintered, the pore former is burned out and a body is formed including the boron-carbide particles in a matrix of aluminum oxide with substantially all boron-carbide particles in the body surrounded by a void.

Abstract: An improved annular burnable poison pellet of aluminum oxide-boron carbide (Al.sub.2 O.sub.3 --B.sub.4 C) adapted for positioning in the annular space of concentrically disposed zircaloy tubes. Each tubular pellet is fabricated from Al.sub.2 O.sub.3 powders of moderate sintering activity which serves as a matrix for B.sub.4 C medium size particle distrbution. Special pellet moisture controls are incorporated in the pellet for moisture stability and the pellet is sintered in the temperature range of 1630.degree.-1650.degree. C. This method of fabrication produces a pellet about 2 inch long with a wall thickness of about 0.020 inch to 0.040 inch. Fabricating each pellet to about 70% theoretical density gives an optimum compromise between fabricability, microstructure, strength and moisture absorption.

Abstract: Disclosed is a method of making a pellet from a powder by placing the powder in a heat-shrinkable container, sealing the container and isostatically pressing the container at a temperature which causes it to shrink, followed by decomposition of the container and sintering of the powder. In preparing nuclear fuel pellets, a free-flowing fissile powder is mixed with a free-flowing fertile powder and the mixture is placed in the heat-shrinkable container. The container is sealed, heated and isostatically pressed, then decomposed and the powder is sintered.

Abstract: A method is disclosed for producing a dimensionally stable UO.sub.2 fuel pellet of large grain mole %, and relatively large pore size. A dopant containing an element selected from the group consisting of aluminum, calcium, magnesium, titanium, zirconium, vanadium, niobium, and mixtures thereof is added to a highly sinterable UO.sub.2 powder, which is a UO.sub.2 powder that is sinterable to at least 97% theoretical density at 1600.degree. C. in one hour, and the UO.sub.2 powder can then be formed into fuel pellets. Alternatively, the dopant can be added at a step in the process of producing ammonium diuranate. The ammonium diuranate is collected with about 0.05 to about 1.7 mole%, based on UO.sub.2, of a compound containing said element. That mixture is then calcined to produce UO.sub.2 and the UO.sub.2 is formed into a fuel pellet. The addition of the dopant can also be made at the hydrolysis stage in the manufacture of UO.sub.2 by a dry conversion process.