Abstract: The present invention relates generally to nuclear reactors, and more particularly, to nuclear reactors having fuel assemblies that employ support grids. A method of reducing friction and physical contact between a fuel rod and support grid in a nuclear fuel assembly is provided. The method includes applying a lubricant composition to the outer surface of the fuel rod during fuel assembly fabrication and removing the lubricant composition afterward.

Abstract: The absorbing rods have a nearly the same shape as the shape of columnar control rods for PWR used in reactivity control of core in a reactor. The absorbing rods can shield neutrons, and are inserted in control rod guide pipes and measuring pipes in fuel assemblies.

Abstract: Process for the production of nuclear fuel pellets based on mixed uranium and plutonium oxide having a specific plutonium content from a charge of UO.sub.2 and PuO.sub.2 powders by lubrification, pelletizing and sintering, in which a solid, sulphur, organic additive of the zwitterion type is incorporated into the mixture during the co-milling stage for the powders.

Abstract: The disclosed invention comprises a method for assembling fuel bundles for service in nuclear reactors which minimizes damage to the assembled components of a nature that renders the components susceptible to destructive corrosion in service, and the enhanced product of the improved method. The invention includes the utilization of a temporary protective barrier, such as water soluble sodium silicate or gelatin, intermediate the components during assembly.

Abstract: In order to prevent the formation of a hydrogen atmosphere in a free gas ce usually available in the storage containers of radioactive waste, potassium permanganate is dispersed in a suitable carrier within the storage barrel provided for the waste. When the radioactive waste is first encased in cement before being put in a storage barrel, the potassium permanganate is introduced into the cement before it sets by mixing in a solution or crystals. Alternatively the compressed or solidified waste is enveloped in a porous non-reducing aggregate of carrier materials, such as particles of aluminum oxide, on the exposed surfaces of which potassium permanganate is applied or which is mixed with potassium per manganate particles. The waste and the enveloping permanganate-containing carrier material are then securely enclosed in a common container.

Abstract: For improving the corrosion resistance of the sheaths of fuel rods used in water cooled and moderated reactors, part at least of the outer surface of the sheath is coated with a dense and adhering carbon layer having a thickness of from 0.1.mu. to 5.mu.. The layer may be deposited by radiofrequency reactive sputtering in a lower alkyl containing atmosphere.

Abstract: Nuclear fuel elements are provided that are resistant to pellet-clad interaction. The closed end nuclear fuel elements comprise a zirconium or zirconium alloy tube that has a layer of lubricant, preferably graphite, on the inner surface thereof, and enriched uranium dioxide pellets that have a coating on the outer surface thereof of a thickness sufficient to absorb fission products. The coating on the pellets may be a burnable absorber or a material that has a relatively low neutron absorption compared to a burnable absorber. The combination of the layer on the tube and the coating on the pellets reduces both the stress level and the concentration of damaging fission products that would contact and react with the layer of lubricant about the inside surface of the tubular cladding and thus reduces conditions for pellet-clad interaction.

Abstract: For safety in storage and transport of nuclear fuel elements outside a nuclear reactor core, they are provided with a coating of a neutron-absorbing substance from a liquid phase, e.g. by immersion, spraying or pouring, utilizing a melt, a solution or immersion so that the possibility of critical mass attainment is eliminated or minimized.

Abstract: A device for transversely restraining the fuel rods of a bundle of fuel rods for a nuclear reactor assembly comprises an upper grid, a lower grid and an intermediate grid arranged in the direction of the axes of the fuel rods, each grid defining cells through which the fuel rods extend, the upper and lower grids being identical and made integral, and the intermediate grid being made of resilient material and arranged with its cells staggered transversely relative to those of the upper and lower grids so that the walls of the cells of the intermediate grid press the rods against the walls of the cells of the upper and lower grids.