Abstract: A control cluster for a water cooled and moderated nuclear reactor, comprises a spider and rods suspended from the spider. Each rod contains neutron-absorbing material. In a lower portion of each rod, the material is a metal neutron absorber. In an upper portion, it is a stack of pellets of boron carbide B.sub.4 C. In a middle fraction occupying a height lying in the range 35% to 45% of the total height, it is zirconium diboride ZrB.sub.2 isotopically enriched in boron 10 or hafnium diboride HfB2.

Abstract: Oxidation treatments by ionic bombardment or post-discharge result in the formation on the surface of passivatable metals and alloys of a layer of oxide having a thickness of a few micrometers which protects the substrates from subsequent corrosion. The gas activated by the electric discharge is put in contact with the surface of the part (2) to be oxidized, which is brought to a temperature of 350.degree. to 650.degree. C. The treatment may be employed in particular for forming a protective covering on an element or a complete framework composed of a zirconium alloy of a fuel assembly of a water-cooled nuclear reactor.

Abstract: An organometallic chromium compound in the gaseous phase is brought into contact with a substrate consisting of the inner surface of the zirconium alloy tubular cladding (5) of the fuel element, or the outer surface of the pellets of fuel material, the substrate being kept at a temperature between 300.degree. and 600.degree. C. The organo metallic compound may consist of chromium acetylacetonate. The process enables a chromium oxide coating to be obtained inside the tubular cladding (5) and/or on the outer surface of the nuclear fuel pellets. Pellet/cladding interaction is thus prevented or limited when this fuel element is used in the reactor.

Abstract: A sheath for a nuclear reactor control rod consists of chromium nickel stainless steel. It is protected against friction wear by nitridation over a depth of from 15 to 50 .mu.m obtained by an electric discharge in a nitrogen containing atmosphere.

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: A hot chamber die casting apparatus for casting aluminum, zinc, magnesium, copper and their alloys as well as other metals which, in the molten state, corrode ferrous materials. The apparatus comprises a crucible, an injection pump in the crucible, and a gooseneck leading from the crucible to an outlet nozzle. The parts of the apparatus have coatings or sleeves of materials which resist corrosion, abrasion, erosion and mechanical or thermal shocks.