| 摘要 |
In the manufacture of nuclear fuel elements, fuel particles are coated either before or after agglomeration into a porous unitary fuel element structure. The coating may be metallic or ceramic, i.e. of carbide, nitride or oxide, and the particles or pores may be coated in any of several ways. Metallic coating may be applied by deposition from the vapour, e.g. Mg, Al, Be and their alloys, or deposition from solution, sol or amalgam, the transfer being aided by heat or electrolysis. Metal coatings e.g. of Zr, Nb, V, Ti and their alloys may be deposited by decomposition of their halides, and coatings of Ni, Mo, Fe, Co and their alloys may be deposited from their carbonyls. Metals and alloys can also be deposited from aqueous or organic solutions of their salts and other compounds, or from emulsion, sols and suspensions. Once deposited the metallic coating may be transformed into oxide, carbide or nitride by exposure to a suitable oxidizing, nitriding or carburizing atmosphere. In an example, wires of U / Mo alloy are cold drawn to make them straight and hard, and are then heated in nickel carbonyl gas to produce a nickel coating, they are then heated in molybdenum carbonyl gas to produce a molybdenum coating. They are then coated with an adhesive and rolled in powdered stainless steel. They are then heated to decompose the adhesive and sinter the stainless steel. The wires so produced are then bundled together and sintered at their points of contact to form the desired fuel element. |
