Coating method for the preparation of coated nuclear fuels with carbides borides or nitrides by using high temperature and high pressure combustion synthesis

Abstract

The present invention relates to a coating method for the preparation of a coated nuclear fuel. Particularly, the present invention relates to the coating method of nuclear fuel surface with more than two coated layers of carbides, borides or nitrides and their compounds comprising deposition or permeation steps of i) elements or mixture that can form carbides, borides or nitrides and ii) a layer of pyrolytic carbon or boron prepared by chemical vapor deposition(CVD) or sputtering in sequence or in reverse sequence, or nitrogen prepared by gas permeation in sequence, on the nuclear fuel surface. The coated layers are formed with carbides, borides, nitrides or their mixture at high temperature and pressure by a combustion synthesis. The coating method of this invention can be applied to various types of nuclear fuels either in particle or in pellet type and control and preserve fine crystal structure without phase transition since the surface of nuclear fuel coated with pyrolytic carbon and silicon is heated only for several seconds by heat source such as laser beam, arc or microwave. Thus, the present invention is excellent method of coating nuclear fuel surface not only for particle type fuel which used in High Temperature Gas-cooled Reactor (HTGR) but also for pellet type fuel used for Water-cooled Reactors.