Method for obtaining samples for measuring the distribution of nuclear fuel and its fission products in HTR fuel particles

To optimize the construction and technology for fabrication of HTR fuel particles it is necessary to have experimental information both on the starting technological contamination of the protective coatings of the fuel particles with the fissioning material and the distribution of the nuclear fuel and fission products in samples subjected to reactor tests. The difficulties in performing such studies are caused by the following: the smaller sizes of the fuel particles (the diameter is less than 1.5 mm and the thickness of the coatings ranges from 10 to 100 μm); the physicochemical stability of the materials of the fuel particles (uranium and thorium oxides and carbides, silicon and zirconium carbides, pyrocarbon); high radioactivity; and extremely high gradient of the concentration of fuel and fission products in the protective coatings. The basic idea tested here consists of the following: a laser beam interacts with the surface of a sample rotating chaotically in a stream of gas, a thin spherical layer of material is vaporized, and the vaporized material is deposited on a sampling collector for further analysis