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Various kinds of clay are used in radioactive waste management as absorbents, buffer materials of repositories and burial sites, and raw materials for obtaining ceramics to immobilize radionuclides. As shown by archeological discoveries, clay ceramic withstands the action of natural factors for hundreds and thousands of years, which promises reliable immobilization of radionuclides in a ceramic matrix for burial of radioactive waste. The strength of clay ceramic is comparable to that of steel but has greater radiation resistance because of the absence of hydroxyl groups, which determine the radiolysis of compounds based on hydraulic binders. The ceramic does not contain readily soluble salts (e.g., nitrates), is not subject to degradation by microorganisms, and is thermally stable.The technology for obtaining a radioactive ceramic and the equipment design for the individual stages of the process can be based on the well developed procedures and equipment of the ceramic industry. In contrast to vitrification during firing of ceramic the entire mix does not melt and so the amount of radionuclides carried off by the vapor-gas phase is decreased and corrosion of the equipment is reduced.Positive results were obtained from laboratory studies on the use of clay as matrix materials for immobilizing wastes containing plutonium and transplutonium elements [1][2][3] as well as intermediate-and low-level wastes [4, 5].In this article we generalize data obtained from work on the conditions for using clay ceramic to immobilize ash, pulps of hydroxides and filter-perlite, and simulators of vat residue from the evaporation of liquid radioactive waste from nuclear power plants.As matrix materials we used four varieties of plastic kaolinite clay with a SIO2/A1203 ratio of 2.2-3.2 and a 3-8 mass % content of fusible materials, i.e., compounds of alkali and alkaline-earth metals. Polymineral easily fusible Cambrian clay with a SiO2/AIzO 3 ratio of 6.7 and a 15 mass % content of fusible materials was also used.The studies were performed on actual ash from the burning of radioactive waste, model and real pulp formed during purification by precipitation with a collector (iron hydroxide) at various stages of fuel reprocessing. Immobilization conditions were also worked out with a model pulp of spent filter perlite and model vat residues from evaporation of waste from a nuclear power plant with a RBMK reactor.The elemental composition of the ash, perlite, and hydroxide pulp was determined on an STI~-I spectrograph by emission analysis (Table 1). The model solution of nuclear power plant waste, chosen in accordance with the data of [6], contained (in g/liter): 60.7 NaNO 3, 9 Na2C204, 9.3 KOH, 8.2 Na3PO4, and 1.3 NaCI.X-ray phase analysis determined that hydroxyapatite Cas(PO4)3OH is the main crystal phase in the ash, other phosphates being represented to a much lesser degree. The diffraction pattern of the initial ash is shown in Fig. 1.Besides an x-ray amorphous phase, the dried residue of hydroxide pulp contains monohydrocalcite CaCO3H...