Abstract: Method for solidifying high and medium radioactivity and/or actinide containing aqueous waste concentrates or fine-grained solid wastes suspended in water for final noncontaminating storage. The waste concentrates or suspensions are set, by evaporation, to a water content in the range between 40 and 80 percent by weight, and a solid content whose metal ion and/or metal oxide component lies between 10 and 30 percent by weight of the evaporate being formed. The pH of the evaporate is set to between 5 and 10. The resulting evaporate is then pelletized with the aid of a clay-like substance. The pellets are then heat treated, including drying at temperatures between room temperature and about 150.degree. C., then calcining at room temperatures up to about 800.degree. C. and subsequently firing at temperatures between 800.degree. C. and 1400.degree. C. to form practically undissolvable mineral phases. The pellets are then enclosed on all sides in a dense, continuous ceramic or metallic matrix.

Abstract: Method for solidifying high and medium radioactivity and/or actinide containing aqueous waste concentrates or fine-grained solid wastes suspended in water for final noncontaminating storage. The waste concentrates or suspensions are set, by evaporation, to a water content in the range between 40 and 80 percent by weight, and a solid content whose metal ion and/or metal oxide component lies between 10 and 30 percent by weight of the evaporate being formed. The pH of the evaporate is set to between 5 and 10. The evaporate is kneaded with a clay-like substance containing a small quantity of cement or such a clay-like substance or mixture of a clay-like substance with a small quantity of cement containing an additive for suppressing the volatility of the alkalis or alkali earths and/or an additive for suppressing the volatility of any decomposing anions which may be present in the evaporate from the group including sulfate, phosphate, molybdate and uranate ions.

Abstract: Solid radioactive waste is incorporated in glass, ceramic or basaltic blocks which are conditioned in waste waters or sludges prior to placement in ultimate storage. The conditioning has the dual benefit of reducing the radioactivity of the radioactive waste and of purifying the waste water or of purifying and facilitating the filterability of the sludge. Such purifying is enhanced by concurrent treatment with oxygen or an oxygen-containing gas and/or with a substance which is readily reduced to radicals.