Abstract: A method for producing UO.sub.2 or (U/Pu)O.sub.2 powder includes obtaining ammonium uranyl carbonate or ammonium uranyl plutonyl carbonate by treating a starting oxide selected from the group consisting of uranium oxide, plutonium oxide and uranium plutonium mixed oxide, with at least one solution selected from the group consisting of aqueous ammonium carbonate solution and aqueous ammonium hydrogen carbonate solution. The ammonium uranyl carbonate or ammonium uranyl plutonyl carbonate is then heated and in particular calcined.

Abstract: Not readily dissolvable nuclear fuel is dissolved in an airtight closed vessel or autoclave. Nitric acid is evaporated and condensed in the vessel and the nitric acid condensate trickles over the nuclear fuel disposed outside of the nitric acid undergoing evaporation.

Abstract: A container for a liquid radioactive and/or fissionable substance includes an outer container. An inner container is disposed in said outer container for receiving the substance. The inner container includes a primary container and a separate, closed secondary container having upper and lower ends. The primary container has an upper end protruding beyond said upper end of said secondary container and a lower end protruding beyond said lower end of said secondary container in longitudinal direction. A first connecting tube leads continuously downward in a direction from said lower end of said secondary container toward said lower end of said primary container. A second connecting tube leads continuously upward from said upper end of said secondary container in a direction toward said upper end of said primary container. The outer container has a fill chamber disposed therein for filling with heat-conducting filler.