Method of stabilizing uranium dicarbide

Uranium dicarbide is metastable at a temperature below 15000C so that it gradually changes into diuranium tricarbide with the liberation of carbon, an undesirable phenomenon from the viewpoint of using uranium dicarbide as a nuclear fuel. The present invention discloses a technique for preparing a stable uranium sulfide (preferably monosulfide) is heated at a temperature above 10000C, particularly in the range of 1500 to 18000C in vacuum or in an inert atmosphere to convert them into a stable solid solution. In one example, a mixture of uranium dicarbide and uranium monosulfide (95 mol : 5 mol) was pulverized, formed into a block, and heated to 18000C for 5 hours to give a solid solution. When heated to 14500C for 5 hours to give a solid solution. When heated to 14500C for 100 hours, the solid solution underwent no change. Uranium carbide itself, when heated to 14500C, formed diuranium tricarbide in one hour or less. (Kaichi, S.)