| abstract |
Compacted pellets of uranium oxide alone or containing one or more additives such as plutonium dioxide, gadolinium oxide, titanium dioxide, silica and alumina are heated to a temperature in the range of 900*-1500*C in the presence of a gas which initially consists essentially of a mixture of hydrogen and carbon dioxide, either alone or with an inert carrier gas such as nitrogen and argon, and held at the desired temperature in this resultant atmosphere to sinter the pellets. The sintered pellets are then cooled in an atmosphere having an oxygen partial pressure in the range of 10 4 to 10 18 atmospheres of oxygen such as an atmosphere of dry hydrogen, wet hydrogen, dry carbon monoxide, wet carbon monoxide, inert gases such as nitrogen, argon, helium, and neon and mixtures of any of the foregoing including a mixture of hydrogen and carbon dioxide. The ratio of hydrogen to carbon dioxide in the gas mixture fed to the furnace is controlled to give a ratio of oxygen to uranium atoms in the sintered particles within the range of 1.98:1 to about 2.10:1. The water vapor present in the reaction products in the furnace atmosphere acts as a hydrolysis agent to aid removal of fluoride should such impurity be present in the uranium oxide. |