The Volatility of Plutonium Dioxide

The volatility of plutonium dioxide has been measured in the temperature range 1320°C to 1790°C by a modification of the Knudsen effusion method. The plutonium dioxide was heated in vacuum in a tantalum oven. Under these conditions the dioxide was reduced to a lower oxide, or oxides, which maintained a constant reproducible vapor pressure throughout further heating. Either an oxide was formed which was stable under the conditions of the experiment or thermal reduction continued with the formation of a second solid or liquid phase. The thermal reduction of the oxide was reversed by heating the reduced oxide in a low pressure atmosphere of oxygen.