Plutonium(IV) precipitation from alkaline solutions: I. Effect of precipitation and coagulation conditions on properties of hydrated plutonium dioxide PuO2 center dot xH(2)O

Samples of hydrated plutonium dioxide PuO2 . xH(2)O were synthesized under various conditions and studied by X-ray diffraction analysis, IR spectrosco py, and thermal analysis. The composition of the above compound depends on conditions of its synthesis and drying. The x value in PuO2 . xH(2)O dried over KOH varies from 0.5 to 1.6 depending on conditions of the precipitate coagulation. PuO2 . xH(2)O is a semi-amorphous compound and loses water at heating to similar to 250 degrees C. However, the hygroscopicity of the deh ydrated product disappears only after calcination at temperatures higher th an 600 degrees C. The reflections in the powder pattern of plutonium dioxid e prepared from PuO2 . xH(2)O at 800 degrees C remain broadened. During the first several minutes of PuO2 . xH(2)O precipitation, the plutonium concen tration in the mother liquor amounts to 10(-6)-10(-5) M and then decreases over the course of several days. The specific volume of precipitates after sedimentation strongly depends on coagulation conditions.