The thermal decomposition of Pu(C204).. 9 6H20 has been studied in both argon and oxygen using a combination of thermogravimetry and infrared spectroscopy. Decomposition in an inert atmosphere involves reduction of the cation to the trivalent state and its subsequent reoxidation to form PuO 2. In an oxidizing atmosphere, with unrestricted access of oxygen, reduction of the cation does not take place and decomposition to PuO 2 is through the oxycarbonate. The reduction of Pu(IV) appears to take place by a carbon monoxide catalyzed mechanism and the presence of carbort in the PuO,, decomposition product is attributed to the disproportionation of CO.Of the several processes used to prepare plutonium metal the most widely used involves the thermal decomposition of Pu(C204)2 " 6 H20 to the oxide (PuO2),. fluorination of the oxide to PuF 4 and the subsequent reduction of the fluoride to the metal with calcium. One particular disadvantage of this process is that the carbon which apparently arises as a consequence of the thermal decomposition of the oxalate, is carried through the process and appears as an impurity in the plutonium metal product. To aid in the removal of this carbon impurity the thermal decomposition of Pu(C20~)2 ' 6 H20 is done in air at 300 to 400 ~ Several earlier studies have been done on this process [1][2][3][4][5][6]. However, the interpretations were at variance with each other and as Glasner points out [7], the thermogravimetric results have had little support by other experimentation or observation.The present study makes use of both infrared spectroscopy and thermogravimetric techniques to follow the thermal decomposition of Pu(C20~)~" 6 H20 in both argon and oxygen to try to define explicitly the source of the carbon and to determine the effect, if any, of oxygen on the mechanism of the thermal decomposition of Pu(C~,O4h" 6 H20 itself.
ExperimentalThe starting material, Pu(C2Oa)2 " 6 H20, was prepared by the method described by Harmon and Reas [8]. Briefly, this involved adding 1 M H~C204 and H202, for valence adjustment, to a Pu(NOa)4 solution (~ 4 M HNO~) held at 50 -55 ~