X‐ray diffraction, differential scanning calorimetry and evolved gas analysis of aged plutonium tetrafluoride (PuF4).

A 30 year-old PuF₄ sample consisting of brown powder (PuF₄-b) and pink granules (PuF₄-p) was analyzed. X-ray diffraction shows the bulk is comprised of three compounds: PuF₄, PuO₂, and PuF₄·1.6H₂O. Broadening of PuF₄ XRD peaks suggests possible α -damage. After annealing at 650 °C, crystalline PuF₄ and PuO₂ remain. Thermogravimetric analysis and differential scanning calorimetry—with simultaneous evolved gas analysis—of the separated PuF₄-p and PuF₄-b components reveal a distinct sequence of reactions. Dehydration occurs between ~ 90 and 300 °C. Exothermic annealing of the α -damage occurs in two stages: at 350–355 °C and at 555–558 °C. Hydrofluoric acid, fluorine and helium desorb during the first exotherm. Above 700 °C, PuF₄ reacts with PuO₂, resulting in oxygen release and mass loss. [ABSTRACT FROM AUTHOR]