Quantitative Microstructural Characterization of Plutonium Oxalate Auto-Degradation and Evidence for PuO2 Nanocrystal Formation

It has been known since the 1950s that plutonium oxalate powders change color and lose mass over time when stored at room temperature in air. Despite several studies monitoring these changes, there are still discrepancies in the literature regarding the speciation of intermediate and final products that result from this decomposition. Presented here for the first time is a comprehensive series of time-resolved powder X-ray diffraction experiments coupled with solid-state optical spectroscopy and electron microscopy of aged plutonium (III) and (IV) oxalate powders. These data provide fresh insight into the chemical and structural changes that occur in these solids over time at room temperature and represent new evidence suggesting both plutonium (III) and plutonium (IV) oxalates auto-decompose to form nanocrystalline plutonium oxide in the solid state.

Automated summary

This study presents a comprehensive analysis of time-resolved powder X-ray diffraction experiments, solid-state optical spectroscopy, and electron microscopy of aged plutonium oxalate powders. The data provide new insights into the chemical and structural changes that occur in these solids over time at room temperature, suggesting the auto-decomposition of plutonium oxalates to form nanocrystalline plutonium oxide.