Identification and Decomposition of Uranium Oxychloride Phases in Oxygen-Exposed UCl₃ Salt Compositions

Complementary X-ray absorption fine structure (XAFS)spectroscopyand Raman spectroscopy studies were conducted on several UCl3 concentrations in several chloride salt compositions. The sampleswere 5% UCl3 in LiCl (S1), 5% UCl3 in KCl (S2),5% UCl3 in LiCl-KCl eutectic (S3), 5% UCl3 in LiCl-KCl eutectic (S4), 50% UCl3 in KCl (S5),and 20% UCl3 in KCl (S6) molar concentrations. Sample S3had UCl3 sourced from Idaho National Laboratory (INL),and all other samples were UCl3 sourced from TerraPower.The initial compositions were prepared in an inert and oxygen-freeatmosphere. XAFS measurements were performed in the atmosphere ata beamline, and Raman spectroscopy was conducted inside a glovebox.Raman spectra were able to confirm initial UCl3. XAFS andlater Raman spectra measured, however, did not correctly match theliterature and computational spectra for the prepared UCl3 salt. Rather, the data shows some complex uranium oxychloride phasesat room temperature that transition into uranium oxides upon heating.Oxygen pollution due to failure of the sealing mechanism can resultin oxidation of the UCl3 salts. The oxychlorides presentmay be both a function of the unknown O-2 exposure concentration,depending on the source of the leak and the salt composition. Evidenceof this oxychloride claim and its subsequent decomposition is justifiedin this work.