Formation of β-U 3 O 8 from UCl 3 Salt Compositions under Oxygen Exposure

• Published in: The journal of physical chemistry. B 2024-11, Vol.128 (45), p.11174-11185
• Main Authors: Tuffy, Benjamin W, Birkner, Nancy R, Schorne-Pinto, Juliano, Davis, Ryan C, Mofrad, Amir M, Dixon, Clara M, Aziziha, Mina, Christian, Matthew S, Lynch, Timothy J, Bartlett, Maxwell T, Besmann, Theodore M, Brinkman, Kyle S, Chiu, Wilson K S
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/acs.jpcb.4c02776

Complementary X-ray absorption fine structure (XAFS) and Raman spectroscopy studies were conducted on various UCl concentrations in alkali chloride salt compositions. The samples were 5 mol % UCl in LiCl (S1), 5 mol % UCl in KCl (S2), 5 mol % UCl in LiCl-KCl eutectic (S4), 50 mol % UCl in KCl (S5), and 20 mol % UCl in KCl (S6) molar concentrations. Samples were heated to 800 °C and allowed to cool to room temperature with measurements performed at selected temperatures; the highest temperatures showed the most stability and will be primarily referenced for conclusions. The processing and interpretation of the Raman and extended X-ray absorption fine structure (EXAFS) peaks revealed several uranium-oxygen bond lengths and symmetries in the samples before, during, and after heating. Based on published thermodynamic data of similar systems, X-ray absorption fine structure spectroscopy, and identification of Raman peaks, a β variation of α-U O , typical at room temperature, is the suspected dominant phase of all samples at high temperatures (800 °C). In the existing literature, this β structure of U O was synthesized by slow cooling of uranium oxides from 1350 °C. This paper suggests the rapid formation of the compound due to the decomposition of the uranium chlorides or oxychlorides at increasing temperatures and O reaction kinetics.