Abstract

Electrochemical processing of used nuclear fuel in molten chloride salts generates complex radioactive salt waste. Dechlorination of waste salt using phosphate compounds at elevated temperatures (∼600 °C) reduces the volume of material for disposal while evolving gaseous chlorine compounds that could be used to transform metallic uranium into UCl3. In this study, the effects of processing temperature, environment (air or argon), and H3PO4 precursor-to-chlorine ratio on the dechlorination efficacy of a simple alkali salt mixture (SSM) and a salt waste simulant (ERV3) were evaluated. For both salts, the highest chlorine release was concurrent with the water boiling. For the SSM, atmospheric O2(g) significantly affected dehydration and condensation reactions of phosphoric acids processed at < 300 °C, which resulted in ∼17 wt % less dechlorination in argon than in air. Processing at >500 °C led to the formation of alkali metaphosphate glasses with < 1 wt % chlorine, irrespective of atmosphere. ERV3 samples required 600 °C and slightly higher H3PO4/Cl ratios than the theoretical value (>1) to consistently dechlorinate < 1 wt %. Monazite was detected in samples with P/Cl = 1. Samples were X-ray amorphous when P/Cl = 1.21. Contamination from the silica crucible was detected in the SSM and ERV3 dechlorinated samples, which also affected crucible integrity.

Department(s)

Materials Science and Engineering

Comments

U.S. Department of Energy, Grant DE-NE0009317

Keywords and Phrases

dechlorination; electrochemical processing; electrochemical salt waste; phosphate glass; used nuclear fuel

International Standard Serial Number (ISSN)

2690-0645

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2025 American Chemical Society, All rights reserved.

Publication Date

01 Jan 2025

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