2019-Sustainable Industrial Processing Summit
SIPS2019 Volume 1: Angell Intl. Symp. / Molten Salt, Ionic & Glass-forming Liquids: Processing and Sustainability
| Editors: | F. Kongoli, M. Gaune-Escard, J. Dupont, R. Fehrmann, A. Loidl, D. MacFarlane, R. Richert, M. Watanabe, L. Wondraczek, M. Yoshizawa-Fujita, Y. Yue |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2019 |
| Pages: | 177 pages |
| ISBN: | 978-1-989820-00-1 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Investigation of lithium chloride distillation from the UO2 metallization products
Alexander Salyulev1; Alexei Potapov1; Alexei Shishkin1; Vladimir Shishkin1; Yurii Zaikov1;1INSTITUTE OF HIGH TEMPERATURE ELECTROCHEMISTRY, Ekaterinburg, Russian Federation;
Type of Paper: Regular
Id Paper: 100
Topic: 13
Abstract:
The possibility to distill the lithium chloride-based electrolyte from metallized products of pyrochemical operations is experimentally verified. The study was carried out in connection with the development of promising options for the industrial method of metallization of uranium dioxide, which is the main component of spent nuclear fuel after its voloxidation. The electrolyte was distilled off from metallized tablets and powders based on uranium dioxide with their continuous vacuuming at 700-900°C [1]. Powders or tablets (4-40 % porosity) of UO2 or UO2 + 5-15 wt% La2O3, CeO2, and Nd2O3, after electrolytic reduction with lithium in the molten LiCl-Li2O (0.8-1.5 wt% Li2O) mixture, were used as the distillation samples.
Metallized powders or tablets were placed in nickel or molybdenum containers. Distillation was carried out in quartz tubes under continuous evacuation (P = 1.2-2.5 mPa) for 1-3 hours. The temperature was 700-900°C. The Li, U, La, Ce, and Nd concentrations in metallized products and in vapor condensates were determined with an atomic emission spectrometry using an Optima 4300DV ICP-OES spectrometer before and after distillation.
It was found that lithium chloride is the main component of sublimates, the content of rare earth elements and uranium is negligible. In our experiments with the electrolyte content of 10-36 wt.%, lithium compounds (98.8-99.9%) were almost completely removed at 780-850°C for 1.5-3.0 hours. After distillation under such (optimal) conditions, the lithium content (mainly Li2O) in the metallized products decreased to hundredths of a percent. At lower temperatures the fraction of distilled lithium (in the form of LiCl) decreases, and the use of higher temperatures as compared to the optimal conditions is not recommended, since an undesired back reaction of metallic uranium oxidation to UO2 by residual lithium oxide occurs:
U + 2Li2O = UO2 + 4Li.
Keywords: Molten salts; UO2; U; LiCl; Vacuum distillation;