2014-Sustainable Industrial Processing Summit
SIPS 2014 Volume 6: Rare Earths & Ionic Liquids
| Editors: | Kongoli F |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2014 |
| Pages: | 432 pages |
| ISBN: | 978-1-987820-08-9 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Determination of solvation free energy of dissolved actinides in molten salts
Angus Gray-Weale1; Patrick Masset2; Cassandra Lutzko3;1UNIVERSITY OF MELBOURNE, Melbourne, Australia; 2FRAUNHOFER UMSICHT, Sulzbach-Rosenberg, Germany (Deutschland); 3SCHOOL OF CHEMISTRY, Melbourne, Australia;
Type of Paper: Regular
Id Paper: 220
Topic: 11
Abstract:
For the pyrochemical reprocessing of nuclear spent fuels, an accurate knowledge of the electrochemical properties is essential, for example the apparent standard potential of actinides and lanthanides dissolved in molten salts. The determination of such quantities is time consuming, especially with radioactive materials at high temperature. The development of computational methods for these properties is a promising alternative.
This work is focused on the calculation of the free energy of solvation of uranium-like and americium-like metal chloride in the LiCl-KCl eutectic using a classical model and a three step thermodynamic cycle. The first step involves the oxidation of the metal dissolved in the eutectic to obtain a free energy. The second step computes the free energy resulting from the insertion of a neutral chloride atom into the mixture. The final step reduces the introduced chloride to balance out the charges. This results in an overall reaction of Mn+(eutectic) + Cl0(eutectic) > Mn+1(eutectic) + Cl-(eutectic) .
The free energy of solvation resulting from the sum of the three free energy components is plotted against temperature and the entropy so obtained compared with already available experimental data. The calculated entropy of solvation, the diffusion co-efficient and activation energies are in reasonable agreement with the values found experimentally. The radial distribution functions confirm that the model behaves in a physically reasonable fashion. We discuss the possibility of improving the accuracy of the method by using more sophisticated models for the interactions of the ions.
This work shows the feasibility of predicting thermodynamic quantities and provides a better local description of the environment of dissolved actinides in molten salts. This method can be further used for metals in more complex mixtures to evaluate the effects of the solvent and can be used as a predictive tool.