The photo is sourced from atomic-energy.ru
The study was based on the use of the molten salt-liquid metal alloy method, which is suitable for processing low-aged nuclear fuel with a high burnup. This kind of fuel cannot be processed using water technologies, such as the selective extraction of uranium and plutonium from solutions using organic compounds. The advantage of the chosen method is environmental safety, since it makes it possible to minimise the amount of nuclear waste after processing.
Spent nuclear fuel (SNF) contains not only uranium compounds, but also plutonium and fission products. The authors of the study dissolved SNF in molten salt, after which they mixed it with a liquid alloy based on gallium and indium – silvery-white metals characterised by a low melting point, as well as high thermal (gallium) and electrical (indium) conductivity. This led to a redistribution of components, with uranium getting concentrated in the metal and unnecessary fission products remaining in the salt.
“The bottom line is that before the fuel is processed, it is subjected to holding so that the short-lived radionuclides disintegrate and the activity of the substance goes down. If we process insufficiently aged fuel using, for instance, the water technology, the water undergoes radiolysis, that is, decomposition, and the process ends up inefficient. The use of molten salts with liquid metal alloys helps reduce the holding time of nuclear fuel,” Alexander Dedyukhin, one of the authors of the study and lead engineer at the Department of Rare Metals and Nanomaterials of UrFU, is quoted as saying by the Russian Science Foundation.
The scientists carried out an experiment and created three alloys based on gallium and indium, which contained 21.8%, 40% and 70% indium. To assess the solubility of nuclear fuel, they conducted chemical analysis using samples of a saturated liquid metal solution. The analysis showed that the higher the indium concentration, the lower the efficiency of separation of uranium and nuclear fuel components. Meanwhile, the alloy with the indium concentration of only 21.8% turned out to be best suited to separate the two.