Russian Scientists from the Federal Research Centre of the Krasnoyarsk Scientific Centre (KSC – part of the Siberian Academy of Sciences) and the Siberian Federal University have developed an economical method for solidifying liquid radioactive waste with a high content of caesium and strontium. The results of the study are published in the Journal of Nuclear Materials.
Enterprises for processing used nuclear fuel and the decommissioning of fast-neutron nuclear reactors, generate large amounts of alkaline radioactive waste containing radionuclides of caesium and strontium. Existing curing technologies reduce the activity of radionuclides by selective extraction of them. This results in secondary radioactive waste. Such multi-stage processing is resource-intensive and not always effective.
Krasnoyarsk chemists have proposed a new approach that allows one-step transfer of caesium and strontium radionuclides contained in waste into an insoluble mineral-like form, which simultaneously reduce their concentration in solution. The processing of alkaline solutions is carried out at a temperature of up to 150 ° C in the presence of hollow aluminosilicate microspheres, also known as "cenospheres”. Such microspheres are obtained from conventional fly ash generated by burning coal. They include aluminium, silicon, impurities of other metals, which under certain conditions are able to enter into chemical reactions with caesium and strontium.
"As a result of hydrothermal processing in a closed volume, the interaction of the aluminosilicate glass of microspheres with dissolved caesium and strontium produces crystalline microspheres. In these, caesium is included in the composition of minerals, pollucite and analcime, and strontium is included in strontium silicate. At the same time, the degree of extraction of radioactive elements from alkaline solutions reaches 90-99% " said Tatyana Vereshchagina, leading researcher at KSC’s Institute of Chemistry and Chemical Technology.
