MOSCOW, April 17 Employees of the Faculty of Chemistry of Lomonosov Moscow State University have found a new way to efficiently extract uranium-235 from spent nuclear fuel ( spent nuclear fuel), which is expected to provide economic benefits for the further use of this main isotope of uranium in nuclear energy and help reduce the risks associated with the disposal of radioactive materials, the press service of Moscow State University said.
The issues of reprocessing fuel that has «expired» its life in nuclear reactors are becoming especially relevant in connection with the development in Russia of technologies for a closed nuclear fuel cycle (CFFC). In such a cycle, the reproduction of nuclear «fuel» will expand and the fuel base of nuclear power will increase significantly, eliminating the need to extract natural uranium in large volumes.
It will also be possible to reduce the amount and biological hazard of radioactive waste remaining after the processing of spent nuclear fuel — the most dangerous substances, the so-called minor actinides, are planned to be «burned out» in fast neutron reactors. In this way it will be possible, as nuclear experts figuratively say, to «take out two key thorns» in the current nuclear power industry, connected with the limited reserves of natural uranium and the deferred problem of spent nuclear fuel.
Reprocessing of spent nuclear fuel and separation of valuable nuclear materials from it is a key stage necessary for closing the nuclear fuel cycle.
“After the spent fuel is removed from the reactor, uranium and plutonium are separated from it to be used again as an energy source. In addition to these two elements, various highly active elements (for example, americium and curium) are extracted. This is necessary in order to bury waste with less radioactivity,” said Svetlana Gutorova, one of the authors of the work, an employee of the Department of Radiochemistry, Faculty of Chemistry, Moscow State University.
Now for the processing of uranium and plutonium, enterprises use the PUREX technology (from the English plutonium-uranium recovery by extraction: first they are extracted from the fuel, and then separated using a redox reaction in a mixture of aqueous and organic phases. But this is not a very convenient process to implement the tasks of closing the nuclear fuel cycle.
One of the alternatives is the GANEX process (from the English group actinide extraction, group actinide extraction). The technology is a two-stage scheme: at the first stage, uranium is selectively isolated from spent nuclear fuel, and then minor actinides are extracted. But for the successful implementation of this scheme, it is necessary to select selective extraction agents with a high capacity (that is, capable of «capturing» large amounts of the desired chemical elements).
Earlier, scientists from the Faculty of Chemistry of Moscow State University proposed a compound based on phenanthroline, a nitrogen-containing polycyclic compound, as such a «producer».
Now a team of employees of the departments of radiochemistry, organic and physical chemistry of the Faculty of Chemistry of Moscow State University has created a new version of the substance based on phenanthroline for extracting uranium from spent nuclear fuel using extraction. The researchers decided to move from laboratory fuel models to process models based on thousands of times higher concentrations of uranium.
As a result, it turned out that the proposed extractant makes it possible to isolate much larger amounts of uranium than before. Scientists continue their research, one of their main tasks is to expand the range of compounds with high uranium capacity. In addition, the authors of the work plan to solve two problems simultaneously: to try not only to selectively extract uranium and plutonium from spent nuclear fuel, but also to separate them.