Scientists from Tomsk Polytechnic University and Rosatom have developed a technology to reprocess irradiated reactor graphite by evaporation. This technology allows making radioactive waste disposal safer and economically feasible.
According to the polytechnicers the technology itself is not new: previously radioactive waste has been processed in plasma. However, this was low-level metal waste. The evaporation and stepwise deposition of reactor graphite is the know-how of scientists of Tomsk Polytechnic University and Rosatom professionals. They have already patented this development.
The technology implies the heating of reactor graphite in a low-temperature plasma to more than three thousand degrees Celsius (5,432 °F). As a result, graphite and radionuclides contained therein sublimate. Further there is a stepwise deposition of substances in a special plasma-chemical reactor. To create such a reactor is a task for the scientists.
"Carbon and radionuclides evaporate together, they are separated one from another in steps in different parts of plasma chemical reactor due to the difference in physicochemical properties. Thus, radioactive nuclei are selectively extracted from graphite. Therefore, carbon black, which is formed by plasma-chemical reactions within the plasma chamber, is getting less active," says Evgeniy Bespala, a PhD student at the Department of Technical Physics.
Evgeniy Bespala has been addressing the issue of nuclear graphite reprocessing for more than five years. Currently, he is an R & D engineer at JSC "Pilot and Demonstration Center for Uranium-Graphite Reactors Decommissioning" (a Rosatom subsidiary, the city of Seversk, Russia). Last year, the polytechnicer became one of the winners of the UMNIK program and received financial support to perform his research. "Within the UMNIK grant I will deal with creating a facility that provides mass graphite processing without human intervention. This will allow automating the entire process and protecting people from hazardous radioactive sources. It is planned, irradiated nuclear graphite will be loading to the facility only and then carbon waste with less activity compared to the original will be removed," says the polytechnicer.
Tomsk scientists and Seversk colleagues already are testing their technology. The Department of technical physics at Tomsk Polytechnic University conducts required experiments for graphite evaporation in low-temperature plasma. All radiation research, in turn, is held in Seversk, as there is an opportunity to follow all the rules of radiation safety. For the present, the technology has been tested on mixtures of carbon stable isotopes. Next year, the scientists plan to test their facility on irradiated reactor graphite.