There is a new technology in development that can reprocess irradiated reactor graphite by evaporation, which could allow making radioactive waste disposal safer and economically feasible.
The technology itself is not new as previously radioactive waste has been processed in plasma. However, this was low-level metal waste. The evaporation and stepwise deposition of reactor graphite comes from the research from scientists of Tomsk Polytechnic University in Tomsk Oblast, Russia and Rosatom State Atomic Energy Corporation, a state corporation in Russia. They have already patented the technology.
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.
“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,” said says Evgeniy Bespala, a PhD student at the Department of Technical Physics. “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.”
Evgeniy Bespala has been addressing the issue of nuclear graphite reprocessing for more than five years. He is currently an R & D engineer at JSC Pilot and Demonstration Center for Uranium-Graphite Reactors Decommissioning (a Rosatom subsidiary in the city of Seversk, Russia). Last year, he was a winner 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,” Bespala said.
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. Right now they are testing the technology on mixtures of carbon stable isotopes. Next year, the scientists plan to test their facility on irradiated reactor graphite.