Analysis of capability of reducing potential hazard of radioactive waste under thermal treatment Bulletin of the Tomsk Polytechnic University. Geo Assets Engineering Vol. 328, № 8
The relevance of the discussed issue is caused by the need to determine and justify the methods of treatment with irradiated nuclear graphite, which was a moderator of neutrons, during decommissioning uranium-graphite nuclear reactor at the variant «Demolition». The main aim of the study is to develop and justify the criteria defining the potential hazard of graphite radioactive waste, and to assess the reduction degree of potential hazard according to the introduced criteria under thermal treatment in gaseous environment. The methods used in the study: experimental investigation of thermal treatment of irradiated graphite in gaseous environments using the samples of irradiated graphite and unbroken graphite elements of stack, which were taken out from stack of uranium-graphite nuclear reactors. The results. The authors have proposed and substantiated the criterion characterizing the potential hazard of graphite radioactive waste, generated during decommissioning of uranium-graphite nuclear reactor at the variant «Liquidation». The criterion A[F.t] has physical meaning of radionuclide extraction intensity from surface unit of radioactive waste (including graphite radioactive waste) and its transfer in mobile form, capable to migration. The authors analyzed the ways of accumulation of radionuclide 14C in irradiated nuclear graphite (as the main radionuclide), which defines the class of radioactive waste. Thermal treatment of irradiated graphite in gaseous environments experiments including definition degree of selective removal of 14C and mass loss of treating samples of graphite were carried out. Based on experimental results and results of analysis of 14C ways of accumulation in irradiated graphite the qualitative dependence of the dynamics of 14C leaching for untreated graphite and treated graphite was obtained. The authors made the conclusion on considerable reduction of potential hazard of graphite radioactive waste comprising long-lived radionuclide under thermal treatment.
radionuclide, radioactive waste, irradiated graphite, thermal treatment