TECHNOLOGY OF REPROCESSING HIGH-LEVEL WASTES BYMETHOD OF SELF-PROPAGATING HIGH-TEMPERATURESYNTHESIS (SPHTS) INTO MINERAL-LIKE MATERIALS

摘要

To reduce the risk of propagation of transuranium actinides, carbon-14 and other radionuclides contained inhigh-level radioactive wastes (RW) of NPPs, Rosenergoatom Concern has made up a decision to develop atechnology of self-propagating high-temperature synthesis with production as the result of a ceramic matrixsuitable for long-term environmentally safe burial of high-level nuclear wastes in deep-seated geologicalformations.The handling of high-level RW (HLW) requires consistent implementation of a defense-in-depthconcept. At present time, there is a broad international consensus on the necessity of burying long-term HLRWin deep-seated geological formations.The system of barriers in the HLW handling should contain:? a physical and chemical form of conditioned (reprocessed) HLW (packaging);? a container with conditioned (reprocessed) HLW inside;? a leak-tight enclosure of subsurface storage rooms (interim storage);? a combination of the safety features of the inherent (passive) and engineered barriers involved inburial in deep-seated geological formations.Subjected to recycling (conditioning with transformation into ceramic packaging) are spent fuel spills,HLW from reprocessing of nuclear fuel, high-level graphite moderators of reactors.The selection of the graphite HLW SPHTS reprocessing method is based on the following mainconditions:? excluding the formation of considerable amounts of gaseous products during reprocessing due to thepresence of a considerable quantity of the biologically significant long-lived radionuclide of 14С in graphite;? producing the end target product characterized by a high chemical stability and ensuring reliablefixation of radionuclides in the matrix;? simplifying the process, especially as to high-temperature chemical transformations;? ensuring the shortest time of the interaction products being under the maximum process temperature.The proposed method of reprocessing the graphite HLW that immobilize radionuclides into a thermally,chemically and radiation stable carbide and corundum matrix is based on the SPHTS process run as a chemicalreaction based on the C+Al+TiO2 system where the component of С is irradiated graphite of the RBMK reactorcore moderators.The submitted paper is a report on the results of the R&D activities for optimizing the SPHTStechnology on a pilot plant using non-irradiated graphite and fuel spill simulators (HLW).