Research and Development on Cementation of Liquid Radioactive Waste (LRW) Resulting from Spent Nuclear Fuel Reprocessing
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Research and Development on Cementation of Liquid Radioactive Waste (LRW) Resulting from Spent Nuclear Fuel Reprocessing in the Experimental Demonstration Center (EDC) of Mountain Chemical Combine Lebedeva A.V. 1, Sukhanov L.P1., Ustinov O.A1 1
Bochvar High-Technology Research Institute of Inorganic Materials, 5a Rogova street,
Moscow, 123098, Russian Federation ABSTRACT The report presents the results of research and development on cementation technology of liquid radioactive waste (LRW) generated in spent nuclear fuel reprocessing in Experimental Demonstration Center (EDC) at the Mountain Chemical Combine, Russian Federation. INTRODUCTION Currently Experimental Demonstration Center for testing of innovative spent nuclear fuel reprocessing technologies is being established at the Mountain Chemical Combine in Russia. One of the main requirements to the technologies being tested is to minimize the radioactive waste generation. Cementation was chosen as a method of low and intermediate-level LRW conditioning. The reasons for the choice of cementing technology were its following advantages over other LRW conditioning technologies: - The cement matrix ability to hold U and Pu due to the formation of complex compounds; - The possibility of the most mobile nuclide (Cs-137) fixing in the cement matrix by means of sorption additives; - The relative equipment simplicity as cementation is carried out at low temperatures; - The availability and low cost of the matrix material; - No secondary waste. EDC LRWs can be conditionally divided into non-technological and technological. The non-technological EDC LRWs includes the so-called “drain waters” – low-salt and low-active solutions consisting of water from the decontamination of facilities, equipment leaks, water from sanitary locks, sanitary inspection rooms, showers, etc. The technological EDC LRWs are solutions containing tritium and acetates. The quality of the cement compound resulting from pulps solidification must meet the regulatory requirements [1-2] on the mechanical strength, radionuclide leachability, radiation, water and frost resistance. In addition to the standard criteria of cement compound quality, some other parameters should be considered. These include, in particular, the compound flowability at the stage of preparation (flowability value must be sufficient to discharge the compound from a mixer) and heat generation during the cement mixture hardening (increase in temperature above 900ɋ may lead to a deterioration of the resulting compound properties).
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EXPERIMENTAL DETAILS Major experiments in VNIINM have been conducted with the use of simulators of radioactive waste. Also, to determine the radionuclide’s leaching rate, samples were marked with Cs-137 and tritium. For the non-technological waste the bottom residue simulator was used, estimated composition of which is shown in table I. Table I. Estimated composition of simulated bottom residue LRW components Content in the Content in the dry solution residue, Solution Sediment g/l % by weight NaNO3 25
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