Известия Томского политехнического университета: Инжиниринг георесурсов (Jun 2025)
Physical-chemical characteristics of slag-lime cement compounds containing liquid phase of accumulated high-level waste
Abstract
Relevance. In the period from 1968 to 1986, as a result of the application of precipitation technologies in processing irradiated nuclear reactor fuel, a significant amount of highly radioactive waste was accumulated. Storing this type of waste in liquid form does not provide an adequate level of safety in the long term. The transfer of the mortar part of the accumulated highly radioactive waste of the Federal State Unitary Enterprise “Mayak Production Association” into a stable cement form will increase the level of radiation safety during their further long-term storage and burial. Aim. To evaluate chemical durability and physical and mechanical properties of cement samples with various degree of salt incorporation. Methods. Continuous leaching in distilled water and evaluation of ultimate compressive strength. Results and conclusions. Filtered material after sorption purification and the concentrated liquid phase of alkaline high-level waste have been cement-solidified into dry mixtures based on blast furnace slag blended with bentonite and vermiculite sorption materials. The content of blast furnace slag in the dry mixture ranged from 87.5 to 96%, bentonite from 0 to 10% and vermiculite from 0 to 1.5%. The degree of inclusion of the components of the solution part of alkaline high-level waste in dry mixtures was 10.9 and 21%. The authors have analyzed chemical durability of cement compound and evaluated the rate and degree of 137Cs leaching. The rate of 137Cs leaching from the cement compound was found to comply with the Safety Requirements NP-019-15. Data on mechanical strength of initial cement compound samples and samples after freeze-thaw cycles were obtained. Mechanical strength of the cement compound after lengthy immersion into water was determined. The tests shown that among the studied dry mixtures, a composition containing 89.7% blast furnace slag and 10% bentonite allows for the solid fixation of 137Cs radionuclide. The resulting compounds meet safety requirements in terms of chemical resistance and mechanical strength.
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