Abstract
Physicochemical and radiochemical processes occurring in the deep repository of liquid radioactive waste Severnyi (Krasnoyarsk-26) have been investigated; however, microbiological aspects of storage of liquid radioactive waste (LRW) virtually have not been studied. The aim of the present work was the physicochemical and microbiological monitoring of horizon 1 of the repository Severnyi, intended for storage of intermediate-level (ILW) radioactive liquid waste.
The obtained results show that horizon 1 is inhabited by aerobic and anaerobic microorganisms. The number of aerobic saprotrophic bacteria reached 100 thousand cells/ml. Anaerobic bacteria were represented by fermentative (10000 cells/ml), denitrifying (10000 cells/ml), sulfate-reducing (hundreds of cells/ml) and methanogenic bacteria (hundreds of cells/ml). Enrichment cultures from horizon 1 exhibited high metabolic potential; they mineralised a range of organic compounds and components of waste (acetate, nitrate, sulfate) both aerobically and anaerobically in the processes of fermentation, denitrification, sulfate reduction and methanogenesis. These cultures were adapted to the temperature and salinity of the environment. Production of biogenic gases (N2, H2, CH4, CO2, H2S) may result in a local increase of the pressure in the repository. The isolated representatives of the genus Acinetobacter and sulfate-reducing bacteria produced surfactants promoting emulsification of subsurface fluids. The obtained results present a background for long-term local monitoring of the repository and show that microbially and radiochemically mediated geochemical changes can influence the filtration of waste and radionuclide migration.
