Enhancing barriers for high-level radioactive waste: The role of microbially induced calcium carbonate precipitation in ecological sustainability

The safe disposal of high-level radioactive waste (HLW) is a critical issue for the sustainable development of nuclear energy, as it requires robust, long-term solutions to prevent environmental contamination. Deep geological disposal, utilizing a multi-barrier system that integrates engineered and natural geological barriers, is widely recognized as the most reliable method for isolating HLW from the biosphere over extended timescales. Microbial-induced calcium carbonate precipitation (MICP), has recently emerged as an innovative and eco-friendly biomineralization technology with significant potential to enhance the safety and sustainability of HLW disposal. By leveraging in-situ microbial processes, MICP enables the formation of stable calcium carbonate precipitates, which can reinforce rock and soil, seal fractures, and control seepage within geological repositories. This study systematically reviews the mechanisms and key influencing factors of MICP, evaluating its effectiveness in various geotechnical media—including sandstone, shale, granite, and bentonite—and summarizing its successful applications in slope stabilization, foundation treatment, and leakage repair, supported by field test data. Special attention is given to the performance of MICP under extreme conditions relevant to HLW disposal, such as elevated temperature, pressure, pH, salinity, irradiation, and oxygen deprivation, with a focus on their impacts on microbial activity, reaction processes, and precipitation stability. Integrating the geological context of China's Beishan Underground Research Laboratory (URL), we propose MICP as a “Biogeochemical Barrier” to further enhance in-situ fracture sealing, interface reinforcement, and radionuclide migration retention. The findings underscore MICP's unique advantages in providing engineering adaptability and promoting ecological sustainability in HLW disposal systems.