Potential influence of microorganisms on the corrosion of the carbon steel in the French high-level long-lived nuclear waste disposal context at 50°C

In this study, short-term experiments were carried out to assess the microbially influenced corrosion (MIC) risk in the context of the French high-level radioactive waste disposal CIGEO (Centre Industriel de Stockage Geologique). The exposures were carried out in different representative media, including the presence of different cement-grout mixtures as filling material. Nonsterile and biotic conditions with nutrients were considered. For biotic conditions, specific preparations of microbial inoculum were carried out from samples collected at ANDRA's Underground Research Laboratory and microorganisms from the library. Corrosion kinetics were determined using both traditional coupons and completed with real-time electrical resistance sensors. Microbiological characterizations consisted of cultural approach, quantitative polymerase chain reaction, and next-generation sequencing. The obtained results show no significant MIC, but a reduced risk was observed using more alkaline filling materials.