In this study, experiments were carried out to assess the microbially influenced corrosion (MIC) risk in the context of the French high-level radioactive waste disposal. The exposures were carried out at 80°C in different repository relevant conditions, including the presence of different cement-grout mixtures as filling material. Biotic conditions with nutrient and nonsterile conditions with indigenous microbes added from Callovo Oxfordian clayey rock and without 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 microbial culture collection centers. Corrosion kinetics were determined using traditional coupons and completed with real-time corrosion sensors. Microbiological characterizations consisted of cultural approach, quantitative polymerase chain reaction, and next-generation sequencing. The obtained results show no significant MIC and a reduced risk with the use of more alkaline filling material. © 2023 The Authors.