Microbiologically influenced corrosion (MIC) threat in the nuclear energy sector

Microbiologically Influenced Corrosion (MIC) is a recognized degradation phenomenon in water-contact systems, and nuclear facilities typically employ stringent material selection, chemistry control, and operating practices to limit corrosion. However, MIC can remain inconsistently diagnosed compared with better-characterized abiotic mechanisms, particularly in auxiliary and raw-water circuits, during stagnation/outages, and in long-lived waste-management settings. This review synthesizes peer-reviewed research and sector guidance to map MIC hotspots across the nuclear lifecycle, from construction/commissioning through operation, wet spent-fuel storage, and deep geological disposal, and to translate current knowledge into practical ageing-management priorities. We frame MIC assessment using a Multiple Lines of Evidence (MLOE) approach that integrates chemistry, microbiology, materials characterization, and operational history, and we summarize monitoring and control options within relevant standards and regulatory contexts. Finally, we identify key knowledge gaps, such as sparse field rate datasets and standardized MIC diagnostics in restricted areas, and present eleven recommendations to strengthen prevention, detection, and lifecycle decision making for MIC in the nuclear energy sector.