Microbial induced corrosion in French concept of nuclear waste underground disposal

Abstract

The objective of this paper is to give a short overview of how the bacteria, that may influence the corrosion behaviour of metals and alloys, are taken into account in the French concept of geological repository. It is important to underline that microbial induced corrosion is not a new corrosion phenomena but the presence of bacteria may modify (increase or decrease) anodic or cathodic corrosion reactions. In aerobic conditions, high corrosion rates may be obtained due to the biooxidation of pyrites. Under anaerobic conditions (longer period), bacteria may have negative (localised corrosion) or positive (consumption of hydrogen) effects. The mixed conditions (with and without oxygen) may be the most dangerous period for localised corrosion of metals and alloys due to the coupling and galvanic corrosion phenomena enhanced by aerobic and anaerobic bacteria. The first conclusions lead to consider that MIC is a 'short term' issue rather than a long term one.

Potential influence of microorganisms on the corrosion of carbon steel in the French high‐ and intermediate‐level long‐lived radioactive waste disposal context

“…Microorganisms do not modify the electrochemical nature of the corrosion, but their activity or the induced modification of the environment affect the anodic and cathodic reactions. [16] The presence of microorganisms in deep underground repositories have been widely described. [6,9,13,[17][18][19][20] The main potential sources of energy possible for their activity could be the hydrogen, the organic matter, and the nutrients provided by the Cox during the resaturation step.…”

Microbial corrosion of metallic materials in a deep nuclear-waste repository

“…Dle Férona a Crusseta jsou náchylné k mikrobiální korozi slitiny železa (uhlíkové oceli, korozivzdorné oceli, litiny), mědi a hliníku, zatímco absolutně odolné jsou pouze slitiny titanu a zirkonia [25].…”

“…Nejvyšší teploty pro přežití bakterií jsou udávány 113°C [29], 115°C [25] či dokonce 120°C [30,31]. Pík povrchové teploty je v horizontu prvních 100 let [31], stejně jako pík minimální relativní vlhkosti (RH).…”

“…V aerobní fázi uložení jsou hlavním nebezpečím bakterie síru-oxidující (Sulfur oxidizing bacteria -SOB), železo oxidující (Iron oxidizing bacteria -IOB) nebo bakterie produkující Fe komplexující sacharidy (Exopolysaccharide producing bacteria -EPB). Sulfát oxidující bakterie produkují kyselinu sírovou až do pH kolem 1, což má za následek korozi uhlíkové oceli na úrovni 200 μm a -1 [25]. Není pravděpodobné, že by takto dokázali bakterie okyselit pórový roztok bentonitu, a osídlení povrchu je pravděpodobné až po poklesu teploty povrchu ukládacího obalového souboru, což už v případě evropského konceptu nebude v aerobní fázi.…”

Contribution of cellular automata to the understanding of corrosion phenomena

“…Here, we shall study aqueous corrosion. And we limit our purpose to simple electrochemical corrosion discarding other processes like stress corrosion cracking, erosion, fatigue or microbial corrosion [7]. Despite these restrictions, corrosion remains a complex phenomenon.…”