Modelling of solute transport and microbial activity in diffusion cells simulating a bentonite barrier of a spent nuclear fuel repository

Microbial sulfate reduction possesses a potential risk for the long-term safety of spent nuclear fuel repositories because under expected repository conditions sulfide is main corroding agent copper and copper-coated steel canisters foreseen in Scandinavian disposal concepts. It thus essential to understand quantify processes factors impacting microbial production within around compacted bentonite, which planned be used as buffer material many In present study reactive transport modelling was applied increase understanding diffusion cell experiments, brought sand layers with or without inoculated microorganisms contact saturated bentonites different mineralogy. Model results obtained sodium bentonite from Wyoming calcium Bulgaria gave strong evidence activation indigenous microorganisms, at least zones reduced density close bentonite/sand interface. For all calculations indicated that after an initial phase favourable conditions, activity limited by (bio-)availability organic carbon. Bulgarian characterized very low gypsum content, model furthermore suggested some intermediate control availability. The demonstrated rapid evolution system settings where are highly microbially-inactive bentonite. Gypsum dissolution calculated determined experimentally significant first 2 cm interface during 450 days. successfully this description experimental followed conceptual models settings. offer insights regarding mechanism magnitude biogeochemical reactions might occur vicinity surrounding waste canister so doing, may relevant near field HLW repositories.