Microbial colonization of cementitious geodisposal facilities, and potential “biobarrier” formation

Abstract Most disposal concepts dictate that higher radioactive waste will be disposed of in a geological disposal facility (GDF) using a cementitious engineered barrier system (EBS), designed to retain radionuclides for the lifetime of the GDF. Overtime, the GDF is expected to be colonized heterogeneously by microorganisms that can survive in micro-niches within the GDF, gradually increasing in numbers and activity through the EBS and into the far field, where physical and (biogeo)chemical conditions become more moderate. Here, microbial activity may influence the fate of radionuclides through a complex range of processes including biomineralization reactions, while also metabolizing excess gases (e.g., hydrogen and methane) and organic chelates produced through chemical and biological processes in the GDF. The interplay between microbes and radionuclides is expected to result in a zonation inside the GDF that will extend into the far-field environment, potentially contributing a “biobarrier” that will augment the EBS.