A numerical approach to evaluating uncertainty associated with microbial activity in near-field systems

Introduction The nuclear fuel cycle has generated large quantities of higher-level radioactive waste, and the preferred long-term management solution for this legacy is disposal into a deep geological repository (GDF). There are several concepts for disposal, dictated by factors including the wasteforms and host geology, but a common theme is the use of a multi-barrier system including; the container where the waste is emplaced, a geotechnical barrier (e.g. bentonite or cement) and the final geological barrier.

Microbial metabolism has the potential to play a significant role in the performance of multi-barrier geodisposal systems. The Manchester geomicrobiology group has worked extensively on largely positive biogeochemical reactions in the “far field”, where anaerobic microbes may immobilise key radionuclides via biomineralization reactions, metabolise gases including hydrogen and methane and also degrade complexants such as ISA. More recently, a parallel work programme has focused on the “near field”, to better understand the potential for microbial colonisation of bentonite clay barrier materials. This is important, as uncontrolled microbial growth in bentonite can impact on the barrier properties of material that make it ideal for use in a GDF.

Project The aim of this industry (RWM) funded cross-disciplinary PhD programme is to build on data from recent and ongoing work in Manchester on bentonite microbiology, and current research priorities in underground research facilities (e.g. Mont Terri in Switzerland), to deliver a rigorous quantitative understanding of microbial activities in near-field bentonite systems. A blend of state of the art experimental techniques, including microbiological, geochemical, mineralogical and spectroscopic approaches, will be used to generate molecular-scale understanding of bentonite biogeochemical processes under realistic GDF conditions. Outputs from these, and other experiments at Mont Terri will be incorporated into state of the art modelling packages with research partners (including the National Nuclear Laboratory and project sponsors RWM) to predict biogeochemical evolution of the GDF system. Overall the project offers exciting opportunities to explore the impact of microbial metabolism on the safe disposal of radioactive waste, a £multi-billion challenge of international and global importance.

Training: This Industry funded PhD project will be based in the Dept of Earth & Environmental Sciences at The University of Manchester with co-supervision at the National Nuclear Laboratory. The successful candidate will join a large (30+) group of researchers in the Dept focused on geomicrobiology and radioactive waste management and disposal. The student will benefit from the excellent facilities within the Williamson Research Centre for Molecular Environmental Science and the newly commissioned NNUF RADER labs, with additional radiation infrastructure at the Dalton Cumbrian Facility, Corrosion Science facilities in the Department of Materials Science and modelling expertise at NNL and Department of Mechanical, Aerospace and Civil Engineering.

Finally, the students will work closely with industrial supervisors within the National Nuclear Laboratory and link to technical teams at RWM and our international collaborators in this area.

Candidate Skills: This project includes both experimental and modelling approaches, and the successful candidates should have a strong background in Microbial, Chemical, Geological or Environmental Sciences (BSc / Masters in Chemistry, Environmental Chemistry, Geochemistry or similar) or Environmental Engineering. Please contact the main supervisor Prof. Jon Lloyd ([Email Address Removed]) for additional information. The start date is January 1st 2021 (or sooner)