Geopolymer cementation of spent inorganic cation exchangers for safe disposal of radioactive waste

This project will resolve the mass transport properties, reaction mechanisms and kinetics of cement-based wasteforms encapsulating inorganic ion exchangers (IEX) for safe disposal of radioactive waste. In the UK alone, approximately 150,000m3 of radioactive waste (enough to fill 60 Olympic size swimming pools) has been produced as of 2016 and 75% will require processing and storing securely to ensure the safety of society and the environment. Radioactive waste streams are often conditioned using IEX that are then immobilised in cements to limit leaching of the radioactive material to the environment. Due to poor compatibility of radioactive wastes with Portland cement, modern alternatives such as ‘geopolymer cements’ are being investigated. The long-term performance of geopolymer cement wasteforms is controlled by the mass transport and solubility processes, in particular the interactions at the cement and IEX interface. However, this is still not well understood. The project aims to understand these factors by using advanced characterisation techniques to monitor the mass transport mechanisms at the nanostructural level. This has never been done before and will yield new insight which is vital to understand the suitability and performance of geopolymer wasteforms for disposal of spent IEX for conditioning radioactive waste. Particular focus will be on advanced spectroscopic and microstructural techniques revealing the atomic/nanostructure and dynamics of these wasteforms, including solid state nuclear magnetic resonance (NMR) spectroscopy and synchrotron-based techniques, with which the Sustainable Materials at Sheffield (SMASH) research group has unique and world-leading expertise.
The successful applicant will have the opportunity to apply chemical/materials/environmental engineering principles to a real-world, globally significant industrial challenge. They will receive training in the production and characterisation of radionuclide-loaded geopolymer cement wasteforms, assessing their performance and durability under industrially relevant conditions. The candidate will gain expertise in advanced spectroscopic and microstructural techniques revealing the atomic/nanostructure and dynamics of materials, including solid state NMR spectroscopy, in which the SMASH research group at The University of Sheffield possess unique, world-leading expertise and facilities. The successful applicant will develop multidisciplinary skills in geopolymer/cement chemistry and engineering. They will be familiarised with Good Laboratory Practice regulations, COSHH, research ethics, confidentiality and development of generic transferable skills including IT, critical evaluation, problem solving, data collection and analysis, team working, time management, written and communications skills will be ensured. The successful applicant will also get a chance to interact and work closely with a world-leading and friendly research community The University of Sheffield, including research members of the Cements@Sheffield and Immobilisation Science Laboratory (ISL) research groups at the Department of Materials Science and Engineering, The University of Sheffield, as well as the Grantham Centre for Sustainable Futures at The University of Sheffield, and the wider cement chemistry and immobilisation science research communities within and outside Sheffield, in addition to relevant industries.

The project will provide the necessary interdisciplinary skills for the successful applicant to pursue research and development in the sustainable use of materials for infrastructure, clean energy and manufacturing sectors, as example sectors.

All the methodology, instrumentation and characterisation equipment required to achieve the objectives of the proposal are available in the applicant’s laboratory and through University-wide facilities. These will be available for the successful applicant during the duration of the project.

This includes the newly appointed laboratories of the Sustainable Materials at Sheffield (SMASH) research group in the Department of Chemical and Biological Engineering, The University of Sheffield, as well as the facilities of the Immobilisation Science Laboratory (ISL) group at the University of Sheffield, including a fully refurbished cements laboratory facility, and the ISL-hosted MIDAS user facility for nuclear materials science analytical instrumentation.