PhD Research Project: Using geopolymers cements to develop bespoke solutions for the treatment of n

Geopolymers cements offer an attractive alternative to Portland cement in the conditioning of nuclear wastes. Because of the aluminosilicate chemistry and pore network structure of geopolymers, they have been identified in research and practice as being a potential matrix for oily or organic-rich wastes. Geopolymers also offer the opportunity to use corrosion inhibitors, such as sodium fluoride, which are incompatible with Portland cement matrices but may offer great advantages in the immobilisation of reactive metals which corrode at high pH, e.g. uranium and aluminium. For these reasons, and considering the complexity of the UK inventory of problematic wastes, it is proposed to use geopolymers to develop bespoke solutions for the treatment of these problematic wastes. Most standard tests which are used to analyse the performance of cemented wasteforms measure the release of ionic radionuclides, and are applied to Portland blended cements. There is only a limited understanding of how the release of organics can be measured and extrapolated to very long service lives, and there are no tests specific to the chemistry (and likely degradation mechanisms) of alternative binding systems including geopolymers. So, a key project target will be to develop appropriate performance tests for the coupled release of organics and contaminant radionuclides from geopolymers. Test protocols will be validated using the newly developed geopolymer matrices, and also benchmarked against the performance of standard UK Portland cement-based grouts. The ability to control the corrosion of reactive metals will also be assessed by monitoring hydrogen evolution and dimensional changes. Test outcomes will be validated through characterisation of the wasteforms via various analytical techniques using the existing 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.

Funding Notes

This project would suit a UK or EU student with a strong background in materials science, chemistry, chemical engineering, mineralogy/geochemistry, or a closely related area. A good 2:1 or Masters degree in one of these fields is highly desirable. The project is funded for 3 years, to be supervised by Professor John Provis (j.provis@sheffield.ac.uk), and co-supervised by researchers from the National Nuclear Laboratory. The target project starting date will be 26 September 2016; candidates will be interviewed during July/August 2016 and the project will remain open until filled.