Next-Generation Low-Carbon Cement Wasteforms for Safe Disposal of Radioactive Waste

In the UK, over 150,000m3 of radioactive waste (enough to fill 60 Olympic size swimming pools) has been produced to date. Most of this radioactive waste needs conditioning by encapsulating it in cement to prevent release to the biosphere.

Blended cements incorporating calcined clays (LC3 encapsulants) are considered the next major step for bulk cement supply within the cement industry along their roadmap towards ‘Net Zero’ and therefore highly likely to become part of the nuclear industries toolbox for waste encapsulation.

However, chemical differences between Portland-limestone calcined clay cement (LC3) encapsulants and Portland cement (PC) encapsulants, and variability in powder physical/chemical characteristics, lead to different physical and chemical characteristics and physical properties, due to extensive differences between aqueous and solid-state chemistry in each case. Little is known about which raw materials are most suitable, and there is little information on what parameters are critical to reliable application.

This PhD examines fluid-particle and particle-particle interactions in LC3 encapsulants produced from a suite of high and low-grade precursor powders, benchmarked against common PC-based encapsulants. It adopts a new in-situ characterisation approach (including surface-specific techniques, spectroscopic and microstructural characterisation) to investigate mechanisms and kinetics of fluid-particle and particle-particle interactions, and effects on performance. 

We will study and reveal the fundamental processes controlling dispersion, fluidisation and reaction of these cements, and design, produce and test novel encapsulant formulations with enhanced performance.

This will allow us to develop next-generation low-carbon cement wasteforms for safe disposal of radioactive waste that will help to protect the wellbeing of society and the environment, and enable clean nuclear energy production.

Based in the School of Chemical, Materials, and Biological Engineering, the successful candidate will be joining a team of multidisciplinary researchers at the University of Sheffield to develop research and innovation for decarbonisation. The successful applicant will join the Sustainable Materials at Sheffield and Cements@Sheffield research teams. They will also benefit from industrial supervision by Sellafield Ltd, and be part of a comprehensive doctoral training programme in this area at the University of Sheffield, led by the primary supervisor Dr Brant Walkley, in collaboration with Sellafield Ltd. and National Nuclear Laboratory, and the Nuclear Decommissioning Authority, that comprises >20 current PhDs in encapsulant/wasteform development across the Faculty of Engineering. They will benefit from being a member of a friendly and collegial group with world-leading expertise and facilities.

The PhD researcher will also have the opportunity to undertake a 3 to 6-month secondment in with Sellafield Ltd at their R&D site for cement research. During this industrial secondment, the PhD researcher will evaluate research findings to date as relevant to Sellafield Ltd.’s cement-focused business needs.

About the Research Team:

The Sustainable Materials at Sheffield (SMASH) group and Cements@Sheffield group are world-leading research teams, located in highly-rated and very successful departments, building from over 100 years of history in cements research at Sheffield. We investigate interesting and important cements and related materials for applications in nuclear and infrastructure sectors, publish our work in the leading journals and conferences in the field, and take great pride in the fact that alumni have gone on to the highest levels of success in both academia and industry. The School of Chemical, Materials, and Biological Engineering ranks among the top in the UK, and has among the highest levels of research income.

About the Primary Supervisor:

Dr Brant Walkley is Senior Lecturer in Chemical Engineering at the University of Sheffield, and has made significant contributions to cement materials chemistry and engineering, particular as related to applications in the nuclear sector. He has unique expertise in formulation development and advanced characterisation of cements and related materials, particularly in spectroscopic and microstructural techniques exploring the effect of raw material powder characteristics and physical properties of cements in both the fresh and hardened state.

Brant currently leads the Sustainable Materials at Sheffield team, which is a friendly group of 10 PhD, 3 postdoctoral, and 12 Masters researchers. He is passionate about fostering excellence in postgraduate research, and is currently Department Director of Postgraduate Research Admissions, leading on PhD research strategy at both department and faculty level. He has been awarded externally funded grants and studentships worth ~£18M total since 2018 from EPSRC, the Nuclear Decommissioning Authority (NDA), Sellafield Ltd., National Nuclear Laboratory (NNL), BEIS e.g. NNL Advanced Fuel Cycle Programme (AFCP), Innovate UK, and UK and international industry.

Brant holds the Sheffield leadership role for the Sellafield/National Nuclear Laboratory-based Encapsulant Integrated Research Team (EIRT) focused on development of cement encapsulants to meet Sellafield and NDA site license company needs. He is Co-Director of the £30M EPSRC CDT SATURN (Skills And Training Underpinning a Renaissance in Nuclear, 2024-2032).

About Sheffield:

According to StudentCrowd, which compiles university rankings by students, for students, the University of Sheffield was ranked the 2^nd Best University Overall in the UK for students, and was recommended to attend by students for the “ultimate uni experience”. The different categories that influenced the ranking included nightlife, national parks, bars, music venues and eateries. Sheffield was commended for its well-connected transport, convenience shops, student-friendly eateries and bars, local music and art scene, and proximity to the Peak District National Park. The cost of living in Sheffield also was a significant factor for the number 2 spot with rental and student accommodation being 4% cheaper than the national average. One student added “Everything in the city in really convenient for students.”

Enquiries:

Interested candidates are strongly encouraged to contact the project supervisor ([email protected]) to discuss their interest in and suitability for the project prior to submitting an application, also register their interest with the EPSRC CDT SATURN ([email protected]) for this project.

Applicants should have a minimum of an upper second class honours degree in chemical engineering, chemistry, bioscience or a related technical subject. If English is not your first language then you must have an International English Language Testing System (IELTS) average of 6.5 or above with at least 6.0 in each component, or equivalent. Please see this link for information: https://www.sheffield.ac.uk/postgraduate/phd/apply/english-language.

Application link: https://www.sheffield.ac.uk/postgradapplication/