The effect of hydrogen isotopes and helium on tritium diffusion and extraction from candidate fusion breeder blanket ceramics. (materials strand project)

Application deadline – Tuesday 5th July 2022.

Supervisor/s: Amy Gandy (University of Sheffield), Rebecca Boston (University of Sheffield), Slava Kuksenko (UKAEA), Anthony Hollingsworth (UKAEA) & Mohamad Abdallah (UKAEA – STEP).

In the fusion power stations of the future, the radioactive fuel tritium will be produced (bred) in a region surrounding the fusion core (the breeder blanket), with both solid and liquid tritium breeder designs being developed around the world. The tritium breeding material will comprise the element lithium, which can absorb fusion neutrons and transform into tritium and helium (transmutation). At the University of Sheffield, solid breeder materials are being developed and tested in fusion-relevant environments. Most solid breeders are poly-crystalline ceramics, specifically lithium-containing ceramics such as lithium metatitanate (Li2TiO3), through which the gaseous tritium will diffuse and be extracted. Previous work has found direct correlations between ceramic grain size and efficient tritium diffusion and extraction, as well as the ceramics ability to resist/recover from fusion neutron irradiation induced damage. In our previous work we found that Li2TiO3 contains small vacancy-type defects which grow at fusion relevant temperatures. These vacancy-type defects and the helium generated transmutation have the potential to trap tritium as it diffuses through the material, and the extent of this trapping must be determined if Li2TiO3 is to be a serious contender for a breeder blanket material. Therefore, the focus of this PhD project is to determine how defects, intrinsic to candidate Li-containing ceramics, as well as helium, impact radiation damage resistance and tritium diffusion and extraction.

This PhD project will take our previous work to the next level, by investigating Li-containing ceramics that have been implanted with protium, deuterium and tritium. The PhD student will make and characterise a range of Li-containing ceramics to investigate the effect of grain size and morphology on gas diffusion. The ceramics nano- and atomic structures will be characterised by the PhD student using scanning and transmission electron microscopies, and crystal structures determined using X-ray diffraction. The ceramics will then be exposed to hydrogen isotope and helium plasmas in the UK Atomic Energy Authority (UKAEA)’s DELPHI facility, and characterised post implantation using thermal desorption spectroscopy (TDS) to gain information on the diffusion of gasses in the ceramics. Implantation induced damage and gas bubble formation will be investigated using transmission electron microscopy at the University of Sheffield.

The PhD student will receive full training in ceramic synthesis and characterisation at the University of Sheffield, and will be a member of several research groups, benefiting from a range of expertise and support. This PhD project will give key information to the global fusion community on the suitability of Li-ceramics as a tritium breeder material, and the materials developed during this PhD project have the potential to be the fuel for future fusion power stations.

NOTE: whilst the PhD student will be a part of the STEP-Fusion CDT cohort, the student will be registered at the University of Sheffield on a standard 4 year PhD programme.

The project will be mainly based in Sheffield, but with trips to the facilities at UKAEA in Oxfordshire required, as well as opportunities for travel to conferences.

This project is offered by University of Sheffield. For further information please contact Dr Amy Gandy (a.gandy@sheffield.ac.uk).

This project may be compatible with part time study, please contact the project supervisors if you are interested in exploring this.

Application deadline: Tuesday 5th July 2022.