Several types of ceramics are being researched around the world for their use in nuclear waste management. This project will focus on the synthesis of Ca, Ti and Zr based ceramics for the immobilisation of plutonium and high-level nuclear waste in the UK and investigate their response to radiation damage, helium bubble formation and corrosion under controlled conditions. The materials will be ion-irradiated in-situ within a TEM at the specialist MIAMI facility and post characterised using techniques such as EXAFS, GIXRD, IR-ATR, ToF-SIMS and TEM to develop a fundamental understanding of the radiation damage and corrosion mechanisms relevant under geological disposal conditions.
Geological disposal is an internationally accepted methodology for the safe long-term management of spent nuclear fuel and high-level nuclear waste. It uses a multi-barrier approach in which the nuclear waste is first transformed into a durable matrix made of glass, ceramic or a glass-ceramic matrix. The matrix is properly encapsulated using metallic canisters which will eventually be disposed of deep underground in a specially designed facility called as geological disposal facility. The multiple barriers protecting the radioactive waste will however be compromised over time due to natural corrosion and the waste matrix will come in direct contact with underground water and the surrounding geological formation. Also, the waste form itself may transform and accumulate nanoscale helium bubbles under persistent radiation damage from the radioactive decays taking place inside the waste matrix (called self-irradiation damage). To validate the assumptions regarding the safety of geological disposal and develop a robust safety case, it is important to develop reliable long-term predictive models addressing the slow degradation of waste forms under disposal conditions and the release of radioactive elements into the biosphere.
One of the materials that is currently being researched in the UK as a potential candidate for the management of nuclear waste, especially, plutonium is a ceramic called zirconolite. It is a crystalline material in its pristine synthetic form but it has been shown that the simple end member zirconolite (CaZrTi2O7) will transform into an amorphous state in a few hundred years after disposal and accumulate helium bubbles in the long-term (Mir et al J. Nucl. Mater. 528, 152836 (2021)). Currently, very little is known about the behaviour of helium in more complex and realistic zirconolite structures (which will contain actinides and neutron absorbers) and how helium bubbles in combination with amorphisation will impact the long-term corrosion resistance of the ceramic waste forms.
This project will focus on the synthesis of complex nuclear ceramics, especially, zirconolites using hot isostatic pressing and evaluate their response towards helium accumulation. The as-synthesized, amorphised and helium bubble bearing ceramics will then be subjected to controlled corrosion and studied using spectroscopic techniques such as EXAFS, GIXRD, IR-ATR in addition to ToF-SIMS and TEM to understand the structural changes taking place as a result of the radiation damage and corrosion. This will help understand the fundamental mechanisms of corrosion of ceramics and how they are affected by self-irradiation damage and nanoscale helium bubbles and cavities, potentially leading to the development of more resilient nuclear ceramics in the future.
For an expected January 2022 start. To apply please fill out the expression of interest form (https://research.hud.ac.uk/research-degrees/researchscholarships/epsrc-phd-studentships/) quoting this project title.
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