Although nuclear waste exists in significant quantities and is continuously produced worldwide, waste management represents a great challenge which has yet to be resolved, but which is becoming pressing under the interest that energy and sustainability-related issues attract. Deep geological repositories are scientifically considered to be the only feasible way to dispose of nuclear waste. A system of engineered barriers is proposed to isolate the waste from the biosphere. It is envisaged that high level waste under elevated temperatures (in excess of 100 oC) will be encapsulated in copper canisters and buried deeply within a suitable host geological formation (depth in the excess of 500 m). To provide further protection and in order to significantly delay any possible leakage of radio-nuclides towards the bedrock, a layer of compacted low permeability soil, referred to as the buffer, will surround the canisters.
The performance of the buffer is crucial in ensuring long-term containment; to perform its designated functions, understanding the resaturation of the buffer is essential. However, in-situ tests have revealed that the resaturation process may be self-limiting and may never reach completion. For low permeability host formations and under the high temperatures imposed by the waste, the impediment may be amplified. It is believed that the reason behind the limited resaturation of the buffer is the dual structure that the bentonite develops during compaction. Compacting the bentonite under different initial conditions (water content and compaction energy) greatly influences its structure, permeability and retention capability (i.e. hydraulic behaviour) but also its overall mechanical and possibly thermal behaviour.
The scope of the proposed project is to study the effect of the compaction process on the hydraulic, mechanical and thermal behaviour of bentonite with the aim of optimising its ability to resaturate while ensuring that its thermo-mechanical behaviour (e.g. swelling potential) is not compromised.
The project will employ both experimental and numerical tools. Newly developed laboratory equipment in the Geotechnics Laboratory at Imperial College will be used to characterise the thermo-hydro-mechanical behaviour of bentonite samples compacted at different initial conditions. The laboratory experiments will be simulated with the Finite Element Program ICFEP, which is developed at Imperial College. Finally, canister retrieval tests (CRT) will be simulated in fully coupled thermo-hydro-mechanical analyses
Prospective candidates are expected to have at least an upper second (2:1) MEng degree (or equivalent) in Civil Engineering or MSc degree in Geotechnical Engineering and, prior to applying, should email the supervisor ([email protected]
• a statement of purpose (one page),
• an up-to-date curriculum vitae and two recent references
• full details of degrees undertaken (including transcripts) and their final or expected outcomes
Funding is available to UK citizens and EU nationals residing in the UK for at least 3 years and covers fees and a stipend of £16,800/annum (tax free), with the possibility of raising extra income (tax free) through Graduate Teaching Assistant work. The successful candidate will have access to bespoke free programmes of career development.