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UK nuclear waste containment research aired at AAAS meeting

14 February 2016

A University of Sheffield researcher is using the Diamond Light Source for a long term study into the performance of nuclear waste containment materials.

Dr Claire Corkill with Prof Trevor Rayment (photo: Sean Dillow/Diamond Light Source)

Dr Claire Corkhill from the University of Sheffield is using the Diamond Light Source's Long-Duration Experiment (LDE) facility to study the way that cement - an important material used in the storage and disposal of radioactive waste - reacts with water as it becomes hydrated over a period of hundreds of years. This important work may help to inform the UK's policy on disposal. She presented the findings of this work at the American Association for the Advancement of Science (AAAS) annual meeting, held last week in Washington.

Much of the UK's nuclear research is supported by the Oxfordshire-based Diamond Light Source facility and it is heavily involved in helping to tackle the challenges associated with radioactive waste disposal. Key to the UK's strategy for disposal is the plan for a Geological Disposal Facility (GDF). Under this plan, highly radioactive waste, immobilised in cement would be interred deep underground.

But it is important to anticipate exactly what impact this approach could have on the surrounding environment. Some of this waste can take hundreds of thousands of years to decay to safe levels, and so scientists are trying to uncover the long-term result of interaction between radionuclides and their surroundings over these long time-scales - that's where the Diamond synchrotron becomes particularly important.

"Time-scales are crucial when it comes to nuclear research. Any facility expected to contain highly radioactive waste will need to remain functional for an extremely long period of time," says Diamond's Director of Physical Sciences, Trevor Rayment. "Until recently, it's been impossible to use synchrotron light to study interactions that take place over extended time-scales.

"But, in a world first, Diamond has engineered a long-duration experimental facility that allows users to study sample behaviour in the intense detail afforded by synchrotron light but over a two year period: much longer than has ever before been possible."

Dr Corkhill is using this facility to study cement's reaction with water over an extended period of time. If it is planned to use cement in the GDF then it becomes vital to know how it will interact with its environment over many thousands of years. Examining changes over this period should make it easier to predict what might happen over a much longer time.

Whilst the two-year long experiment is still ongoing, the work has already yielded some interesting results. Dr Corkhill has discovered that a new cement material for the GDF, developed by her research team, forms a number of mineral phases known to sorb highly radioactive elements, such as technetium-99.

"Armed with the knowledge that these phases form, and knowing how quickly, supports the use of our new cement material in the GDF," she says. "We hope that these results will influence the design of the GDF and help improve it's long term safety. The pattern of peaks identified in cement essentially act as a 'fingerprint' telling us which cement minerals are present. The really exciting thing about using the LDE facility is that we are able to obtain very high resolution, time resolved patterns, something that is not possible using a normal laboratory instrument."

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