Ewen Silvester

Australian know-how is being used in a French laboratory, part of a European Union funded project dealing with the long-term stability of nuclear waste in underground storages.

The work, at Grenoble University, is based on a process for measuring the redox reactivity of soils developed by Associate Professor Ewen Silvester, a chemist at La Trobe University's Albury- Wodonga campus.

Dr Silvester has proven the concept on synthetic iron oxide minerals in laboratories of the Department of Environmental Management and Ecology, and the technique is now being tested on iron-containing clay minerals in France.

'Decisions on the location of nuclear waste storage are largely based on geological considerations,' Dr Silvester says. 'This work deals with the geochemical stability of the storage environment, particularly the mobility of radionuclides in soils. Better understanding of geochemical conditions will lead to safer storage.

'Our work was originally focused only on the geochemistry of iron in these systems, and the role of iron in controlling radionuclide speciation and mobility.

'Instead, what we have developed is a generic technique, and ultimately a device, which aims to provide information about the redox potential of many other soils.'

Redox potential, he explains, is tendency of a soil to accept (oxidise) or donate (reduce) electrons.

'To measure this in soils and sediments is notoriously difficult due to the poor electrical contact between soil particles and the sensing electrode,' says Dr Silvester. So he came up with the idea of using a "shuttle molecule" to transfer electrons between the soil particles and an electrode, amplifying the signal so that it can be measured.

'The principle may sound simple, but it has taken three years of laboratory work to get a result that could help the European Union in its bid to solve the potential environmental problems associated with nuclear waste.'

The next phase of the project, he says, will be the development of a prototype device that could be used in any soil or sediment system.

The European connection with La Trobe was established by Dr Silvester during the early nineties when he spent three years at Grenoble University on a post-doctoral fellowship.
 
This connection has been maintained, with funding from the Agence Nationale pour la Gestion des Dechets Radioactifs – and by the visit of Annaleise Klein, a La Trobe BSc student working on the project, who spent February in Grenoble.

'This was a fantastic opportunity for Annaleise who worked in the laboratory of Professor Laurent Charlet, an expert in clay mineral chemistry,' Dr Silvester says.

'The experience will develop her skills in chemistry, and will no doubt inspire and motivate her for the future – and they will be used here at the Albury-Wodonga campus to further the study of clay mineral systems.'

Ms Klein describes it as a 'fascinating field of research'. 'There is definitely a future there for me,' she says. 'There is a lot to be done.'