Research News: BIogeochemical Gradients and RADionuclide transport (BIGRAD)

September 2010

Dr Nick Bryan and Professor Francis Livens from the School of Chemistry are partners in a major £3M consortium project, recently funded by the Natural Environment Research Council, and led by Professor Kath Morris with Professor Jonathan Lloyd from the School of Earth, Atmospheric and Environmental Sciences at the University of Manchester. This new research initiative in radioactive waste disposal is a joint project between the Universities of Manchester, Leeds, Loughborough and Sheffield, the British Geological Survey (BGS), the ANKA KIT Synchrotron, Karlsruhe, the UK DIAMOND Synchrotron and industry /regulators including the National Nuclear Laboratory (NNL) and the Nuclear Decommissioning Authority Radioactive Waste Management Directorate (NDA-RWMD).

BIGRAD Graphic

Figure 1. The Multi-Barrier Disposal Concept (from Generic Post-Closure Performance Assessment. Nirex Report N/080, UK Nirex Ltd, 2003)

Details:

The UK is in the early stages of planning the disposal, deep underground, of large volumes of radioactive waste left over from the early years of the nuclear programme. The current plan (Figure 1) is to emplace waste containers in cement-filled vaults, which will be sealed and allowed to resaturate, generating conditions which will restrict the mobility of radioactivity released from the wastes. The cement backfill in the vaults is extremely alkaline, and the pore fluid will react with the rock in which the wastes have been emplaced. Such reaction will change the physical and chemical characteristics of the rock; it could increase permeability, or seal flow paths and reduce it; it could promote the generation of colloids, which can transport radioactivity, or it could suppress colloid formation. The interface between the cement backfill and the host rock is known as the chemically disturbed zone, and is thus a region of steep biogeochemical gradients, which is poorly understood but which could have major effects on the release or retention of radioactivity. The work from the School of Chemistry work will focus particularly on the effects of colloids, and on experimental studies of the chemical form of key radioactive elements, including plutonium. The total award to the consortium is £3.0M with £1.7M to the team at the University of Manchester.

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