For many years Nirex has been assessing the suitability of a site at Sellafield in Cumbria as a potential location for a deep repository.
Extensive site investigations have been carried out. The photograph shows the Sellafield area. Some of the exploratory boreholes in the region of the potential repository can be seen in the foreground.
The proposed host-rock for the repository was the low permeability Borrowdale Volcanic Group. This is overlain by a range of Carboniferous, Permo Triassic and Quaternary rocks.
Many hydrogeological units have been identified, and faults and fault zones are present. At depth offshore (in the distance of the photograph) the groundwater salinities are high, which has a major impact on the flow.
As part of the Nirex 97 performance assessment, undertaken by Serco Assurance on behalf of United Kingdom Nirex Limited, groundwater flow and radionuclide transport from the potential repository were calculated using NAMMU.
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