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.

This case study shows how the facilities of NAMMU have been used in groundwater flow and radionuclide transport calculations performed as part of the Nirex 97 assessment of the performance of a potential repository at Sellafield. The key elements of this case study are: