title: Geoelectrical monitoring of simulated subsurface leakage to support high-hazard nuclear decommissioning at the Sellafield Site, UK.
abstract: A full-scale field experiment applying 4D (3D time-lapse) cross-borehole Electrical Resistivity Tomography (ERT) to the monitoring of simulated subsurface leakage was undertaken at a legacy nuclear waste silo at the Sellafield Site, UK. The experiment constituted the first application of geoelectrical monitoring in support of decommissioning work at a UK nuclear licensed site. Images of resistivity changes occurring since a baseline date prior to the simulated leaks revealed likely preferential pathways of silo liquor simulant flow in the vadose zone and upper groundwater system. Geophysical evidence was found to be compatible with historic contamination detected in permeable facies in sediment cores retrieved from the ERT boreholes. Results indicate that laterally discontinuous till units forming localized hydraulic barriers substantially affect flow patterns and contaminant transport in the shallow subsurface at Sellafield. We conclude that only geophysical imaging of the kind presented here has the potential to provide the detailed spatial and temporal information at the (sub-)meter scale needed to reduce the uncertainty in models of subsurface processes at nuclear sites.
authors.affiliation: British Geological Survey, Keyworth, Nottingham NG12 5GG, UK. Electronic address: oku@bgs.ac.uk.
authors.forename: Oliver
authors.initials: O
authors.lastname: Kuras
authors.affiliation: British Geological Survey, Keyworth, Nottingham NG12 5GG, UK.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Wilkinson
authors.affiliation: British Geological Survey, Keyworth, Nottingham NG12 5GG, UK.
authors.forename: Philip I
authors.initials: PI
authors.lastname: Meldrum
authors.affiliation: British Geological Survey, Keyworth, Nottingham NG12 5GG, UK.
authors.forename: Lucy S
authors.initials: LS
authors.lastname: Oxby
authors.affiliation: British Geological Survey, Keyworth, Nottingham NG12 5GG, UK; ETH-Swiss Federal Institute of Technology, Institute of Geophysics, Sonneggstr. 5, 8092 Zurich, Switzerland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Uhlemann
authors.affiliation: British Geological Survey, Keyworth, Nottingham NG12 5GG, UK.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Chambers
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Binley
authors.affiliation: National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale, Cumbria CA20 1PG, UK.
authors.forename: James
authors.initials: J
authors.lastname: Graham
authors.affiliation: National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale, Cumbria CA20 1PG, UK; School of Earth, Atmospheric and Environmental Sciences, Williamson Building, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: Smith
authors.affiliation: Sellafield Ltd, Albion Square, Swingpump Lane, Whitehaven CA28 7NE, UK.
authors.forename: Nick
authors.initials: N
authors.lastname: Atherton
mesh_terms: D004553:Electric Conductivity; D004739:England; D004784:Environmental Monitoring / Q000379:methods*; D060587:Groundwater / Q000032:analysis*; D055848:Nuclear Power Plants; D014054:Tomography / Q000379:methods; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D014875:Water Pollutants, Radioactive
keywords: Contaminant transport; Electrical resistivity tomography; Geophysics