Distribution, Geochemistry and Geochronology of Sellafield Waste in Contaminated Solway Firth Floodplain Deposits

Allan, Robert Lindsay (1993) Distribution, Geochemistry and Geochronology of Sellafield Waste in Contaminated Solway Firth Floodplain Deposits. PhD thesis, University of Glasgow.

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This thesis describes a studv of the distribution and geochemical behaviour of 137Cs, 241Amand 239 + 240Pu within the floodplain deposits of south west Scotland. These sediments have been contaminated with low level effluent discharged from BNFL's reprocessing plant at Sellafieid on the Cumbrian coast. The study establishes that the dominant supply mechanism of anthropogenic radionuclides to the floodplain is via on-shore transfer of contaminated particulate material which has been mathematically modelled. A series of lateral transects across the floodplain has confirmed previous observations of highest concentrations furthest inland, illustrating the relationship between particle size and radionuclide concentration. The inventories observed for 137Cs were of the order of ~10e6 to 10e7 Bq m-2 and were somewhat higher than previously published data. The vertical distribution of radionuclides was investigated at Southwick merse and indicated a declining depth of occurrence of maximum radionuclide concentrations with distance inland. The observations from a series of transects, using a variety of sample collection methods permitted the construction of a schematic model of the merse. This model identified three distinct zones within the floodplain and enabled estimation of the total inventory for the coastline of south west Scotland. By these estimates less than 1% of the total environmental inventory of 137Cs discharged from Sellafieid has been returned on-shore. Speciation studies on the availability of 137Cs and 239 + 240Pu indicate that 137Cs is strongly retained within the residual phase of the sediment and that 239+240Pu exhibits slightly enhanced availability, being associated with the organics and secondary Fe/Mn mineral phases. Evidence suggests that despite the increased environmental availability of both these radionuclides and 137Cs are not generally in a form which is available for plant uptake. Flow desorption studies have indicated that 137Cs is tightly bound to the sediment particles producing a of a KD of ~10e5 lkg-1.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: G T Cook
Keywords: Geochemistry, Nuclear chemistry
Date of Award: 1993
Depositing User: Enlighten Team
Unique ID: glathesis:1993-74850
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 27 Sep 2019 15:51
Last Modified: 27 Sep 2019 15:51
URI: http://theses.gla.ac.uk/id/eprint/74850

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