Accumulation and Mobility of Radionuclides in the Sellafield Near-Shore.

  • Daisy Ray

Student thesis: Master of Science by Research

Abstract

The authorised pipeline discharge of Low Level Waste (LLW) from Sellafield into the Irish Sea has been taking place since operations commenced in 1952 until termination of the effluent discharge took place in 1992. As a consequence of this activity, radionuclides such as caesium (Cs), americium (Am), plutonium (Pu) and neptunium (Np) that were present in liquid effluents, have been transported in marine waters and become associated with sediments in the Irish Sea. Tidal currents coupled with biological processes have then resulted in the redistribution and deposition of these radionuclides in intertidal areas on the West Cumbrian coastline. The Ravenglass saltmarsh, in particular, has received significant radionuclide inputs during tidal processes. This, coupled with the fine-grained sedimentology of the saltmarsh has resulted in the accumulation of actinides and fission products in estuarine sediments. In past work, the mobility and accumulation of these contaminants has been interpreted by natural geochemical processes and correlated with maximum discharge histories from the 1970s.In this project, a sediment core was taken from the Ravenglass saltmarsh, located by the mouth of River Esk, 5 km from the Sellafield site. Gamma spectroscopy was used to measure the activities of 137Cs and 241Am in the core and isotopes of Pu were determined by alpha-spectroscopy after chemical separation and electrodeposition. The depth profiles obtained for 137Cs, 241Am, and Pu isotopes all showed elevated activities in the middle of the core (11-13 cm). This reflects the heightened discharges that took place from Sellafield in the 1970's and the burial of the contaminants with time. The similarity in shape of the depth profiles with those measured in previous decades may be indicative of the lack of post-depositional remobilisation taking place in estuarine sediments.
Date of Award31 Dec 2013
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorGareth Law (Supervisor), Francis Livens (Supervisor) & Nicholas Bryan (Supervisor)

Keywords

  • Sellafield
  • Radionculides

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