Publication Abstract

Accumulation of Technetium-99 in the Irish Sea?

K.S. Leonard, D. McCubbin, R. Bonfield and S. Conney

An assessment has been carried out to determine the impact from continued discharges of ⁹⁹Tc, released into the Irish Sea from the nuclear reprocessing plant at Sellafield. Samples of seawater, sediment and seafood have been collected from the Irish Sea and analysed for ⁹⁹Tc. The information has been used, together with supporting data, to determine the effect of continued ⁹⁹Tc releases on the concentrations in seawater, to examine the likelihood that sediments provide a secondary sink for future remobilisation, and to determine the effect of summer stratified waters upon the concentrations in seafood.

Significant variability in the rate of dilution and dispersion was observed for ⁹⁹Tc surface seawater concentration following discharge from Sellafield into the eastern Irish Sea. In comparison, the impact of releases on seawater concentrations in the western Irish Sea was noticeably less significant. It was not possible to detect any significant increase in ⁹⁹Tc concentrations in surficial sediments (from equivalent sampling sites) between surveys carried out in 1995 and 1998. Two sediment cores were collected to determine the ⁹⁹Tc depth distributions in the eastern and western Irish Sea. The core off the Sellafield pipeline contained a step decrease in concentrations below 10 cm, whilst in contrast, the concentration profile was exponential for the western Irish Sea core. Hydrographic data provide clear evidence of thermal stratification of waters above the muddy sediment in the western Irish Sea. Higher ⁹⁹Tc concentrations were observed in surface water samples and concentrations with depth were inversely related to water salinity. From the analysis of a variety seafoods (Neprops noregius, Cancer pagurus and Pleurnectes platessa), concentration factors have been determined and dose arising from annual consumption rates have been estimated.

Reference:

K.S. Leonard, D. McCubbin, R. Bonfield and S. Conney (2004) Accumulation of Technetium-99 in the Irish Sea? Science of The Total Environment, 322(1-3): 255-270