Modelling super(99)Tc Concentrations in Fucus vesiculosus from the North-East Irish Sea

An increase in the quantity of technetium 99 discharged into the north-east Irish Sea from BNFL Seallfield nuclear complex in the UK in 1994 coincided with improvements in waste treatment procedures. A simple numerical model was applied to time-series data of super(99)Tc concentrations in the brown seaweed, Fucus vesiculosus, collected from three UK sites near Sellafield. A good fit between predicted and observed concentrations was evident, but the degree of uncertainty varied inversely with the frequency of sampling. When applied to discharge scenarios depicting future management of super(99)Tc releases, the model showed that concentrations in the seaweed reached asymptotic values in 3-10 yr.