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1.
Sci Total Environ ; 669: 856-871, 2019 Jun 15.
Article in English | MEDLINE | ID: mdl-30897442

ABSTRACT

Following a potential nuclear accident, river run-off may potentially become a significant source of radionuclide contamination to the coastal marine environment. In the present work, code for radionuclide speciation and dynamic transfer of radionuclides between the different species was implemented in a Lagrangian marine dispersion model. A case study was performed where the model system utilized ocean circulation fields at relatively high spatial (160 mâ€¯× 160 m in horizontal direction) and temporal resolution (1 hour), considering a hypothetical accident scenario including river discharges of 137Cs to the marine environment. Results from a number of simulations were compared to identify how factors associated with radionuclide speciation and transfer between the model compartments could affect the predicted radiocesium activity concentrations. The results showed that by including dynamic transfer of radionuclides between the model compartments, the total activity concentrations at far-field sites could vary with more than two orders of magnitude, demonstrating that this model configuration enables prediction of potential local hot-spots. However, the total activity concentration near the river outlets was less affected (< factor 10). The radionuclide speciation in the river discharges and the parameterization of 137Cs particle affinity greatly affected the specie distribution (> factor 103 increase in concentration of particle-associated 137Cs) as well as the settling of radionuclides towards the seabed (up to factor 102 increase in 137Cs sediment concentrations). These factors were therefore identified as important contributors to the overall uncertainty.

2.
J Environ Radioact ; 177: 100-112, 2017 Oct.
Article in English | MEDLINE | ID: mdl-28645090

ABSTRACT

In the present work, numerical models are used to study the fate of the 99Tc discharges from Sellafield with a specific focus on the role of mesoscale eddy and tidal advection on the transport and dispersion of this radionuclide. Transport estimates are made with an ocean model that resolves a large part of the ocean mesoscale eddy field and also includes tides. Equivalent estimates are also computed with another model in which these processes are either absent or parametrized. Comparison with field observations shows that the coarse-resolution model can reproduce the general features of the observed time-space 99Tc distribution if the diffusivity in its eddy parametrization scheme is suitably chosen. However, the eddy-permitting simulations capture regional details better and show an overall higher prediction skill, with the model predictions agreeing with the observations within a factor of two to four. The importance of tidal advection is investigated by comparing transport in the eddy-permitting model when this is run either with tides included or with tides filtered out. The results point to systematic Lagrangian tidal drift in the Irish Sea and the North Sea that eventually impacts the 99Tc activity concentration levels also far downstream.


Subject(s)
Models, Chemical , Seawater/chemistry , Technetium/analysis , Water Movements , Water Pollutants, Radioactive/analysis
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