Best practices for predictions of radionuclide activity concentrations and total absorbed dose rates to freshwater organisms exposed to uranium mining/milling
Résumé
Predictions of radionuclide dose rates to freshwater organisms can be used to evaluate the radiological environmental
impacts of releases from uranium mining and milling projects. These predictions help inform decisions
on the implementation of mitigation measures. The objective of this study was to identify how dose rate
modelling could be improved to reduce uncertainty in predictions to non-human biota. For this purpose, we
modelled the activity concentrations of 210Pb, 210Po, 226Ra, 230Th, and 238U downstream of uranium mines and
mills in northern Saskatchewan, Canada, together with associated weighted absorbed dose rates for a freshwater
food chain using measured activity concentrations in water and sediments. Differences in predictions of radionuclide
activity concentrations occurred mainly from the different default partition coefficient and concentration
ratio values from one model to another and including all or only some 238U decay daughters in the dose rate
assessments. Consequently, we recommend a standardized best-practice approach to calculate weighted absorbed
dose rates to freshwater biota whether a facility is at the planning, operating or decommissioned stage. At the
initial planning stage, the best-practice approach recommend using conservative site-specific baseline activity
concentrations in water, sediments and organisms and predict conservative incremental activity concentrations
in these media by selecting concentration ratios based on species similarity and similar water quality conditions
to reduce the uncertainty in dose rate calculations. At the operating and decommissioned stages, the best-practice
approach recommends relying on measured activity concentrations in water, sediment, fish tissue and wholebody
of small organisms to further reduce uncertainty in dose rate estimates. This approach would allow for
more realistic but still conservative dose assessments when evaluating impacts from uranium mining projects and
making decision on adequate controls of releases.
Domaines
Sciences de l'environnement
Origine : Fichiers éditeurs autorisés sur une archive ouverte