CanmetMINING, Natural Resources Canada, Canada; Department of Earth Sciences, University of Ottawa, Canada.
Camborne School of Mines, University of Exeter, United Kingdom.
J Environ Radioact. 2022 Apr;244-245:106826. doi: 10.1016/j.jenvrad.2022.106826. Epub 2022 Feb 5.
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 Pb, Po, Ra, Th, and U 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 U 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 whole-body 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.
预测放射性核素剂量率可用于评估铀矿开采和加工项目释放对放射性环境的影响。这些预测有助于为实施缓解措施提供决策依据。本研究的目的是确定如何改进剂量率建模，以减少对非人类生物群预测的不确定性。为此，我们使用水中和沉积物中的实测活度浓度，模拟了加拿大萨斯喀彻温省北部铀矿和加工厂下游的 Pb、Po、Ra、Th 和 U 的活度浓度，以及相关的淡水食物网加权吸收剂量率。放射性核素活度浓度预测的差异主要来自于一个模型与另一个模型之间不同的默认分配系数和浓度比值，以及在剂量率评估中是否包含所有或仅部分 U 衰变产物。因此，我们建议采用标准化的最佳实践方法来计算淡水生物加权吸收剂量率，无论设施处于规划、运行还是退役阶段。在规划的初始阶段，最佳实践方法建议使用保守的现场特定基线水中、沉积物和生物体中的活度浓度，并通过选择基于物种相似性和类似水质条件的浓度比来预测这些介质中保守的增量活度浓度，以减少剂量率计算中的不确定性。在运行和退役阶段，最佳实践方法建议依靠水中、沉积物、鱼类组织和小型生物体整体的实测活度浓度，以进一步降低剂量率估计的不确定性。这种方法将允许在评估铀矿开采项目的影响和做出适当释放控制决策时进行更现实但仍然保守的剂量评估。
