Department of Mathematical and Physical Sciences, Central University of Technology, Private Bag X 20539, Bloemfontein 9300, South Africa.
Faculty of Science, School of Physics, University of the Witwatersrand, Private Bag 3, Braamfontein 2050, South Africa.
Int J Environ Res Public Health. 2022 Jul 5;19(13):8201. doi: 10.3390/ijerph19138201.
The USA Environmental Protection Agency's (EPA) Industrial Source Complex Short Term 3 (ISCST3) dispersion modelling code was used to evaluate radon transport and the effects of local variations around tailings dam using a Gaussian plume model. The tailings dam was modelled as point, flat ground and top level, total emitting surface area (true geometry) and volume source geometries. The true area geometry was considered as the baseline source geometry. To improve the accuracy of the model predictions as compared to traditional approaches, the true geometry area source term was corrected to account for cracks and fissures on the tailings and the geometry of tailings dam was modelled by considering all emitting surfaces as sources. Compared to the baseline, the model overpredicted the flat ground area source by up to 274% and underpredicted the top-level area source by up to 50%. The volume emission source was overpredicted by up to 300% in 60% of the modelling runs and underpredicted by 55% in 40% of the volume model runs. While the top-level area source term produced lower concentrations at near-field ground-level receptors, accounting for the wakes effect increased the radon concentrations from the top-level area source of the tailings dam by up to 239%. From the modelling results, the highest concentration predicted by the model from the true geometry source was found to be 0.843 Bq m, which corresponds to the dose of 0.012 mSv/y to the public due to radon from the tailings. This value is less than the 1 mSv/y dose constraint stipulated by the National Nuclear Regulator.
美国环境保护署（EPA）的工业源综合短期 3（ISCST3）扩散模型代码被用于评估氡的迁移以及尾矿坝周围局部变化的影响，采用高斯烟羽模型。尾矿坝被建模为点状、平坦地面和顶部水平、总排放表面面积（真实几何形状）和体积源几何形状。真实面积几何形状被认为是基准源几何形状。为了提高模型预测的准确性，与传统方法相比，真实几何形状面积源项被修正，以考虑尾矿上的裂缝和裂隙，并且通过考虑所有排放表面作为源，对尾矿坝的几何形状进行建模。与基准相比，模型对平坦地面面积源的预测最高可达 274%，对顶部水平面积源的预测最低可达 50%。在 60%的模拟运行中，体积排放源的预测最高可达 300%，在 40%的体积模型运行中，预测最低可达 55%。虽然顶部水平面积源项在近场地面水平受体处产生较低的浓度，但考虑尾迹效应会使尾矿坝顶部水平面积源的氡浓度增加最高可达 239%。从模拟结果来看，真实几何源模型预测的最高浓度为 0.843 Bq m，这对应于由于尾矿中的氡而对公众造成的 0.012 mSv/y 的剂量。该值小于国家核监管机构规定的 1 mSv/y 剂量限值。
