Nuclear and Radiochemistry Group, Los Alamos National Laboratory, P.O. Box 1663, MS J514, Los Alamos, New Mexico 87545, USA.
Environ Sci Technol. 2010 Mar 1;44(5):1579-86. doi: 10.1021/es902689e.
Uranium-series data for groundwater samples from the Nopal I uranium ore deposit were obtained to place constraints on radionuclide transport and hydrologic processes for a nuclear waste repository located in fractured, unsaturated volcanic tuff. Decreasing uranium concentrations for wells drilled in 2003 are consistent with a simple physical mixing model that indicates that groundwater velocities are low ( approximately 10 m/y). Uranium isotopic constraints, well productivities, and radon systematics also suggest limited groundwater mixing and slow flow in the saturated zone. Uranium isotopic systematics for seepage water collected in the mine adit show a spatial dependence which is consistent with longer water-rock interaction times and higher uranium dissolution inputs at the front adit where the deposit is located. Uranium-series disequilibria measurements for mostly unsaturated zone samples indicate that (230)Th/(238)U activity ratios range from 0.005 to 0.48 and (226)Ra/(238)U activity ratios range from 0.006 to 113. (239)Pu/(238)U mass ratios for the saturated zone are <2 x 10(-14), and Pu mobility in the saturated zone is >1000 times lower than the U mobility. Saturated zone mobility decreases in the order (238)U approximately (226)Ra > (230)Th approximately (239)Pu. Radium and thorium appear to have higher mobility in the unsaturated zone based on U-series data from fractures and seepage water near the deposit.
从 Nopal I 铀矿床的地下水样本中获得了铀系数据，以限制位于断裂、不饱和火山凝灰岩中的核废料处置库的放射性核素迁移和水文过程。2003 年钻探的井中铀浓度的降低与简单的物理混合模型一致，表明地下水速度较低（约 10 m/y）。铀同位素约束、井产能和氡系统也表明饱和区地下水混合有限且流速缓慢。矿坑入口处收集的渗漏水的铀同位素系统学显示出空间依赖性，这与位于矿床前方的更长的水岩相互作用时间和更高的铀溶解输入相一致。主要为非饱和区样品的铀系不平衡测量表明，(230)Th/(238)U 活度比范围为 0.005 至 0.48，(226)Ra/(238)U 活度比范围为 0.006 至 113。饱和区的(239)Pu/(238)U 质量比<2 x 10(-14)，并且 Pu 在饱和区中的迁移率比 U 高 1000 多倍。饱和区的迁移率按(238)U 大致 (226)Ra > (230)Th 大致 (239)Pu 的顺序降低。根据矿床附近裂缝和渗漏水的 U 系数据，镭和钍在非饱和区的迁移率似乎更高。
