科研之友
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摘要
Many long-lived radionuclides are present in groundwater at the Nevada Test Site (NTS) as a result of 828 underground nuclear weapons tests conducted between 1951 and 1992. In conjunction with a comprehensive geochemical review of radionuclides (H-3, C-14, Cl-36, Tc-99 and I-129) that are presumably mobile in the subsurface, we synthesized a body of radionuclide activity data measured from groundwater samples collected at 18 monitoring wells, to qualitatively assess their migration at the NTS over distances of hundreds of meters and over timescales of decades. Tritium and Cl-36 showed little evidence of retardation, while the transport of C-14 may have been retarded by its isotopic exchange with carbonate minerals in the aquifer. Observed local reducing conditions (either natural or test-induced) will impact the mobility of certain redox-sensitive radionuclides (especially Tc-99) that were otherwise soluble and readily transported under oxidizing conditions. Conversely, strongly oxidizing conditions may impact the mobility of I-129 which is mobile under reducing conditions. The effect of iodine speciation on its transport deserves further attention. Indication of delayed transport of some "mobile" radionuclides (especially Tc-99) in the groundwater at the NTS suggested the importance of redox conditions of the natural system in controlling the fate and transport of radionuclides, which has implications in the enhanced performance of the potential Yucca Mountain repository, located adjacent to the NTS, to store high-level nuclear wastes as well as management of radionuclide contamination in legacy nuclear operations facilities.
- 出版日期2008-10
- 单位北京师范大学
