| DOI: | 10.2172/1251034
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| 报告号: | LLNL--TR-671402
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| 报告题名: | Hydrothermal Alteration of Glass from Underground Nuclear Tests: Formation and Transport of Pu-clay Colloids at the Nevada National Security Site |
| 作者: | Zavarin, M.; Zhao, P.; Joseph, C.; Begg, J.; Boggs, M.; Dai, Z.; Kersting, A. B.
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| 出版年: | 2015
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| 发表日期: | 2015-05-27
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| 总页数: | 28
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| 国家: | 美国
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| 语种: | 英语
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| 中文主题词: | 铅
; 元素
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| 主题词: | LEAD
; ELEMENTS
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| 英文摘要: | The testing of nuclear weapons at the Nevada National Security Site (NNSS), formerly the Nevada Test Site (NTS), has led to the deposition of substantial quantities of plutonium into the environment. Approximately 2.8 metric tons (3.1Ă104 TBq) of Pu were deposited in the NNSS subsurface as a result of underground nuclear testing. While 3H is the most abundant anthropogenic radionuclide deposited in the NNSS subsurface (4.7Ă106 TBq), plutonium is the most abundant from a molar standpoint. The only radioactive elements in greater molar abundance are the naturally occurring K, Th, and U isotopes. 239Pu and 240Pu represent the majority of alpha-emitting Pu isotopes. The extreme temperatures associated with underground nuclear tests and the refractory nature of Pu results in most of the Pu (98%) being sequestered in melted rock, referred to as nuclear melt glass (Iaea, 1998). As a result, Pu release to groundwater is controlled, in large part, by the leaching (or dissolution) of nuclear melt glass over time. The factors affecting glass dissolution rates have been studied extensively. The dissolution of Pu-containing borosilicate nuclear waste glasses at 90ÂşC has been shown to lead to the formation of dioctahedral smectite colloids. Colloid-facilitated transport of Pu at the NNSS has been observed. Recent groundwater samples collected from a number of contaminated wells have yielded a wide range of Pu concentrations from 0.00022 to 2.0 Bq/L. While Pu concentrations tend to fall below the Maximum Contaminant Level (MCL) established by the Environmental Protection Agency (EPA) for drinking water (0.56 Bq/L), we do not yet understand what factors limit the Pu concentration or its transport behavior. To quantify the upper limit of Pu concentrations produced as a result of melt glass dissolution and determine the nature of colloids and Pu associations, we performed a 3 year nuclear melt glass dissolution experiment across a range of temperatures (25-200 °C) that represent hydrothermal conditions representative of the underground nuclear test cavities (when groundwater has re-saturated the nuclear melt glass and glass dissolution occurs). Colloid loads and Pu concentrations were monitored along with the mineralogy of both the colloids and the secondary mineral phases. The intent was to establish an upper limit for Pu concentrations at the NNSS, provide context regarding the Pu concentrations observed at the NNSS to date and the Pu concentrations that may be observed in the future. The results provide a conceptual model for the risks posed by Pu migration at the NNSS. |
| URL: | http://www.osti.gov/scitech/servlets/purl/1251034
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| Citation statistics: |
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| 资源类型: | 研究报告
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/41861
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| Appears in Collections: | 过去全球变化的重建
影响、适应和脆弱性
科学计划与规划
气候变化与战略
全球变化的国际研究计划
气候减缓与适应
气候变化事实与影响
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| 1251034.pdf（2742KB） | 研究报告 | -- | 开放获取 | | View
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| Recommended Citation: | |
Zavarin, M.,Zhao, P.,Joseph, C.,et al. Hydrothermal Alteration of Glass from Underground Nuclear Tests: Formation and Transport of Pu-clay Colloids at the Nevada National Security Site. 2015-01-01.
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