Migration of<sup>99</sup>Tc in unsaturated Chinese loess under artificial rainfall condition: an<i>in situ</i>test

Liu, C. L.; Li, S. S.; Wang, X. Y.; Wang, Z. M.; Xin, C. T.; Wang, H.F.; Li, R. J.; Li, B.; Tang, Linbo; Jiang, Ling

doi:10.1524/ract.2001.89.10.643

Cited by 3 publications

(5 citation statements)

References 8 publications

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“…The existence of oxidizing conditions, however, does not necessarily result in high mobility. In a study of 99 Tc transport in unsaturated Chinese loess under artificial recharge, Liu et al (2001) reported a slight retardation relative to 3 H. An average retardation coefficient of 1.14 ± 0.23 corresponding to an apparent distribution coefficient of 1.98 ± 0.42 × 10 -2 mL g -1 was calculated for the medium. In general, sorption ratios for natural sediments are of the order of 0.1 mL g -1 .…”

Section: Bulk Density and Distribution Coefficientmentioning

confidence: 93%

Vadose Zone Contaminant Fate and Transport Analysis for the 216-B-26 Trench

Ward¹,

Gee²,

Zhang³

et al. 2004

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U. Owing to the potential risk, remediation is being accelerated at this site. Developing an effective remediation plan and evaluating remedial options for the site requires a detailed analysis of fate and transport for this site and such an analysis must rely on numerical modeling. The purpose of this study was to develop a conceptual model for contaminant fate and transport at the 216-B-26 Trench site to allow interpretation of the current contaminant distributions and to support identification, development, and evaluation of remediation alternatives.In developing the conceptual model, the presence of large concentrations of 99 Tc high above the water table implicated stratigraphy in the control of the downward migration. The resulting conceptual model therefore included 1) small-scale stratigraphy and changes in physical and chemical properties, 2) tilted layers to accommodate the natural slope to the formation, and 3) lateral spreading along multiple strata with contrasting physical properties. Flow and transport properties were derived using physically based pedotransfer functions that were coupled with high-resolution neutron moisture logs taken on a vertical spacing of 0.076 m. Heterogeneity in the longitudinal and transverse horizontal directions was incorporated by using geostatistical methods to overlay the spatial correlation structure of flow variables from the well-characterized 299-E24-111 test site on to the simulation domain. Two approaches were used to compare no-action and capping remedial alternatives. The first approach, based on a simple analytical convolution solution to the convective-dispersive equation, assumed steady downward flow and allowed for spatially averaged or variable water content. This approach was combined with a soil screening protocol to calculate soil screening levels (Tables S1 and S2) and contaminant concentrations reaching hypothetical receptors down gradient of the site. In the second approach the STOMP simulator was used to predict contaminant transport through the vadose zone and into a 5-m thick confined aquifer during transient multidimensional flow.Both modeling approaches show that leachate concentrations reaching the water table would exceed the MCLs under the no-action alternatives with hypothetical recharge rates of 25 and 3.5 mm/yr. Soil screening levels were exceeded under the no-action alternatives and concentrations of mobile contaminants reaching hypothetical receptor wells consistently exceeded the MCLs (Tables S3 and S4). Owing to the large inventory of 99 Tc and NO 3 -, the high mobility of the two contaminants, and the long half life of 99 Tc, additional measures appear necessary to meet the appropriate soil screening levels. In this respect, on-site capping was evaluated simply by reducing surface recharge to mimic the design performance of hypothetical surface barriers. Both modeling approaches show capping to be an effective technology for remediating the site. Capping successful removed the threat to ground water through a reduction in mass flux ...

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Section: Bulk Density and Distribution Coefficientmentioning

confidence: 93%

Vadose Zone Contaminant Fate and Transport Analysis for the 216-B-26 Trench

Ward¹,

Gee²,

Zhang³

et al. 2004

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“…The artificial rainfall system (Fig. 3) consists of a water reservoir, a high position water reservoir, a water level controller, a filter, a flow-meter, an electromagnetic valve and a sprayer [15,17]. The sprayer was designed to supply a uniform artificial rainfall of 4-10 mm/h over an area of 2 m × 2 m. The asymmetry for different rainfall densities was < 15% and the asymmetry for any single rainfall density in 8 h was < 8%.…”

Section: Application Of Artificial Rainfall Over the Pitmentioning

confidence: 99%

“…However the migration behavior of radionuclides in the unsaturated zone is not yet well understood, although some related research work has been published [10][11][12][13][14][15]. This paper presents the result of a field experiment investigating the migration of 90 Sr, 237 Np, 238 Pu and 241 Am in unsaturated Chinese loess.…”

Section: Introductionmentioning

confidence: 99%

Field study of the migration of⁹⁰Sr,²³⁷Np,²³⁸Pu and²⁴¹Am in unsaturated Chinese loess under artificial rainfall condition

Li¹,

Liu²,

Zhao³

et al. 2004

Radiochimica Acta

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The migration of 90 Sr, 237 Np, 238 Pu and 241 Am in unsaturated Chinese loess under artificial rainfall condition was investigated at the CIRP's field test site. Quartz containing 90 Sr, 237 Np, 238 Pu and 241 Am was introduced into an experimental pit and the pit was backfilled. Artificial rainfall of 10-15 mm/d was applied to the experimental pit for 1078 days. HTO was used for obtaining the migration rate of moisture water in the pit. Vertical core soil samples were taken twice a year and cut into 0.5 cm long section soil samples. The section soil samples were weighed and wind dried. Radioactivity of 237 Np and 241 Am in the section soil samples was measured with a low energy photon detector (HPGe); 90 Sr and 238 Pu were determined with a low background α & β detector after chemical separation. During the experiment, moisture water at different depths was taken on a daily basis and 3 H in the moisture water samples was determined with liquid scintillation technique. Experimental result indicates that the downward migration rate of moisture water was 2.27 cm/d and the retardation factors of 90 Sr, 237 Np, 238 Pu and 241 Am in the loess unsaturated zone were 9.9 × 10 2 , 3.2 × 10 3 , 3.2 × 10 3 and 4.5 × 10 3 , respectively. This result suggests that 90 Sr, 237 Np, 238 Pu and 241 Am could be effectively retarded by the loess unsaturated zone.

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“…). 1,[7][8][9][10][11][12] At the U.S. Department of Energy's Hanford Site, located in southeastern Washington State, 99 Tc was produced as a by-product of nuclear fission in the site's nine plutonium production reactors. Both inadvertent and planned releases of waste solutions to the environment have resulted in widespread 99 Tc contamination in the Hanford groundwater system.…”

mentioning

confidence: 99%

“…Box 999, MSIN P7-22, Richland, Washington 99352, USA. E-mail: christopher.brown@pnl.gov; Fax: (509) 376-4890; Tel: (509) 376-8389 w Presented at 2006 Winter Conference on Plasma Spectrochemistry, Tucson, AZ, USA, January [8][9][10][11][12][13][14]2006. z The T single-shell tank farm consists of twelve 500 000 gallon and four 55 000 gallon underground storage tanks built in 1943/44 and used for active storage of high-level nuclear waste until 1980.…”

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confidence: 99%

Precise ruthenium fission product isotopic analysis using dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS)

Brown

Dresel

Geiszler

et al. 2006

J. Anal. At. Spectrom.

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surface environments and is a key contributor to long-term risk. However, as a mono-isotopic fission product, 99 Tc is limited in its use as a signature to differentiate between different waste disposal pathways that could have contributed to sub-surface contamination at these facilities. Ruthenium fission-product isotopes are attractive analogues for the characterization of 99 Tc sources because of their direct similarity to technetium with regard to subsurface mobility, their large fission yields, and low natural background concentrations. We developed an inductively coupled plasma mass spectrometry (ICP-MS) method capable of measuring ruthenium isotopes in groundwater samples and water extracts of vadose zone sediments. Samples were analyzed directly on a PerkinElmer ELAN DRC II ICP-MS after a single pass through a 1-ml bed volume of Dowex AG 50W-X8 100-200 mesh hydronium-based cation exchange resin. Precise ruthenium isotopic ratio measurements were achieved using a low-flow Meinhard-type nebulizer and long sample acquisition times (150 000 ms). Relative standard deviations of triplicate replicates were maintained at less than 0.5% when the total ruthenium solution concentration was 0.1 ng ml À1 or higher. Further work was performed to minimize the impact caused by mass interferences using the dynamic reaction cell (DRC) with O 2 as the reaction gas. Aqueous concentrations of 96 Mo and 96 Zr, two potential interferents to the analysis of total ruthenium concentration, were reduced by more than 99.7% in the reaction cell prior to injection of the sample into the mass analyzer quadrupole. The DRC was used in combination with mass correction to quantitatively analyze samples containing up to two orders of magnitude more zirconium and molybdenum than ruthenium. The analytical approach documented herein provides an efficient and cost-effective way to precisely measure ruthenium isotopes and quantitate total ruthenium (natural versus fission-product) in aqueous matrixes.

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Migration of⁹⁹Tc in unsaturated Chinese loess under artificial rainfall condition: anin situtest

Cited by 3 publications

References 8 publications

Vadose Zone Contaminant Fate and Transport Analysis for the 216-B-26 Trench

Vadose Zone Contaminant Fate and Transport Analysis for the 216-B-26 Trench

Field study of the migration of⁹⁰Sr,²³⁷Np,²³⁸Pu and²⁴¹Am in unsaturated Chinese loess under artificial rainfall condition

Precise ruthenium fission product isotopic analysis using dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS)

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Migration of99Tc in unsaturated Chinese loess under artificial rainfall condition: anin situtest

Cited by 3 publications

References 8 publications

Vadose Zone Contaminant Fate and Transport Analysis for the 216-B-26 Trench

Vadose Zone Contaminant Fate and Transport Analysis for the 216-B-26 Trench

Field study of the migration of90Sr,237Np,238Pu and241Am in unsaturated Chinese loess under artificial rainfall condition

Precise ruthenium fission product isotopic analysis using dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS)

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Migration of⁹⁹Tc in unsaturated Chinese loess under artificial rainfall condition: anin situtest

Field study of the migration of⁹⁰Sr,²³⁷Np,²³⁸Pu and²⁴¹Am in unsaturated Chinese loess under artificial rainfall condition