Retention of neptunium, americium, and curium by diffusible soil particles

Sheppard, J.C.; Campbell, M. J.; Kittrick, J. A.; Hardt, T.L.

doi:10.1021/es60154a006

Cited by 21 publications

(14 citation statements)

References 6 publications

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“…These techniques are intended to be transferred for implementation at contaminated sites operated by DOE and private sector. For example, similar techniques could be applied to plutonium contamination at Johnston Atoll (Bramlitt, 1988), Hanford (Cleveland, and Rees, 1981), and Maxey Fats (Sheppard, 1979 (Stohl and Smith, 1981). Fig.…”

Section: Discussionmentioning

confidence: 99%

Uranium‐contaminated soils: Ultramicrotomy and electron beam analysis

Buck

Dietz

Bates

1995

Microscopy Res & Technique

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Uranium-contaminated soils from the U.S. Department of Energy (DOE) Fernald Site, Ohio, have been examined by a combination of backscattered electron imaging (BSE) and analytical electron microscopy with electron diffraction (AEM). The inhomogeneous distribution of particulate uranium phases in the soil required the development of a method for using ultramicrotomy to prepare transmission electron microscopy (TEM) thin sections from the SEM mounts. A water-miscible resin was selected that allowed comparison between SEM and TEM images, permitting representative sampling of the soil. Uranium was found in iron oxides, silicates (soddyite), phosphates (autunites), and uraninite (UO2 + x). No uranium was detected in association with phyllosilicates in the soil.

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Section: Discussionmentioning

confidence: 99%

Uranium‐contaminated soils: Ultramicrotomy and electron beam analysis

Buck

Dietz

Bates

1995

Microscopy Res & Technique

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“…However, the tendency of Am(III) to strongly sorb to sediment and soil particles suggests that there is potential for colloid-facilitated transport of Am(III). For example, studies by Sheppard et al (1979), Penrose et al (1990), and Kaplan et al (1994) have shown colloid-facilitated transport of Am(III) in certain systems.…”

Section: C3 Americium-241mentioning

confidence: 99%

A Review of Subsurface Behavior of Plutonium and Americium at the 200-PW-1/3/6 Operable Units

Cantrell¹,

Riley²

2008

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(PNNL) review available information and data pertaining to Pu and americium mobility in the subsurface at Hanford, with emphasis on vadose zone contamination within the 200-PW-1/3/6 operable units, to address this inconsistency between perception and data. In response to this request, PNNL compiled, analyzed, and summarized information and data on relevant waste site structures and associated subsurface geologies, waste composition and disposal histories, Pu and americium subsurface geochemistry, and contaminant characterization underlying key operable unit waste sites. Summarized information and data were used to develop a conceptual model that attempts to explain historical Pu and americium distributions in the subsurface and their potential for future migration based on current vadose zone characteristics in the 200-PW-1/3/6 operable units. Technical data gaps and information needs for refinement of the conceptual model were identified. This report begins with a brief summary of the history and current status of 200-PW-1/3/6 operable units in Section 2. This is followed by a description of the PNNL conceptual model of Pu/Am migration at the 200-PW-1/3/6 operable units, during conditions of both past artificial recharge and current natural recharge (Section 3). Section 4 discusses data gaps and information needs. Section 5 provides recommendations for further work to address the data gaps and information needs identified in Section 4. A more detailed account of the waste disposal history, chemistry, and available characterization data for the 200-PW-1/3/6 operable units is presented in Appendix A. A summary geologic description of the 200-PW-1/3/6 operable units is presented in Appendix B. A brief discussion of the environmental geochemistry of Pu and Am is presented in Appendix C. 2.0 History and Current Status of 200-PW-1/3/6 Operable Units This section briefly summarizes the history and current status of the 200-PW-1/3/6 operable units. A more detailed account of the waste disposal history, chemistry, and summary of available characterization data for the 200-PW-1/3/6 operable units is presented in Appendix A.

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Section: A3 Americium-241mentioning

confidence: 99%

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

Cantrell¹,

Zachara²,

Dresel³

et al. 2007

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Companion reports that review other subject matter areas relevant to contaminant transport within the vadose zone beneath the SST WMAs, the IDF, and groundwater have been recently published. The specific subject areas include the geology of the SST WMAs iv contaminants released to the vadose zone exhibit a wide range of mobility behaviors. Many tank waste contaminants have been strongly retarded by adsorption and precipitation reactions (e.g., cesium, plutonium, americium, and europium), while others have remained mobile (e.g., technetium, nitrate, and selenium). Still others show variable, waste-specific behaviors (e.g., cesium [where sodium concentrations are very high], strontium, chromium, and uranium) that are closely tied to evolving composition of pore water in the sediments, and for chromium, a change in oxidation state. The temperature of in-ground tank waste has moderated by heat exchange with the subsurface sediment, and high concentrations of base (OH -) have been neutralized through reactions with sediment minerals and secondary mineral precipitation. Major geochemical features that may potentially affect the mobility of key contaminants of interest in the vadose zone include oxidation state, aqueous speciation, solubility, and adsorption reactions.Processes suspected of facilitating the far-field migration of immobile radionuclides, such as formation of stable aqueous complex formation and mobile colloids, were found to be potentially operative, but unlikely to occur in the field. An exception is the enhanced migration of cobalt-60 facilitated by the formation of highly stable aqueous-cyanide complexes. Certain fission-product oxyanions (e. • Adsorption is suppressed by large concentrations of tank waste anions (e.g., NO 3 -, OH -, and CO 3 2-)• Surface charge of clay-size minerals is negative and will therefore tend to repel anions• Unlike chromium, their less-soluble, less-mobile reduced forms are unstable in oxidizing environments.Laboratory studies conducted through PNNL's Vadose Zone Characterization Project and basic-science geochemical studies are expected to continue in partnership to provide information to further refine the conceptual model used for risk assessment modeling. Results of these studies can be used to help ascertain uncertainties associated with the refinement of the conceptual models for contaminant migration in the vadose zone beneath the single-shell tanks. Results can also provide improved parameterization, such as distribution coefficients (K d ), and mathematical constructs used by modelers to predict contaminant mobility under these conditions, and to decrease the degree of conservatism incorporated in these models.For various reasons, risk assessment models typically use various approximations to represent the conceptual model developed for the site. Adsorption is frequently approximated using empirical distribution coefficients (K d s). Although the use of empirical distribution coefficients can potentially lead to erroneous results under certain conditions where the...

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Retention of neptunium, americium, and curium by diffusible soil particles

Cited by 21 publications

References 6 publications

Uranium‐contaminated soils: Ultramicrotomy and electron beam analysis

Uranium‐contaminated soils: Ultramicrotomy and electron beam analysis

A Review of Subsurface Behavior of Plutonium and Americium at the 200-PW-1/3/6 Operable Units

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

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