Characterization of Vadose Zone Sediments Below the T Tank Farm: Boreholes C4104, C4105, 299-W10-196, and RCRA Borehole 299-W11-39

Serne, R. Jeffrey; Bjornstad, Bruce N.; Horton, Duane G.; Lanigan, David C.; Schaef, Herbert T.; Lindenmeier, Clark W.; Lindberg, Michael J.; Clayton, Ray E.; Legore, Virginia L.; Geiszler, Keith N; Baum, Steven R.; Valenta, Michelle M; Kutnyakov, Igor V.; Vickerman, Tanya S; Orr, Robert D.; Brown, Christopher F.

doi:10.2172/939046

Cited by 14 publications

(24 citation statements)

References 21 publications

(75 reference statements)

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“…The uranium concentrations in Boring C3832 pore water, derived from water extracts (1:1 by mass) peaked at 2850 µg/L within the Upper Cold Creek Unit (Serne et al 2004a). The uranium concentrations in Boring C4104 derived from sediment:water extracts reached 17,800 µg/L and peaked just above the Upper Cold Creek Unit (Serne et al 2004b). Only low levels (less than 2 µg/L) of uranium were detected in the groundwater samples from wells near these two borings, and low U-236/U-238 ratios (<5.1x10 -7 ) indicated less than 1% contaminant contribution to the groundwater uranium.…”

Section: 15mentioning

confidence: 92%

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

Zachara¹,

Brown²,

Christensen³

et al. 2007

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Executive SummaryUranium (U) is an important risk-driving contaminant at the Hanford Site. Over 200,000 kg have been released to the vadose zone over the course of site operations, and a number of vadose zone and groundwater plumes containing the uranyl cation [UO 2 2+ , U(VI)] have been identified. U is recognized to be of moderate-to-high mobility, conditions dependent. The site is currently making decisions on several of these plumes with long-lasting implications, and others are soon to come.Uranium is one of nature's most intriguing and chemically complex elements. The fate and transport of U(VI) has been studied over the long lifetime of the Hanford Site by various contractors, along with the Pacific Northwest National Laboratory (PNNL) and its collaborators. Significant research has more recently been contributed by the national scientific community with support from the U.S. Department of Energy's (DOE) Office of Science through its Environmental Remediation Sciences Division (ERSD). This report represents a first attempt to integrate these findings into a cohesive view of the subsurface geochemistry of U at the Hanford Site. The objective is to inform all interested Hanford parties about the in-ground inventory of U and its geochemical behavior. This report also comments on the prospects for the development of a robust generic model to more accurately forecast future U(VI) migration at different Hanford waste sites, along with further research necessary to reach this goal.To accomplish the report objectives, the environmental geochemistry of U at the Hanford Site is discussed in terms of both the vadose and saturated zone, to the extent that it is known. Hexavalent uranium [U(VI)] is the dominant valence form of U under the predominantly oxidizing subsurface conditions at the Hanford Site, and the researchers' analyses consequently emphasize this species. The nature and concentration of background U in Hanford subsurface sediments is identified to place contaminant U(VI) concentrations and behavior in perspective to the natural system. In-ground U-waste inventories are quantified and characterized with regard to source term, to the extent possible, and the most important sites from an inventory perspective are identified. The U-isotopic content of various waste streams are discussed from the perspective of waste-source tracking. The geochemical attenuation processes responsible for slowing the rate of subsurface U migration, relative to the transporting water front, are illustrated through careful consideration of both field characterization studies of existing U vadose-zone and groundwater plumes, and laboratory studies of derived contaminated and uncontaminated sediments. Both empirical and more mechanistic models of these attenuation processes are considered as well as the parameters that define attenuation magnitude. Attention is given to the behavior of contaminant U(VI) that has been in contact with Hanford sediments for extended periods (circa 10-50 years), as long contact imparts unique characte...

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Section: 15mentioning

confidence: 92%

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

Zachara¹,

Brown²,

Christensen³

et al. 2007

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“…The mineralogy in sediments from the BX and TX Tank Farm boreholes were characterized in other studies (Serne et al 2008a(Serne et al , 2008b. This characterization was conducted in the same BX-102 borehole as sediments 1 and 2 in this study (and similar depths, as shown in Tables 3.1 and 3.2).…”

Section: Sediments Used In Studymentioning

confidence: 92%

“…In this study, the calcite content of the mixture of sediments 3a and 3b should average ~1% (Table 3.2), so other than this calcite content, the higher clay content of the Cold Creek and Hanford formation sediments at the TX Tank Farm (8% to 10%, compared to 2.5% to 5.5%) could result in higher reactivity for sediment 3 compared to sediments 1 and 2. Serne et al (2008aSerne et al ( , 2008b.…”

Section: Sediments Used In Studymentioning

confidence: 99%

Remediation of Uranium in the Hanford Vadose Zone Using Ammonia Gas: FY 2010 Laboratory-Scale Experiments

Szecsody¹,

Truex²,

Zhong³

et al. 2010

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Executive SummaryThis investigation is focused on refining an in situ technology for vadose zone remediation of uranium by the addition of ammonia (NH 3 ) gas with no addition of water. The objectives were to: a) refine the technique of ammonia gas treatment, b) identify the geochemical changes in uranium surface phases, c) identify broader geochemical changes that occur, and d) predict and test injection of ammonia gas for intermediate-scale systems to identify process interactions that could impact field-scale implementation. For ammonia gas injection into vadose zone sediments to be successful as a uranium remediation technology, it needs to show decreased U mobility of the most mobile U phases (aqueous, adsorbed) in a variety of field conditions. Uranium is present in Hanford sediment include in multiple phases including aqueous U(VI)-carbonate complexes, adsorbed, uranium coprecipitated with carbonates, and U-bearing minerals Na-boltwoodite and uranophane. Ammonia treatment of sediments raises the pH in Hanford sediments from 8.0 to 11-13, which has resulted in a decrease in uranium mobility, as evidenced by decrease in aqueous and adsorbed uranium in 85% of the different sediments tested (different U surface phase distributions or NH 3 treatments) and an increase in 8M HNO 3 extracted U (hard to extract U phases, silicates/phosphates/oxides) for 79% of sediments tested. There were also inconsistent changes in two acetate extractions, likely the result of dissolution of multiple surface U phases (U-carbonates, Na-boltwoodite, uranophane). Surface phase analysis by laser induced fluorescence spectroscopy and extended x-ray absorption structure has showed essentially no U surface mineral change in sediments initially containing Na-boltwoodite, but some U surface phase changes in U-calcite coprecipitates to uranyl oxyhydroxide, Na-boltwoodite, and uranyl tricarbonate. Therefore, the ammonia gas treatment appears most effective for U present in the most mobile phases: aqueous U, adsorbed U, and carbonate associated U. NH 3 -treated sediments containing Na-boltwoodite and uranophane showed decreased leaching even though solid phase analysis showed little changes in the U mineralogy. The decreased leaching may be the result of other mineral precipitates coating these phases. Minerals that leached the most significant mass of ions were montmorillonite, muscovite, and kaolinite. A greater understanding of these dissolution/precipitation/coating processes is needed to predict the long-term impact on uranium mobility.Ammonia gas injection experiments conducted in 20-to 30-ft long 1-D systems and a layered 2-D radial flow system were used to characterize the physicochemical changes at the NH 3 reaction front and treatment coverage in heterogeneous sediments. For 5% NH 3 (95%N 2 ) injection, an average of 234 pore volumes were needed to achieve the elevated pH (10.2 to 11.4) of the reaction front observed, with 465 pore volumes needed to achieve pH equilibrium (pH = 11.88), at 4% water content and 35% porosity. The des...

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“…Due to sample mass limitations, no analyses could be performed on material recovered from the shoe in push hole C5170. It has been well documented in several borehole reports that uncontaminated Hanford sediments have soil pH values ranging from 7.0 to 8.0 (Serne et al 2002a(Serne et al , 2004bLindenmeier et al 2003;Brown et al 2006). Sediment pH values are considered slightly elevated between 8.0 and 8.5 and are significantly elevated above 8.5.…”

Section: Ph and Electrical Conductivitymentioning

confidence: 96%

Characterization of Direct-Push Vadose Zone Sediments from the 241-B and 241-BX Tank Farms

Brown¹,

Icenhower²,

Um³

et al. 2007

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Executive SummaryGeochemical tests provide evidence for the transit of a plume of caustic waste solution through the sediment column at the Hanford 241-B and -BX Tank Farms. Direct-push samples recovered from boreholes surrounding Tanks 241-B-110 and 241-BX-102 and related waste transfer lines and diversion boxes included sediments typical of those previously recovered from other localities on the Hanford Site. The Hanford formation sediments are dominantly quartzo-feldspathic sands containing lithic fragments, displaying a range of particle size distributions and sorting characteristics. Some moderately well-sorted, fine-grained lithologies are interpreted as lenticular bodies irregularly dispersed in coarser-grained, more poorly sorted sediments. Tier I tests conducted on the vadose zone sediments revealed an inverse correlation between moisture content and sediment size fraction (i.e., there is greater moisture content in finergrained sediments). The Tier I tests also showed that the pore water solutions were likely sodium-rich, moderately saline, and possessed higher pH values than background (uncontaminated) sediments. These data are characteristic of sediments that have encountered sodium-rich, saline, caustic waste solution, as documented in other reports at other suspect contamination sites around Hanford. Analyses of solutions from 1:1 water extracts reveal relatively balanced cation and anion concentrations, indicating that most of the geochemical species have been accounted for. The water extract data for affected sediments also indicate unusually high concentrations of aluminum, iron, and phosphorus. The relatively high concentrations of aluminum and iron may be the result of dissolution of secondary amorphous phases that precipitated after a reactive plume partially dissolved aluminum-and iron-bearing phases as it migrated through the sediment column. On the other hand, the presence of elevated concentrations of phosphorous may be the tell-tale signature of wastes derived from the bismuth phosphate separation process. Elements typically mobile in the subsurface, such as technetium-99, are present at either low concentrations or are below the analytical detection limit. However, we expect that the mobile elements would be present mainly along a narrow plume front, and if this front had passed deeper into the sediment profile than depths sampled, the retention of these elements would be minor. Alternatively, uranium-238 was detected in nearly all the direct-push sediments (by acid extract experiments) from around the BX Tank Farm at concentrations above the natural crustal average (0.76 pCi/g), and we also detected the presence of several anthropogenic radioisotopes, such as cobalt-60, cesium-137, europium-154, and europium-155 (by gamma energy analysis). These data confirm contamination of the sediments.We selected a pair of lithologies from a single direct-push hole from near BX-102 that we anticipated would reveal details of the mechanism of radionuclide binding in the sediments and subjected them ...

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Characterization of Vadose Zone Sediments Below the T Tank Farm: Boreholes C4104, C4105, 299-W10-196, and RCRA Borehole 299-W11-39

Cited by 14 publications

References 21 publications

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

A Site Wide Perspective on Uranium Geochemistry at the Hanford Site

Remediation of Uranium in the Hanford Vadose Zone Using Ammonia Gas: FY 2010 Laboratory-Scale Experiments

Characterization of Direct-Push Vadose Zone Sediments from the 241-B and 241-BX Tank Farms

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