Mobility of plutonium and americium through a shallow aquifer in a semiarid region

Penrose, W.R.; Polzer, W.L.; Essington, E.H.; Nelson, D.M.; Orlandini, K.A.

doi:10.1021/es00072a012

Cited by 262 publications

(152 citation statements)

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“…in effect, Pu losses are considered colloidal only), or via equation 1, which does not include the effects of sorptive losses to the CFF system in the calculation of colloid abundances. We are fortunate in this study that the CFF mass balances are close to 100%, however this is not always the case and how one interprets CFF losses can have a large impact on reported colloid data (Buesseler et al, 2003 Colloid facilitated Pu transport has received a great deal of attention (Honeyman, 1999;Kaplan et al, 1994;Kersting et al, 1999;Kim, 1994;Kim et al, 1984;Marty et al, 1997;McCarthy and Zachara, 1989;Penrose et al, 1990). In SRS F-Area seepage basin groundwater, we found low colloidal Pu (<4%) using this same combination of low-flow rate pumping and on-site CFF processing techniques (Dai et al, 2002).…”

mentioning

confidence: 76%

“…These researchers suggested that Pu transport was enhanced by colloid facilitated transport in groundwater. Similarly, the detection of Pu in groundwater some 3400 m downstream in Mortandad Canyon at the Los Alamos National Laboratory, is cited widely as an example of colloid facilitated transport (Penrose et al, 1990). More recent review of these data suggests that Pu detected in downstream wells could not have entered through groundwater and thus the potential for Pu migration via colloidal transport may have been overstated (Marty et al,3 1997).…”

Section: Introductionmentioning

confidence: 99%

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Plutonium in groundwater at the 100K-Area of the U.S. DOE Hanford Site

Dai

Buesseler

Pike

2005

Journal of Contaminant Hydrology

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We examined the concentration, size distribution, redox state and isotopic composition of plutonium (Pu) in groundwater at the 100K-Area at the US Department of Energy's (DOE) Hanford Site. Total concentrations of Pu isotopes were extremely low (10 -4 to 10 -6 pCi/kg, ≈ 10 4 to 10 6 atoms/kg), but measurable for the first time in the 100K-Area wells using mass spectrometric analyses that are much more sensitive than alpha spectroscopy methods used previously. Size fractionation data from two wells suggests that 7-29% of the Pu is associated with colloids, operationally defined here as particles between 1 kDa -0.2 µm in size. These colloids were collected using a 1 kDa cross-flow ultrafiltration system developed specifically for groundwater actinide studies to include careful controls both in the field and during processing to ensure in-situ geochemical conditions are maintained and size separations can be well characterized. Pu in this colloidal fraction was exclusively in the more reduced Pu(III/IV) form, consistent with the higher affinity of Pu for particle surfaces in the lower oxidation states. While the overall concentrations of Pu were low, the Pu isotopic composition suggests at least two local sources of groundwater Pu, namely local Hanford reactor operations at the 100K-Area, and spent nuclear fuel from the N reactor, which was stored in concrete pools at this site.Differences between this site and the Savannah River Site (SRS) are noted, since groundwater Pu at the F-Area seepage basin at SRS has been found using these same 2 methods, to be characterized by much lower colloidal abundances and higher oxidation states. This difference is not directly attributable to groundwater redox potential or geochemical conditions, but rather the physical-chemical difference in Pu sources, which at SRS appear to be dominated downstream from the seepage basins by decay of 244 Cm, resulting in more oxidized forms of 240 Pu. There is no clear evidence for colloid facilitated transport of Pu in groundwater at this site, since downstream wells have both an order of magnitude lower concentrations of Pu, but also a lower fractional colloidal distribution.

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confidence: 76%

Section: Introductionmentioning

confidence: 99%

Plutonium in groundwater at the 100K-Area of the U.S. DOE Hanford Site

Dai

Buesseler

Pike

2005

Journal of Contaminant Hydrology

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“…Americium was found to be very immobile in most of the studies located in the literature (for example, Means et al 1978;Carpenter et al 1987). The main uncertainty regarding the surficial behavior of americium appears to be the degree to which it is mobilized through colloidal transport (Penrose et al 1990). …”

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confidence: 99%

Unsaturated Zone and Saturated Zone Transport Properties (U0100)

Conca¹

2000

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“…Based on laboratory experiments using site-specific materials, Pu and Am transport at Los Alamos National Laboratory was predicted to be limited to less than a few meters (Penrose et al 1990). However, both radionuclides were detected in monitoring wells as far as 3390 m downgradient.…”

Section: Radioactive Contaminant Transport With Mobile Colloidsmentioning

confidence: 99%

“…The authors suggested that organic ligands enhanced the mobility of Co, Ce, Cs, Eu, Sb, and Zr through the formation of mobile complexes. They reported detection of significant particulate nuclides on the 400-nm filter for 6oCo, "Zr, '06Ru, and 13' Cs, and '@Ce.Based on laboratory experiments using site-specific materials, Pu and Am transport at Los Alamos National Laboratory was predicted to be limited to less than a few meters (Penrose et al 1990). However, both radionuclides were detected in monitoring wells as far as 3390 m downgradient.…”

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confidence: 99%

Colloid suspension stability and transport through unsaturated porous media

McGraw¹,

Kaplan²

1997

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Executive SummaryContaminant transport is traditionally modeled in a two-phase system: a mobile aqueous phase and an immobile solid phase. Over the last 15 years, there has been an increasing awareness of a third, mobile solid phase. This mobile solid phase, or mobile colloids, are organic or inorganic submicron-sized particles that move with groundwater flow. When colloids are present, the net effect on radionuclide transport is that radionuclides can move faster through the system. It is not known whether mobile colloids exist in the subsurface environment of the Hanford Site. Furthermore, it is not known if mobile colloids would likely exist in a plume emanating from a Low Level Waste (LLW) disposal site. No attempt was made in this study to ascertain whether colloids would form. Instead, experiments and calculations were conducted to evaluate the likelihood that colloids, if formed, would remain in suspension and move through saturated and unsaturated sediments.The objectives of this study were to evaluate three aspects of colloid-facilitated transport of radionuclides as they specifically relate to the LLW Performance Assessment. These objectives were: 1) determine if the chemical conditions likely to exist in the near and far field of the proposed disposal site are prone to induce flocculation (settling of colloids from suspension) or dispersion of naturally occurring Hanford colloids, 2) identify the important mechanisms likely involved in the removal of colloids from a Hanford sediment, and 3) determine if colloids can move through unsaturated porous media.Mobile colloid formation is commonly described as a three-step process: genesis, stabilization, and transport. Colloid genesis describes how the micron-sized particles are formed in groundwater. Stabilization describes how the colloids are brought into suspension, which is a function of the colloid and groundwater chemical composition and water flow (kinetic) forces. Transport describes how the suspended colloid move through the porous media or are retained by the porous media by physical forces (such as diffusion, straining, or gravitation settling) or physicochemical attraction of the colloid to the matrix.As the second step in mobile colloid formation indicates, colloids must remain in suspension, i.e., not flocculate, in order to be transported with groundwater flow. A series of batch experiments was conducted to identify the chemical conditions where dispersion and flocculation (settling out of suspension) of Hanford sediment colloids (

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Mobility of plutonium and americium through a shallow aquifer in a semiarid region

Cited by 262 publications

References 10 publications

Plutonium in groundwater at the 100K-Area of the U.S. DOE Hanford Site

Plutonium in groundwater at the 100K-Area of the U.S. DOE Hanford Site

Unsaturated Zone and Saturated Zone Transport Properties (U0100)

Colloid suspension stability and transport through unsaturated porous media

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