Diffusion of Iodine and Rhenium in Category 3 Waste Encasement Concrete and Soil Fill Material

Wellman, Dawn M.; Mattigod, Shas V.; Whyatt, Greg A.; Powers, Laura; Parker, Kent E.; Wood, M.I.

doi:10.2172/900213

Cited by 4 publications

(9 citation statements)

References 5 publications

(6 reference statements)

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“…The behavior of I and Re at 7% and 15% moisture content was generally greatest within the first 10 mm, with a more gradual decrease over the remaining 20 to 30 mm. This, in accordance with previous results, suggests a direct relationship between diffusion within concrete monoliths and the degree of moisture content in the contacting soil half cells (Wellman et al 2006;Mattigod et al 2001). However, the comparison of diffusion of I and Re at 7% and 15% shows a number of deviations.…”

Section: Concrete-soil Half Cellssupporting

confidence: 92%

“…The absence of iron in the uncarbonated core likely limited the potential formation of any micro-cracks, thus limiting diffusion of I and Re into the concrete monolith from the contaminated sediment. Increased micro-cracking in the presence of Fe and for concrete monoliths that had undergone carbonation agrees with results of previous investigations (Wellman et al 2006 The concentrations of I and Re quantified within the monoliths were much lower at the interface than that measured at 4% moisture content (40-60 mg/g at 4% moisture content versus 10-20 mg/g at 7% and 15% moisture content). Furthermore, the depth of diffusion of I and Re into the concrete monoliths was greater at higher moisture contents.…”

Section: Concrete-soil Half Cellssupporting

confidence: 90%

“…This set of concrete monoliths displayed a more rapid decrease in concentration within the first 10 to 20 mm. As demonstrated previously, the inclusion of iron and the effect of carbonation result in the formation of micro-cracks within the concrete monoliths (Wellman et al 2006) that apparently facilitate diffusion. The absence of iron in the uncarbonated core likely limited the potential formation of any micro-cracks, thus limiting diffusion of I and Re into the concrete monolith from the contaminated sediment.…”

Section: Concrete-soil Half Cellsmentioning

confidence: 57%

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Diffusion and Leaching Behavior of Radionuclides in Category 3 Waste Encasement Concrete and Soil Fill Material – Summary Report

Mattigod¹,

Wellman²,

Bovaird³

et al. 2011

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ICP-MS inductively coupled plasma mass spectrometry ICP-OES inductively coupled plasma optical emission spectrometry LI leachability index LSC liquid scintillation counting MC moisture content NO 3 nitrate PVC polyvinyl chloride RNIP reactive nanoscale zero-valent iron particles SO 4 sulfate STAR-CD computational fluid dynamics code ZVI zero-valent iron 1-D one-dimensional 3.1 Dynamic leach test: cumulative leaching fraction as a function of time for iodine-125 ..

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Section: Concrete-soil Half Cellssupporting

confidence: 92%

Section: Concrete-soil Half Cellssupporting

confidence: 90%

Section: Concrete-soil Half Cellsmentioning

confidence: 57%

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Diffusion and Leaching Behavior of Radionuclides in Category 3 Waste Encasement Concrete and Soil Fill Material – Summary Report

Mattigod¹,

Wellman²,

Bovaird³

et al. 2011

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“…Also, a consistent decrease in the relative fraction of Re within the soil half-cell was evident as a function of moisture content. Comparable behavior was previously observed in concrete-soil half-cell experiments wherein diffusion of I and Re from concrete to soil was quantified as a function of moisture content (Mattigod et al 2001;Wellman et al 2006). A similar trend for I was not evident in results of half-cell diffusion tests presented here.…”

Section: Concrete-soil Half Cellssupporting

confidence: 86%

Concrete Property and Radionuclide Migration Tests

Wellman¹,

Mattigod²,

Powers³

et al. 2008

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Assessing long-term performance of Category 3 waste cement grouts for radionuclide encasement requires knowledge of the radionuclide-cement interactions and mechanisms of retention (i.e., sorption or precipitation). This understanding will enable accurate prediction of radionuclide fate when the waste forms come in contact with groundwater. A set of experiments was initiated during Fiscal Year (FY) 2006 to study the diffusion of rhenium (Re) and iodine (I) from spiked soil into concrete. These half-cells experiments were conducted with concrete half cells that were prepared with and without metallic iron and carbonation and the soil half-cells poised at moisture contents of 4%, 7%, and 15% by mass. Initial concentrations of I and Re were approximately the same in all experiments (between 12.5 and 15 mg/g of soil). The data showed that the greatest concentration of I and Re were measured within the first 10 mm of the concrete monolith (~10-20 mg/g) with a gradual decrease in concentrations of both elements over the remaining 20 to 30 mm of concrete monolith. Higher moisture contents and carbonation enabled greater depths of diffusion into the concrete monoliths. At 4% moisture content, the behavior of I and Re were markedly different. The concentration of I was 40 to 60 mg/g within the first 5 mm of the concrete half-cell in contact with sediment, whereas the diffusion of Re was limited to < 5 mg/g within the same depth of concrete. Such disparity in diffusivity of I and Re into concrete from spiked low-moisture content (4%) soil half cell suggested potential vapor-phase diffusion of I. Vaporization of I from relatively dry soil (4% moisture content) in the half cell was confirmed by extracting I-stained polyvinyl chloride sections of the soil half cell with isopropanol. These extracts contained 250 to 800 ppb I, but no Re was detected. Dynamic leach tests (American National Standards Institute ANSI-16.1) were conducted on a set of Re/I and technetium (Tc)/I spiked concrete specimens containing 4%, 8%, and 12% by mass-40 to +60 mesh iron powder or reactive nanoscale zero valent iron particles (RNIP) (Toda America, Inc., Schaumburg, IL). The objective of these tests was to examine whether these iron additives would influence leaching of redox-sensitive contaminant species. The results indicate that inclusion of RNIP relative to metallic iron particles significantly increases the leachability of Re and I from waste-form specimens. The leaching behavior of I and Re in the presence of RNIP was at a significantly increased rate throughout the duration of the test. The leaching indices indicate that in the presence of 4% and 8% zero valent iron (ZVI), Tc had higher leachability than Re. However, there was no difference in leachability of Tc and Re when the waste form contained 12% ZVI. The RNIP formulation consists of elemental iron, magnetite, water, and a water-soluble polymer to maintain a stabilized iron slurry. It is hypothesized that the polymer may form a surface coating on the iron particles that reduces their r...

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“…This specification was used as the basis to prepare concrete for fabrication of test specimens. Details of concrete composition and test specimen fabrication has been described in a technical report (Wellman et al 2006). …”

Section: Concrete Composition and Fabrication Of Test Specimensmentioning

confidence: 99%