Iodine speciation in a silver-amended cementitious system

Kaplan, Daniel I.; Price, Kimberly A.; Xu, Chen; Li, Dien; Lin, Peng; Wang, Xing; Nichols, R.L.; Schwehr, Kathleen A.; Seaman, John C.; Ohnuki, Toshihiko; Chen, Ning; Santschi, Peter H.

doi:10.1016/j.envint.2019.02.070

Cited by 17 publications

(17 citation statements)

References 27 publications

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“…However, the crux of the issue is that there is no existing process to convert the aqueous iodine scrubbed from off-gas streams into an inert final wasteform. The combination of the labile oxidation state of iodine and reducing conditions encountered in geological disposal tend to enable reductive dissolution and anion-exchange mechanisms, promoting leaching [16,17]. Because of these challenges, current practice follows a "dilute and disperse" approach, releasing this fraction (after neutralisation) into the ocean [18].…”

Section: Radioiodine In Recycling Used Nuclear Fuelmentioning

confidence: 99%

Capture of aqueous radioiodine species by metallated adsorbents from wastestreams of the nuclear power industry: a review

et al. 2021

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Iodine-129 poses a significant challenge in the drive towards lowering radionuclide emissions from used nuclear fuel recycling operations. Various techniques are employed for capture of gaseous iodine species, but it is also present, mainly as iodide anions, in problematic residual aqueous wastestreams, which have stimulated research interest in technologies for adsorption and retention of the radioiodine. This removal effort requires specialised adsorbents, which use soft metals to create selectivity in the challenging chemical conditions. A review of the literature, at laboratory scale, reveals a number of organic, inorganic and hybrid adsorbent matrices have been investigated for this purpose. They are functionalised principally by Ag metal, but also Bi, Cu and Pb, using numerous synthetic strategies. The iodide capacity of the adsorbents varies from 13 to 430 mg g−1, with ion-exchange resins and titanates displaying the highest maximum uptakes. Kinetics of adsorption are often slow, requiring several days to reach equilibrium, although some ligated metal ion and metal nanoparticle systems can equilibrate in < 1 h. Ag-loaded materials generally exhibit superior selectivity for iodide verses other common anions, but more consideration is required of how these materials would function successfully in industrial operation; specifically their performance in dynamic column experiments and stability of the bound radioiodine in the conversion to final wasteform and subsequent geological storage. Article highlights Metallated adsorbents for the capture and retention of radioiodine in the nuclear industry are assessed. The strengths and weaknesses of organic, inorganic and hybrid support matrices and loading mechanisms are discussed. Pathways for progression of this technology are proposed. Graphic abstract

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Section: Radioiodine In Recycling Used Nuclear Fuelmentioning

confidence: 99%

Capture of aqueous radioiodine species by metallated adsorbents from wastestreams of the nuclear power industry: a review

et al. 2021

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“…The waste tanks in C Farm at Hanford will be filled with grout and disposed of in place [8]. The chemical form of iodine in residual waste in the tanks as well as its reaction products with grout may influence the rate at which the iodine leaches from the tanks over time [32][33][34]. The Performance Assessment for C Farm evaluated the risk to groundwater overtime for closing the tanks in this manner [9,10].…”

Section: Resultsmentioning

confidence: 99%

Silver-iodine association in Hanford nuclear waste

Reynolds

Lachut

Meznarich

et al. 2020

J Radioanal Nucl Chem

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The Hanford Site in the United States has over 200 million liters of alkaline nuclear waste. Radioactive iodine is frequently the limiting radionuclide for disposing of the waste in a repository due to the assumption of high solubility. There has been minimal actual data on the speciation of iodine, however. This study dissolved soluble salts from a Hanford waste sample to concentrated insoluble species and then searched for iodine-species using Scanning Electron Microscopy. Silver-iodine associations were found in the sample using Energy Dispersive Spectroscopy, indicating that this iodine was in the form of silver iodide or iodate. These silver bearing species have relatively low water solubility, which may limit the release of iodine to the environment.

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“…All examples to date related to liquid waste immobilization have used formulations which contain blast furnace slag. There is a known interference on AgI stability from slag, resulting from the sulfide content and reducing environment in the waste form (Asmussen et al 2017a;Kaplan et al 2018a;Kaplan et al, 2018b;Asmussen et al 2019) but this interference has been demonstrated to be overcome with an excess of Ag in the waste form. Although the impact on other species that rely on reduction to be sequestered (Cr(VI), Tc(VII)) is unknown.…”

Section: Lines 15 and 16 -Ag Or Non-rcra Particulate Getters On Inorganic Substratementioning

confidence: 99%

Evaluation of Technologies for Enhancing Grout for Immobilizing Hanford Supplemental Low-Activity Waste (SLAW)

Skeen

Langston

McCabe

et al. 2020

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An expert panel consisting of the document authors was assembled by Washington River Protection Solutions, LLC (WRPS) and tasked with (1) identifying technical and regulatory limitations to treating and disposing of grouted low-activity waste (LAW), and (2) with identifying and evaluating a wide range of technical solutions to these limitations. The analysis included technologies to allow inventory management and/or improve retention of iodine, technetium, and nitrate either in the waste packages, or within the Integrated Disposal Facility (IDF), and, technologies to ensure regulated organics are below Resource Conservation and Recovery Act of 1976 (RCRA) Land Disposal Restriction (LDR) levels.The expert panel completed their analysis in three distinct phases. In Phase I, the team reviewed the chemical and physical characteristics of the most recent projected supplemental LAW (SLAW) feed vector along with disposal site waste acceptance criteria and the fiscal year 2019 results from Pacific Northwest National Laboratory that identified the level of improvement that would be needed to meet onsite disposal requirements in the IDF (Asmussen et al. 2019a). The two regulatory constraints targeted for technology solutions by the expert panel were (1) current estimates based on performance assessment fate-andtransport modeling indicate that if the entire quantity of LAW currently designated for supplemental treatment were solidified as a cementitious material, nitrate, 99-Tc, and 129-I could exceed groundwater standards after DOE's time of compliance (1,000 years) but within 10,000 years after IDF closure and (2) LAW may contain RCRA LDR organics at levels that require removal to meet LDR concentration-based limits. It should also be noted that the first issue is only applicable to on-site disposal, not offsite at WCS and is based on calculations that assume either a low-performing grout is used, or high-performance grout does not maintain its performance (SRNL-RP-2018-00687). Asmussen et al. (2019a) estimated that the inventory of grouted SLAW could meet IDF groundwater requirements if the release rate of nitrate, 99-Tc, and 129-I were reduced by a factor of approximately 3.2, 10, and 32, respectively versus baseline formulation performance.In Phase II, an extensive list of technologies and engineering approaches was identified and subjected to an initial assessment by the group. Current knowledge associated with technology maturation needs and constraints to implementation at Hanford were recorded in 13 distinct categories. In the final phase of the process (Phase III), the expert panel selected 7 of the 13 categories for qualitative rating and a series of meetings were held between the expert panel to discuss and rate each technology in each category. All ratings were developed by consensus. After the qualitative rating was complete, a numerical scoring criterion for each category was applied and a composite score for the individual technologies was calculated. An uncertainty score was also developed for each technolo...

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Iodine speciation in a silver-amended cementitious system

Cited by 17 publications

References 27 publications

Capture of aqueous radioiodine species by metallated adsorbents from wastestreams of the nuclear power industry: a review

Capture of aqueous radioiodine species by metallated adsorbents from wastestreams of the nuclear power industry: a review

Silver-iodine association in Hanford nuclear waste

Evaluation of Technologies for Enhancing Grout for Immobilizing Hanford Supplemental Low-Activity Waste (SLAW)

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