Iodine speciation in cementitious environments

Journal Article · Mon Feb 11 00:00:00 EST 2019 · Applied Geochemistry

DOI:https://doi.org/10.1016/j.apgeochem.2019.02.007· OSTI ID:1513683

Kaplan, Daniel I.  ^[1]; Xu, Chen ^[2]; Li, Dien ^[2]; Lin, Peng ^[2]; Xing, Wei ^[2]; Nichols, Ralph ^[1]; Schwehr, Kathleen ^[2]; Santschi, Peter H.  ^[2]

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1. Savannah River National Lab, Aiken, SC (United States)
2. Texas A&M Univ. at Galveston, Galveston, TX (United States)

Iodine-129 is a key risk driver in most low-level waste cementitious waste repositories. Objectives of this study were to determine iodine speciation in cementitious materials with slag (Grout_+slag) and without slag (Grout_–slag) and its impact on iodine immobilization. Irrespective of which iodine species was amended to the aqueous phase, there were no significant differences in uptake-K_d values (~3 L/kg). However, when the various iodine species were hydrated with the grout, the release-K_d values (6.1–121.8 L/kg) were significantly greater than the uptake-K_d values, and the amended iodine speciation (I^–<< org-I ≤ IO₃^–) and grout formulation (Grout_–slag < Grout_+slag) had a significant impact on release-Kd values. In grout samples amended with I^– and IO₃^–, org-I was formed and comprised a majority of the iodine in the leachate after 28 days of equilibration. The formed org-I originated from organic carbon (C) in the grout material (~1200 mg/kg C). For the first time, these studies demonstrate that multiple iodine species can co-exist simultaneously in grout porewater, the iodine species initially added to the grout can greatly affect iodine immobilization, and the addition of slag to the grout formulation increased iodine immobilization. Furthermore, these results may have important implications on radioiodine waste disposal.

• Research Organization: Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC09-08SR22470
• OSTI ID: 1513683
• Report Number(s): SRNL-STI-2018-00502
• Journal Information: Applied Geochemistry, Vol. 103, Issue C; ISSN 0883-2927
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Iodine speciation
Cement
Slag
Immobilization
Redox