Silver-iodine association in Hanford nuclear waste
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Silver-iodine association in Hanford nuclear waste Jacob G. Reynolds1 · James S. Lachut1 · Huei K. Meznarich1 · Tom M. Ely1 · Andrew M. Templeton1 · Gary A. Cooke1 Received: 13 June 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract 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. Keywords Hanford · Silver iodate · Miersite · Iodargyrite · Silver reactors · Trona
Introduction Radioactive iodine-129 is a long-lived fission product of uranium-235 created in nuclear power and plutonium production. Its shorter lived sister iodine-131 gets more attention in the fuel recycling literature because of a higher specific activity which results in higher radiation releases during fuel dissolution [1, 2]. Iodine-129, however, is a higher risk to groundwater contamination because of its 15.7 million year half-life and because it is relatively mobile in the environment [3]. Indeed, iodine-129 frequently is the limiting radionuclide in the performance assessment of nuclear waste disposal landfills because it forms water soluble species such as iodide and iodate [3–5]. The Hanford site, near Richland, WA, in the United States has about 200 million liters, waste left over from plutonium production. There is extensive contamination of ground water by I-129 at Hanford [6, 7]. Much of the I-129 resides in tanks on site, waste that has been there for many years, some since 1945. The site is currently removing waste from Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10967-020-07347-7) contains supplementary material, which is available to authorized users. * Jacob G. Reynolds [email protected] 1
Washington River Protection Solutions, LLC, P.O. Box 850, Richland, WA, USA
old single shell tanks into newer double-shell tanks. Once as much waste as practical is transfered from the tanks, the tanks will be filled with grout and disposed in place [8]. Any radionuclides remaining in the tank represents the potential source term to the groundwater after closure [9, 10]. The chemical form of I-129 in the liquid waste is unknown. The iodine species depends on the redox potential and can be altered by radiation [11, 12]. However, it is difficult to describe the redox potential of Hanford waste because of redox disequilibrium. There are gas bubbles filled with highly reduc
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