Aqueous Dissolution of Silver Iodide and Associated Iodine Release under Reducing Conditions with FeCl_2 Solution
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概要
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An empirical and analytical study was performed on the aqueous dissolution of silver iodide (AgI) to release iodine under reducing conditions with Fe2+ in order to understand the fundamental chemical and/or physical behavior of potential radioactive iodine waste forms under geological disposal conditions. Aqueous dissolution tests of AgI powder in FeCl2 solutions (10−6 M to 10−3 M) were performed in a glove box purged with a gas mixture (Ar + 5% H2). The test results showed that AgI dissolves to release iodine at extremely slow rates, being controlled by a diffusion process in any FeCl2 solution. The comparison with thermodynamic calculations based on redox equilibria suggested that the AgI dissolution proceeds by redox reaction between Ag+ and Fe2+; however, it was far from the thermodynamic equilibrium. These results suggested that the form of AgI itself has a potential to immobilize iodine for a long time even under the disposal conditions. Solid-phase analysis for the reacted AgI by using SEM/EDS showed a certain amount of silver (maybe metallic silver) precipitated at the surface. On the basis of these results and discussion, a potential mechanism for the actual AgI dissolution was proposed as follows. The AgI dissolution proceeds by redox reaction between Ag+ and Fe2+ to release I−, which results in the precipitation of metallic silver as a reduction product of Ag+ at the AgI surface to form a thin layer covering the AgI surface. The silver layer evolves to be protective against the transport of reactant species, by which the further dissolution to reach the equilibrium is suppressed. Consequently, the dissolution proceeds at extremely slow rates, being controlled by a diffusion process.
- 社団法人 日本原子力学会の論文
- 2008-09-01
著者
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Inagaki Yaohiro
Department Of Applied Quantum Physics & Nuclear Engineering Kyushu University
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Asano Hidekazu
Radioactive Waste Management Funding And Research Center
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IDEMITSU Kazuya
Department of Applied Quantum Physics & Nuclear Engineering, Kyushu University
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IMAMURA Toshitaka
Department of Applied Quantum Physics & Nuclear Engineering, Kyushu University
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ARIMA Tatsumi
Department of Applied Quantum Physics & Nuclear Engineering, Kyushu University
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KATO Osamu
Kobe Steel, Ltd.
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NISHIMURA Tsutomu
Kobe Steel, Ltd.
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Nishimura Tsutomu
Kobe Steel Ltd.
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Tatsumi Arima
Department Of Applied Quantum Physics & Nuclear Engineering Kyushu University
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Idemitsu Kazuya
Department Of Applied Quantum Physics & Nuclear Engineering Kyushu University
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Imamura Toshitaka
Department Of Applied Quantum Physics & Nuclear Engineering Kyushu University
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Kato Osamu
Kobe Steel Ltd.
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IDEMITSU Kazuya
Department of Applied Quantum Physics & Nuclear Engineering, Kyushu University
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