Evaluation of adsorption properties of U(VI) for various inorganic adsorbents

Hitoshi Mimura, Minoru Matsukura, Tomoya Kitagawa, Fumio Kurosaki, Akira Kirishima, Daisuke Akiyama, Nobuaki Sato

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Large amounts of highly contaminated water over 800,000 m3 accumulated in the reactor, turbine building and the trench in the facility were generated from the nuclear accident of Fukushima NPS (BWR) caused by the Great East Japan Earthquake. At present, the cold shutdown is completed stably by the circulating injection cooling system (SARRY, KURION) for the decontamination of radioactive nuclides such as134Cs and137Cs using zeolites and crystalline silicotitanate (CST). Further, the Advanced Liquid Processing System (ALPS) is under operation for the decontamination of 62 nuclides such as90Sr,129I and60Co, etc. However, the adsorption behaviors of actinoids through the decontamination systems are complicated, and especially their adsorption properties for zeolites and CST, major inorganic adsorbents, are not yet clarified. In near future, the decontamination of actinoids leached from the crushed fuel debris will be an important subject. In this study, the practical adsorption properties of U(VI) for various inorganic adsorbents were evaluated under different solution conditions. The adsorption properties (distribution behaviors and adsorption kinetics) were evaluated by batch adsorption method; 19 kinds of inorganic adsorbents including zeolites and CST (crystalline silicotitanate) were contacted with U(VI)) solutions. The conditions of 5 kinds of U(VI) solutions were as follows; Solution 1: [U(VI)]= 50 ppm, initial pH= 0.5∼ 5.5 Solution 2: [U(VI)]= 50 ppm, [NaCl]= 0.1 M, initial pH= 4.0 Solution 3: [U(VI)]= 50 ppm, [CaCl2]= 0.1 M, initial pH= 4.0 Solution 4: [U(VI)]= 4.84 mM, [NaCl]= 0.1 M, initial pH= 3.18 Solution 5: [U(VI)]= 4.86 mM, 2,994 ppm boric acid/30% seawater, initial pH= 4.25 The uptake (%) and distribution coefficient (Kd. cm3/g) were estimated by counting the radioactivity using NaI(Tl) scintillation counter and liquid scintillation counter. In the simple Solution 1, the Kd values for zeolites increased linearly with equilibrium pH up to pH 7. The Kd value for tin hydroxide had a maximum profile around pH 7 and a relatively large Kd value above 104 cm3/g was obtained. In the presence of NaCl and CaCl2 (Solution 2 and 3), relatively large Kd values above 102 cm3/g were obtained, other than mordenite and clinoptilolite, and the effect of [Ca2+] on U(VI) uptake was larger than that of [Na+]. In Solution 4 containing high concentration of U(VI), the uptake(%) was considerably lowered, while that for zeolite A, X and Y was estimated over 20%. Similar tendency was observed in Solution 5, and, in the case of granulated potassium titanate, yellow precipitate was observed on the surface due to the increase of equilibrium pH up to 5.25. The adsorption behavior of U(VI) on inorganic adsorbents is mainly governed by three steps; ion exchange, surface precipitation of hydrolysis species and sedimentation depending on equilibrium pH, and hence it should be noted the change of U(VI) chemical species. These basic adsorption data are useful for the selection of inorganic adsorbents in the Fukushima NPS decontamination process.

Original languageEnglish
Title of host publicationDecontamination and Decommissioning, Radiation Protection, and Waste Management; Mitigation Strategies for Beyond Design Basis Events
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Print)9784888982566
DOIs
Publication statusPublished - 2018 Jan 1
Event2018 26th International Conference on Nuclear Engineering, ICONE 2018 - London, United Kingdom
Duration: 2018 Jul 222018 Jul 26

Publication series

NameInternational Conference on Nuclear Engineering, Proceedings, ICONE
Volume7

Conference

Conference2018 26th International Conference on Nuclear Engineering, ICONE 2018
CountryUnited Kingdom
CityLondon
Period18/7/2218/7/26

ASJC Scopus subject areas

  • Nuclear Energy and Engineering

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    Mimura, H., Matsukura, M., Kitagawa, T., Kurosaki, F., Kirishima, A., Akiyama, D., & Sato, N. (2018). Evaluation of adsorption properties of U(VI) for various inorganic adsorbents. In Decontamination and Decommissioning, Radiation Protection, and Waste Management; Mitigation Strategies for Beyond Design Basis Events (International Conference on Nuclear Engineering, Proceedings, ICONE; Vol. 7). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/ICONE26-81338