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Metakaolin-based Geopolymer for Immobilizing Concentrated Cs Generated by Volume Reduction of ¹³⁷Cs-contaminated Waste

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Title: Metakaolin-based Geopolymer for Immobilizing Concentrated Cs Generated by Volume Reduction of ¹³⁷Cs-contaminated Waste
Other Titles: ¹³⁷Csで汚染された廃棄物の減容化で生じた濃縮Csを固定化する材料としてのメタカオリン由来ジオポリマー
Authors: Ichikawa, Tsuneki1 Browse this author →KAKEN DB
Watanabe, Sadayuki2 Browse this author
Arai, Hiroyuki3 Browse this author
Haga, Kazuko4 Browse this author
Yamada, Kazuo5 Browse this author
Authors(alt): 市川, 恒樹1
渡邊, 禎之2
新井, 裕之3
芳賀, 和子4
山田, 一夫5
Keywords: radioactive waste
volume reduction
water glass
Issue Date: Mar-2020
Publisher: 環境放射能除染学会
Journal Title: 環境放射能除染学会誌
Journal Title(alt): Journal of the Society for Remediation of Radioactive Contamination in the Environment
Volume: 8
Issue: 1
Start Page: 3
End Page: 16
Abstract: Cs-loaded geopolymer, cation exchangeable amorphous aluminosilicate prepared by mixing metakaolin, water glass and water-soluble CsCl at ambient temperature, was found to immobilize Cs strongly and to release it bery slowly into sea water. The leaching test of geopolymer containing 9.1% by mass of Cs showed that geopolymer prepared from 10 : 15 weight ratio of metakaolin and water glass held more than 97% of Cs after prolonged immersion in deionized water. The leaching restarted in seawater, though the effective diffusion coefficient for Cs leaching was as low as 1.96×10⁻⁵cm²/h. The theoretical analysis of the leaching process including ionic diffusion and ion exchanging revealed that the slow release was due to the high selectivity coefficient of cation exchange sites for Cs+ adsorption and much higher concentration of adsorbed cations in the pore solution of geopolymer than that of cations penetrated from sea water. The low leaching ratio in deionized water and the slow leaching rate in seawater indicate that geopolymer is possible to be used as an immobilizer-solidifier for concentrated Cs generated by volume reduction of ¹³⁷Cs-contaminated waste.
メタカオリンと水ガラスや苛性ソーダなどのアルカリ源に水溶性のCsCl を加えて室温で固化したカチオン交換性非晶質アルミノケイ酸塩であるCs担持ジオポリマーは、Csを固定化するとともに、海水中でも非常にゆっくりとしかCs放出をしないことが分かった。メタカオリンと水ガラスの混合比が10:15でCs を9.1重量%含むジオポリマーは脱イオン水中で97%以上のCsを永続的に保持する。海水中でのCs漏出は非常に遅く、漏出の実効拡散係数は1.96×10⁻⁵ cm²/h だった。漏出が非常に遅いのは、ジオポリマー細孔中での吸着カチオンの実効濃度が海水濃度に比べて非常に高く、かつジオポリマーのカチオン交換基のCsイオン選択係数が非常に高いので、海水イオン-吸着Csイオン間のイオン交換が非常に遅くなるためであることが分かった。 漏出が非常に遅いため、ジオポリマーは¹³⁷Cs汚染廃棄物の減容処理で生じたCs濃縮物の固定化材として使用できることが判明した。
Type: article
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 市川 恒樹

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