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論文

Sorption of Cs$$^{+}$$ and Eu$$^{3+}$$ ions onto sedimentary rock in the presence of gamma-irradiated humic acid

Zhao, Q.*; 齊藤 毅*; 宮川 和也; 笹本 広; 小林 大志*; 佐々木 隆之*

Journal of Hazardous Materials, 428, p.128211_1 - 128211_10, 2022/04

令和2年度以降の幌延深地層研究計画において原子力機構が取り組んでいる課題の1つである「実際の地質環境における人工バリアの適用性確認」では、坑道周辺の掘削損傷領域において物質移行に関するデータの取得が必要である。本研究では、地下水中に含まれる腐植物質であるフミン酸に着目し、放射線によるフミン酸の分解反応がCsイオンとEuイオンの収着能へ与える影響について、幌延地域の堆積岩を例として調べた。放射線を照射していないフミン酸の存在下では、Euはフミン酸と錯体を形成することで、岩石への収着能は低下する。一方で、放射線の照射によりフミン酸が分解されると、岩石へ収着するEuイオンが増加することが確認された。また、Csの岩石への収着能はフミン酸の影響を受けることが無く、また、放射線により分解されたフミン酸の影響も見られないことが分かった。以上のことから、廃棄体の近傍ではフミン酸の放射線分解により、岩石への収着するEuイオンの割合が大きくなることが考えられる。

論文

Volatilization of B$$_{4}$$C control rods in Fukushima Daiichi nuclear reactors during meltdown; B-Li isotopic signatures in cesium-rich microparticles

笛田 和希*; 高見 龍*; 蓑毛 健太*; 諸岡 和也*; 堀江 憲路*; 竹原 真美*; 山崎 信哉*; 斉藤 拓巳*; 塩津 弘之; 大貫 敏彦*; et al.

Journal of Hazardous Materials, 428, p.128214_1 - 128214_10, 2022/04

Boron carbide control rods remain in the fuel debris of the damaged reactors in the Fukushima Daiichi Nuclear Power Plant, potentially preventing re-criticality; however, the state and stability of the control rods remain unknown. Sensitive high-resolution ion microprobe analyses have revealed B-Li isotopic signatures in radioactive Cs-rich microparticles (CsMPs) that formed by volatilization and condensation of Si-oxides during the meltdowns. The CsMPs contain 1518-6733 mg kg$$^{-1}$$ of $$^{10+11}$$B and 11.99-1213 mg kg$$^{-1}$$ of Li. The $$^{11}$$B/$$^{10}$$B (4.15-4.21) and $$^{7}$$Li/$$^{6}$$Li (213-406) isotopic ratios are greater than natural abundances ($$sim$$4.05 and $$sim$$12.5, respectively), indicating that $$^{10}$$B(n,$$alpha$$)$$^{7}$$Li reactions occurred in B$$_{4}$$C prior to the meltdowns. The total amount of B released with CsMPs was estimated to be 0.024-62 g, suggesting that essentially all B remains in reactor Units 2 and/or 3 and is enough to prevent re-criticality; however, the heterogeneous distribution of B needs to be considered during decommissioning.

論文

Sewage sludge ash contaminated with radiocesium; Solidification with alkaline-reacted metakaolinite (geopolymer) and Portland cement

香西 直文; 佐藤 淳也; 大杉 武史; 下山 巖; 関根 由莉奈; 坂本 文徳; 大貫 敏彦

Journal of Hazardous Materials, 416, p.125965_1 - 125965_9, 2021/08

 被引用回数:1 パーセンタイル:0(Engineering, Environmental)

Radiocesium-bearing SSA was solidified in geopolymer (GP) and ordinary Portland cement (OPC) and the characteristics of the solidified bodies were investigated by various aspects including mechanical strength, transformation of SSA components during solidification, and radiocesium confinement ability by leaching test. After static leaching test at $$^{60}$$C, $$^{137}$$Cs was hardly leached out from the GP-solidified bodies containing SSA at 30 wt% to ultrapure water ($$<$$ 0.1%), whereas more than 30% $$^{137}$$Cs was leached from the OPC-solidified bodies containing SSA at 30 wt%. GP is far superior to OPC for solidifying radiocesium-bearing SSA.

論文

Spectroscopic and first-principles investigations of iodine species incorporation into ettringite; Implications for iodine migration in cement waste forms

Guo, B.*; Xiong, Y.*; Chen, W.*; Saslow, S. A.*; 香西 直文; 大貫 敏彦*; Dabo, I.*; 笹木 恵子*

Journal of Hazardous Materials, 389, p.121880_1 - 121880_11, 2020/05

 被引用回数:20 パーセンタイル:95.57(Engineering, Environmental)

To elucidate retention mechanism of cement waste form for radioactive iodine, this paper investigated interaction mechanism between iodine and ettringite, which is a component mineral of cement and has anion exchange ability. We revealed that ettringite has a high capacity for accommodating IO$$_{3}$$$$^{-}$$ via anion substitution for SO$$_{4}$$$$^{2-}$$. The combined iodine K-edge extended X-ray absorption fine structure spectra and first-principles calculations using density functional theory suggested that IO$$_{3}$$$$^{-}$$ was stabilized in ettringite by hydrogen bonding and electrostatic forces. The bonding charge density analysis of the substituted IO$$_{3}$$$$^{-}$$ into the ettringite structure revealed the interaction between intercalated IO$$_{3}$$$$^{-}$$ with the structural water molecules. These results provided valuable insight into the long-term stabilization of anionic iodine species and their migration in cementitious nuclear waste repository or alkaline environments.

論文

Selective removal of radiocesium from micaceous clay for post-accident soil decontamination by temperature-controlled Mg-leaching in a column

Yin, X.; Zhang, L.*; Meng, C.*; 稲葉 優介*; Wang, X.*; 二田 郁子; 駒 義和; 竹下 健二*

Journal of Hazardous Materials, 387, p.121677_1 - 121677_10, 2020/04

The effective and efficient removal of radioactive Cs from contaminated soil is highly urgent for the nuclear post-accident remediation. In present study, we achieved rapid Cs desorption from both a typical micaceous clay (i.e., vermiculitized biotite, VB) and actually contaminated soil by high-speed ion exchange through temperature-controlled continuous leaching with Mg-solutions in a column reactor. Cs-sorbed VB was firstly employed as a soil surrogate to explore the macro-Cs desorption process and micro-mechanism in detail.

論文

Stabilization of lead with amorphous solids synthesized from aluminosilicate gel

佐藤 淳也; 塩田 憲司*; 高岡 昌輝*

Journal of Hazardous Materials, 385, p.121109_1 - 121109_9, 2020/03

 被引用回数:4 パーセンタイル:62.5(Engineering, Environmental)

アルミノシリケート硬化体は、有害な重金属を構造中に固定化することが報告されているが、固定化のメカニズムは未だ不明瞭である。この原因は、アルミノシリケート硬化体を構成する、結晶相及び非晶質相への各相への鉛の取り込まれ方を分けて評価できていないためである。そのため本研究では、アルミノシリケート硬化体の非晶質相に着目し、鉛の固定化のメカニズムを調査した。試薬から合成したSi-Alゲルを材料として、鉛の添加量を変えたアルミノシリケート硬化体を作製した。ラマン分光分析の結果、鉛の添加量に伴い、Si-O振動に由来するバンドが低波数側へシフトした。このラマンシフトは、鉛とSi-O由来の酸素が共有結合していることを示唆した。加えて、逐次抽出法の結果から、硬化体に加えた鉛のうち75-90%の鉛が難溶性であることを示した。これらの結果から、アルミノシリケート硬化体の非晶質相への鉛の固定化は、主に非晶質相との共有結合によることが示唆された。

論文

A New technique for removing strontium from seawater by coprecipitation with barite

徳永 紘平; 香西 直文; 高橋 嘉夫*

Journal of Hazardous Materials, 359, p.307 - 315, 2018/07

 被引用回数:11 パーセンタイル:59.27(Engineering, Environmental)

本研究では、有効な処理処分技術が乏しい海水中のストロンチウム(Sr)に対する新規の除去法として、バライトへの共沈反応を用いた手法の開発を行った。これらSrのバライトに対する共沈過程を分子レベルで明らかにし、取り込みに最適な条件を見出すことで、天然海水の条件において液相中のSr(1mg/L)の90%以上(分配係数10000kg/L以上)の除去が達成された。このように、バライトへの共沈反応を用いたSr除去はカルシウムなどの競合イオンを多く含む海水の系においても有効であることが示された。

論文

Ultimate selenium(IV) monitoring and removal from water using a new class of organic ligand based composite adsorbent

Awual, M. R.; 矢板 毅; 鈴木 伸一; 塩飽 秀啓

Journal of Hazardous Materials, 291, p.111 - 119, 2015/06

 被引用回数:152 パーセンタイル:98.7(Engineering, Environmental)

This work reports the selenium (Se(IV)) detection and removal from water by ligand functionalized organic-inorganic based novel composite adsorbent. The adsorbent exhibited distinct color change in the presence of various concentrations of Se(IV). This was characterized by UV-vis spectroscopy, and the color change was observed by naked-eye observation. The data fitted well to the Langmuir isotherm model, and the maximum Se(IV) sorption capacity was 111.12 mg/g. The presence of diverse competing ions did not affect the Se(IV) sorption capacity, and the adsorbent had almost no sorption capacity for these coexisting ions, which suggests the high selectivity to Se(IV) ions.

論文

Selective cesium removal from radioactive liquid waste by crown ether immobilized new class conjugate adsorbent

Awual, M. R.; 矢板 毅; 田口 富嗣; 塩飽 秀啓; 鈴木 伸一; 岡本 芳浩

Journal of Hazardous Materials, 278, p.227 - 235, 2014/08

AA2014-0217.pdf:0.96MB

 被引用回数:228 パーセンタイル:99.2(Engineering, Environmental)

Conjugate materials can provide chemical functionality, enabling an assembly of the ligand complexation ability to metal ions that are important for applications, such as separation and removal devices. In this study, we developed ligand immobilized conjugate adsorbent for selective cesium (Cs) removal from wastewater. The adsorbent was synthesized by direct immobilization of DB24C8 onto inorganic mesoporous silica. The obtained results revealed that adsorbent had higher selectivity towards Cs even in the presence of a high concentration of Na and K and this is probably due to the Cs-$$pi$$ interaction of the benzene ring. The proposed adsorbent was successfully applied for radioactive Cs removal to be used as the potential candidate in Fukushima nuclear wastewater treatment. The adsorbed Cs was eluted with suitable eluent and simultaneously regenerated into the initial form for the next removal operation after rinsing with water.

論文

Selective lanthanide sorption and mechanism using novel hybrid Lewis base (N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide) ligand modified adsorbent

Awual, M. R.; 小林 徹; 宮崎 有史; 元川 竜平; 塩飽 秀啓; 鈴木 伸一; 岡本 芳浩; 矢板 毅

Journal of Hazardous Materials, 252-253, p.313 - 320, 2013/05

 被引用回数:135 パーセンタイル:97.43(Engineering, Environmental)

The oxygen and nitrogen donor atoms containing Lewis base N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide (MePhPTA) ligand was synthesized and subsequently an adsorbent was prepared by direct immobilization onto mesoporous silica. The crystallography for the Sm-MePhPTA complex suggested that MePhPTA was strongly coordinated to Sm(III) with oxygen and nitrogen by forming a stable complex with two 5-membered rings. The data clarified that bond lengths between Sm(III) and amide oxygen (2.475 ${AA}$) were shorter than Sm-N (2.662 ${AA}$) in phenanthroline moiety indicating strong oxygen driven adsorbent.

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