Structural changes of polystyrene particles in subcritical and supercritical water revealed by in situ small-angle neutron scattering

柴田 基樹*; 中西 洋平*; 阿部 淳*; 有馬 寛*; 岩瀬 裕希*; 柴山 充弘*; 元川 竜平; 熊田 高之; 高田 慎一; 山本 勝宏*; et al.

Polymer Journal, 55(11), p.1165 - 1170, 2023/11

https://doi.org/10.1038/s41428-023-00817-1

Marine ecosystem degradation due to micro plastics is a significant environmental problem, as acknowledged by Sustainable Development Goal 14. Decomposition of plastics using near critical or supercritical water is one of the promising methods to reduce micro plastics. To attain the optimization of the method for improving environmental friendliness, it is necessary to clarify the structural change of materials during the process. We, thus, investigated the decomposition processes of polystyrene particles dispersed in deuterated water (DO) during heating under near critical or supercritical conditions by using in situ small-angle neutron scattering. Under subcritical conditions, the PS particles were swollen by DO due to increased compatibility with temperature. Near the critical point in subcritical conditions, the cleavage of PS chains in the particles occurred, so that the swollen ratio was much enhanced though the PS particles kept their shapes. In a supercritical condition, the PS particles were degraded into oil including oligomers or monomers and the phase-separated structures with styrene-rich and DO-rich regions.

Influence of plutonium content in dissolver solutions derived from irradiated fast reactor fuels on plutonium stripping in multistage countercurrent liquid-liquid extraction with acid split flowsheet

中原 将海; 柴田 淳広

Journal of Nuclear Science and Technology, 60(7), p.849 - 858, 2023/07

https://doi.org/10.1080/00223131.2022.2162137

高い核拡散抵抗性を有する酸分離法を開発するためPu逆抽出に及ぼす照射済高速炉燃料溶解液中のPu富化度の影響について実験と計算により評価した。溶解液中のPu富化度が増加するに従い、U/Pu及びUプロダクト中のPu富化度が増加した。また、計算においてPu逆抽出液の低温操作により、UプロダクトへのPuリークはある程度抑えられることが確認できた。

Quasielastic neutron scattering probing H dynamics in the H conductors LaHO

玉造 博夢; 福井 慧賀*; 飯村 壮史*; 本田 孝志*; 多田 朋史*; 村上 洋一*; 山浦 淳一*; 倉本 義夫*; 佐賀山 基*; 山田 武*; et al.

Physical Review B, 107(18), p.184114_1 - 184114_8, 2023/05

https://doi.org/10.1103/PhysRevB.107.184114

Using an incoherent quasi-elastic neutron scattering (QENS) technique, we investigate H dynamics in a series of oxyhydrides LaHO that exhibit characteristic high H conductivity. In the end member LaH ( = 0), two kinds of H dynamics are identified: the jump diffusion and the localized motion. The jump length in the jump diffusion mode increases with increasing . The localized motion is identified as a jump between the two inequivalent sites. These dynamics are corroborated by our molecular dynamical simulations. Our QENS data suggest that similar H dynamics occurs also in oxyhydrides LaHO ( 0), whose H concentration dependence is consistent with the previous measurement of ionic conductivity. We also discuss the possibility that LaHO is an example of H ion conductors governed by the concerted migration mechanism. The identified H dynamics is a key to understanding the anomalous hydrogen concentration dependence of the diffusion coefficient in lanthanum hydrides, which has been a longstanding mystery in this compound.

高温ガス炉の実用化に向けた研究開発; カーボンニュートラルへの貢献

篠原 正憲; 角田 淳弥; 稲葉 良知; 柴田 大受

第59回X線材料強度に関する討論会講演論文集, p.22 - 28, 2022/11

地球温暖化の原因とされる温室効果ガスの排出量を削減する「脱炭素化」が世界的に取り組まれる中、日本は2050年カーボンニュートラルの達成と再生可能エネルギーの主力電源化を目標として掲げている。高温ガス炉は950Cの高温の熱を供給可能な原子炉であり、水素製造、高効率発電、化学・石油プラントへの高温蒸気供給、低温排熱を利用した海水淡水化、地域暖房など、多様かつ高効率の熱利用が期待されている。発電分野のみならず、運輸、製鉄等の原子力エネルギーを未利用の分野で高温ガス炉システムを利用することにより、温室効果ガスの排出量削減が期待できる。本稿では、2050年カーボンニュートラルの実現に貢献しうる原子力システムとして、高温ガス炉の実用化に向けた日本原子力研究開発機構の取組みを紹介する。

令和2年度評価及び第3期中長期計画見込み評価 研究開発・評価報告書; 評価課題「高温ガス炉とこれによる熱利用技術の研究開発」

篠原 正憲; 角田 淳弥; 柴田 大受; 平田 勝

JAEA-Evaluation 2022-001, 104 Pages, 2022/06

JAEA-Evaluation-2022-001.pdf:28.15MB

日本原子力研究開発機構(以下、「原子力機構」)は、外部有識者からなる高温ガス炉及び水素製造研究開発・評価委員会において、令和2年度の年度評価、令和3年度の研究計画及び第3期中長期計画(平成27年度から令和3年度)の見込評価に関する評価を受けた。その結果、年度評価については、技術系委員10名のうち、1名の委員がS評価、8名の委員がA評価及び1名の委員がB評価とし、総合評価としてA評価を受けた。また、人文社会系委員2名の委員がB評価とした。一方、第3期中長期計画の見込評価については、技術系委員10名のうち、1名の委員がS評価、8名の委員がA評価及び1名の委員がB評価とし、総合評価としてA評価を受けた。また、人文社会系委員2名の委員がB評価とした。本報告書は高温ガス炉及び水素製造研究開発・評価委員会の構成、評価項目、評価結果及び原子力機構の措置について記載したものである。

Ten years after the NPP accident at Fukushima; Review on fuel debris behavior in contact with water

Grambow, B.; 二田 郁子; 柴田 淳広; 駒 義和; 宇都宮 聡*; 高見 龍*; 笛田 和希*; 大貫 敏彦*; Jegou, C.*; Laffolley, H.*; et al.

Journal of Nuclear Science and Technology, 59(1), p.1 - 24, 2022/01

https://doi.org/10.1080/00223131.2021.1966347

Following the NPP accident, some hundred tons of nuclear fuel elements of 3 damaged nuclear reactor units were partly molten with even larger masses of steel and concrete structures, creating a big mass of corium and fuels debris. Since ten years, this heat generating mass has been cooled permanently by millions of m of water flowing over them. Knowledge on the interaction of this solid mass with water is crucial for any decommissioning planning. Starting from analyses of the evolutions of the accident in the 3 reactor cores and associated fuel debris formations and some additional isotopic and physiochemical information of debris fragments collected in soils of Fukushima, we review the temporal evolution of the chemistry and leached radionuclide contents of the cooling water. Measured concentration ratios of the actinides and fission products in the water where compared to reported results of laboratory leaching studies with either spent nuclear fuel or simulated fuel debris under a variety of simulated environmental conditions.

Oxidative decomposition of ammonium ion with ozone in the presence of cobalt and chloride ions for the treatment of radioactive liquid waste

粟飯原 はるか; 渡部 創; 柴田 淳広; Mahardiani, L.*; 大友 亮一*; 神谷 裕一*

Progress in Nuclear Energy, 139, p.103872_1 - 103872_9, 2021/09

https://doi.org/10.1016/j.pnucene.2021.103872

To prevent unexpected accidents at nuclear facilities caused by accumulated ammonium nitrate in an aqueous liquid waste containing ammonium salts and nitric acid, NH in the liquid waste must be decomposed under mild reaction conditions. In this study, we investigated the oxidative decomposition of NH with O at 333 K in the presence of a homogeneous Co catalyst and Cl in the wide pH range of the test solution. The reaction behavior was greatly affected by pH of the test solution. In a basic solution at pH 12, high conversion of NH was obtained even in the absence of Co and Cl and the main product was NO . However, Co and Cl in the solution greatly enhanced the decomposition rate of NH in acidic to mild basic solutions (pH 1-8), while only low conversion of NH was observed unless both Co and Cl were present. For the reaction with Co and Cl in the solutions, NH was transformed mainly into chloramines (NH Cl , x = 1-3) by the reaction with HClO, which was formed by the reaction of Cl with O catalyzed by the homogeneous Co catalyst, and led to the high decomposition rate of NH . Cl suppressed the formation of the precipitate CoO(OH) during the reaction and consequently the Co catalyst stably existed in the reaction solution, which was another reason for the high decomposition rate of NH in the presence of Cl. Owing to the swift decomposition of NH under mild reaction conditions and small formation of secondary waste, the oxidative decomposition of NH in the presence of the homogeneous Co catalyst and Cl is suitable and applicable for the treatment of the aqueous liquid waste containing ammonium salts and nitric acid.

Observation of Eu adsorption band in the CMPO/SiO-P column by neutron resonance absorption imaging

宮崎 康典; 渡部 創; 中村 雅弘; 柴田 淳広; 野村 和則; 甲斐 哲也; Parker, J. D.*

JPS Conference Proceedings (Internet), 33, p.011073_1 - 011073_7, 2021/03

https://doi.org/10.7566/JPSCP.33.011073

中性子共鳴吸収イメージングを、抽出クロマトグラフィに使用するマイナーアクチノイド回収用CMPO/SiO-Pカラムで形成したEu吸着バンドの観測に適用した。軽水や重水で調製した湿潤カラムと乾燥吸着材を充填した乾燥カラムを比較し、中性子透過を評価した。中性子透過スペクトルから、乾燥カラムは45%、軽水調製カラムは20%、重水調製カラムは40%の中性子透過を確認した。得られた結果から、CMPO/SiO-Pカラムに形成したEu吸着バンドを観測するには、重水の使用によって、より鮮明になることを明らかにした。今後、カラム操作による吸着バンドのカラム内移行挙動を明らかにする。

High temperature gas-cooled reactors

武田 哲明*; 稲垣 嘉之; 相原 純; 青木 健; 藤原 佑輔; 深谷 裕司; 後藤 実; Ho, H. Q.; 飯垣 和彦; 今井 良行; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

https://doi.org/10.1016/C2018-0-05383-9

本書は、原子力機構における今までの高温ガス炉の研究開発の総括として、HTTRの設計、燃料、炉内構造物や中間熱交換器などの要素技術の開発、出力上昇試験、950Cの高温運転、安全性実証試験などの運転経験及び成果についてまとめたものである。また、HTTRでの知見をもとに、商用炉の設計、高性能燃料、ヘリウムガスタービン、ISプロセスによる水素製造などの要素技術開発の現状について記述しており、今後の高温ガス炉の開発に非常に有用である。本書は、日本機械学会の動力エネルギーシステム部門による化石燃料及び原子力によるエネルギーシステムの技術書のシリーズの一冊として刊行されるものである。

STRAD project for systematic treatments of radioactive liquid wastes generated in nuclear facilities

渡部 創; 小木 浩通*; 荒井 陽一; 粟飯原 はるか; 高畠 容子; 柴田 淳広; 野村 和則; 神谷 裕一*; 浅沼 徳子*; 松浦 治明*; et al.

Progress in Nuclear Energy, 117, p.103090_1 - 103090_8, 2019/11

AA2019-0193.pdf:1.29MB

https://doi.org/10.1016/j.pnucene.2019.103090

A new collaborative research project for systematic treatments of radioactive liquid wastes containing various reagents generating in nuclear facilities was started from 2018 initiated by Japan Atomic Energy Agency. The project was named as STRAD (Systematic Treatments of RAdioactive liquid wastes for Decommissioning) project. Tentative targets to be studied under the project are aqueous and organic liquid wastes which have been generated by experiments and analyses in a reprocessing experimental laboratory of JAEA. Currently fundamental studies for treatments of the liquid wastes with complicated compositions are underway. In the STRAD project, process flow for treatment of ammonium ion involved in aqueous waste was designed though the inactive experiments, and decomposition of ammonium ion using catalysis will be carried out soon. Adsorbents for recovery of U and Pu from spent solvent were also developed. Demonstration experiments on genuine spent solvent is under planning.