幌延深地層研究計画 令和7年度調査研究計画

中山 雅; 石井 英一; 早野 明; 青柳 和平; 村上 裕晃; 大野 宏和; 武田 匡樹; 望月 陽人; 尾崎 裕介; 木村 駿; et al.

JAEA-Review 2025-027, 80 Pages, 2025/09

JAEA-Review-2025-027.pdf:6.22MB

幌延深地層研究計画は、日本原子力研究開発機構が堆積岩を対象に北海道幌延町で実施しているプロジェクトである。令和7年度は、「令和2年度以降の幌延深地層研究計画」で示した、「実際の地質環境における人工バリアの適用性確認」および「処分概念オプションの実証」について、引き続き調査研究を行う。令和7年度に実施する主な調査研究は以下のとおりである。「実際の地質環境における人工バリアの適用性確認」では、人工バリア性能確認試験のデータ取得を継続するとともに、解体試験計画の具体化や原位置試験を対象とした解析検討の準備を行う。「処分概念オプションの実証」では、坑道スケールピットスケールでの調査・設計・評価技術の体系化について、坑道スケールピットスケールにおける閉じ込め性能の評価手法の整理を行う。500m調査坑道において先行ボーリング調査を行い、岩石の強度や岩盤の透水性などのデータを取得するとともに、トモグラフィ調査による試験坑道周辺の掘削損傷領域の広がりに関するデータを取得する。埋め戻し材や止水プラグの施工については、原位置施工試験に向けた計画検討を進める。深度500mの坑道掘削に伴う湧水量を観測するとともに、解析において予測された湧水量の範囲に収まるかどうかを確認する。500m調査坑道で施工予定のピット周辺の掘削損傷領域の広がりについて原位置における掘削損傷領域の把握のための試験計画を検討する。また、割れ目からの湧水量やピット周辺の掘削損傷領域の広がりについて調査・評価手法の整理を進める。地下施設の建設・維持管理では、令和6年度に引き続き西立坑と500m調査坑道の掘削を行い、令和7年度末に施設整備を完了する予定である。国内外の資金や人材の活用に関する取り組みとして、幌延国際共同プロジェクトにて「実際の地質環境における人工バリアの適用性確認」および「処分概念オプションの実証」に関わる3つのタスク(タスクA:物質移行試験、タスクB:処分技術の実証と体系化、タスクC:実規模の人工バリアシステム解体試験)について調査研究を継続する。

Fukushima Daiichi Nuclear Power Plant Accident; Understanding Formation Mechanism of Radioactive Particles through Sr and Pu Quantities

五十嵐 淳哉*; 二宮 和彦*; Zheng, J.*; Zhang, Z. J.*; 福田 美保*; 青野 辰雄*; 箕輪 はるか*; 吉川 英樹*; 末木 啓介*; 佐藤 志彦; et al.

Environmental Science & Technology, 58(33), p.14823 - 14830, 2024/08

https://doi.org/10.1021/acs.est.4c03428

The Fukushima Daiichi Nuclear Power Plant accident released considerable radionuclides into the environment. Radioactive particles, composed mainly of SiO, emerged as distinctive features, revealing insights into accident's dynamics. While studies extensively focused on high-volatile radionuclides like Cs, investigations into low-volatile nuclides such as Sr and Pu remain limited. Understanding their abundance in radioactive particles is crucial for deciphering the accident's details, including reactor temperatures and injection processes. Here we aimed to determine Sr and Pu amounts in radioactive particles and provide essential data for understanding the formation processes and conditions within the reactor during the accident. We employed radiochemical analysis on nine radioactive particles and determined the amounts of Sr and Pu in these particles. Sr and Pu quantification in radioactive particles showed Sr/Cs radioactivity ratio (corrected to March 11, 2011) aligned with core temperature expectations. However, Pu/Cs activity ratio indicated non-volatile Pu introduction, possibly through fuel fragments. Analyzing Sr and Pu enhances our understanding of the Fukushima Daiichi accident. Deviations in Pu/Cs activity ratios underscore non-volatile processes, emphasizing the accident's complexity. Future research should expand this dataset for a more comprehensive understanding of the accident's nuances.

Cr doping-induced ferromagnetism in the spin-glass CdMnTe studied by X-ray magnetic circular dichroism

Verma, V.*; 坂本 祥哉*; 石川 弘一郎*; Singh, V. R.*; 石上 啓介*; 芝田 悟朗; 門野 利治*; 小出 常晴*; 黒田 真司*; 藤森 淳*

Physica B; Condensed Matter, 642, p.414129_1 - 414129_5, 2022/10

https://doi.org/10.1016/j.physb.2022.414129

The prototypical diluted magnetic semiconductor CdMnTe is a spin glass () or an antiferromagnet () but becomes ferromagnetic upon doping with a small amount of Cr atoms. To investigate the origin of the ferromagnetism in CdMnCrTe, we have studied its element specific magnetic properties by X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). Measured XAS and XMCD spectra indicate that both Cr and Mn atoms are divalent and that the magnetic moments of Cr and Mn are aligned parallel. By analyzing the element-specific magnetization curves, we conclude that Cr doping leads to the formation of ferromagnetic or superparamagnetic clusters consisting of several Cr ions surrounded by a much larger number of Mn ions.

An Automotive intelligent catalyst that contributes to hydrogen safety for the Decommissioning of Fukushima Daiichi Nuclear Power Station (1FD)

田中 裕久*; 正木 清香*; 青谷 拓朗*; 稲川 康平*; 岩田 宗悟*; 相田 樹哉*; 山本 忠亮*; 喜多 知輝*; 大野 瞳*; 竹中 啓恭*; et al.

SAE Technical Paper 2022-01-0534 (Internet), 10 Pages, 2022/03

https://doi.org/10.4271/2022-01-0534

The catalyst called a Passive Autocatalytic Recombiner (PAR) is required to have robustness that can maintain its activity for more than 30 years in an environment where temperature, humidity, gas concentration, etc. cannot be controlled. Here, it is expected that "An Intelligent Catalyst" for automotive emissions control exhibits excellent performance even in such a harsh environment. The intelligent catalyst is the nanostructure designed perovskite catalyst that has the rejuvenating function instead of preventing aging. The authors emphasize that the technology developed as a catalyst for automobiles is expected to be useful not only in other industries but also as a relief technology from the national crisis.

Performance tests of catalysts for the safe conversion of hydrogen inside the nuclear waste containers in Fukushima Daiichi

Reinecke, E.-A.*; 竹中 啓恭*; 大野 瞳*; 喜多 知輝*; 谷口 昌司*; 西畑 保雄; 日野 竜太郎; 田中 裕久*

International Journal of Hydrogen Energy, 46(23), p.12511 - 12521, 2021/03

https://doi.org/10.1016/j.ijhydene.2020.08.262

安全な廃炉は福島第一原子力発電所の事故による放射性物質の除染同様に今後の大きな課題である。現在、廃棄物長期保管容器の研究開発は日本の国際協力における緊急の課題となっている。容器中の放射線分解による大量の水素と酸素は、海水を含んでいるために問題となっている。放射線分解による可燃性ガスの発生は容器の内圧を上昇させ、引火による設備の健全性喪失のリスクとなる。日本の文部科学省のプロジェクト「廃棄物長期保管容器内に発生する可燃性ガスの濃度低減技術に関する研究開発」では、保管容器内における水素再結合触媒装置の適用可能性について調べた。ここで適用したのは、インテリジェント触媒と呼ばれており、自動車排ガス浄化用の大量生産のために開発されたもので、Pd, Pt, Rhの貴金属がペロブスカイト酸化物中に固溶しており、自己再生機能を有している。水素再結合触媒評価装置REKO-4によって、触媒の基本的な特性を評価した。

Spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Heusler films

角田 一樹; 桜庭 裕弥*; 増田 啓介*; 河野 嵩*; 鹿子木 将明*; 後藤 一希*; Zhou, W.*; 宮本 幸治*; 三浦 良雄*; 奥田 太一*; et al.

Communications Materials (Internet), 1, p.89_1 - 89_9, 2020/11

https://doi.org/10.1038/s43246-020-00088-w

Weyl semimetals are characterized by the presence of massless band dispersion in momentum space. When a Weyl semimetal meets magnetism, large anomalous transport properties emerge as a consequence of its topological nature. Here, using in-situ spin- and angle-resolved photoelectron spectroscopy combined with ab initio calculations, we visualize the spin-polarized Weyl cone and flat-band surface states of ferromagnetic CoMnGa films with full remanent magnetization. We demonstrate that the anomalous Hall and Nernst conductivities systematically grow when the magnetization-induced massive Weyl cone at a Lifshitz quantum critical point approaches the Fermi energy, until a high anomalous Nernst thermopower of 6.2 VK is realized at room temperature. Given this topological quantum state and full remanent magnetization, CoMnGa films are promising for realizing high efficiency heat flux and magnetic field sensing devices operable at room temperature and zero-field.

Preliminary study on separation of Dy and Nd by multi-step extraction using TDdDGA

佐々木 祐二; 伴 康俊; 森田 圭介; 松宮 正彦*; 小野 遼真*; 城石 英伸*

Solvent Extraction Research and Development, Japan, 27(1), p.63 - 67, 2020/00

https://doi.org/10.15261/serdj.27.63

Ndマグネット中のDyを溶媒抽出で分離回収する方法の基礎研究を行った。DyはNdよりも価値が高く、これを回収して再利用することは意義深い。我々はランタノイドを効率よく抽出するDGA(ジグリコールアミド化合物)を用いてDyを単離する条件の検討を行った。抽出容量の高いTDdDGA(テトラドデシルジグリコールアミド)を用いて溶媒抽出を行うと、Dy/Nd分離比は17-18であった。効率よく相互分離を行うために、向流接触の溶媒抽出を採用した。0.1M TDdDGA/n-ドデカン、0.3M硝酸の条件で4段の向流接触抽出を行ったところ、有機相にDyを92%、その中にNd 0.7%回収できることを確認した。

Research on hydrogen safety technology utilizing the automotive catalyst

大野 瞳*; 竹中 啓恭*; 喜多 知輝*; 谷口 昌司*; 松村 大樹; 西畑 保雄; 日野 竜太郎; Reinecke, E.-A.*; 高瀬 和之*; 田中 裕久*

E-Journal of Advanced Maintenance (Internet), 11(1), p.40 - 45, 2019/05

https://www.jsm.or.jp/ejam/Vol.11No.1/AA/AA155/AA155.html

Safety management technology of hydrogen gas is extremely important not only for nuclear power generation but also for future society. A brand-new passive autocatalytic recombiner (PAR) system utilizing the monolithic "intelligent catalyst" has been studied for the long-term storage of high-concentration radioactive materials related to the decommissioning of nuclear reactors. The monolith-type automotive catalyst showed high hydrogen conversion activity from a room temperature in a large scale reactor of REKO-4. It became clear that natural convection by reaction is greatly improved by roughening the cell density of the monolith catalyst especially under static environmental conditions such as in a storage container. Taking advantage of this superior catalytic property, we aim to complete the safety technology for storage containers at an early stage and advance the development of highly active catalyst from further low temperature.

Analysis of two forms of radioactive particles emitted during the early stages of the Fukushima Dai-ichi Nuclear Power Station accident

佐藤 志彦; 末木 啓介*; 笹 公和*; 吉川 英樹; 中間 茂雄; 箕輪 はるか*; 阿部 善也*; 中井 泉*; 小野 貴大*; 足立 光司*; et al.

Geochemical Journal, 52(2), p.137 - 143, 2018/00

https://doi.org/10.2343/geochemj.2.0514

Two types of radioactive particles have been isolated from environmental samples collected at various distances from the Fukushima Dai-ichi Nuclear Power Station. "Type A" particles are 2-10 m in diameter and display characteristic Cs X-ray emissions when analysed by energy-dispersive X-ray spectrometry (EDS). "Type B" particles are considerably larger, up to 400 m in diameter, with Cs concentrations too low to be detectable by EDS. These larger particles were isolated from the region to the north of the nuclear reactor site, which was contaminated on March 12, 2011. The specific activity of Type B particles is much lower than Type A, and the mean CsCs ratios are 0.93 and 1.04, respectively. The Type B ratio indicates power station Unit 1 as the source, implying that these larger radioactive particles were discharged on March 12. This study found that different type of radioactive particle was released not only on March 15 but also on March 12.

Thickness-dependent magnetic properties and strain-induced orbital magnetic moment in SrRuO thin films

石上 啓介*; 吉松 公平*; 豊田 大介*; 滝沢 優*; 吉田 鉄平*; 芝田 悟朗*; 原野 貴幸*; 高橋 文雄*; 門野 利治*; Verma, V. K.*; et al.

Physical Review B, 92(6), p.064402_1 - 064402_5, 2015/08

https://doi.org/10.1103/PhysRevB.92.064402

Thin films of the ferromagnetic metal SrRuO (SRO) show a varying easy magnetization axis depending on the epitaxial strain, and undergo a metal-to-insulator transition with decreasing film thickness. We have investigated the magnetic properties of SRO thin films with varying thicknesses fabricated on SrTiO(001) substrates by soft X-ray magnetic circular dichroism at the Ru M2,3 edge. Results have shown that, with decreasing film thickness, the film changes from ferromagnetic to nonmagnetic at around 3 monolayer thickness, consistent with previous magnetization and magneto-optical Kerr effect measurements. The orbital magnetic moment perpendicular to the film was found to be 0.1B/Ru, and remained nearly unchanged with decreasing film thickness while the spin magnetic moment decreases. A mechanism for the formation of the orbital magnetic moment is discussed based on the electronic structure of the compressively strained SRO film.