Hydrogenation of silicon-bearing hexagonal close-packed iron and its implications for density deficits in the inner core

森 悠一郎*; 鍵 裕之*; 青木 勝敏*; 高野 将大*; 柿澤 翔*; 佐野 亜沙美; 舟越 賢一*

Earth and Planetary Science Letters, 634, p.118673_1 - 118673_8, 2024/05

https://doi.org/10.1016/j.epsl.2024.118673

水素による鉄の体積膨張に対するケイ素の効果を調べるため、高圧高温下でのhcp-FeSiの中性子回折実験とX線回折実験を行った。中性子回折実験は重水素化hcp-FeSiに対して13.5GPa, 900K及び12.1GPa, 300Kで行い、得られたプロファイルからリートベルト解析を用いて水素占有率を決定した。hcp-Fe-SiのP-V-T状態方程式を組み合わせることにより、hcp-FeSiの水素による体積膨張が純粋なhcp鉄の体積膨張よりも10%大きいことを示した。得られた値を用いて、内核の密度欠損を再現できる水素量を見積もったところ、シリコンの影響がない場合に比べて50%減少した。hcp-FeSiで内核の密度欠損を再現した場合、内核と外核で可能な水素量xはそれぞれ0.07と0.12-0.15と計算された。

Development of a DO/HO vapor generator for contrast-variation neutron scattering

有馬 寛*; 高田 慎一; 笠井 聡*; 大内 啓一*; 森川 利明*; 宮田 登*; 宮崎 司*; 青木 裕之; 岩瀬 裕希*; 廣井 孝介; et al.

Journal of Applied Crystallography, 56(6), p.1802 - 1812, 2023/12

https://doi.org/10.1107/S1600576723009780

The contrast-variation technique in neutron scattering experiments plays a pivotal role in distinguishing partial structures within multi-component complexes, facilitating the elucidation of distinct sample constituents. This differentiation is achieved using different isotopes, namely hydrogen and deuterium, which possess varying neutron scattering characteristics. This study presents a novel vapor generator designed for neutron scattering experiments, enabling continuous control of the DO/HO ratio of the vapor. This feature is especially useful for contrast-variation studies. The generator features two saturators and four mass flow controllers, allowing for the rapid and independent generation of DO/HO vapors. Additionally, the incorporation of the two-temperature method ensures accurate dew point control within a margin of 0.2Cdp. This setup proves useful for conducting time-resolved experiments and can accelerate research on functional polymers, such as polymer electrolyte membranes for fuel cells, where water potential assumes critical importance.

Impact of the Ce states in the electronic structure of the intermediate-valence superconductor CeIr

藤森 伸一; 川崎 郁斗; 竹田 幸治; 山上 浩志; 雀部 矩正*; 佐藤 芳樹*; 清水 悠晴*; 仲村 愛*; Maruya, A.*; 本間 佳哉*; et al.

Electronic Structure (Internet), 5(4), p.045009_1 - 045009_7, 2023/11

https://doi.org/10.1088/2516-1075/ad0a3d

The electronic structure of the -based superconductor was studied by photoelectron spectroscopy. The energy distribution of the state was revealed by the resonant photoelectron spectroscopy. The state was mostly distributed in the vicinity of the Fermi energy, suggesting the itinerant character of the state. The contribution of the state to the density of states (DOS) at the Fermi energy was estimated to be nearly half of that of the states, implying that the state has aconsiderable contribution to the DOS at the Fermi energy. The core-level and X-ray absorption spectra were analyzed based on a single-impurity Anderson model. The number of the state in the ground state was estimated to be 0.8-0.9, which is much larger than the values obtained in the previous studies (i.e., 0-0.4).

もんじゅ燃料体取出し作業報告書; 第1段階「燃料体取出し」作業

塩田 祐揮; 工藤 淳貴; 津野 大海; 竹内 遼太郎; 有吉 秀夫; 塩濱 保貴; 浜野 知治; 高木 剛彦; 長沖 吉弘

JAEA-Technology 2023-002, 87 Pages, 2023/06

JAEA-Technology-2023-002.pdf:8.53MB

高速増殖原型炉もんじゅは、2018年から廃止措置に移行し、約30年を経て廃止措置を完了する予定である。なお、廃止措置は4段階に分けて実施する計画である。もんじゅは、原子炉容器及び炉外燃料貯蔵槽(EVST)に多量のナトリウムを保有し、大規模なナトリウム火災との重畳による燃料破損という残留リスクがあった。このため、もんじゅ廃止措置計画の第1段階では約5.5年をかけて「燃料体取出し」作業を実施し、速やかにこれらの燃料体を全て燃料池に貯蔵し残留リスクを排除することとした。燃料体取出し作業では、炉心の燃料体を燃料池に移送し貯蔵することを目的に、炉外燃料貯蔵槽に貯蔵中の燃料体を洗浄し、燃料池に貯蔵する「燃料体の処理」、炉心にある燃料体を模擬燃料体等と交換し、炉外燃料貯蔵槽に貯蔵する「燃料体の取出し」を交互に行い、4キャンペーンに分け炉心に存在する燃料体370体と炉外燃料貯蔵槽に貯蔵されている燃料体160体の計530体の燃料体を全て安全かつ計画通りに燃料池への貯蔵を完了した。本報告書は、第1段階での燃料体取出し作業の総括として、作業の進め方、事前の機器・設備点検やリスク評価といった作業前の準備、キャンペーン内での運転や点検等の作業の実績、作業の評価について取り纏めたものである。

Validation of evaluation model for analysis of steam reformer in HTGR hydrogen production plant

石井 克典; 青木 健; 井坂 和義; 野口 弘喜; 清水 厚志; 佐藤 博之

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 9 Pages, 2023/05

JAEA initiated High Temperature engineering Test Reactor (HTTR) heat application test project to establish coupling technologies between HTGR and a hydrogen production plant necessary to achieve large-scale, low cost, and carbon-free hydrogen production. One important element for the coupling technologies is a system analysis code which can simulate dynamic behavior of a HTGR hydrogen production system to design a plant control system for the effects of circulated helium heat through both facilities. The code is required to deal with a complex system which involves several subsystems and different physics with different timescales. As a first step of the development, we developed a heat and mass balance evaluation model of a helium-heated steam reformer. This report will present the outline of the developed model and simulation results with comparison to the experimental results.

Development plan for coupling technology between high temperature gas-cooled reactor HTTR and hydrogen production facility, 1; Overview of the HTTR heat application test plan to establish high safety coupling technology

野本 恭信; 水田 直紀; 守田 圭介; 青木 健; 沖田 将一朗; 石井 克典; 倉林 薫; 安田 貴則; 田中 真人; 井坂 和義; et al.

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05

JAEA initiated an HTTR heat application test plan to develop for coupling technology between HTGR and hydrogen production facility. The principal objective of this test plan is to establish the high safety coupling technology for coupling a hydrogen production facility to HTGR through the demonstration of a hydrogen production by the proven technology of methane steam reforming method utilizing the HTTR as a high temperature heat source. The other objective is to develop for coupling equipment such as a high temperature isolation valve, a helium gas circulator and a high temperature insulation pipe. This paper describes the overview of an HTTR heat application test plan such as a draft test schedule and test targets for the demonstration of a hydrogen production. This paper also presents basic specifications of an HTTR heat application test facility such as the HTTR modification strategy, overall system configuration and heat and mass balance at rated test operation for the demonstration of a hydrogen production. Furthermore, the operation plan during the normal start-up and shut-down processes is proposed.

Hydrogen occupation and hydrogen-induced volume expansion in FeNiD at high conditions

市東 力*; 鍵 裕之*; 柿澤 翔*; 青木 勝敏*; 小松 一生*; 飯塚 理子*; 阿部 淳*; 齋藤 寛之*; 佐野 亜沙美; 服部 高典

American Mineralogist, 108(4), p.659 - 666, 2023/04

https://doi.org/10.2138/am-2022-8348

FeNiH(D)の12GPa, 1000Kまでの高温高圧下における相関係と結晶構造をその場X線及び中性子回折測定により明らかにした。今回実験した温度圧力下において、FeNiH(D)ではFeH(D)とは異なり、重水素原子は面心立方構造(fcc)中の四面体サイトを占有しないことが明らかになった。単位重水素あたりの水素誘起膨張体積は、fcc相で2.45(4) 、hcp相で3.31(6) であり、FeDにおけるそれぞれの値より著しく大きいことが明らかになった。また、は温度の上昇に伴いわずかに増加した。この結果は、鉄に10%ニッケルを添加するだけで、金属中の水素の挙動が劇的に変化することを示唆している。が圧力に関係なく一定であると仮定すると、地球内核の最大水素含有量は海洋の水素量の1-2倍であると推定される。

Neutron reflectivity study on the nanostructure of PMMA chains near substrate interfaces based on contrast variation accompanied with small molecule sorption

下北 啓輔*; 山本 勝宏*; 宮田 登*; 中西 洋平*; 柴田 基樹*; 竹中 幹人*; 山田 悟史*; 瀬戸 秀樹*; 青木 裕之; 宮崎 司*

Soft Matter, 19(11), p.2082 - 2089, 2023/03

https://doi.org/10.1039/D2SM01482C

In the case of poly(methyl methacrylate) (PMMA) thin films on a Si substrate, thermal annealing induces the formation of a layer of PMMA chains tightly adsorbed near the substrate interface, and the strongly adsorbed PMMA remains on the substrate, even after washing with toluene (hereinafter called adsorbed sample). Neutron reflectometry revealed that the concerned structure consists of three layers: an inner layer (tightly bound on the substrate), a middle layer (bulk-like), and an outer layer (surface) in the adsorbed sample. When an adsorbed sample was exposed to toluene vapor, it became clear that, between the solid adsorption layer (which does not swell) and bulk-like swollen layer, there was a "buffer layer" that could sorb more toluene molecules than the bulk-like layer. This buffer layer was found not only in the adsorbed sample but also in the standard spin-cast PMMA thin films on the substrate. When the polymer chains were firmly adsorbed and immobilized on the Si substrate, the freedom of the possible structure right next to the tightly bound layer was reduced, which restricted the relaxation of the conformation of the polymer chain strongly. The "buffer layer" was manifested by the sorption of toluene with different scattering length density contrasts.

LASSO reconstruction scheme to predict radioactive source distributions inside reactor building rooms; Practical applications

町田 昌彦; Shi, W.*; 山田 進; 宮村 浩子; 吉田 亨*; 長谷川 幸弘*; 岡本 孝司; 青木 勇斗; 伊藤 倫太郎; 山口 隆司; et al.

Proceedings of Waste Management Symposia 2023 (WM2023) (Internet), 11 Pages, 2023/02

In order to find radioactive hot spots inside reactor building rooms from structural data together with air dose rate measurement data, Least Absolute Shrinkage and Selection Operator (LASSO) has been recently suggested as a promising scheme. The scheme has been examined in simplified room models and its high estimation feasibility has been confirmed by employing Particle and Heavy Ion Transport code System (PHITS) as a radiation simulation code. In this paper, we apply the scheme to complex room models inside real reactor buildings. The target rooms are pool canal circulation system room and main circulation system room in Japan Materials Testing Reactor (JMTR) at Oarai area, Japan Atomic Energy Agency (JAEA). In these real rooms, we create STL format structural data based on Computer Aided Design (CAD) models made directly from their point group data measured by laser scanning devices, and we notice that the total number of their surface meshes in these real rooms reaches to the order of 1 million. Then, this order of the mesh number clearly indicates that one needs a simplified radiation simulation code considering only direct transmission of gamma ray as a radiation calculation instead of PHITS demanding high computational costs. By developing such a simplified code and customizing it to perform LASSO scheme, we consequently confirm that LASSO scheme driven by the simplified simulation can also successfully predict unknown radioactive hot spots on real structural models.

Interfacial distribution of Nafion ionomer thin films on nitrogen-modified carbon surfaces

吉宗 航*; Kikkawa, Nobuaki*; Yoneyama, Hiroaki*; Takahashi, Naoko*; Minami, Saori*; Akimoto, Yusuke*; Mitsuoka, Takuya*; Kawaura, Hiroyuki*; Harada, Masashi*; 山田 悟史*; et al.

ACS Applied Materials & Interfaces, 14(48), p.53744 - 53754, 2022/11

https://doi.org/10.1021/acsami.2c14574

Chemically modified carbon supports for the cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) show considerable promise for boosting the oxygen reduction reaction. This study evaluated the ionomer distribution of Nafion ionomer thin films on nitrogen (N)-modified carbon surfaces along their depth direction. Neutron reflectivity (NR) measurements performed using the double-contrast technique with HO and DO revealed that the introduction of N functional groups to carbon thin films promoted ionomer adsorption onto the surface under wet conditions (22C, 85% relative humidity). Molecular dynamics (MD) simulations conducted to verify the origin of the robust contact between the ionomer and N-modified carbon surface revealed an ionomer adsorption mechanism on the N-modified carbon surfaces, which involved Coulomb interactions between the positively charged carbon surface and the ionomer side chains with negatively charged sulfonic acid groups. The positive surface charge, which was determined using the contents of the N functional groups estimated by X-ray photoelectron spectroscopy, was found to be sufficient as an impetus for ionomer adsorption. This strategy involving NR measurements and MD simulations can provide insights into the solid-ionomer interfacial structures in a cathode catalyst layer and can therefore be extensively employed in studies on PEFCs.