Sm synchrotron-radiation-based Mssbauer spectroscopy of Sm-based heavy fermion compounds

筒井 智嗣; 東中 隆二*; 水牧 仁一朗*; 小林 義男*; 中村 仁*; 伊藤 孝; 依田 芳卓*; 松田 達磨*; 青木 勇二*; 佐藤 英行*

Interactions (Internet), 245(1), p.9_1 - 9_10, 2024/12

https://doi.org/10.1007/s10751-024-01851-y

Sm synchrotron-radiation-based Mssbauer spectroscopy has been applied to Sm-based heavy fermion intermetallics, SmAl ( = Ti, V and Cr) and SmOsSb. The isomer shifts obtained demonstrate that the Sm valence states in these compounds are intermediate. Since the difference of the isomer shifts in 22.502 keV Sm Mssbauer effect between Sm and Sm state is comparable to the 2nd order Doppler shift, consideration of the 2nd order Doppler shift is required to precisely discuss Sm valence state through the shifts of the Mssbauer spectra. In addition, the plots of the isomer shifts obtained by the Mssbauer spectroscopy against the Sm valence states estimated from Sm L-edge X-ray absorption spectroscopy exhibit a linear correlation except for that in SmOsSb. This implies that the origin of the intermediate valence state in SmOsSb differs from that in SmAl ( = Ti, V and Cr).

核破砕中性子源水銀標的容器の材料劣化評価に対する押込み試験技術の適用

涌井 隆; 斎藤 滋; 二川 正敏

実験力学, 24(4), p.212 - 218, 2024/12

J-PARCの核破砕中性子源水銀ターゲット容器の寿命を決定する主要な要因の一つは照射損傷である。使用済み容器の材料劣化を把握するため、使用済み容器の構造材料に対する押込み試験と数値実験による逆解析を用いた評価を行う予定である。照射量の異なる2種類のイオン照射材料に対して、この評価手法を適用した。照射量の増加に伴い、引張強度が増加し、全伸びが減少することが確認された。これらの傾向は、ばらつきを考慮した微小試験片の引張試験によって報告されている材料劣化挙動と同等である。さらに、容器は繰り返し熱負荷を受け、定格最大ビーム出力では容器の温度が140Cを超えると推定されるため、温度上昇に伴う全伸びと照射材料の疲労強度の低下について検討した。

Development of a radiation tolerant laser-induced breakdown spectroscopy system using a single crystal micro-chip laser for remote elemental analysis

田村 浩司; 中西 隆造; 大場 弘則; 狩野 貴宏; 柴田 卓弥; 平等 拓範*; 若井田 育夫

Journal of Nuclear Science and Technology, 61(8), p.1109 - 1116, 2024/08

https://doi.org/10.1080/00223131.2023.2298485

For the development of the remote elemental analysis method in a radiation environment based on the laser-induced breakdown spectroscopy (LIBS), the radiation effects on the laser oscillation properties of the single crystal (SC) Nd: YAG microchip laser (MCL) were investigated and compared with those of ceramics Nd: YAG MCL. The laser oscillation properties were measured under gamma-ray irradiation as a function of dose rate. The effects on the SC MCL properties were found to be very small compared to those on the ceramics, indicating minimal radiation effects on the LIBS signal when using SC MCL. Pulse energy and oscillating build-up time (BUT) were measured for a cumulative dose exceeding 1400 kGy. The pulse energy remained stable, and the laser continued to oscillate under irradiation. The BUT also remained stable, demonstrating negligible optical loss accumulation that could affect laser properties even at the demonstrated cumulative dose. The results indicate that the effects of dose rate and cumulative dose on SC MCL laser properties were minimal. The SC MCL was then integrated into the LIBS system, and the gadolinium signal of composite oxides, simulating fuel debris, was successfully measured at the dose rate of 5 kGy/hr. These findings highlight the radiation tolerance of SC MCL as a laser medium for remote LIBS applications in harsh radiation environments.

Detailed visualization of radioactive hotspots inside the Unit 1 reactor building of the Fukushima Daiichi Nuclear Power Station using an integrated Radiation Imaging System mounted on a Mecanum wheel robot

佐藤 優樹; 寺阪 祐太; 大浦 正利*

Journal of Nuclear Science and Technology, 61(7), p.856 - 870, 2024/07

https://doi.org/10.1080/00223131.2023.2282551

In the decommissioning of the Fukushima Daiichi Nuclear Power Station, understanding the distribution of radioactive substances and dose-equivalent rates is crucial to develop detailed decontamination plans and minimize worker exposure. In this study, we remotely visualized radioactive hotspots and dose-equivalent rate distribution in Unit 1 reactor building of the station using a Mecanum wheel robot equipped with a Compton camera, simultaneous localization and mapping device, and survey meter. We successfully visualized high-concentration radiation hotspots on the U-shaped piping of the drywell humidity control system and the atmospheric control piping in the ceiling in front of the transverse in-core probe room. Furthermore, the hotspot location was identified in three dimensions using the Compton camera used to analyze the atmospheric control piping. By simultaneously analyzing the dose-equivalent rate data acquired by the survey meter and the hotspot locations visualized by the Compton camera, it was confirmed that the hotspots caused elevated dose-equivalent rates in the surrounding area. Using this robot system in unexplored areas, such as the higher floors of reactor buildings, in future will enable us to obtain information on radiation hotspot locations and dose-equivalent rate distribution.

Development of a radioactive substance detection system integrating a Compton camera and a LiDAR camera with a hexapod robot

佐藤 優樹; 角藤 壮*; 田中 孝幸*; 嶋野 寛之*; 諸橋 裕子; 畠山 知圭*; 中島 準作; 石山 正弘

Nuclear Instruments and Methods in Physics Research A, 1063, p.169300_1 - 169300_7, 2024/06

https://doi.org/10.1016/j.nima.2024.169300

A system for locating radioactive substances using a hexapod robot equipped with a Compton camera and light detection and ranging camera was developed, and its performance evaluation test was conducted at FUGEN, a nuclear facility owned by Japan Atomic Energy Agency. In the test, by projecting images of radioactive substances acquired with the Compton camera onto a three-dimensional model of the work environment acquired with a light detection and ranging camera, the locations where radioactive substances have accumulated and the dose rate is higher than the surrounding area were successfully visualized and identified.

First demonstration of a single-end readout position-sensitive optical fiber radiation sensor inside the Fukushima Daiichi Nuclear Power Station based on wavelength-resolving analysis

寺阪 祐太; 佐藤 優樹; 瓜谷 章*

Nuclear Instruments and Methods in Physics Research A, 1062, p.169227_1 - 169227_6, 2024/05

https://doi.org/10.1016/j.nima.2024.169227

We have developed a new position-sensitive optical fiber radiation sensor that achieves single-end readout and high dose rate application. The sensor determines the incident position of radiation on the optical fiber by using the wavelength dependency of light attenuation within the fiber. Through the analysis of the output wavelength spectrum from the fiber end, the incident position of radiation on the optical fiber can be inversely estimated using the spectrum unfolding procedure. Using this optical fiber sensor, we conducted a measurement of radiation distribution inside the Fukushima Daiichi Nuclear Power Station (FDNPS). The actual trend of incident position of radiation was successfully reproduced in a high dose rate area, with a maximum dose rate exceeding 100 mSv/h. This validates the effectiveness of our new position-sensitive optical fiber radiation sensor.

Convection and joint characteristics in aluminum alloy melting zone during resistance spot welding of dissimilar Fe-Al material in external magnetic field

船引 雄太*; 伊與田 宗慶*; 菖蒲 敬久; 松田 朋己*; 林 雄二郎*; 佐野 智一*; 他8名*

Journal of Manufacturing Processes, 115, p.40 - 55, 2024/04

https://doi.org/10.1016/j.jmapro.2024.01.049

In resistance spot welding (RSW) of Fe and Al alloy, an intermetallic compound (IMC) is formed at the joining interface, and it is known that the joining strength of the joint decreases as the IMC becomes thicker. In this study, the convection behavior in the Al alloy melting zone of an Fe-Al alloy RSW was varied and the effect on the joint characteristics was investigated. For this study, focusing on the electromagnetic force generated in the Al alloy melting zone, the convection behavior in the Al alloy melting zone was changed by adding an external magnetic field using neodymium magnets. In-situ evaluation of the convection behavior using synchrotron radiation and cross-sectional macro-observation of the joint revealed that the addition of an external magnetic field causes a non-axisymmetric change in the convection behavior in the Al alloy melting zone, which results in the deflection of the Al alloy melting zone. The addition of an external magnetic field increases the driving force of convection and homogenizes the temperature field at the joining interface, suggesting that the IMC near the center is formed thin and uniform. Furthermore, from the cross tension test and the observation of the fracture surface of the joint after the test, it was clarified that the CTS of the joint with an external magnetic field was improved by the propagation of cracks into the Al alloy melting zone during the test.

令和4年度原子力発電所周辺における航空機モニタリング(受託研究)

普天間 章; 眞田 幸尚; 長久保 梓; 川崎 義晴*; 岩井 毅行*; 平賀 祥吾*; 萩野谷 仁*; 松永 祐樹*; 圷 雄一郎*; 新井 仁規*; et al.

JAEA-Technology 2023-027, 146 Pages, 2024/03

JAEA-Technology-2023-027.pdf:18.12MB

2011年3月11日に発生した東北地方太平洋沖地震による津波に起因した東京電力福島第一原子力発電所事故によって、大量の放射性物質が周辺環境に飛散した。事故直後より、放射線の分布を迅速かつ広範囲に測定する手法として、航空機等を用いた空からの測定方法が適用されている。日本原子力研究開発機構では、有人ヘリコプターを使用した航空機モニタリングを福島第一原子力発電所周辺において継続的に実施してきた。本報告書では、令和4年度に実施した福島第一原子力発電所周辺におけるモニタリング結果について取りまとめると共に、過去のモニタリング結果から空間線量率等の変化量を評価し、その変化要因について考察した。また、航空機モニタリングによる空間線量率の換算精度向上に資するために、航空機モニタリングデータを用いて地形の起伏を考慮に入れた解析を行った。地形の起伏を考慮に入れる前後での解析結果を比較し、本手法による精度向上効果を評価した。さらに、空気中のラドン子孫核種の弁別手法を測定結果に適用して、空気中のラドン子孫核種が航空機モニタリングに与える影響について評価した。

耐放射線プロセッサを用いた組み込みシステムの開発(委託研究); 令和4年度英知を結集した原子力科学技術・人材育成推進事業

廃炉環境国際共同研究センター; 岡山大学*

JAEA-Review 2023-038, 48 Pages, 2024/03

JAEA-Review-2023-038.pdf:2.58MB

日本原子力研究開発機構(JAEA)廃炉環境国際共同研究センター(CLADS)では、令和4年度英知を結集した原子力科学技術・人材育成推進事業(以下、「本事業」という)を実施している。本事業は、東京電力ホールディングス株式会社福島第一原子力発電所の廃炉等をはじめとした原子力分野の課題解決に貢献するため、国内外の英知を結集し、様々な分野の知見や経験を、従前の機関や分野の壁を越えて緊密に融合・連携させた基礎的・基盤的研究及び人材育成を推進することを目的としている。平成30年度の新規採択課題から実施主体を文部科学省からJAEAに移行することで、JAEAとアカデミアとの連携を強化し、廃炉に資する中長期的な研究開発・人材育成をより安定的かつ継続的に実施する体制を構築した。本研究は、令和4年度に採択された研究課題のうち、「耐放射線プロセッサを用いた組み込みシステムの開発」の令和4年度分の研究成果について取りまとめたものである。本研究は、集積回路に光技術を導入し、10MGyのトータルドーズ耐性を持つ耐放射線光電子プロセッサ、既存の集積回路のみで4MGyのトータルドーズ耐性を持つ耐放射線プロセッサ、同4MGyのトータルドーズ耐性の耐放射線メモリ、そして、それらに必要となる1MGyのトータルドーズ耐性を持つ耐放射線電源ユニットの4つを開発する。マンチェスター大学とはロボットやLiDARに対する耐放射線プロセッサ、耐放射線FPGA、耐放射線メモリ、耐放射線電源ユニットの面で連携し、これまでに無い高いトータルドーズ耐性を持つ耐放射線ロボットを実現していく。また、ランカスター大学とは耐放射線FPGA、耐放射線電源ユニットの面で連携し、放射線の種類、強度を正確に特定できるセンサー類を開発していく。

Phase transformation and equation of state in Ti-45Al alloy under high pressure

Li, X.*; Zhu, R.*; Xin, J.*; Luo, M.*; Shang, S.-L.*; Liu, Z.-K.*; Yin, C.*; 舟越 賢一*; Dippenaar, R. J.*; 肥後 祐司*; et al.

CALPHAD; Computer Coupling of Phase Diagrams and Thermochemistry, 84, p.102641_1 - 102641_6, 2024/03

https://doi.org/10.1016/j.calphad.2023.102641

The phase transformations and pressure-volume dependencies of the Ti-45Al alloy with respect to pressure have been investigated by means of in-situ observation using multi anvil-type high-pressure devices and synchrotron radiation. Under hydrostatic compression from 0 to 10.1 GPa, about 2.3 vol. % of transforms continuously to 2. Lattice parameters as well as volume fractions of these two phases have been determined as a function of pressure. Bulk moduli estimated using Birch-Murnaghan's equation of state are 148 GPa for the phase, 138 GPa for the 2 phase, and 149 GPa for their two-phase mixture of Ti-45Al alloy. First-principles have also applied to investigate bulk moduli of two single phases, and the deviation between calculations and measurements is discussed and attributed to mainly phase transformation. The presently study provides useful insights into thermodynamics of 2 and phases under high pressure.