Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
)
(SrAl
TaO)
with 
伊藤 孝; 髭本 亘; 幸田 章宏*; 中村 惇平*; 下村 浩一郎*
Interactions (Internet), 245(1), p.25_1 - 25_7, 2024/12
We report on muon spin relaxation (
SR) measurements in a mixed perovskite compound, (LaAlO)
(SrAlTaO) with (LSAT), which is widely used as a single-crystalline substrate for thin film deposition. In zero applied field (ZF), muon depolarization due to the distribution of nuclear dipole fields was observed in the temperature range from 4 K to 270 K. Interestingly, SR time spectra in ZF maintained a Gaussian-like feature over the entire range, while the depolarization rate exhibited a monotonic decrease with increasing temperature. This behavior may be attributed to the thermally activated diffusion of muons between a few adjacent sites within a confined space of the angstrom scale, where the motionally averaged local field that each muon experiences can remain non-zero and result in maintaining the Gaussian-like line shape. The spatial distribution of electrostatic potential at lattice interstices evaluated via density functional theory calculations suggests that such a restriction of muon diffusion paths can be caused by the random distribution of cations with different nominal valences in the mixed perovskite lattice.
下村 浩一郎*; 幸田 章宏*; Pant, A. D.*; 砂川 光*; 藤森 寛*; 梅垣 いづみ*; 中村 惇平*; 藤原 理賀; 反保 元伸*; 河村 成肇*; et al.
Interactions (Internet), 245(1), p.31_1 - 31_6, 2024/12
J-PARC Muon Facility: MUSE (Muon Science Establishment) is responsible for the inter-university user program and the operation, maintenance, and construction of the muon beamlines, namely D-line, S-line, U-line, and H-line, along with the muon source at J-PARC Materials and Life Science Facility (MLF). In this paper, recent developments are briefly presented.
安部 諭; 柴本 泰照
Annals of Nuclear Energy, 202, p.110461_1 - 110461_16, 2024/07
During a severe accident in a nuclear containment vessel, jets released from the primary system exhibit complex thermohydraulic behavior due to buoyancy effects and impingement on internal obstacles such as inner walls and floors. Thus, the obstacle-influenced jets are of interest in recent research activities. This paper describes an experimental investigation of the behavior of jets passing through a grid-type obstacle. The flow field was acquired by a particle image velocimetry system. The experiment captured the jet fragmentation by the grid-type obstacle and their recoupling. The mean velocity field obtained by postprocessing indicates a "Rectifying effect," with the axial velocity increasing at the center and the magnitude of the radial velocity decreasing. The meandering flow was suppressed due to this effect. In the near grid-obstacle region, the axial turbulence intensity was relatively large at the edge of each fragmented region due to shear stress. Moreover, the spatial distribution of the radial turbulence fluctuation became more complex. Further investigation is required to clarify the budget of the transport equation for turbulence fluctuation. The experimental data shown in this paper is useful for computational fluid dynamics validation.
Pu
O
powder using master sintering curve theory中道 晋哉; 砂押 剛雄*; 廣岡 瞬; Vauchy, R.; 村上 龍敏
Journal of Nuclear Materials, 595, p.155072_1 - 155072_11, 2024/07
Using dry recycled powders for uranium and plutonium mixed oxide (MOX) fuel production can reduce unnecessary storage and accountability of nuclear material in facilities. The shrinkage behavior of green compacts of dry recycled powders differs from that of conventional raw powders because the dry recycled MOX powder is obtained from the fabrication scrap of sintered pellets. The shrinkage behavior of dry recycled MOX powder has been investigated by dilatometry. Based on the shrinkage curves, sintering apparent activation energies were evaluated using the master sintering curve (MSC) and the constant rate of heating methods. The obtained values were higher than the energy evaluated for raw powder experiments. The sigmoid sintering prediction equation using the MSC function was constructed. The accumulation of data on the activation energy for various sintering conditions will lead to the wide application of this prediction formula in the future.
compoundsFrazer, D.*; Saleh, T. A.*; 松本 卓; 廣岡 瞬; 加藤 正人; McClellan, K.*; White, J. T.*
Nuclear Engineering and Design, 423, p.113136_1 - 113136_7, 2024/07
ナノインデンテーション法では、微小な試験片を用いてヤング率,硬度及びクリープ強度といった機械物性を評価することが可能である。本研究ではMOX燃料の代替物質として(U,Ce)Oを用いて、高温ナノインデンテーション試験を実施した。試料のCe含有率は0.1、0.2及び0.3mol%とし、温度は800
Cまでの測定を行い、ヤング率、硬度及びクリープ強度の評価を行った。温度の上昇に伴い、ヤング率は線形的に低下し、硬度は指数関数的に低下する結果が得られた。また、800Cにおいては、応力指数n=4.7
6.9のクリープ変形が得られた。
Li, L.*; 宮本 吾郎*; Zhang, Y.*; Li, M.*; 諸岡 聡; 及川 勝成*; 友田 陽*; 古原 忠*
Journal of Materials Science & Technology, 184, p.221 - 234, 2024/06
被引用回数：0 パーセンタイル：0(Materials Science, Multidisciplinary)Dynamic transformation (DT) of austenite (
) to ferrite (
) in the hot deformation of various carbon steels was widely investigated. However, the nature of DT remains unclear due to the lack of quantitative analysis of stress partitioning between two phases and the uncertainty of local distribution of substitutional elements at the interface in multi-component carbon steels used in the previous studies. Therefore, in the present study, a binary Fe-Ni alloy with + duplex microstructure in equilibrium was prepared and isothermally compressed in + two-phase region to achieve quantitative analysis of microstructure evolution, stress partitioning and thermodynamics during DT. to DT during isothermal compression and to reverse transformation on isothermal annealing under unloaded condition after deformation were accompanied by Ni partitioning. The lattice strains during thermomechanical processing were obtained via in-situ neutron diffraction measurement, based on which the stress partitioning behavior between and was discussed by using the generalized Hooke's law. A thermodynamic framework for the isothermal deformation in solids was established based on the basic laws of thermodynamics, and it was shown that the total Helmholtz free energy change in the deformable material during the isothermal process should be smaller than the work done to the deformable material. Under the present thermodynamic framework, the microstructure evolution in the isothermal compression of Fe-14Ni alloy was well explained by considering the changes in chemical free energy, plastic and elastic energies and the work done to the material. In addition, the stabilization of the soft phase in Fe-14Ni alloy by deformation was rationalized since the to transformation decreased the total Helmholtz free energy by decreasing the elastic and dislocation energies.
佐藤 一憲; 吉川 信治; 山下 拓哉; 下村 健太; Cibula, M.*; 溝上 伸也*
Nuclear Engineering and Design, 422, p.113088_1 - 113088_24, 2024/06
The accident progression of the in-vessel phase of Fukushima Daiichi Nuclear Power Station Unit 1 was analyzed using the MAAP code. Although there is a large uncertainty in the initial stage of accident progression behavior in Unit 1 with little measurement data, it is presumed to have similarities to that of Unit 3. As a result, in Unit 1, since there was almost no alternative water injection during the in-vessel phase, cooling of the debris transferred to the lower plenum was small. It was likely that a large molten pool of metals had formed, and that the steam supply to the high-temperature core materials was suppressed and metal oxidation was relatively small. The analysis results for Unit 1 were compared with those for Units 2 and 3, and differences between units such as the thermal conditions of the debris that relocated to the pedestal and the degree of metal oxidation were shown.
CNguyen, B. V. C.*; 村上 健太*; Chena, L.*; Phongsakorn, P. T.*; Chen, X.*; 橋本 貴司; Hwang, T.*; 古澤 彰憲; 鈴木 達也*
Nuclear Materials and Energy (Internet), 39, p.101639_1 - 101639_9, 2024/06
In reactor pressure vessel materials, the formation of Mn- and Ni-rich nanoclusters is a major cause of neutron irradiation embrittlement. The segregation of these solute atoms into dislocation loops has attracted attention as a mechanism to accelerate solute clustering. In this study, the behaviors of solute Mn and Ni atoms in Fe-0.6wt.%Ni, Fe-1.4wt.%Mn, and Fe-1.4wt.%Mn-0.6wt.%Ni alloys irradiated at 400 C up to 3 dpa were analyzed using three-dimensional atom probe tomography. Solute atom clusters were observed in all materials, and their shapes were spherical, flat, and torus in FeNi, FeMn, and FeMnNi, respectively. In ternary alloy FeMnNi, Mn and Ni atoms were concentrated in the sample in the form of arcs, and the orientation of the plane containing the arcs was estimated by comparing field desorption images. The size, number density, and orientation of this structure were found to be in good agreement with those of both types of dislocation loops, namely, b = 1/2 
111
and b = 100, identified in a previous study using the same material. The positions of Ni and Mn enrichment did not fully overlap. Ni atoms tended to be concentrated more in the inner part of the loop than the Mn atoms. Mn atoms were enriched only in the vicinity of the dislocation loops, whereas Ni atoms showed a higher concentration inside the dislocation loops than in the bulk.
C powder and BC pellet regarding the eutectic reaction with stainless steelHong, Z.*; Ahmed, Z.*; Pellegrini, M.*; 山野 秀将; Erkan, N.*; Sharma, A. K.*; 岡本 孝司*
Progress in Nuclear Energy, 171, p.105160_1 - 105160_13, 2024/06
本研究では、BC粉末とステンレス鋼(SS)間との共晶反応はBC粉ペレットとSS間とのそれより相当に速いことが分かった。粉末及びペレットに対して導出された反応速度定数は参考文献値によく一致している。また、粉末とペレットの場合の詳細微細構造をSEM/EDSを用いて組成分析を行った。粉末の場合、(Fe,Cr)Bからなる反応層として厚肉層が見られた。一方、ペレットの場合、2つの反応層が見られた。
孫 昊旻; 功刀 資彰*; 横峯 健彦*; Shen, X.*; 日引 俊*
Experimental Thermal and Fluid Science, 154, p.111171_1 - 111171_24, 2024/05
Taking the importance of gas-liquid two-phase flows in large square channels for advanced nuclear reactors, such as ESBWR, we experimented with upward cap-bubbly flows in a large square channel. Local void fractions, axial gas velocities, and interfacial area concentrations for two bubble-size groups were measured at three axial locations. Based on the database, cap-bubbly flow characteristics in a large square channel were understood. The existing drift-flux and interfacial area concentration correlations were validated. The void fraction covariances were obtained and used to validate their existing correlations.
石角 元志*; 高橋 竜太*; 山内 康弘*; 中村 雅俊*; 石丸 宙*; 山内 沙羅*; 河村 聖子; 吉良 弘*; 坂口 佳史*; 渡辺 真朗; et al.
JPS Conference Proceedings (Internet), 41, p.011010_1 - 011010_7, 2024/05
Recent status of cryogenic sample environment equipment at the Materials and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC) has been reported. We have reviewed the specifications and performance of cryogenic sample environment equipment and a newly installed Gifford-McMahon (GM) cryofurnace, which are mainly managed by the Cryogenic and Magnet group in the sample environment team at the MLF. Moreover, the recent maintenance and update of each piece of equipment, the improved temperature-control function, and the expansion of the usable beamline of the cryogenic sample environment equipment are described.
Micheau, C.; 上田 祐生; 元川 竜平; 阿久津 和宏*; 山田 悟史*; 山田 雅子*; Moussaoui, S. A.*; Makombe, E.*; Meyer, D.*; Berthon, L.*; et al.
Journal of Molecular Liquids, 401, p.124372_1 - 124372_12, 2024/05
Supramolecular organization of extractant molecules impacts metal ions separation behavior. Probing bulk and interfacial structures of the relevant systems is expected to provide key insights into the metal ion selectivity and kinetic aspects. The supramolecular features of two solvent extraction systems based on malonamide extractants, N,N,N′,N′-tetrahexylmalonamide (THMA) in toluene and N,N′-dimethyl-N,N′-dibutyl-2-tetradecylmalonamide (DBMA) in n-heptane, were studied using small-angle X-ray scattering for the organic bulk phases, as well as interfacial tension and neutron reflectivity measurements for the interfaces. In the bulk solution, THMA forms dimeric/trimeric associates but no aggregates in toluene, while DBMA forms large aggregates in n-heptane. On the other hand, THMA accumulates in a diffuse layer at the interface at high THMA concentration, whereas DBMA forms a compact but thinner layer. After Pd(II) extraction, the thickness of interfacial layers decreases in the case of THMA, and totally vanishes in the case of DBMA. Based on these new structural information, two mechanisms are proposed for Pd(II) and Nd(III) extraction with malonamides. In toluene, THMA associates slightly accumulate in the vicinity of the interface, then coordinate Pd(II) and diffuse into the organic bulk phase. In n-heptane, DBMA aggregates adsorb at the interface then pick up Nd(III) cations in their polar cores and finally diffuse into the bulk.
加藤 正人; 沖 拓海; 渡部 雅; 廣岡 瞬; Vauchy, R.; 小澤 隆之; 上羽 智之; 生澤 佳久; 中村 博樹; 町田 昌彦
Journal of the American Ceramic Society, 107(5), p.2998 - 3011, 2024/05
被引用回数：0 パーセンタイル：0.01(Materials Science, Ceramics)Herein, a science-based uranium and plutonium mixed oxide (MOX) property model (Sci-M Pro) is derived for determining properties of MOX fuel and analyzing their performance as functions of Pu content, minor-actinide content, oxygen-to-metal ratio, and temperature. The property model is constructed by evaluating the effect of phonons and electronic defects on heat capacity and thermal conductivity of MOX fuels. The effect of phonons was evaluated based on experimental datasets related to lattice parameter, thermal expansion, and sound speeds. Moreover, the effect of electronic defects was determined by analyzing oxygen-potential data based on defect chemistry. Furthermore, the model evaluated the effect of the Bredig transition on the thermal properties of MOX fuel by analyzing the irradiation test results. The derived property model is applied to the performance code to analyze fast reactor fuel pins.
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
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.
眞田 幸尚; 押切 圭介*; 菅野 麻里奈*; 阿部 智久
Nuclear Instruments and Methods in Physics Research A, 1062, p.169208_1 - 169208_7, 2024/05
福島第一原子力発電所(FDNPP)の廃炉作業の一環として、2023年から貯蔵処理水の放出が開始される。本研究では、FDNPPでのバッチサンプリング測定により確認されたトリチウム水の濃度を連続的に監視する実用的なトリチウムモニタを開発した。このモニターは、安価なプラスチックシンチレータペレットからなるフローセル検出器を配置し、3つの検出器による同時測定、ベト検出器、環境線の影響を低減するための鉛遮蔽を組み込んだ。このシステムは、測定時間30分で911Bq L-1の検出限界に達し、これはトリチウム水の排出基準1,500Bq L-1よりも低い。このシステムはまた、
線スペクトルを用いて、トリチウム以外の妨害放射性核種やバックグラウンド放射線による妨害の存在を定性的に区別することができる。また、線スペクトルを用いて、トリチウム以外の妨害放射性核種やバックグラウンド放射線による妨害の有無を定性的に区別することができる。
吉川 龍志; 今井 康友*; 菊地 紀宏; 田中 正暁; 大島 宏之
Nuclear Technology, 210(5), p.814 - 835, 2024/05
ナトリウム冷却高速炉安全性強化研究では、燃料ピンの構造健全性を評価するために各種運転条件下におけるワイヤスペーサ型燃料集合体内熱流動特性の解明が重要である。そこで有限要素法による集合体詳細熱流動解析コードSPIRALが開発されている。本研究では、SPIRALにおける壁近傍低Re数効果を考慮したハイブリッド型乱流モデルの妥当性を確認するために、層流-乱流遷移条件及び乱流条件を含む異なるRe数条件下の37本ピンバンドルナトリウム実験の再現解析を実施した。SPIRALによる予測された温度分布はナトリウム実験で測定され温度と一致した。以上によって、SPIRALにおけるハイブリッド型乱流モデルの広範囲Re数条件下ナトリウム冷却集合体熱流動評価への適用性を確認した。
Yuan, X.*; Hu, Q. H.*; Fang, X.*; Wang, Q. M.*; Ma, Y.*; 舘 幸男
Sedimentary Geology, 465, p.106633_1 - 106633_14, 2024/05
Archie's cementation factor, m, is a critical parameter for petrophysical studies, and the value is influenced by several factors such as the shape, type, and size of grains, degrees of diagenesis, and associated pore structure. Using integrated experimental and theoretical approaches, the goal of this study is to obtain the cementation factor of rocks (both reservoir rock and caprock) and assess the impact of diagenesis processes on the values of the cementation factor. Thirteen samples of geologically diverse rocks (six mudstones, four fossiliferous limestones, two marbles, and one sandstone) were selected to achieve these research objectives. Two approaches, the diffusion of gas tracers and the Bosanquet formula calculation using pore-throat sizes from mercury intrusion porosimetry analyses, were used to derive the cementation factors of these rock samples. These rocks were categorized into two groups based on the correlation between average pore-throat diameter and diffusivity, and an exponential-law relationship between the cementation factor and porosity was determined for these sample groups. In addition, thin-section petrography and field emission-scanning electron microscopy observations were utilized to investigate diagenetic processes, with four diagenetic patterns being established: (1) strong compaction, strong cementation, and weak dissolution-diagenesis pattern; (2) weak compaction, medium cementation, and weak dissolution-diagenesis pattern; (3) weak compaction, medium cementation, and strong dissolution-diagenesis pattern; and (4) fracture-matrix pattern. The results indicated that diagenetic processes and microfractures contribute to the variability in the cementation factors in these rock samples.
Sr in highly radioactive aqueous samples via conversion to a kinetically stable 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex followed by concentration-separation-fractionation based on capillary electrophoresis-liquid scintillation大内 和希; 原賀 智子; 廣瀬 和生*; 黒澤 結香*; 佐藤 義行; 渋川 雅美*; 齋藤 伸吾*
Analytica Chimica Acta, 1298, p.342399_1 - 342399_7, 2024/04
従来の高線量試料分析法では被ばくリスクが高く、大量の二次放射性廃棄物が発生することから、放射線放出量を低減できる迅速な分析法が強く望まれている。このニーズに取り組むため、我々は液体シンチレーションカウンティングと2点検出によるキャピラリー過渡的等速電気泳動(ctITP)を組み合わせたSr定量法を開発した。これは、1,4,7,10-テトラアザシクロドデカン-1,4,7,10-テトラ酢酸(DOTA)-Sr錯体を1回の操作で分離・分画する方法である。高線量の放射性試料をマイクロリットルレベルで取り扱うことができ、従来のイオン交換法よりも大幅に高速であるこの方法により、実高線量廃棄物中のSrを選択的に定量した。ctITPにおける濃縮・分離の成功は、Sr-DOTA錯体が解離不活性であることに起因する。
横村 亮太*; 後藤 雅貴*; 吉田 健人*; 割澤 伸一*; 羽成 敏秀; 川端 邦明; 福井 類*
IEEE Robotics and Automation Letters (Internet), 9(4), p.3275 - 3282, 2024/04
廃炉作業におけるロボットの遠隔操作のエラーを低減するため、作業環境を常時観察できるRail DRAGONを開発した。Rail DRAGONは、原子炉格納容器(PCV)内に長尺の軌道構造体(レールモジュール)を組み立てて押し込み、そのレール上に複数台のモニタリングロボットを繰り返し配置することで構築され、高放射線環境下での常時監視を可能にしたものである。特に、Rail DRAGONの構成要素である屈曲可能なレールモジュール、直線状のレールモジュール、基部ユニット、モニタリングロボットを開発した。具体的には、可搬性・作業性に優れた超長尺多関節構造物の実現手法を提案・実証している。また、処分を考慮しつつ、容易に展開・交換が可能な観測機器の展開手法を提案し、その実現可能性を検証する。
入澤 恵理子; 加藤 千明
Journal of Nuclear Materials, 591, p.154914_1 - 154914_10, 2024/04
被引用回数：0核燃料再処理施設における濃縮運転時の溶液組成及び沸騰の変化を考慮して、オーステナイト系ステンレス鋼R-SUS304ULCの腐食量を評価した。オーステナイト系ステンレス鋼R-SUS304ULCは、日本の使用済燃料再処理施設の高放射性廃液濃縮装置の構造材料であり、濃縮運転時に腐食性の高い硝酸溶液を処理する。本研究の結果、カソード反応活性化によるステンレス鋼の腐食速度を加速する要因として、硝酸濃度、酸化性金属イオン濃度、減圧沸騰に着目する必要があることがわかった。
