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)
(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.
SR studies on copper minerals藤原 理賀; 岡部 博孝*; 幸田 章宏*
Interactions (Internet), 245(1), p.13_1 - 13_6, 2024/12
量子状態を実験的に観測することは難しい。さらに、エキゾチックな量子状態が実現すると予測されている格子系の中には、理想的なモデル物質が見つかっていない系も存在する。銅鉱物の中には、未研究の低次元量子磁性体がまだまだ多く存在し、その数は年々増加している。我々は、銅鉱物が発見された自然環境を模倣することで7種類の銅鉱物の人工合成に成功し、さらにその量子状態を報告した。パルスミュオンの特性は、人工銅鉱物のスピン状態の調査に大変適している。その有用性を、fedotoviteのSR測定の結果を示しながら、紹介する。
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。
迫田 晃弘; 石森 有; Jin, Q.*; 飯本 武志*
Applied Radiation and Isotopes, 207, p.111180_1 - 111180_8, 2024/05
建物内壁のラドン(
Rn)及びトロン(
Rn)散逸率のin-situ測定におけるデータ解析技術の向上を目的に、解析で用いる数理モデルと関連パラメータの影響を調べた。その結果、測定系内の放射能濃度の不均一性を考慮すべきなのは、ラドンよりもトロンの場合であることがわかった。また、解析結果の品質をより向上させるために、屋内ラドンの日内変動を解析で考慮すべきであることがわかった。散逸率測定の目的と要求精度の下で、適切なモデルを作成・選択する必要があることが示された。
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
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-Fe
Si
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。
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.
山口 瑛子; 栗原 雄一*; 永田 光知郎*; 田中 万也; 桧垣 正吾*; 小林 徹; 谷田 肇; 小原 義之*; 横山 啓一; 矢板 毅; et al.
Journal of Colloid and Interface Science, 661, p.317 - 332, 2024/05
被引用回数：0ラジウム(Ra)は放射性元素であり、放射性廃棄物処理やウラン鉱山周辺の環境問題で重要なため、環境中Ra挙動の解明は急務である。しかし、Raは安定同位体が存在しないため分子レベルの実験が難しく、環境中で重要と考えられる粘土鉱物への吸着反応についても詳細なデータは得られていない。本研究では、広域X線吸収微細構造(EXAFS)法によりRaの分子レベルの情報を得る手法を確立し、さらに第一原理計算を利用することでRaの粘土鉱物への吸着構造を明らかにした。また、同族元素との比較を行い、粘土鉱物への吸着反応の系統的な理解に資する結果を得た。
Baccou, J.*; Glantz, T.*; Ghione, A.*; Sargentini, L.*; Fillion, P.*; Damblin, G.*; Sueur, R.*; Iooss, B.*; Fang, J.*; Liu, J.*; et al.
Nuclear Engineering and Design, 421, p.113035_1 - 113035_16, 2024/05
In the Best-Estimate Plus Uncertainty (BEPU) framework, the use of best-estimate code requires to go through a Verification, Validation and Uncertainty Quantification process (VVUQ). The relevance of the experimental data in relation to the physical phenomena of interest in the VVUQ process is crucial. Adequacy analysis of selected experimental databases addresses this problem. The outcomes of the analysis can be used to select a subset of relevant experimental data, to encourage designing new experiments or to drop some experiments from a database because of their substantial lack of adequacy. The development of a specific transparent and reproducible approach to analyze the relevance of experimental data for VVUQ still remains open and is the topic of this contribution. In this paper, the concept of adequacy initially introduced in the OECD/NEA SAPIUM (Systematic APproach for model Input Uncertainty quantification Methodology) activity is formalized. It is defined through two key properties, called representativeness and completeness, that allows considering the multifactorial dimension of the adequacy problem. A new systematic approach is then proposed to analyze the adequacy of a set of experimental databases. It relies on the introduction of two sets of criteria to characterize representativeness and completeness and on the use of multi-criteria decision analysis method to perform the analysis. Finally, the approach is applied in the framework of the new OECD/NEA ATRIUM activity which includes a set of practical IUQ exercises in thermal-hydraulics to test the SAPIUM guideline in determining input uncertainties and forward propagating them on an application case. It allows evaluating the adequacy of eight experimental databases coming from the Super Moby-dick, Sozzi-Sutherland and Marviken experiments and identifying the most adequate ones.
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。
緒方 一介*; 吉田 数貴; 茶園 亮樹*
Computer Physics Communications, 297, p.109058_1 - 109058_16, 2024/04
被引用回数：0PIKOEは陽子による核子ノックアウト反応の三重微分断面積、四重微分断面積、ベクトル偏極分解能および残留核の運動量分布を計算するFortran 90の数値計算コードである。歪曲波インパルス近似を用い、歪曲波は量子力学に基づいて計算される。散乱粒子の運動学は相対論的に扱われ、その漸近状態は3体系の平面波極限と一致する。
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。
伊藤 孝; 門野 良典*
Journal of the Physical Society of Japan, 93(4), p.044602_1 - 044602_7, 2024/04
We propose a model to describe the fluctuations in the internal magnetic field due to ion dynamics observed in muon spin relaxation (SR) by an Edwards-Anderson-type autocorrelation function that separates the quasi-static and dynamic components of the correlation by the parameter 
(where 
). Our Monte Carlo simulations for this model showed that the time evolution of muon spin polarization deviates significantly from the Kubo-Toyabe function. To further validate the model, the results of simulations were compared with the SR spectra observed in a hybrid organic-inorganic perovskite FAPbI [with FA referring to HC(NH
)], where local field fluctuations associated with the rotational motion of FA molecules and quasi-static fields from the PbI lattice are presumed to coexist. The least-squares curve fitting showed reasonable agreement with the model with 
, and the fluctuation frequency of the dynamical component was obtained. This result opens the door to the possibility of experimentally distinguishing fluctuations due to the dynamics of ions around muons from those due to the self-diffusion of muons. On the other hand, it suggests the need to carefully consider the spin relaxation function when applying SR to the issue of ion dynamics.
竹内 徹也*; 本多 史憲*; 青木 大*; 芳賀 芳範; 木田 孝則*; 鳴海 康雄*; 萩原 政幸*; 金道 浩一*; 軽部 皓介*; 播磨 尚朝*; et al.
Journal of the Physical Society of Japan, 93(4), p.044708_1 - 044708_10, 2024/04
Electrical and magnetic properties of divalent europium antiferromagnet EuTe are studied on single crystals grown from Te-flux method. Antiferromagnetism occurs at 11 K with an insulating ground state. Application of magnetic field induces a sudden resistance drop leading to a phase transition to metallic state. Energy band calculations reveal the appearance of a Fermi surface pocket with Te-5p character induced by the polarized Eu moments.
廣瀬 意育; 安部 諭; 石垣 将宏*; 柴本 泰照; 日引 俊*
Progress in Nuclear Energy, 169, p.105085_1 - 105085_13, 2024/04
被引用回数：0Immersed boundary methods (IBMs) have been developed as complementary methods for computational fluid dynamics (CFD). They allow a flow simulation in a mock-up model that includes complex-shaped inner structures and/or boundaries with a non-body conformal mesh. Such a model might force us to create a complicated body-fitted mesh with a high cost in the conventional CFD (CCFD) approach. We focus on the Brinkman penalization (BP) method and its extended version, which we call here the extended Brinkman penalization method (EBP), among the different types of IBMs, aiming to apply them to the phenomena that occur during severe accidents in a nuclear reactor containment vessel and explore the possibility that the methods can partially replace the CCFD. In this paper, as a preliminary step to validate the applicability of these methods, we measure the jet flow rectified by a grating-type structure used for the validation of numerical techniques and apply them to simulate the behavior of an upward jet rectified by a horizontally placed grating-type structure modeled as an immersed body. This type of structure is generally used in reactor buildings, and it is crucial to evaluate their influence on gaseous flows because the behaviors of hydrogen produced during severe accidents may be influenced by them. The structure is selected as our subject because it has moderate complexity, enabling us to examine the effects of the IBMs and compare them with CCFD. We investigate whether these methods can reproduce a result of corresponding CCFD in which the grating is modeled as body-conformal mesh and show that the former can produce the latter with equivalent accuracy. All these results are also compared with the experimental data on the flow velocity distributions downstream of the grating measured using particle image velocimetry.
