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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。
CoSi山内 宏樹; Sari, D. P.*; 安井 幸夫*; 坂倉 輝俊*; 木村 宏之*; 中尾 朗子*; 大原 高志; 本田 孝志*; 樹神 克明; 井川 直樹; et al.
Physical Review Research (Internet), 6(1), p.013144_1 - 013144_9, 2024/02
-Mn-type family alloys Mn
have three-dimensional antiferromagnetic (AFM) corner-shared triangular network. The antiferromagnet MnRhSi shows magnetic short-range order (SRO) over a wide temperature range of approximately 500 K above the N
el temperature 
= 190 K. MnCoSi has the smallest lattice parameter and the lowest in the family compounds. The quantum critical point (QCP) from AFM to the quantum paramagnetic state is expected near a cubic lattice parameter of 6.15 
of MnCoSi is only 140 K, quantum critical behavior is observed in MnCoSi as the enhancement of the electronic specific heat coefficient 
. We study how the magnetic SRO appears in MnCoSi by using neutron scattering, 
SR, and physical property measurements. The experimental results show that the neutron scattering intensity of the magnetic SRO does not change much regardless of the suppressed magnetic moment in the long-range magnetic ordered state compared to those of MnRhSi. The initial asymmetry drop ratio of SR above becomes small, and the magnetic SRO temperature 
is suppressed to 240 K. The results suggest that the MnCoSi is close to the QCP in the Mn system.
Li, C.-Y.; Wang, K.*; 内堀 昭寛; 岡野 靖; Pellegrini, M.*; Erkan, N.*; 高田 孝*; 岡本 孝司*
Applied Sciences (Internet), 13(13), p.7705_1 - 7705_29, 2023/07
被引用回数：1 パーセンタイル：0(Chemistry, Multidisciplinary)For a sodium-cooled fast reactor, the capability for stable cooling and avoiding re-criticality on the debris bed is essential for achieving in-vessel retention when severe accidents occur. However, an unexploited uncertainty still existed regarding the compound effect of the heterogeneous configuration and dynamic particle redistribution for the debris bed's criticality and cooling safety assessment. Therefore, this research aims to develop a numerical tool for investigating the effects of the different transformations of the heterogeneous configurations on the debris bed's criticality/cooling assessment. Based on the newly proposed methodology in this research, via integrating the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD) and Monte-Carlo-based Neutronics (MCN), the coupled CFD-DEM-MCN solver was constructed with the originally created interface to integrate two existing codes. The effects of the different bed configurations' transformations on the bed safety assessments were also quantitively confirmed, indicating that the effect of the particle-centralized fissile material had the dominant negative effect on the safety margin of avoiding re-criticality and particle re-melting accidents and had a more evident impact than the net bed-centralized effect. This coupled solver can serve to further assess the debris bed's safety via a multi-physics simulation approach, leading to safer SFR design concepts.
Hong, Z.*; Pellegrini, M.*; Erkan, N.*; Liao, H.*; Yang, H.*; 山野 秀将; 岡本 孝司*
Annals of Nuclear Energy, 180, p.109462_1 - 109462_9, 2023/01
被引用回数：0 パーセンタイル：0.01(Nuclear Science & Technology)実機制御棒の模擬材として、BC材とSUS304を用いて一連の実験を実施した。1450K-1500Kの温度範囲で共晶反応速度定数を得た結果、本研究で得られた反応速度定数は参照値と一致した。また、反応面の微細構造を観察し、組成分析を行った。
and 
shell gap for Ti and V by the first high-precision multireflection time-of-flight mass measurements at BigRIPS-SLOWRI飯村 俊*; Rosenbusch, M.*; 高峰 愛子*; 角田 佑介*; 和田 道治*; Chen, S.*; Hou, D. S.*; Xian, W.*; 石山 博恒*; Yan, S.*; et al.
Physical Review Letters, 130(1), p.012501_1 - 012501_6, 2023/01
被引用回数：5 パーセンタイル：94.66(Physics, Multidisciplinary)The atomic masses of 
Sc, 
Ti, and 
V have been determined using the high-precision multireflection time-of-flight technique. The radioisotopes have been produced at RIKEN's Radioactive Isotope Beam Factory (RIBF) and delivered to the novel designed gas cell and multireflection system, which has been recently commissioned downstream of the ZeroDegree spectrometer following the BigRIPS separator. For Ti and V, the mass uncertainties have been reduced down to the order of 10 keV, shedding new light on the shell effect in Ti and V isotopes by the first high-precision mass measurements of the critical species 
Ti and 
V. With the new precision achieved, we reveal the nonexistence of the empirical two-neutron shell gaps for Ti and V, and the enhanced energy gap above the occupied 
p
orbit is identified as a feature unique to Ca. We perform new Monte Carlo shell model calculations including the d
and g
orbits and compare the results with conventional shell model calculations, which exclude the g and the d orbits. The comparison indicates that the shell gap reduction in Ti is related to a partial occupation of the higher orbitals for the outer two valence neutrons at 
.
山野 秀将; 高井 俊秀; 江村 優軌; 福山 博之*; 東 英生*; 西 剛史*; 太田 弘道*; 守田 幸路*; 中村 勤也*; 深井 尋史*; et al.
Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 12 Pages, 2022/09
本発表はプロジェクト全体概要及び2020年度までの進捗概要について報告する。この論文における具体的成果は、共晶反応速度の測定並びに、SS坩堝の中にBCペレットを置いたBC-SS共晶反応速度実験の数値解析を通じて、解析コード内の共晶反応を記述する物理モデルの妥当性を確認したことである。
Do, S.-H.*; Paddison, J. A. M.*; Sala, G.*; Williams, T. J.*; 金子 耕士; 桑原 慶太郎*; May, A. F.*; Yan, J.*; McGuire, M. A.*; Stone, M. B.*; et al.
Physical Review B, 106(6), p.L060408_1 - L060408_6, 2022/08
被引用回数：10 パーセンタイル：83.82(Materials Science, Multidisciplinary)For topological magnon spectra, determining and explaining the presence or absence of a gap at a magnon crossing point is a central issue. An inelastic neutron scattering study of a single crystals is a powerful experimental technique to investigate the spin dynamics and hence is widely employed to probe the magnetic excitation spectra of topological materials. However, when the neutron intensity rapidly disperses, such as near a crossing point for a Dirac magnon, the apparent spectrum is extremely sensitive to experimental conditions including sample mosaic, resolution, and integration range. Here we study a gapless Dirac magnon candidate CrCl
to show how the quantification of a gapless or gaped spectrum at the Dirac point is extremely sensitive to the integration range of data. Our work calls for a careful examination of reports of gaps in inelastic neutron scattering spectra to ensure that topological gaps are not misdiagnosed or overestimated due to experimental factors.
高木 里奈*; 松山 直文*; Ukleev, V.*; Yu, L.*; White, J. S.*; Francoual, S.*; Mardegan, J. R. L.*; 速水 賢*; 齋藤 開*; 金子 耕士; et al.
Nature Communications (Internet), 13, p.1472_1 - 1472_7, 2022/03
被引用回数：55 パーセンタイル：99.61(Multidisciplinary Sciences)Magnetic skyrmions are topologically stable swirling spin textures with particle-like character, and have been intensively studied as a candidate of high-density information bit. While magnetic skyrmions were originally discovered in noncentrosymmetric systems, recently a nanometric skyrmion lattice has also been reported for centrosymmetric rare-earth compounds. For the latter systems, a novel skyrmion formation mechanism mediated by itinerant electrons has been proposed, and the search of a simpler model system allowing for a better understanding of their intricate magnetic phase diagram is highly demanded. Here, we report the discovery of square and rhombic lattices of nanometric skyrmions in a centrosymmetric binary compound EuAl
, by performing small-angle neutron and resonant elastic X-ray scattering experiments. Unlike previously reported centrosymmetric skyrmion-hosting materials, EuAl shows multiple-step reorientation of the fundamental magnetic modulation vector as a function of magnetic field, probably reflecting a delicate balance of associated itinerant-electron-mediated interactions. The present results demonstrate that a variety of distinctive skyrmion orders can be derived even in a simple centrosymmetric binary compound, which highlights rare-earth intermetallic systems as a promising platform to realize/control the competition of multiple topological magnetic phases in a single material.
小山 真一; 中桐 俊男; 逢坂 正彦; 吉田 啓之; 倉田 正輝; 池内 宏知; 前田 宏治; 佐々木 新治; 大西 貴士; 高野 公秀; et al.
廃炉・汚染水対策事業事務局ホームページ(インターネット), 144 Pages, 2021/08
令和2年度に原子力機構が補助事業者となって実施した「廃炉・汚染水対策事業費補助金(燃料デブリの性状把握のための分析・推定技術の開発(燃料デブリの分析精度の向上及び熱挙動の推定のための技術開発))」の成果概要を、最終報告として取りまとめた。本報告資料は、廃炉・汚染水対策事業事務局ウェブサイトにて公開される。
Li, C.-Y.; 内堀 昭寛; 高田 孝; Pellegrini, M.*; Erkan, N.*; 岡本 孝司*
第25回動力・エネルギー技術シンポジウム講演論文集(インターネット), 4 Pages, 2021/07
溶融炉心の原子炉容器内保持を達成するためには、デブリベッドの安定冷却と再臨界回避が重要である。本研究では、異なる物質から構成され、密度成層化したデブリベッドの挙動を評価するため、数値流体力学(CFD),個別要素法(DEM),モンテカルロ法を連成させた解析手法を構築した。本解析手法により、デブリベッドにおける密度成層化の挙動等を解析できることを確認した。
WB-STEM observation of dislocation loop behavior in reactor pressure vessel steel during post-irradiation annealingDu, Y.*; 吉田 健太*; 嶋田 雄介*; 外山 健*; 井上 耕治*; 荒河 一渡*; 鈴土 知明; Milan, K. J.*; Gerard, R.*; 大貫 惣明*; et al.
Materialia, 12, p.100778_1 - 100778_10, 2020/08
長期に原子炉圧力容器の健全性を確保するためには、照射が材料に及ぼす影響を理解する必要がある。本研究では我々が新規開発したWB-STEMを用いて、中性子照射された原子炉圧力容器試験片を焼鈍中、照射誘起転位ループの観察を行った。焼鈍温度を上げると
ループの割合が増加していることが確認された。また、2つの
ループが衝突してループになる現象の観察に初めて成功した。転位に転位ループがデコレートする現象も観察され、分子動力学シミュレーションによってそのメカニズムが説明することができた。
Bh in the 
Cm(
Na,5
)Bh reaction and its decay properties羽場 宏光*; Fan, F.*; 加治 大哉*; 笠松 良崇*; 菊永 英寿*; 小森 有希子*; 近藤 成美*; 工藤 久昭*; 森本 幸司*; 森田 浩介*; et al.
Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08
被引用回数：6 パーセンタイル：59.56(Physics, Nuclear)The nuclide Bh was produced in the Cm(Na,5n)Bh reaction at beam energies of 125.9, 130.6, and 135.3 MeV. Decay properties of Bh were investigated with a rotating wheel apparatus for 
and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. The half-life of Bh was measured to be 
= 10.0
s. The -particle energies of Bh disperse widely in the range of 8.62 - 9.40 MeV. The maximum production cross section for the Cm(Na,5n)Bh reaction was determined to be 
= 57 
14 pb at 130.6 MeV.
Rizaal, M.; 斉藤 拓巳*; 岡本 孝司*; Erkan, N.*; 中島 邦久; 逢坂 正彦
Mechanical Engineering Journal (Internet), 7(3), p.19-00563_1 - 19-00563_10, 2020/06
福島第一原子力発電所2号機において、一次冷却系の断熱材に使用されているケイ酸カルシウムへのセシウム(Cs)の吸着がペデスタル領域の高線量に影響している可能性が指摘されている。本研究では、高温でのCs吸着挙動評価の前段階として、室温でCsをケイ酸カルシウムに吸着させる試験を行った。吸着速度の解析の結果、基本的な吸着機構は化学吸着であることが示唆された。また、等温における吸着量のCs濃度依存性の評価により、単分子層の形成の後に多分子層が形成することが示唆された。
Zhan, Y.*; 桑田 裕介*; 丸山 清嵩*; 大川 富雄*; 榎木 光治*; 青柳 光裕; 高田 孝
Experimental Thermal and Fluid Science, 112, p.109953_1 - 109953_8, 2020/04
被引用回数：13 パーセンタイル：73.8(Thermodynamics)The breakup process of liquid jet was explored through visualization to develop a prediction model for liquid splash. Water, ethanol aqueous solution, and glycerin aqueous solution were used as the test liquids to explore the effects of surface tension and viscosity. Since the droplets were produced due to jet breakup, the impact frequency was zero just downstream of the nozzle and increased asymptotically with an increase in the distance from the nozzle. Thus, auxiliary correlations were developed for the minimum breakup length where the jet breakup is initiated, the maximum breakup length where the jet breakup is completed, the mean droplet size and the impact frequency. It was demonstrated that the impact frequencies calculated by the proposed model agree with the experimental data fairly well. For the application to coolant leakage in sodium-cooled fast reactors, a simple method to ensure conservative estimation of the impact frequency was also proposed.
田中 泰貴*; 森田 浩介*; 森本 幸司*; 加治 大哉*; 羽場 宏光*; Boll, R. A.*; Brewer, N. T.*; Van Cleve, S.*; Dean, D. J.*; 石澤 倫*; et al.
Physical Review Letters, 124(5), p.052502_1 - 052502_6, 2020/02
被引用回数：19 パーセンタイル：81.08(Physics, Multidisciplinary)The excitation functions for quasielastic scattering of 
Ne+Cm, 
Mg+Cm, 
Ca+
U are measured using a gas-filled recoil ion separator The quasielastic barrier distributions are extracted for these systems and are compared with coupled-channel calculations. The results indicate that the barrier distribution is affected dominantly by deformation of the actinide target nuclei, but also by vibrational or rotational excitations of the projectile nuclei, as well as neutron transfer processes before capture. From a comparison between the experimental barrier distributions and the evaporation residue cross sections for Sg (Z=106), Hs (108), Cn (112), and Lv (116), it is suggested that the hot fusion reactions take advantage of a compact collision, where the projectile approaches along the short axis of a prolately deformed nucleus. A new method is proposed to estimate the optimum incident energy to synthesize unknown superheavy nuclei using the barrier distribution.
PtTsekhanovich, I.*; Andreyev, A. N.; 西尾 勝久; Denis-Petit, D.*; 廣瀬 健太郎; 牧井 宏之; Matheson, Z.*; 森本 幸司*; 森田 浩介*; Nazarewicz, W.*; et al.
Physics Letters B, 790, p.583 - 588, 2019/03
被引用回数：32 パーセンタイル：94.9(Astronomy & Astrophysics)Fragment mass distributions from fission of the excited compound nucleus Pt have been deduced from the measured fragment velocities. The Pt nucleus was created at the JAEA tandem facility in a complete fusion reaction 
Ar+
Nd, at beam energies of 155, 170 and 180 MeV. The data are indicative of a mixture of the mass-asymmetric and mass-symmetric fission modes associated with higher and lower total kinetic energies of the fragments, respectively. The measured fragment yields are dominated by asymmetric mass splits, with the symmetric mode contributing at the level of 
1/3. This constitutes the first observation of a multimodal fission in the sub-lead region. Most probable experimental fragment-mass split of the asymmetric mode, 
/
79/99, is well reproduced by nuclear density functional theory using the UNEDF1-HFB and D1S potentials. The symmetric mode is associated by theory with very elongated fission fragments, which is consistent with the observed total kinetic energy/fragment mass correlation.
Zhan, Y.*; 大箭 直輝*; 榎木 光治*; 大川 富雄*; 青柳 光裕; 高田 孝
Experimental Thermal and Fluid Science, 98, p.86 - 94, 2018/11
被引用回数：15 パーセンタイル：67.77(Thermodynamics)In sodium-cooled fast reactors, liquid sodium leakage may lead to fire accident. In the case that the liquid sodium is discharged as a liquid jet, a number of droplets are produced during liquid jet impingement on the structures. In the present work, a liquid jet was emanated vertically downward from a circular nozzle hole onto a horizontal disk to measure the total amount and the maximum size of splashed droplets. It was found that a significant amount of liquid was splashed when the liquid jet impinged as a broken jet. Thus, a prediction method was first developed for the impact frequency of the primary droplets produced due to the jet breakup. It was then shown that a phenomenological model using the impact frequency and the impact Weber number as the important variables can predict the splashing rate well. It was also indicated that the size of the maximum splashed droplets was fairly proportional to the size of primary droplets.
Phan, L. H. S.*; 大原 陽平*; 河田 凌*; Liu, X.*; Liu, W.*; 守田 幸路*; Guo, L.*; 神山 健司; 田上 浩孝
Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 12 Pages, 2018/10
燃料デブリベッドの自己平坦化挙動は、ナトリウム冷却高速炉(SFR)での炉心崩壊事故(CDA)の安全評価における主要現象の1つである。SIMMERコードはSFRのCDA解析のために開発され、安全評価のみならずCDA時の主要な伝熱流動現象の数値解析に適切に適用されてきた。しかしながら、SIMMERの流体モデルは、個々の粒子特性のみならず、粒子間の強い相互作用を表現することは困難である。この問題を解決するため、SIMMERの多流体モデルと粒子に対する個別要素法(DEM)とを結合させた新しい手法を開発し、多相流における流体と粒子との相互作用および粒子挙動を適切に評価することを試みてきた。本研究では、DEMと結合したSIMMERコードの多流体モデルを検証するため、円筒状の粒子ベッドにガスを吹き込んだ自己平坦化試験シリーズの数値シミュレーションを行った。さらに検証を進める必要があるが、シミュレーション結果と試験結果とは適切に一致し、デブリベッドの自己平坦化を評価する手法としての潜在的な可能性を示した。DEMと結合したSIMMERコードは、SFRで粒子ベッドに関する安全評価のための次世代の計算手法として期待される。
桑田 裕介*; Zhan, Y.*; 榎木 光治*; 大川 富雄*; 青柳 光裕; 高田 孝
Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 10 Pages, 2018/10
ナトリウム冷却高速炉の冷却材が漏洩した場合の熱影響解析精度向上に向けて、ノズルより鉛直下向きに液体を噴射し、水平固体面に衝突した場合の粘度を考慮した飛散液滴量相関式について検討した。
Shamsuzzaman, M.*; 堀江 達郎*; 浮池 亮太*; 神山 基紀*; 森岡 徹*; 松元 達也*; 守田 幸路*; 田上 浩孝; 鈴木 徹*; 飛田 吉春
Annals of Nuclear Energy, 111, p.474 - 486, 2018/01
被引用回数：17 パーセンタイル：85.18(Nuclear Science & Technology)Particle bed characteristics are experimentally investigated for the sedimentation and subsequent bed formation of solid particles, related to the coolability aspects in core-disruptive accidents. Presently a series of experiments with gravity driven discharge of solid particles into a quiescent water pool was performed to evaluate bed formation characteristic in the course of particle sedimentation. We evaluated the effects of the crucial factors: nozzle diameter, particle density, particle diameter and nozzle height on four key quantitative parameters of bed shape: mound dimple area, mound dimple volume, repose angle and mound height to illustrate the role of the crucial factors on forming the particle bed shape. The investigated crucial factors exhibit a significant role that diversifies the particle bed formation process. Based on the data obtained in the experimental observations, we developed an empirical correlation to compare the predicted results with the experimental bed heights. The proposed empirical correlation can reasonably demonstrate the general trend of the experimental bed height. This correlation could be useful to assess the particle bed elevation, and to identify the governing parameters.
