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Nguyen, 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.
Vauchy, R.; 廣岡 瞬; 村上 龍敏
Materialia, 32, p.101934_1 - 101934_12, 2023/12
The construction of the fluorite unit-cell from the ionic radii of the constitutive species is proposed with the use of our hybrid model, considering flexible anion and cation radii. 27 binary and stoichiometric compounds crystallizing in this structure were investigated to find a correlation between the anion's radius as a function of the cation's size.
Vauchy, R.; 廣岡 瞬; 村上 龍敏
Materialia, 32, p.101943_1 - 101943_8, 2023/12
The construction of the halite unit-cell from the ionic radii of the constitutive species is proposed with the use of our hybrid model, considering flexible anion and cation radii. 312 binary halite-structured stoichiometric compounds were analyzed. This systematic study focuses first on the revision of the ionic radii of the considered species then on the proposition of relations between the anionic radius as a function of the cation's size.
廣岡 瞬; 堀井 雄太; 砂押 剛雄*; 宇野 弘樹*; 山田 忠久*; Vauchy, R.; 林崎 康平; 中道 晋哉; 村上 龍敏; 加藤 正人
Journal of Nuclear Science and Technology, 60(11), p.1313 - 1323, 2023/11
被引用回数:3 パーセンタイル:95.99(Nuclear Science & Technology)収率が高く燃料に固溶するFP(模擬FP)としてNdO及びSmOを添加したMOXの焼結試験を行い、焼結後の微細組織を評価した。熱膨張計を用いて取得した焼結中の収縮曲線から、模擬FP含有MOXは通常のMOXよりも高温で焼結が進むことが分かった。焼結後の密度評価及び金相組織の観察から、模擬FP含有MOXは通常のMOXよりも粒成長と高密度化が進むことが分かった。これは、添加元素の影響を受けて一部のUが4価から5価に変化し、拡散速度が大きくなったことが原因と考えられる。また、XRDの結果から焼結後の試料は均質に固溶した結晶構造が示されたが、EPMAによる元素マッピングの結果からは模擬FPの濃度が一様でなく、完全には均質に分布していない微細組織が示された。不均質に分布したNdO含有MOXを微粉砕し、再焼結を行う過程を繰り返すことで、均質性が向上し、密度も十分に高い模擬FP含有MOXペレットを作製することができた。
沖田 将一朗; 後藤 実
Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 10 Pages, 2023/10
The recently released JENDL-5 and ENDF/B-VIII.0 have adopted porosity-dependent thermal neutron scattering law (TSL) data for reactor graphite, and they improve neutronic calculation accuracy of criticality for graphite-moderated cores. Currently, we can only handle neutronic calculations for three graphite porosities of 0%, 10%, and 30%. The uncertainties associated with the difference between the porosity of actual reactor graphite (20%) and the porosity remains. Toward the future update of JENDL-5, we are planning to preparing new TSL data of reactor graphite. As a first step, it is essential to evalute phonon density state distribution of reactor graphite. In this study, in order to evalute it, molecular dynamic (MD) analysis is performed for three MD models: ideal crystalline graphite (Ideal model), 20%-porous reactor graphite with monoatomic random pore (Monoatomic random model), and 20%-porous reactor graphite with atomic cluster random pore (Cluster random model). The ideal crystalline graphite is modeled without any pores for reference. The 20%-porous reactor graphite with monoatomic random pore is modeled by randomly removing atoms from the ideal crystalline graphite. The 20%-porous reactor graphite with cluster random pore is modeled by randomly removing atomic clusters of approximately 2 nm in diameter from the ideal crystalline graphite. Their interatomic interactions are on the basis of Reactive Empirical Bond Order (REBO) potential. Velocity autocorrelation functions and phonon density of states distributions are calculated for these models. For validation, specific heat for each model is evaluated, and they are compred with experimental values.
鈴木 誠也; 根本 善弘*; 椎木 菜摘*; 中山 佳子*; 竹口 雅樹*
Annalen der Physik, 535(9), p.2300122_1 - 2300122_12, 2023/09
被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)Germanene is a two-dimensional (2D) germanium (Ge) analogous of graphene, and its unique topological properties are expected to be a material for next-generation electronics. However, no germanene electronic devices have yet been reported. One of the reasons for this is that germanene is easily oxidized in air due to its lack of chemical stability. Therefore, growing germanene at solid interfaces where it is not oxidized is one of the key ideas for realizing electronic devices based on germanene. In this study, the behavior of Ge at the solid interface at high temperatures was observed by transmission electron microscopy (TEM). To achieve such in situ heating TEM observation, we fabricated a graphene/Ge/graphene encapsulated structure. In situ heating TEM experiments revealed that Ge like droplets moved and coalesced with other Ge droplets, indicating that Ge remained as a liquid phase between graphene layers at temperatures higher than the Ge melting point.
沖田 将一朗; 深谷 裕司; 左近 敦士*; 佐野 忠史*; 高橋 佳之*; 宇根崎 博信*
Nuclear Science and Engineering, 197(8), p.2251 - 2257, 2023/08
被引用回数:0 パーセンタイル:0.01(Nuclear Science & Technology)In this paper, integral experiments on a graphite-moderated core were conducted at the B-rack of the Kyoto University Criticality Assembly in order to develop an integral experiment database for the applicability of data assimilation techniques to the neutronic design of a high-temperature gas-cooled reactor. The calculation/experiment-1 (C/E-1)values for the values at critical cores with the major nuclear data libraries, such as JENDL-4.0, JENDL-5, JEFF-3.2, ENDF/B-VII.1, and ENDF/B-VIII.0, were calculated for the core. Of these, the values with JENDL-5 with thermal neutron scattering law data for 30% porous graphite showed the best agreement with experimental values within 0.02% accuracy.
Tsai, T.-H.; 佐々木 新治; 前田 宏治
Journal of Nuclear Science and Technology, 60(6), p.715 - 723, 2023/06
被引用回数:1 パーセンタイル:31.61(Nuclear Science & Technology)A method for processing and visualizing X-ray computed tomography (CT) images of a fuel assembly is developed and applied to a JOYO MK-III fuel assembly. The method provides vertical-section-like images to observe the spatial distribution of CT values in fuel pins and also supplies images that show the relationship between the linear heat rate (LHR) and radial CT-value distribution. In addition, an attempt to analyze the radial cracks in the CT images is proposed, and the results demonstrate the correlation between LHR and the radial cracks.
吉田 幸彦
IL Nuovo Cimento, 46(2), p.33_1 - 33_8, 2023/03
JAEA is addressing the back-end issues with the steadfast promotion of sustainable measures. The R&D plans are being rationally pursued by considering priorities based on indicators such as bottleneck issues in waste streams, relevance to WAC settings, and effectiveness of cost reduction. In addition, the future vision (JAEA 2050+) has been formulated to promote cross-disciplinary R&D through a new approach that cannot be reached by conventional methods, and active incorporation of information technologies, such as AI technologies. Currently, we are developing intelligent sensing that combines sensing and information processing technologies to realize automatic sorting technology, and non-destructive evaluation technology using high-energy X-ray CT, for legacy wastes. The core technology common to these technologies is image evaluation technology using deep learning models, which was confirmed to perform very well in the evaluation of waste object recognition.
植田 祥平; 今井 良行; 渡部 雅; 瀬川 智臣; Yan, X.
International Journal of Applied Ceramic Technology, 20(1), p.261 - 265, 2023/01
被引用回数:2 パーセンタイル:29.05(Materials Science, Ceramics)Ceramic stereolithography (CSL)-additive manufacturing (AM) technology is used to create a functionally graded ceramic (FGC) green body made of silicon carbide (SiC) and graphite. For the SiC/graphite FGC, the mixing parameters of ceramics powders and ultraviolet (UV) curing resin are improved, and correlations of the resultant slurry curing depth with integrated light intensity are discovered. Therefore, the SiC/graphite FGC-produced green body has no flaws, pores, or cracks on its surfaces. According to the association between cure depth and integrated light density for each slurry's composition, several interfacial collapses discovered in a cracked cross-section might be decreased.
勅使河原 誠; 池田 裕二郎*; Yan, M.*; 村松 一生*; 須谷 康一*; 福住 正文*; 能田 洋平*; 小泉 智*; 猿田 晃一; 大竹 淑恵*
Nanomaterials (Internet), 13(1), p.76_1 - 76_9, 2023/01
被引用回数:2 パーセンタイル:54.89(Chemistry, Multidisciplinary)冷中性子以下の中性子強度を高めるため、ナノサイズグラフェンの集合体が、ナノダイヤモンドと同様に中性子のコヒーレント散乱を促進できることを提案した。さらには、グラフェンの強いsp2結合は、高い耐放射線性を有する可能性を秘める。理研の加速器駆動型小型中性子源やJ-PARCのiMATERIAを用いて、ナノサイズグラフェンの中性子全断面積測定,中性子小角散乱測定を行った。測定結果より、ナノサイズのグラフェン集合体は、コヒーレント散乱に起因すると考えられる冷中性子エネルギー領域での全断面積と小角散乱を増大させ、ナノダイヤモンドと同様に高い中性子強度をもたらすことを世界で初めて明らかにした。
Idham, M. F.*; Falyouna, O.*; Eljamal, R.*; Maamoun, I.; Eljamal, O.*
Journal of Water Process Engineering (Internet), 50, p.103289_1 - 103289_16, 2022/12
被引用回数:13 パーセンタイル:92.56(Engineering, Environmental)Due to synthesis variation affecting various graphene oxide (GO) physicochemical parameters and cost efficiency aspects, the present study investigated the influence of GO precursor components for GO precipitated nZVI nanocomposite (nZVI/GO) and optimized removal conditions to remove chloramphenicol (CAP) from water. In order to synthesize nZVI/GO nanocomposites, four methods of GO precursor synthesis were used, denoted GO1, GO2, GO3, and GO4. A novel synthesis process is introduced based on economic and time-less-consuming protocols to produce GO precursor. A series of desorption experiments were also implemented in various eluents to clarify the CAP removal mechanism. Interestingly, this study demonstrated the substantial impact of GO precursor on the nanocomposite performance in eliminating CAP. The introduced novel GO successfully served as an excellent nZVI precipitation medium and enhanced CAP removal efficiency. Empirical optimization demonstrated that nZVI/GO4-1:1 could eliminate up to 91% of 100 mg/L CAP by dosage as low as 0.25 g/L at pH 5. nZVI/GO4 displayed CAP removal stability throughout a more comprehensive pH range, and remarkable recyclability, making it more promising and practical than bare nZVI and other analyzed nanocomposites. Kinetics data demonstrated a high degree of compatibility with the pseudo-first-order (PFO) and pseudo-second-order (PSO). Through kinetics and statistical analyses, desorption experiments, FTIR spectroscopy, and EDX analysis, nZVI/GO4 removed some of the CAP through the adsorption mechanism controlled by physisorption and chemisorption. In contrast, the oxidation mechanism eliminated the remaining CAP.
Simanullang, I. L.*; 中川 直樹*; Ho, H. Q.; 長住 達; 石塚 悦男; 飯垣 和彦; 藤本 望*
Annals of Nuclear Energy, 177, p.109314_1 - 109314_8, 2022/11
被引用回数:0 パーセンタイル:0.01(Nuclear Science & Technology)Power distribution plays a significant role in preventing the fuel temperature exceeds the safety limit of 1600C in high-temperature gas-cooled reactors. The experiment to measure the power distribution in the graphite-moderated system was carried out with the Very High Temperature Reactor Critical Assembly facility. In the previous study, the power distribution in the VHTRC was calculated using a nuclear design code system based on diffusion calculation. The results showed a maximum discrepancy of up to 20 between the experiment and calculated values in the axial direction. The large discrepancy occurred near the boundary of fuel and reflector regions. This study describes the evaluation results of pin-wise power distribution of the VHTRC with the Monte Carlo MVP3 code. The calculation results were in good agreement with the measured results. In the axial direction, the discrepancy was less than 1 around the boundary of fuel and reflector regions.
中村 詔司; 芝原 雄司*; 遠藤 駿典; 木村 敦
Journal of Nuclear Science and Technology, 59(11), p.1388 - 1398, 2022/11
被引用回数:0 パーセンタイル:0.01(Nuclear Science & Technology)本研究は、放射性核種のNpを取り上げて、よく熱化された中性子場を用いて放射化法によりNpの熱中性子捕獲断面積を測定した。Npの標準溶液を、照射試料に用いた。照射位置の中性子束は、Sc, Co, Mo, TaそしてAuを、中性子束モニタに使用した。Np試料とモニタを一緒に、京都大学研究炉の黒鉛照射設備にて30分間照射した。同様の照射を2回繰り返した。照射後に、Np試料を、それと放射平衡の関係にあるPaからの312keVガンマ線を測定して定量した。Npの反応率を、生成されたNpから放出されるガンマ線の収量から求めた。Npの熱中性子捕獲断面積は、2回照射の結果の加重平均を取って173.84.4barnと導出された。この結果は、飛行時間法により測定されたデータと、誤差の範囲で一致した。
西山 成哲; 後藤 翠*; 塚原 柚子; 川村 淳; 梅田 浩司*; 丹羽 正和
JAEA-Testing 2022-003, 51 Pages, 2022/09
高レベル放射性廃棄物の地層処分における地質環境の長期安定性に係る評価のうち、火山・火成活動に関する技術的課題の一つとして、マグマ活動範囲の評価技術の高度化は必要不可欠である。そのための有効な手法として、火山体の地形解析による岩脈の分布範囲の把握が期待される。近年では、手作業では作業量が膨大で困難であった作業が、コンピュータによる地形解析技術の発達により、多くの作業量を簡易的に行えるようになった。本報告では、GISソフトウェアを用いた火山体を形作る等高線の形状解析手法について記述する。
Yakushev, A.*; Lens, L.*; Dllmann, Ch. E.*; Khuyagbaatar, J.*; Jger, E.*; Krier, J.*; Runke, J.*; Albers, H. M.*; 浅井 雅人; Block, M.*; et al.
Frontiers in Chemistry (Internet), 10, p.976635_1 - 976635_11, 2022/08
被引用回数:11 パーセンタイル:79.28(Chemistry, Multidisciplinary)114番元素フレロビウム(Fl)は現在その化学的性質が研究されている最も重い元素である。Flに関する最初の化学実験では、Flは貴ガス的な性質を持つ元素であると報告された。一方、2番目の研究では、Flは揮発性金属の性質を示すと報告された。より信頼性の高い結論を得るため、我々は更なる実験的研究を行い、二酸化ケイ素と金表面におけるFlの吸着挙動を調べた。その結果、Flは揮発性金属の水銀よりも高い揮発性と低い反応性を示し、一方、貴ガスのラドンよりは反応性が高いことを明らかにした。
中村 詔司; 遠藤 駿典; 木村 敦; 芝原 雄司*
KURNS Progress Report 2021, P. 93, 2022/07
核廃棄物中のマイナーアクチニドの核変換の観点から、本研究はNpを選定して、その熱中性子捕獲断面積を、良く熱化された中性子場を用いて放射化法により測定した。Np標準溶液を試料に使用した。熱中性子場は、中性子束モニタSc, Co, Mo, TaとAuを用いて測定した。Np試料は、モニタと一緒に、京大炉の黒鉛照射設備にて30分間照射した。結果の再現性を確認するために、同様の照射を繰り返した。照射後、Np試料は、Npと放射平衡の関係にあるPaからの312-keVガンマ線を用いて定量した。Npの反応率は、生成されたNpから放出されるガンマ線のピークカウント,検出効率,実験条件を用いて求めた。得られた反応率を熱中性子束で割り込むことで、Npの熱中性子捕獲断面積を173.84.7 barnと導出した。この結果は、飛行時間測定法で得られた報告値と不確かさの範囲内で一致した。
土肥 輝美; 飯島 和毅; 町田 昌彦; 数納 広哉*; 大村 嘉人*; 藤原 健壮; 木村 茂*; 菅野 太志*
PLOS ONE (Internet), 17(7), p.e0271035_1 - e0271035_21, 2022/07
被引用回数:1 パーセンタイル:14.8(Multidisciplinary Sciences)Many lichens are well known to accumulate radiocaesium and, thus acting as biomonitors of contamination levels. Here, we use autoradiography and demonstrate for the first time microscale localisation of radiocaesium within thallus tissues to investigate the radiocaesium forms and their accumulation mechanism. The radiocaesium was localised in the brown pigmented parts i.e., melanin-like substances, in the lower cortex of lichen thallus. Quantum chemical calculations showed that functional group of melanin-like substances can chelate Cs ion, which indicates that the Cs ions form complexes with the substances. Based on these findings, we suggest that radiocaesium ions may be retained stably in melanin-like substances for long periods (two to six years) due to steric factors, such as those seen in porphyrin-like structures and multimer formation in the lower cortex.
沖田 将一朗; 深谷 裕司; 左近 敦士*; 佐野 忠史*; 高橋 佳之*; 宇根崎 博信*
Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) (Internet), 9 Pages, 2022/05
As a commercial reactor require high economic efficiency, the High Temperature Gas-cooled Reactor (HTGR) would be a more attractive proposition if a full mock-up experiment for the first commercial HTGR could be avoided in the future. In this paper, preliminary experiments were conducted in order to obtain basic core characteristics data, such as the criticality, necessary to demonstrate the applicability of a generalized bias factor method to neutronic design of HTGR. The graphite-moderated core with only highly enriched uranium fuels in the B-rack of Kyoto University Criticality Assembly (KUCA) was configured as a reference core. The C/E-1 values (Calculation/Experiment -1 values) for the keff values at the three critical states and the thermal neutron spectra with the major nuclear data libraries, such as JENDL-4.0, JEFF-3.2, ENDF/B-VII.1, and ENDF/B-VIII.0, were calculated for the core. The result shows that the keff values are overestimated for JEFF-3.2, ENDF/B-VII.1, and ENDF/B-VIII.0 by 0.14% - 0.18%, while they are underestimated for JENDL-4.0 by 0.07% - 0.09%. The calculation result with JENDL-4.0 shows a slightly better agreement with this experiment than the others. In addition, the thermal neutron spectrum calculated with ENDF/B-VIII.0 is softer than the others. The Thermal Scattering Law (TSL) data of graphite stored in ENDF/B-VIII.0 suggests that the thermal neutron spectrum become softer than that of traditional TSL data stored in the others. The core characteristics of the reference core, which are necessary for future studies, were obtained.
Song, F.*; Chen, H.*; 林田 洋寿*; 甲斐 哲也; 篠原 武尚; 薮塚 武史*; 八尾 健*; 高井 茂臣*
Solid State Ionics, 377, p.115873_1 - 115873_6, 2022/04
被引用回数:2 パーセンタイル:31.08(Chemistry, Physical)Lithium tracer diffusion coefficients have been measured in LiAlTi(PO) (LATP) and LATP - LaPO composite solid electrolytes in the temperature range between 300C and 500C by means of neutron radiography technique that utilizes the difference in neutron attenuation of Li and Li isotopes. The diffusion coefficient of LATP - LaPO composite is higher than that of pristine LATP, although the difference is much smaller than that estimated from the room temperature conductivity. This suggests that the bulk diffusion becomes the predominant diffusion mechanism at 300C to 500C instead of the diffusion along the space charge layer formed around the LaPO dispersants.