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under high temperatures and various water vapor concentrationsMohamad, A. B.; 中島 邦久; 井元 純平*; 高野 公秀
Journal of Nuclear Materials, 631, p.156826_1 - 156826_12, 2026/09
被引用回数：0It is estimated that considerable amounts of Cs remain in the reactors at the Fukushima Daiichi nuclear power plant and may react with the reactor materials such as UO fuel as reported by our previous paper. In order to understand the chemisorption behavior of CsOH vapor on UO fuel, chemisorption tests between CsOH vapor on UO under different water vapor concentrations and temperatures were performed. As predicted by the thermodynamic analysis, the experimental result indicated that, under the poor water vapor condition, chemisorption to form CsUO
occurred even at 1273 K. On the other hand, as predicted by the thermodynamic analysis, the experimental result indicated that, under the rich water vapor condition, chemisorption to form CsUO
occurred at 1273 K and 1473 K. Therefore, this study demonstrates the crucial role of thermodynamics in predicting the conditions under which chemisorption occurs. In addition, it was suggested that the chemisorption rate of CsOH vapor on UO pellet was considerably higher than that onto type 304 stainless steel.
Gil, J.; 板倉 充洋; 小林 恵太
Computational Materials Science, 273, p.114924_1 - 114924_10, 2026/08
液体金属中の不純物の熱力学的性質を正確に把握することは、腐食や物質移動の予測に重要であるが、第一原理計算には大きな計算コストがかかる。本研究では、高精度な電子状態計算法であるSCAN系の計算と機械学習分子動力学法を組み合わせ、液体ナトリウム中の酸素溶解エンタルピーを評価した。SCAN、rSCAN、r
SCANのデータで学習した原子間相互作用モデルにより、高精度かつ長時間の液体状態計算を実現した。計算値は酸素分子への経験的補正なしに実験推定値と一致し、従来のPBE法の主な誤差が液体ではなく気相酸素の計算に由来することが示された。本手法は、液体金属中の不純物熱力学を高精度かつ効率的に予測できる。
Jing, Z.*; 山口 敏男*; 服部 高典; 山田 武*; 玉造 博夢; 松浦 直人*; Zhou, Y.*
Journal of Physical Chemistry Letters (Internet), 17(29), p.8419 - 8428, 2026/07
被引用回数：0一連のアルカリ塩化物水溶液に対して高圧中性子回折および準弾性中性子散乱実験を行い、圧力およびイオンによって引き起こされる水構造および拡散の変化が、それぞれ異なる物理的メカニズムに起因することを明らかにした。ギガパスカル級の圧力を加えると、イオンの種類にかかわらず、第2および第3配位殻の崩壊と格子間水分子数の増加により、水の四面体状水素結合ネットワーク構造がデンス・ランダム・パッキング構造へと変化する。これに対し、溶解したイオンは常圧下では第2配位殻を乱すものの、水本来の四面体状ネットワーク構造を維持する。常圧条件下でLi
からCsにかけて見られた水の拡散に関する異常な傾向は、ギガパスカル級の圧力下では消失し、すべてのイオンが構造形成イオンの挙動を示す。
小澤 沙記*; 塩沢 優大*; 西條 佳孝*; 宮嶋 達也*; 松村 大樹; 辻 卓也; 中瀬 正彦*; 前原 輝敬*
Journal of the American Ceramic Society, 109(3), p.e70621_1 - e70621_10, 2026/03
被引用回数：1 パーセンタイル：0.00(Materials Science, Ceramics)The optical properties of glass are strongly influenced by the redox states of trace multivalent elements. Ce
ions are commonly added to soda-lime glass to remove Fe
-induced coloration via the redox reaction Ce + Fe 
Ce
+ Fe during cooling. Herein, the redox dynamics of cerium ions in soda-lime glass melts during model industrial cooling processes (from 1523 K at 20 K
min
) were investigated using in situ time-resolved Ce K-edge dispersive X-ray absorption fine-structure (DXAFS) spectroscopy. To evaluate the effect of the iron concentration, three soda-lime glass samples containing 2 mass% CeO were examined: Fe-free, Fe-05 (0.5 mass% FeO
), and Fe-20 (2.0 mass% FeO). Above 1383 K, the Ce/total Ce ratio remained stable for all samples, showing no significant change during cooling. Below 1383 K, the ratio decreased for the Fe-free glass, indicating the oxidation of Ce ions, and increased for the Fe-containing glass owing to the reduction of Ce ions. The temperature dependence of the redox change (
Ce redox) showed Fe-dependent behavior: Fe-20 exhibited more pronounced Ce reduction above 1200 K, while Fe-05 showed accelerated changes mainly below approximately 1100 K. These results indicate that cerium oxidation in Fe-free glass is strongly influenced by oxygen transport limitations, while cerium reduction is closely associated with availability of Fe ions, providing quantitative insights into the control of Ce-based decolorization during industrial cooling.
篠原 佑也*; 岩下 拓哉*; 中西 真大*; Liu, Y.*; Cooper, V. R.*; 古府 麻衣子*; 楡井 真実; Dmowski, W.*; Hickner, M. A.*; 江上 毅*
Journal of Physical Chemistry B, 129(47), p.12330 - 12337, 2025/11
被引用回数：0 パーセンタイル：0.00(Biophysics)Enhancing proton transport in polymer electrolytes is crucial for advancing next-generation solid-state batteries, yet our understanding of proton conductivity in nonaqueous environments remains limited due to a lack of atomic-scale insights. In this study, we investigated the atomic-scale dynamics of 1,2,3-triazole, a small molecule capable of dynamic hydrogen bonding, as a model system for proton hopping in nonaqueous environments. Using the real-space correlation function determined by the double Fourier transformation of inelastic neutron scattering spectra, we identified that the self-motion of protons and intermolecular dynamics occur on comparable time scales. Furthermore, we observed that the activation energy associated with the intermolecular dynamics matches the energy barrier for molecular rotations determined through Density Functional Theory calculations. These findings underscore the importance of controlling molecular dynamics at the atomic scale to control proton transport. Additionally, we demonstrated that intermolecular dynamics in systems involving protons can be studied using inelastic neutron scattering even without deuteration, thereby providing a broader avenue for studying atomic-scale dynamics in soft matter systems.
茂木 孝介; 松本 俊慶; 塩津 弘之
Proceedings of 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21) (Internet), 10 Pages, 2025/08
Since the hydrogen explosion at the Fukushima Daiichi Nuclear Power Plants accident in March 2011, hydrogen management during severe accidents at nuclear power plants has attracted attention as an important issue. In order to improve hydrogen management under severe accident conditions, the propagation of flames and the resulting loads on structures need to be predicted accurately. For this reason, the use of computational fluid dynamics methods is expected. Various benchmark experiments have been carried out and turbulence models, turbulent combustion models and chemical reaction models have been discussed, but the uncertainties of each model have not been treated independently. Analysis including uncertainty assessment is necessary to promote efficient research activities through uncertainty-based prioritisation and to reflect the latest findings in best practice guidelines. The aim of this study is to establish a methodology for quantifying the chemical reaction uncertainty in turbulent premixed flame CFD and to perform CFD and uncertainty analyses on existing benchmark experiments.
Kim, Y. S.*; Kang, T.*; Hong, S.-K.*; Brechtl, J.*; Lebyodkin, M.*; Cheng, Y.-H.*; Huang, E.-W.*; Liaw, P. K.*; Harjo, S.; Gong, W.; et al.
Acta Materialia, 292, p.120970_1 - 120970_16, 2025/06
被引用回数：15 パーセンタイル：96.30(Materials Science, Multidisciplinary)Metallic materials can exhibit low-temperature serrated deformation (LTSD) at cryogenic temperatures, potentially causing sudden failures. Understanding LTSD is thus crucial for ensuring material reliability in such environments. LTSD has been explained by two main mechanisms: (i) dislocation-based mechanical instability and (ii) thermomechanical instability, but each has limitations when considered alone. To address this, we propose a new LTSD mechanism, a thermally induced dislocation dynamics model, based on cryogenic experimental evidence. This model accounts for dislocation avalanches and localized heating, leading to hierarchical dislocation networks and transitions in deformation modes. A modified deformation-mechanism map for SS316L is also presented. Our findings highlight the rate-dependent nature of LTSD and negative strain-rate sensitivity, including the first observation of links between small stress fluctuations and large serrations.
大橋 智典*; 坂巻 竜也*; 舟越 賢一*; Steinle-Neumann, G.*; 服部 高典; Yuan, L.*; 鈴木 昭夫*
Journal of Mineralogical and Petrological Sciences (Internet), 120(1), p.240926a_1 - 240926a_13, 2025/06
被引用回数：1 パーセンタイル：36.35(Mineralogy)0-6GPa, 1000-1300Kのドライおよび含水Na
Si
O
融体の構造と高温高圧から回収したガラスの構造をその場中性子回折及びX線回折により調べた。また、0-10GPa, 3000Kの融体の構造をab-initio分子動力学シミュレーションにより調べた。その場中性子実験から、-O-D-O-架橋種の形成によりD-O距離が圧縮とともに増加することが明らかになり、分子動力学シミュレーションでも再現された。圧力による-O-D-O-形成は、水素がより強固に取り込まれることを反映しており、実験的に観測されたケイ酸塩融体中の水の高い溶解度のメカニズムとして働く。一方、0-10GPa, 3000KにおけるドライNaSiOの圧縮は、Si-O-Si角の曲げに支配される。さらに、含水NaSiO融体の分子動力学シミュレーションから、圧力上昇とともに、2(![$$^{[4]}$$](/search/images/ERPHWWZULV4SI.gif)
Si-O
+ Na) Si-(O-![$$^{[5]}$$](/search/images/ERPHWWZVLV4SI.gif)
Si-O)
+ 2NaおよびSi-O + Na + Si-OH Si-(O-H-O-Si) + Naで示される反応により、ナトリウムイオンがネットワーク修飾の役割を果たさなくなることを示唆している。
曽根原 正晃; 岡野 靖; 内堀 昭寛; 大木 裕*
Journal of Nuclear Science and Technology, 62(5), p.403 - 414, 2025/05
被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)ナトリウム冷却高速炉では、ナトリウム漏えい事故を管理するためにナトリウムの燃焼挙動を理解することが極めて重要である。本研究では、多次元熱流動解析コードAQUA-SFを用いて、サンディア国立研究所(SNL)のT3実験のベンチマーク解析を実施した。この実験は、容器容積100m
、ナトリウム流量1kg/sの密閉空間で実施され、ナトリウム注入直後の局所的な温度上昇がもたらす多次元的な影響を明らかにした。本研究では、AQUA-SFの機能を拡張することを目的として、このような多次元的な温度変動、特に容器底部における高温領域の形成のシミュレーションに焦点を当てた。提案したモデルには、ナトリウム液滴着火の一時停止と床面上のナトリウム飛沫の噴霧燃焼が含まれる。さらに、底部高温域の再現性を高めるためには、床部近傍に熱源を追加することが不可欠であることを示した。そこで、噴霧円錐角の感度解析と床面上の液滴の長時間燃焼を含むケーススタディを実施した。この包括的なアプローチにより、ナトリウム冷却高速炉におけるナトリウム燃焼のダイナミクスと安全対策に関する貴重な知見を得ることができた。
Hamdani, A.; 相馬 秀; 安部 諭; 柴本 泰照
Progress in Nuclear Science and Technology (Internet), 7, p.53 - 59, 2025/03
This paper presents the experimental study and computational fluid dynamics (CFD) analysis on the effect of thermal radiation in the humid atmosphere inside the containment vessel. The experiment was conducted in the Containment InteGral effects Measurement Apparatus (CIGMA) facility at Japan Atomic Energy Agency (JAEA). The numerical analysis was carried out using the open-source CFD code OpenFOAM. The initial gas condition inside the CIGMA containment consists of three gases, helium, air, and water vapor, at room temperature 30 
C and a pressure of 1 atm. Initial helium stratification was located 6 m above the bottom vessel, and its molar fraction was 55 %. The initial water vapor molar fraction was set to 0.1% in order to minimize the thermal radiation absorption by the water molecule. Pure helium was injected through a nozzle from the top, leading to increased vessel pressure and a corresponding rise in gas temperature. The numerical validation at low water vapor, i.e., 0.1% HO, was performed by comparing the transient profile of pressure, gas molar fraction, and temperature with the experimental data. A Weighted Sum of Gray Gases (WSGG) model was implemented in the OpenFOAM solver. The numerical results showed a reasonable agreement compared to the experimental data. In addition, the numerical simulation with various water vapor mass fractions, i.e., 0.0%, 0.1%, 0.3%, 0.5%, and 60%, was performed to analyze the effect of humidity on the radiative heat transfer. The predicted temperature was overestimated when the numerical model neglected thermal radiation. Therefore, it indicated that thermal radiation should be considered when modeling the containment thermohydraulic.
福田 航大
Annals of Nuclear Energy, 208, p.110748_1 - 110748_10, 2024/12
被引用回数：2 パーセンタイル：19.36(Nuclear Science & Technology)The Windscale Works criticality accident in 1970 resulted from mixing an aqueous solution with an organic solvent with different plutonium concentrations and densities. Although this accident has been studied using improved computer capabilities in recent years, a precise criticality scenario has not yet been identified. This study aims to clarify a possible criticality scenario of the accident-the time variation of reactivity and its mechanism. The accident was simulated by combining the multiphase computational fluid dynamics solver of OpenFOAM and the delta-tracking-based Monte Carlo neutron transport code Serpent2. Consequently, the periodic uneven arrangement of fluids might have caused oscillations in neutron leakage and absorption, resulting in periodic wavy reactivity changes. Furthermore, the emulsion, which was thought to be the primary cause, might not be the dominant mechanism for reactivity change, although it contributed to the criticality of the accident.
井上 倫太郎*; 長田 裕也*; 富永 大輝*; 佐藤 宗太*; 川北 至信; 山脇 大昇*; 守島 健*; 杉野目 道紀*; 杉山 正明*
Journal of Chemical Physics, 161(5), p.054905_1 - 054905_8, 2024/08
被引用回数：0 パーセンタイル：0.00(Chemistry, Physical)The side chain dynamics of poly(quinoxaline-2,3-diyl)s (PQXs) are expected to influence their conformation. To investigate these dynamics experimentally, quasielastic neutron scattering (QENS) was performed for PQXs in deuterated tetrahydrofuran (THF-
) and deuterated 1,1,2-trichloroethane/THF (1,1,2-TCE-/THF-), in which they formed right-handed and left-handed helical structures, respectively. The mean-square displacement of the PQX side chains in 1,1,2-TCE-/THF- was lower than that in THF-. Furthermore, QENS complementary studies and molecular dynamics simulations unraveled a coupling between the main-chain and side chain dynamics of PQXs, suggesting the possibility of controlling the main-chain helical chirality through the dynamics of chiral side chains. These insights present a novel strategy for the design of synthetic helical macromolecules with precise chirality control.
寺田 敦彦; 永石 隆二
Journal of Nuclear Science and Technology, 61(8), p.1135 - 1154, 2024/08
被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)天井と側面に換気口を設けた部屋の床面から漏洩した水素の挙動について、CFD解析を用いて実験結果との照合を行うことで、部屋周囲の風況による影響を明らかにした。室内の水素濃度の経時変化は、天井と床面付近の間で成層化がみられ、計算結果については局所的な流れ場の特性変化を反映できる乱流モデルと比較的大きな乱流シュミット数(1.0)を組み合わせた場合に実験結果の再現性が向上した。風況によって、室内に水素が滞留したケースについて、天井開口部にシンプルな板を設置することで換気の改善が図れることを示した。
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：13 パーセンタイル：67.31(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.
伊藤 孝; 門野 良典*
Journal of the Physical Society of Japan, 93(4), p.044602_1 - 044602_7, 2024/04
被引用回数：8 パーセンタイル：72.66(Physics, Multidisciplinary)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.
Yu, C.*; 川北 至信; 菊地 龍弥*; 古府 麻衣子*; 本田 孝志*; Zhang, Z.*; Zhang, Z.*; Liu, Y.*; Liu, S. F.*; Li, B.*
Journal of Physical Chemistry Letters (Internet), 15(1), p.329 - 338, 2024/01
被引用回数：2 パーセンタイル：23.60(Chemistry, Physical)The atomic dynamic behaviors of formamidinium lead iodide [HC(NH)PbI] are critical for understanding and improving photovoltaic performances. However, they remain unclear. Here, we investigate the structural phase transitions and the reorientation dynamics of the formamidinium cation [HC(NH)
, FA
] of FAPbI using neutron scattering techniques. Two structural phase transitions occur with decreasing temperature, from cubic to tetragonal phase at 285 K and then to another tetragonal at 140 K, accompanied by gradually frozen reorientation of FA cations. The nearly isotropic reorientation in the cubic phase is suppressed to reorientation motions involving a two-fold (C) rotation along the 
axis and a four-fold (C) rotation along the C-H axis in the tetragonal phase, and eventually to local disordered motion as a partial C along the C-H axis in another tetragonal phase, thereby indicating an intimate interplay between lattice and orientation degrees of freedom in the hybrid perovskite materials. The present complete atomic structure and dynamics provide a solid standing point to understand and then improve photovoltaic properties of organic-inorganic hybrid perovskites in the future.
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.
中村 秀夫; Bentaib, A.*; Adorni, M.*
Proceedings of 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20) (Internet), p.5668 - 5678, 2023/08
The OECD NEA Working Group on Analysis and Management of Accidents (WGAMA) is responsible for activities related to potential accidental situations in nuclear power plants address the safety aspects of existing reactors and emerging safety challenges to enable safety design and operation of advanced nuclear technologies, including those for SMRs. The WGAMA objective is to assess and, where necessary, strengthen the technical basis needed for the prevention, mitigation and management of potential accidents in NPPs, and to facilitate international convergence on safety issues and accident management analyses and strategies. The achievements of WGAMA have been outstanding in preparing technical reports, becoming reference materials, and in organizing workshops and conferences to discuss innovative methods, materials and technologies in the fields of thermal-hydraulics (T/Hs), CFD and severe accidents. This paper aims to review and summarize the recent WGAMA activities and outcomes, as well as future perspectives, focusing on nuclear reactor T/Hs safety analysis in water cooled reactors and possible applications to advanced designs.
奥村 拓馬*; 橋本 直; 他40名*
Physical Review Letters, 130(17), p.173001_1 - 173001_7, 2023/04
被引用回数：28 パーセンタイル：91.86(Physics, Multidisciplinary)To test bound-state quantum electrodynamics (BSQED) in the strong-field regime, we have performed high-precision X-ray spectroscopy of the 5
-4
and 5-4 transitions (BSQED contribution of 2.4 eV and 5.2 eV, respectively) of muonic neon atoms in the low-pressure gas phase without bound electrons. Muonic atoms have been recently proposed as an alternative to few-electron high-Z ions for BSQED tests by focusing on circular Rydberg states where nuclear contributions are negligibly small. We determined the 
-
transition energy to be 6297.08 
0.04 (stat.) 0.13 (syst.) eV using superconducting transition-edge sensor microcalorimeters (5.2-5.5 eV FWHM resolution), which agrees well with the most advanced BSQED theoretical prediction of 6297.26 eV.
山本 智彦; 加藤 篤志; 早川 雅人; 下山 一仁; 荒 邦章; 畠山 望*; 山内 和*; 江田 優平*; 由井 正弘*
Proceedings of 2023 International Congress on Advanced in Nuclear Power Plants (ICAPP 2023) (Internet), 6 Pages, 2023/04
In the secondary cooling system of sodium-cooled fast reactor (SFR), a rapid detection of hydrogen explosion due to sodium-water reaction by water leakage from heat exchanger tube is steam generator (SG) is important in terms of safety and property protection. For the hydrogen detection, Ni-membrane hydrogen detectors using atomic transmission phenomenon were used in Japanese proto-type sodium-cooled fast reactor "Monju". However, during the plant operation, many alarms of water leakage were occurred without sodium-water reaction in relation to temperature up and down. The authors focus on the difference in composition of hydrogen and the difference between the background hydrogen under normal operation and the hydrogen generated by the sodium-water reaction and theoretically estimate the hydrogen behavior in liquid sodium by using ultra-accelerated quantum chemical molecular dynamics (UA-QCMD). As the results of theoretical estimation, dissolved H or NaH, rather than H, is the predominant form of the background hydrogen in liquid sodium, and hydrogen produced in large amounts by sodium-water reaction can exist stably as fine bubbles with a NaH layer on their surface. Currently, the authors study the new hydrogen detector system focusing on the difference between the background hydrogen (dissolved H) and the hydrogen by sodium-water reaction (fine bubbles H). This paper describes the comparison between the theoretical estimation and experimental results based on hydrogen form in sodium.
