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Luu, V. N.; 谷口 良徳; 宇田川 豊; 田崎 雄大; 勝山 仁哉
Annals of Nuclear Energy, 230, p.112114_1 - 112114_14, 2026/06
被引用回数：1 パーセンタイル：0.00(Nuclear Science & Technology)Fracture behavior of chromium (Cr) coated cladding under loss of coolant accident (LOCA) conditions was investigated utilizing the FEMAXI fuel performance code. Cr coating degradation models were introduced to FEMAXI to calculate oxygen diffusion behavior within the cladding tube. The FEMAXI code reasonably simulated the observed evolution of cladding metallic and oxide layers under the simulated LOCA conditions, accounting for factors such as wall thinning due to cladding high temperature creep, Cr layer thinning by Cr
O
formation and Cr/Zr interdiffusion, weight increase by oxygen absorption, associated oxide growth, and increased oxygen concentration in 
-Zr phase. According to sensitivity analyses of the cladding oxygen concentration, where the effects of wall thickness change and eutectic reactions were taken into account, the fracture condition of the Cr-coated cladding samples can be reasonably modelled by the fracture criteria based on the remaining -Zr thickness with an oxygen concentration of 
0.9 wt%.
Nguyen, H. H.
Annals of Nuclear Energy, 230, p.112171_1 - 112171_13, 2026/06
被引用回数：0本研究では、炉心中心部の燃料集合体は溶融して燃料デブリとなる一方、外周部の燃料集合体は損傷を受けていない状態にある、部分的に損傷した原子炉モデルの中性子特性に、減速材と燃料の体積比、燃料デブリの形状、および損傷した燃料集合体の数が及ぼす影響を調べた。調査は、SerpentコードとJENDL-5ライブラリを用いて実施した。結果、燃料デブリが損傷のない燃料集合体に囲まれている場合、k
は燃料デブリの形状に基づいて2つのグループに分類できることが示された。逆に、燃料デブリが損傷のない燃料集合体に完全に囲まれていない場合、燃料デブリの形状はkにほとんど影響を与えない。さらに、燃料デブリに出入りする中性子数の関係によって、燃料デブリの形状がkにどのように影響するかが決まる。
谷口 良徳; Luu, V. N.; 田崎 雄大; 宇田川 豊; 勝山 仁哉
Annals of Nuclear Energy, 231, p.112177_1 - 112177_16, 2026/06
被引用回数：0Advanced technology fuels (ATF) with improved oxidation resistance are under development to enhance the safety of light water reactors. Cr-coated Zr alloy cladding, a promising near-term ATF, exhibits excellent oxidation resistance below the Cr-Zr eutectic temperature. However, its gradual loss of protective effect over time, even without mechanical damage, indicates the need to understand its degradation mechanisms. This article presents a phenomenological model describing degradation due to high-temperature oxidation, focusing on Zr ingress into the Cr coating and the formation of oxygen pathways that accelerate oxygen uptake into the Zr matrix. The model was validated against experimental data at 1200
C and 1300C, reproducing key trends such as oxide growth, weight gain, and oxygen concentration profiles. Applying the same parameters to a different PVD-coated cladding test gave reasonable agreement at 1200C, while discrepancies at 1300C suggest Cr-Zr eutectic reactions from local temperature variations, highlighting the model's sensitivity near the eutectic point.
高見澤 悠; 西山 裕孝
Journal of Pressure Vessel Technology, 148(3), p.031501_1 - 031502_12, 2026/06
原子炉圧力容器(RPV)鋼の中性子照射脆化は、プラント運転中の監視試験試験(シャルピー衝撃試験)で得られる延性‐脆性遷移温度(DBTT)を用いて評価されてきた。RPVの構造健全性評価の信頼性を確保するためには、監視試験に内包される不確かさを考慮した十分な安全余裕を考慮する必要がある。本研究では、日本と米国で製造された約1,900の未照射および照射済み材料のデータセットを用いて、シャルピー吸収エネルギー変動の温度依存性を評価するモデルを開発した。次に、モンテカルロサンプリングとベイズ推定を用いてシャルピー試験データの確率分布を推定し、41Jエネルギーレベル(
)におけるシャルピー延性‐脆性遷移温度の確率分布を評価した。試験片数との不確かさの関係を詳細に評価した結果、日本製鋼材と米国製鋼材のの不確かさはほぼ同等であり、中性子照射によっても変化がない(材料の不均質性に明確な変化がない)ことがわかった。一方、製造方法に関しては、母材と溶接金属のの不確かさはほぼ同等であったが、熱影響部(HAZ)の不確かさが大きいことが示された。
古田 琢哉; 橋本 慎太郎; 小川 達彦; 谷村 嘉彦
Nuclear Instruments and Methods in Physics Research A, 1086, p.171320_1 - 171320_8, 2026/06
被引用回数：0物質に対する中性子照射から荷電粒子が放出される反応において、放出粒子と特定の励起状態にある残留核を同時に扱う核データライブラリを組み込むための新機能を、モンテカルロシミュレーションコードである 粒子・重イオン輸送計算コードPHITSに実装した。本機能により、残留核の生成および脱励起ガンマ線の放出を考慮しつつ、各事象における全エネルギーおよび運動量保存を満たした上で、核データライブラリに基づく放出粒子のエネルギースペクトルおよび角度分布の高精度な予測が可能となる。この機能を用いることで、検出器応答や材料中の放射線損傷の高精度シミュレーションが実施できる。
高柳 智弘; 植野 智晶*; 堀野 光喜*; 杉田 萌; 不破 康裕; 篠崎 信一
IEEE Transactions on Applied Superconductivity, 36(3), p.4900905_1 - 4900905_5, 2026/05
被引用回数：0 パーセンタイル：0.00(Engineering, Electrical & Electronic)Compared to DC magnets with constant current, pulsed magnets with instantaneous current flow are superior in terms of energy conservation because the time required to generate Joule heat due to the electrical resistance of the coil is limited. However, the magnetic field distribution that affects beam orbit control cannot be known accurately until the pulse power supply is excited, because the current path through the coil and the load resistance changes with time due to the current skin effect, respectively. For this reason, we have introduced model-based development (MBD), which integrates electromagnets and power supplies, whereas previous simulation analysis was performed separately for electromagnets and power supplies. For the simulation, we combined OPERA-3D transient analysis, which has a proven track record in the development of pulsed magnets for the J-PARC accelerator, and MATLAB/Simulink for circuit simulation. The introduction of MBD is expected to reduce the number of actual prototypes and development costs and shorten the development period because highly accurate results can be obtained in a short period of time. In addition, simulation of trouble cases that cannot be covered by verification of actual machines alone is possible, which is expected to improve safety. In this presentation, we will report the evaluation results compared to the actual machine.
茂木 孝介; 塩津 弘之; 松本 俊慶; 日引 俊詞*; 柴本 泰照
International Journal of Heat and Mass Transfer, 258, p.128275_1 - 128275_15, 2026/05
被引用回数：0 パーセンタイル：0.00(Thermodynamics)We established a methodology to quantify chemical kinetic uncertainties, specifically the uncertainty in reaction rate constants, in Reynolds-Averaged Navier-Stokes (RANS) simulations of turbulent premixed combustion. The methodology consists of three main steps. First, an uncertainty database for the hydrogen combustion reaction was constructed. Second, these uncertainties were propagated to the laminar flame speed, which served as the input data for the subsequent RANS simulation, through a freely propagating flat flame simulation. Third, the uncertainty in the laminar flame speed was propagated to quantities of interest (QoIs) through the RANS simulation. We employed the non-intrusive polynomial chaos method to reduce the number of demanding RANS simulation runs. The established methodology was applied to the flame acceleration benchmark experiments in the ENACCEF facility, revealing that the analysis successfully quantified the uncertainty within an acceptable computational cost. The uncertainty analysis showed that the uncertainty in the propagating flame was closely related to the physical mechanisms involved in the acceleration process. Finally, we discussed the factors influencing the results and examined the validity of the proposed uncertainty analysis.
Kreinder, B.; Cox, I.*; Grzywacz, R.*; 西尾 勝久; 他24名*
Nuclear Instruments and Methods in Physics Research A, 1085, p.171298_1 - 171298_7, 2026/05
被引用回数：0In recent experiments, inorganic scintillators have been used to study the decays of exotic nuclei, providing an alternative to silicon detectors and enabling measurements that were previously impossible. However, proper use of these materials requires us to understand and quantify the scintillation process, specifically in response to very heavy nuclei. In this work, we show a simplified method based on the models of Birks (1951) and Meyer and Murray (1962) to parametrize the light output of inorganic scintillators in response to beams of energetic heavy ions over a broad range of energies. We test the accuracy of our parametrization approach by calculating light output and quenching factors for various ions and comparing them with experimental data from Lutetium Yttrium Orthosilicate (LYSO:Ce), a common inorganic scintillator. The Meyer-Murray model suggests that, for sufficiently heavy ions at high energies, the majority of the light output is associated with the creation of delta electrons, which are induced by the passage of the beam through the material. These delta electrons dramatically impact the response of detection systems when subject to ions with velocities typical of beams in modern fragmentation facilities. To illustrate this, we also present a qualitative estimate of the effects of delta rays on overall light output using the Birks-Meyer-Murray parametrization. The approach presented herein will serve as a basic framework for further, more rigorous studies of scintillator response to heavy ions. This work is a crucial first step in planning future experiments where energetic exotic nuclei are interacting with scintillator detectors.
塩津 弘之
Progress in Nuclear Energy, 195, p.106300_1 - 106300_11, 2026/05
被引用回数：0The transport and release behavior of fission products (FPs) during nuclear power plant accidents is strongly influenced by their chemical forms, particularly gaseous species, which can lead to enhanced environmental release. For iodine, one of the most volatile FPs, condensable cesium iodide (CsI) has traditionally been regarded as the dominant chemical form in state-of-the-art source term evaluations. However, recent experiments have indicated that molybdenum (Mo), a semi-volatile FP, can promote the formation of gaseous iodine through gas-phase reactions with CsI. The key controlling factor of these reactions is the oxygen potential of the atmosphere. In the TeRRa experiments, CsI-Mo gas-phase reactions were observed at 1150 K under Ar-20%O-0.8%O conditions (-31.7 kJ/mol-O), whereas no reaction occurred under Ar-20%HO conditions (-149 kJ/mol-O). Nevertheless, the specific reactive conditions governing these reactions have not yet been fully clarified. In this study, the oxygen-potential dependence of gas-phase reactions between CsI and Mo vapors in the TeRRa-CsIMo series experiments was numerically investigated using chemical equilibrium, mass transport, and reaction kinetics analyses. Chemical equilibrium and transport analyses were performed using the VICTORIA code, while detailed kinetic analyses were conducted with the Cantera software and the ECUME database. The results demonstrate that although CsI-Mo gas-phase reactions are thermodynamically favorable under oxidizing conditions that stabilize Mo in the MoO form (
-158 kJ/mol-O), their contribution to gaseous iodine formation is strongly constrained by kinetic limitations under lower oxygen potential conditions, even at high temperatures around 1150 K. These findings suggest that both thermodynamic and kinetic effects must be considered for reliable evaluation of iodine source terms during severe accidents, particularly under oxygen-starved environments.
近藤 正聡*; 北村 嘉規*; 瓦井 篤志*; 斎藤 滋; 大林 寛生
Corrosion Science, 262, p.113646_1 - 113646_14, 2026/04
被引用回数：0流動鉛ビスマス共晶合金(LBE)中におけるFeCrAl合金APMT(Fe-21Cr-5Al-3Mo)の耐食性を、非等温強制循環ループ(OLLOCHI)を用いた腐食試験により調べた。試験温度は723K、LBE中の酸素濃度は1
10
wt%に制御した。流動LBEに2000時間及び4000時間浸漬した試験片では、深刻な腐食や侵食は検出されなかった。腐食試験中、APMT表面にはFeリッチ層、Crリッチ層、Alリッチ層からなる多重酸化物層が形成され、これらが腐食と侵食を抑制した。これらの酸化物層を研磨により除去した試験片をさらに2000時間流動LBE中に再浸漬した。その結果、研磨面に酸化層が再形成された。この挙動はこのFeCrAl合金が自己修復能力を有することを示唆している。2000時間の腐食試験後のマイクロスクラッチ試験の結果から、その場形成された多重酸化皮膜はせん断方向において高い付着強度を示したことが確認された。
Mohamad, A. B.; Chen, J.*; 井岡 郁夫*; 鈴木 恵理子; 近藤 啓悦; 阿部 陽介; 山下 真一郎; 大久保 成彰; 根本 義之; 岡田 裕史*; et al.
Journal of Nuclear Materials, 625, p.156513_1 - 156513_9, 2026/04
被引用回数：0Ion irradiation was carried out on Cr coating Zry cladding to investigate their microstructure evolution and mechanical properties. The sample was irradiated at reactor normal operation conditions. Microstructural observation and mechanical testing of non-irradiated samples and irradiated samples were performed to understand irradiation damage to the Cr-coated Zry cladding. Results of High Resolution Transmission Electron Microscopy and chemical analysis revealed Fe enrichment at the Cr coating and Zr substrate interface of irradiated samples due to irradiation enhanced diffusion or irradiation induced mixing. Irradiation led to the formation of Fe enrichment at the Cr Zr interface approximately 15nm. Moreover, hardening of the Cr coating and Zr substrate regions was observed in the irradiated sample.
下平 昌樹; 河 侑成; 高見澤 悠; 勝山 仁哉; 鬼沢 邦雄
Journal of Pressure Vessel Technology, 148(2), p.021504_1 - 021504_10, 2026/04
最新の原子炉圧力容器の構造健全性評価においては、マスターカーブ法に基づく正確な破壊靭性参照温度T
の取得が必要である。破壊靭性参照温度TはMini-C(T)破壊靭性試験片によって取得可能であり、この試験片の寸法や亀裂形状に関しては、ASTM規格のE1921や日本電気協会電気技術規程JEAC4216に規定されている。最近、ASTM E1921では評価の正確性や試験を行う上での利便性を向上させるために、亀裂形状に関する規定の変更が行われてきた。このような規格の改定に伴うMini-C(T)試験片の許容亀裂形状の変化は、亀裂先端の塑性拘束状態を変化させ、T評価に影響を及ぼす可能性がある。本研究では、ASTM E1921やJEAC4216に規定される亀裂形状に関する要求の妥当性について議論するため、Mini-C(T)試験片の亀裂湾曲が破壊靭性評価に及ぼす影響について、ワイブル応力解析を含む有限要素解析によって定量的に評価した。その結果、ASTM E1921-21で定められた最大湾曲を有する亀裂形状の場合、亀裂先端の塑性拘束が弱められ、理想的な直線状亀裂を有するMini-C(T)試験片で得られる破壊靭性値に比べて高めの破壊靭性値が得られる可能性を示した。また、上述の最大湾曲を許容した場合、非保守的なTが取得されることをワイブル応力解析によって示した。一方、JEAC4216で許容される最大湾曲を有する亀裂形状の場合は、理想的な直線状亀裂の場合と比べてTの有意な差は見られなかった。
山田 逸平; 小島 邦洸; 地村 幹
Nuclear Instruments and Methods in Physics Research A, 1084, p.171261_1 - 171261_12, 2026/04
被引用回数：0 パーセンタイル：0.00(Instruments & Instrumentation)大強度粒子加速器の安定運転には、非破壊型のビーム形状(プロファイル)モニタが不可欠であり、ガスを導入してビームとの相互作用で形状を測るモニタ開発を進めている。ガス導入型は、高い二次粒子収量により高速かつ高精度なプロファイル計測を可能にする一方、ビームと導入したガスの相互作用がビーム品質に影響を与える可能性があるため、その非破壊性の定量的な評価が必須である。本研究では、3MeV負水素イオンビームを用いて、導入ガス流量に対するビーム電流値及び位相空間分布の変化を評価した。ビーム電流値については、予想通り導入ガス流量に対して線形に減少し、その減少率は荷電変換断面積と一致した。位相空間分布については、ビームライン圧力が10
Pa未満の範囲では変化が見られず、10 Pa以上に増加させた場合には、逆に分布の広がりに約5%の減少が見られた。本測定結果を解析的および数値的に検証した結果、ビーム・ガス相互作用により生成された正イオンが水素負イオンビームの電気的斥力を中和し、負電荷同士の反発力を抑制したため、分布の広がりの相対的な減少を起こすことがわかった。以上により、開発したモニタは、使用に際してビームを広げることなく、逆にビーム品質を向上させる事が分かり、加速器の安定運転に貢献可能であると言える。
岡垣 百合亜; 日引 俊詞*
Progress in Nuclear Energy, 194, p.106267_1 - 106267_23, 2026/04
被引用回数：0Pool scrubbing is an essential filtration process that prevents the release of radioactive aerosols into the environment during severe accidents at nuclear reactors. During such events, a mixture of steam and/or various noncondensable gases containing radioactive aerosols is injected into the pool, where it forms bubbles. During aerosol particle transport, bubble dynamics play a notable role in determining the efficiency of particle removal within the bubbles. Clarifying these mechanisms is crucial for accurately modeling pool scrubbing processes. In practice, pool scrubbing codes based on the lumped parameter (LP) approach incorporate particle removal models; however, key hydrodynamic parameters - such as bubble rise (terminal) velocity and bubble aspect ratio - are modeled using simplified assumptions. The present study aimed to verify the validity of existing correlations for terminal velocity and bubble aspect ratio, with the long-term objective of proposing improved models. As part of this fundamental research, the behavior of a single bubble rising in a stagnant liquid, simulating a pool environment, was visualized through computational fluid dynamics (CFD) simulations employing an interface tracking/capturing method. The effective aspect ratio was calculated based on the bubble interfacial area and volume. Furthermore, correlations for single-bubble terminal velocity and aspect ratio were developed, taking into account the transition in bubble shape as the volume-equivalent diameter increased. The findings from the present study are expected to provide a foundation for the development and evaluation of future standalone pool scrubbing codes, including improved correlations for terminal velocity for bubble swarm, bubble aspect ratio, and other relevant hydrodynamic parameters.
:Ce using PHITS track-structure simulations平田 悠歩; 甲斐 健師; 小川 達彦; 松谷 悠佑; 佐藤 達彦; 渡辺 賢一*; 加藤 匠*; 河口 範明*; 柳田 健之*
Radiation Measurements, 193, p.107651_1 - 107651_8, 2026/04
被引用回数：0CaF:Ceは高い光刺激蛍光(OSL)強度を示すため線量計として有用であると期待されている。しかし、CaF:Ceなどの蛍光体に粒子線を照射すると、消光効果により蛍光体の線量当たりの発光強度が低下する。従来、蛍光体の消光効果は線エネルギー付与(LET)などを指標としたエネルギー付与密度に基づいて評価されてきた。しかし、粒子線の種類によりCaF:Ceにおける消光現象とLETの関係性が異なり、LETから正確に消光現象を予測することは困難であったが、放射線輸送計算コードPHITSのTrack structure機能は、放射線による相互作用を個別に追跡することが可能である。そこで、PHITSを用いて粒子線により蛍光体が発光する過程を精密に計算し、予測したCaF:Ceの応答を実験データと比較したところ、CaF:Ceの消光現象にはOSLの量子収率が重要なパラメータであることが示唆された。この成果は、蛍光体検出器のさらなる開発に貢献するものと期待される。
三上 奈生; 相澤 康介; 栗原 成計; 植木 祥高*
AI Thermal Fluids (Internet), 5, p.100029_1 - 100029_15, 2026/03
Early detection of water/steam leakage is important in the prevention of failure propagation of heat transfer tubes in a steam generator of a sodium-cooled fast reactor. This study proposes an unsupervised learning-based acoustic method to detect gas leakage in liquid and evaluates its noise resistance based on parametric receiver operating characteristic (ROC) analysis. An autoencoder is trained, validated, and tested on time-frequency representations of simulated noise and leak signals for various signal-to-noise ratios (SNRs). To calculate a false positive rate and a true positive rate, the probability density function is assumed to be either as a normal distribution, a power transformed normal distribution, or a power normal distribution. As a result, the power normal distribution that shows the best goodness-of-fit was used as the probability density function to draw an ROC curve. The predictive ability of the autoencoder is evaluated as excellent for 
, 
, 
, and 
dB, good for 
dB, and poor for 
dB. The autoencoder can detect leakage at relatively low-noise levels and has the potential to detect leakage at relatively high-noise levels equivalent to actual noise levels. Segmentation of the noise and leak signals can also be achieved from input, reconstructed, and residual images. These results suggest that the proposed method contributes to laying the foundation for detection and accident analysis of water/steam leakage in a steam generator of a sodium-cooled fast reactor.
山根 斗和*; 稲津 將*; 川野 潤*; 佐藤 拓人; 日下 博幸*
Agricultural and Forest Meteorology, 379, p.111052_1 - 111052_9, 2026/03
被引用回数：0本研究の目的は、シラカバ花粉飛散の実地観測を行うことで高解像度で正確なモデリングのための基礎的な知見を得ることである。2024年の飛散のピーク日において、シンプルな花粉補足機をシラカバ樹木の風下3地点に設置した。気象観測も同じタイミングに行った。本研究では、まず、機械学習アルゴリズムであるYOLOを用いて花粉を自動的にカウントする手法を開発した。この手法は、主観的なカウントと比較して検証され、従来なかった自動カウントを実現した。観測結果から、花粉の数はシラカバ樹列から200m風下において最大となることが示唆され、いずれの風下距離においても日変化が観察された。花粉の数と気象要素に関する線形回帰分析の結果から、気温と花粉の数の間に顕著な正の相関が見られた。さらには、樹木のごく近くのポイントにおいて花粉の数と風速に性の相関が見られた。Large-eddy simulationによる花粉の移流シミュレーションの結果は、花粉が沈降する場所が観測より樹木近くに集まっているものの、この観測結果を支持するものであった。
樋川 智洋; 宝徳 忍; 熊谷 友多; 阿部 侑馬*; 小山 幹一*; 深谷 洋行; 伴 康俊; 木田 孝; 長谷川 聡*; 中野 正直*; et al.
Journal of Nuclear Science and Technology, 63(3), p.322 - 327, 2026/03
被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)燃料再処理施設における水素安全に資するため、放射線分解により生成する水素発生に対する温度の影響を調べた。プルトニウム硝酸水溶液の放射線分解による水素発生量を、室温から溶液の沸騰温度までの温度について実験的に取得した。その結果、沸騰条件まで温度を上昇させても有意な水素発生量の上昇は見られなかった。さらに溶液の撹拌が水素生成に与える影響についても検討したところ、室温での静的条件と混合条件の間で水素生成に違いがみられなかった。これらの知見は、溶液の温度上昇や沸騰が水素生成を大幅に増加させないことを示唆しており、重大事故時の水素リスク評価に貢献する。
-ray beam measurementsOmer, M.; 静間 俊行*; 小泉 光生; 平 義隆*; Zen, H.*; 大垣 英明*; 羽島 良一*
Radiation Physics and Chemistry, 240, p.113467_1 - 113467_8, 2026/03
被引用回数：0 パーセンタイル：0.00(Chemistry, Physical)Coaxial high-purity germanium detectors are widely used in applications requiring high-resolution -ray spectroscopy. However, the internal structure of these detectors, particularly the geometry of the inactive volumes inside the detector core, can significantly influence their performance in beam detection configurations. This study investigates the impact of detector structure on the spectral response to pencil-like -ray beams, based on a comparison of -ray spectra measured with two coaxial high-purity germanium detectors that have similar active volumes but distinct internal geometries. Experimental measurements were conducted at the UVSOR synchrotron facility using collimated laser Compton scattered -ray beams with an energy of 
MeV. Monte Carlo simulations using the Geant4 toolkit were performed to refine the detector models and replicate experimental results. The results reveal that the front layer thickness and the presence of structural elements such as the cold finger strongly affect the spectral features, particularly the appearance of a coincidence sum peak of the annihilation radiation at 1.022 MeV. Off-axis irradiation significantly improves the detection efficiency and reduces undesired induced interactions within inactive volumes. Additionally, the observed pair production signatures are validated through the available theoretical cross section data, confirming the dominant role of internal structures in shaping the detector response under beam geometry. These findings are essential for optimizing detector configurations in precision -ray beam experiments. This work is a contribution of the Japan Atomic Energy Agency (JAEA) to the International Atomic Energy Agency (IAEA) under the agreement of the coordinated research program (CRP), J02015 (Facilitation of Safe and Secure Trade Using Nuclear Detection Technology - Detection of RN and Other Contraband). A part of this work was conducted at the BL1U of UVSOR Synchrotron Facility, Institute for Molecular Science (IMS program 23IMS6602).
植野 雄大; 大内 和希; 渡邉 雅之
Results in Engineering (Internet), 29, p.109246_1 - 109246_10, 2026/03
Depleted uranium is a byproduct of the production of nuclear fuel, and various efforts have been made to develop new applications of it. The utilization of depleted uranium as an active material in redox-flow batteries is one of the promising applications. Quite recently we demonstrated a new static battery system using uranium and iron as active materials (UFe battery), but the potential performance is poorly understood. It is because the focus was on whether uranium works as an active material. Besides, there was limited information about the electrode reactions and the electrical conductivity of the electrolytic solutions. To clarify the ideal performance of the UFe battery, we investigated redox behaviors of uranium (IV) chloride and iron (II) chloride in chloride-containing non-aqueous solution by cyclic voltammetry and chronoamperometry techniques. In addition, the electrical conductivity of the solution was estimated by electrochemical impedance spectroscopy. As a result, the standard rate constants of both U(IV)/U(III) and Fe(III)/Fe(II) redox reactions were comparable to those in all-vanadium redox flow batteries (VRFBs), whereas the conductivity of the electrolytic solution was about 10 times lower than that of conventional aqueous batteries. The simulation using these electrochemical parameters suggested that the ideal performance of the UFe battery may be comparable to that of VRFBs when the distance between electrodes is sufficiently reduced. While there are many challenges for the application to the flow battery system, the UFe battery has the potential to be a new energy storage system and to utilize large amounts of depleted uranium.
