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真野 晃宏; 山口 義仁; 勝山 仁哉
International Journal of Pressure Vessels and Piping, 222, p.105792_1 - 105792_11, 2026/08
被引用回数：0PASCAL-SPは、日本原子力研究開発機構(JAEA)が開発したPFM解析コードであり、加圧水型原子炉及び沸騰水型原子炉の両方の環境における応力腐食割れや疲労等の経年劣化を考慮して配管の破損確率を評価できる。PASCAL-SPの解析結果の信頼性を高めるために、米国NRCがEPRIと共同で開発したPFM解析コードxLPRを用いたベンチマーク解析を実施した。この解析は、共通の解析条件に基づく決定論的解析と確率論的解析から構成される。ベンチマーク解析の結果、決定論的解析と確率論的解析の両方でPASCAL-SPとxLPRがほぼ同じ結果を出力することが確認された。本論文では、使用した解析条件の詳細と、解析結果の比較を示す。
Negyesi, M.*; 長谷川 邦夫
Journal of Pressure Vessel Technology, 148(4), p.044501_1 - 044501_4, 2026/08
When flaws are detected in power plant pipes, they are evaluated to determine their impact on component integrity. According to the ASME Code Section XI, the maximum allowable flaw depth should be less than 75% of the pipe wall thickness. The current code maximum allowable flaw length is defined as the length at which through-wall flawed piping fails due to applied stress. Therefore, the current length is irrespective of flaw depth. This paper uses a flat plate model with surface flaws to examine the characteristics of flaw lengths and propose a new methodology for determining the maximum allowable flaw lengths.
阿部 拓海; 鈴木 大河*; 岡村 知拓*; 中瀬 正彦*
Annals of Nuclear Energy, 232, p.112224_1 - 112224_7, 2026/07
被引用回数：0Reprocessed uranium is important for sustainable nuclear fuel use. It contains isotopes such as U-232, U-234, and U-236, which influence enrichment and later nuclear fuel cycle steps. To evaluate these effects, nuclear fuel cycle simulators require cascade models capable of handling multi-isotopic uranium. In this study, an ideal cascade model based on the matched abundance ratio cascade was implemented in a nuclear fuel cycle simulator NMB4, developed by the Institute of Science Tokyo and Japan Atomic Energy Agency. A three-component approximation was introduced to simplify calculations. Validation against numerical solutions and experimental data showed good agreement. Compared with the simple coefficient method, the ideal cascade model improved predictions for isotopes such as U-232 and U-236, which affect radiation, separative work, and actinide production. These results demonstrate that the new model enhances the accuracy of reprocessed uranium evaluation, aiding future fuel cycle planning.
Nguyen, H. H.
Annals of Nuclear Energy, 230, p.112171_1 - 112171_13, 2026/06
被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)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。
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：98.37(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%.
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：0 パーセンタイル：0.00(Nuclear Science & Technology)Advanced 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 パーセンタイル：0.00(Instruments & Instrumentation)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。
小林 大志*; Moniruzzaman, M.*; 元川 竜平; 佐々木 隆之*
Applied Geochemistry, 202, p.106780_1 - 106780_11, 2026/05
被引用回数：0The geochemical environment for lanthanide (Ln) oxides and hydroxides involves aquatic system processes where Lns are mobilized or immobilized by dissolution and precipitation. In the current study, solubility experiments were performed using lanthanum (La), europium (Eu), and thulium (Tm) oxides as starting materials in the undersaturation method and La, Eu, and Tm nitrate solutions as starting materials in the oversaturation method. After aging at 25 or 90C for given periods, the crystal structure, particle size, and solid-phase surface-charge states were investigated to interpret the La, Eu, and Tm solubilities. In aqueous systems, La is stable as La(OH)(cr), which dominates the bulk structure, surface-charge state, and solubility. In the oversaturation method at 25C, the presence of fine primary La(OH)(cr,np) particles with higher solubility was observed, suggesting the possible particle-size effect. However, in the undersaturation method at 90C, the surface-charge state was found to be more negative than that of other solid phases, resulting in lower solubility. The EuO and Eu(OH) stabilities are competitive in aqueous systems. The bulk solid phase was Eu(OH)(cr) in the oversaturation method at 25 and 90C, and in the undersaturation method at 90C, whereas the surface-charge state appeared to be controlled by EuO when aged at 90C. The stability of TmO increased further, so that TmO(cr) dominated the bulk, surface-charge state, and solubility, aged at both 25 and 90C in the undersaturation method. In contrast, Tm(OH)(am) was formed using the oversaturation method and dominated the bulk, surface-charge state, and solubility at both temperatures. These findings are expected to provide important clues for understanding the evolution of lighter-to-heavier Ln oxides and hydroxides in aqueous systems, which is important for radioactive waste disposal.
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.
相澤 直人*; 渡邉 友章; 千葉 豪*; 多田 健一; 藤田 達也*; 山本 章夫*
Nuclear Engineering and Technology, 58(5), p.104176_1 - 104176_16, 2026/05
被引用回数：0A quick neutron spectrum reconstruction module based on proper orthogonal decomposition (POD) and a regression model for fast reactors is developed for the general-purpose burnup calculation code SWAT-X. This module enables burnup calculations to be performed quickly for arbitrary conditions based on a few parameters, eliminating the need for computationally intensive calculation codes. Reduced-order and regression models are constructed by applying the POD technique to the snapshot data of the multi-group neutron fluxes calculated using randomly-sampled parameter sets for a single hexagonal pin-cell of a sodium-cooled fast reactor. The neutron spectrum is reconstructed using a linear combination of POD basis vectors with the coefficients obtained from the regression model. The applicability of a pin-cell model, the accuracy of the reconstruction module itself, and its integration with SWAT-X are verified by comparing with the calculation results from the reactor physics code system CBZ.
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：0 パーセンタイル：0.00(Instruments & Instrumentation)In 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.
Noseck, U.*; Sch
fer, T.*; Alonso, U.*; 浜本 貴史*; Havlova, V.*; Hibberd, R.*; 石寺 孝充; 北村 暁; Klajmon, M.*; Missana, T.*; et al.
Applied Geochemistry, 201, p.106762_1 - 106762_23, 2026/04
被引用回数：0グリムゼル試験場(GTS)での長期原位置試験(LIT)および対応するモックアップ実験において、地球化学的条件が変化する環境での
Se(VI)、
Tc(VII)、
U(VI)、
Np(V)、
Am(III)、Th(IV)および
Pu(IV)の挙動をより深く理解するために、熱力学ベンチマーク計算を実施した。本計算では、これらの元素の地球化学的な溶存状態評価モデルとデータベースの状況を確認することも目的としている。これらの実験は、結晶質岩石中に設置されたベントナイト人工バリアを含む放射性廃棄物処分場概念における廃棄体近傍の場をシミュレートしており、その知見は放射性廃棄物処分場の長期安全性評価に貢献する。
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 パーセンタイル：0.00(Materials Science, Multidisciplinary)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。
河村 拓馬; 下村 和也; 井戸村 泰宏
Journal of Advanced Simulation in Science and Engineering (Internet), 13(1), p.29 - 43, 2026/04
本論文では、計算流体力学におけるシミュレーションを対象として、VR IS-PBVRと呼ぶ仮想現実(VR)ベースのIn-situ制御フレームワークを提案する。本フレームワークにより、ユーザはスーパーコンピュータ上でシミュレーションが実行されている間に、その結果を没入型のVR環境で観察し、可視化結果に基づいてシミュレーション条件を対話的に調整することが可能となる。VR IS-PBVRでは、圧縮された可視化用粒子とファイルベースの通信を駆使することでシミュレーションの実行を妨げることなくIn-situ制御が可能である。更にVR IS-PBVRのベースとなっている可視化ライブラリKVSをOpenXRで拡張することで、汎用的なヘッドマウントディスプレイで動作する実装を実現した。本フレームワークの有効性は、OpenFOAMを用いた都市風況シミュレーションを通じて示されている。この例により、没入型VR可視化と対話的なステアリングを組み合わせることで、シミュレーション実行中の挙動をより直感的に理解・解析できることを示している。
Jiang, L.*; Wang, H. H.*; Su, Y. H.; 徐 平光; 篠原 武尚; Xia, B.*; Wang, Y. W.*
Journal of Materials Science, 61(14), p.9754 - 9775, 2026/04
被引用回数：0In this study, pulsed neutron Bragg-edge transmission imaging was employed to characterize plastic deformation of high-manganese austenitic steel during cryogenic impact fracture. Electron backscatter diffraction was used to examine the microstructural evolution. The results reveal that the Bragg-edge width was identified as the critical value for large plastic deformation. Both crack initiation and stable crack growth regions exhibited higher levels of plastic deformation, twin density, and dislocation density compared to unstable crack growth regions. As the test temperature decreased from 273 K to 77 K, the transition point from stable to unstable crack growth occurred earlier. This is responsible for the reduction in impact absorbed energy. These findings provide new insights into the cryogenic toughening mechanism of high-manganese steel.
O solution熊谷 友多; 日下 良二; 高野 公秀; 渡邉 雅之
Journal of Nuclear Materials, 625, p.156553_1 - 156553_7, 2026/04
被引用回数：0U-Zr酸化物固溶体は、重大な原子炉事故時に形成される燃料デブリ中に一般的に含まれる相である。本研究では、放射線分解により生成する主要な酸化剤である過酸化水素に対するU-Zr酸化物固溶体の耐性を研究した。過酸化水素との繰り返し接触により、ウランの溶解は初期に進行するが次第に抑制され、ジルコニウムの溶解はより緩やかに進行した。ラマン分光およびX線回折により、表面の化学変化は限定的であり、ウラニル過酸化物の生成もわずかであった。表面に酸化還元活性サイトが存在するとした反応速度論モデルにより実験結果を再現した。解析の結果は反応活性サイトの表面密度は低いことを示唆した。これらの結果は、U-Zr酸化物固溶体の高い耐久性が保護被膜の形成によるものではなく、表面の酸化還元反応性の低さ自体に起因することを示唆する。
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：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)Ion 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.
