クリープ破断時間および高温引張強度予測モデルの連合学習

櫻井 惇也*; 鳥形 啓輔*; 松永 学*; 高梨 直人*; 日比野 真也*; 木津 健一*; 森田 聡*; 井元 雅弘*; 下畠 伸朗*; 豊田 晃大; et al.

鉄と鋼, 111(5), p.246 - 262, 2025/04

https://doi.org/10.2355/tetsutohagane.TETSU-2024-124

Creep testing is time-consuming and costly, leading institutions to limit the number of tests conducted to the minimum necessary for their specific objectives. By pooling data from each institution, it is anticipated that predictive models can be developed for a wide range of materials, including welded joints and degraded materials exposed to service conditions. However, the data obtained by each institution is often highly confidential, making it challenging to share with others. Federated learning, a type of privacy-preserving computation technology, allows for learning while keeping data confidential. Utilizing this approach, it is possible to develop creep life prediction models by leveraging data from various institutions. In this paper, we constructed global deep neural network models for predicting creep rupture life of heat-resistant ferritic steels in collaboration with eight institutions using the federated learning system we developed for this purpose. Each institution built a local model using only its own data for comparison. While these local models demonstrated good predictive accuracy for their respective datasets, their predictive performance declined when applied to data from other institutions. In contrast, the global model constructed using federated learning showed reasonably good predictive performance across all institutions. The distance between each institution's data was defined in the space of explanatory variables, with the NIMS data, which had the largest dataset, serving as the reference point. The global model maintained high predictive accuracy regardless of the distance from the NIMS data, whereas the predictive accuracy of the NIMS local model significantly decreased as the distance increased.

高速炉燃料用SUS316相当鋼の高温強度及び照射特性評価

宮澤 健; 上羽 智之; 矢野 康英; 丹野 敬嗣; 大塚 智史; 鬼澤 高志; 安藤 勝訓; 皆藤 威二

JAEA-Technology 2024-009, 140 Pages, 2024/10

JAEA-Technology-2024-009.pdf:8.03MB

SUS316相当鋼を用いた高速炉燃料設計の高信頼性化に向けて、SUS316相当鋼被覆管及びラッパ管の高温強度及び照射データを材料学的及び統計学的な観点で評価・解析することで、高温強度及び高照射量までの照射特性に係る設計用強度式を導出した。異常な過渡変化の上限温度を超える900CまでのSUS316相当鋼被覆管及びラッパ管(非照射材)の高温引張試験データ及び高温クリープ試験データを拡充し、0.2%耐力、引張強さ、クリープ破断強度の最適近似式と下限式並びに熱クリープひずみの最適近似式と上下限式を導出した。また、高速実験炉「常陽」、仏国・高速原型炉Phenix及び米国・FFTFで高照射量まで中性子照射したSUS316相当鋼被覆管及びラッパ管の照射後引張試験データ及びSUS316相当鋼被覆管の炉内クリープ破断試験データを解析することで、炉内Na中照射による引張強度及びクリープ強度の低下を表す強度補正係数を導出した。導出した式を実測値と比較することで、その妥当性を確認した。

Convection and joint characteristics in aluminum alloy melting zone during resistance spot welding of dissimilar Fe-Al material in external magnetic field

船引 雄太*; 伊與田 宗慶*; 菖蒲 敬久; 松田 朋己*; 林 雄二郎*; 佐野 智一*; 他8名*

Journal of Manufacturing Processes, 115, p.40 - 55, 2024/04

https://doi.org/10.1016/j.jmapro.2024.01.049

In resistance spot welding (RSW) of Fe and Al alloy, an intermetallic compound (IMC) is formed at the joining interface, and it is known that the joining strength of the joint decreases as the IMC becomes thicker. In this study, the convection behavior in the Al alloy melting zone of an Fe-Al alloy RSW was varied and the effect on the joint characteristics was investigated. For this study, focusing on the electromagnetic force generated in the Al alloy melting zone, the convection behavior in the Al alloy melting zone was changed by adding an external magnetic field using neodymium magnets. In-situ evaluation of the convection behavior using synchrotron radiation and cross-sectional macro-observation of the joint revealed that the addition of an external magnetic field causes a non-axisymmetric change in the convection behavior in the Al alloy melting zone, which results in the deflection of the Al alloy melting zone. The addition of an external magnetic field increases the driving force of convection and homogenizes the temperature field at the joining interface, suggesting that the IMC near the center is formed thin and uniform. Furthermore, from the cross tension test and the observation of the fracture surface of the joint after the test, it was clarified that the CTS of the joint with an external magnetic field was improved by the propagation of cracks into the Al alloy melting zone during the test.

Constraints on the dipole photon strength for the odd uranium isotopes

Moreno-Soto, J.*; 木村 敦; 他130名*

Physical Review C, 105(2), p.024618_1 - 024618_14, 2022/02

https://doi.org/10.1103/PhysRevC.105.024618

The -ray spectra from neutron-capture reactions on the U, U, and U nuclei have been measured with the total absorption calorimeter of the n_TOF facility at CERN. The background-corrected sum-energy and multi-step-cascade spectra were extracted for several isolated s-wave resonances up to about 140 eV. The experimental spectra were compared to statistical model predictions coming from a large selection of models of photon strength functions (PSFs) and nuclear level density (NLD). No combination of PSF and NLD models from literature is able to globally describe our spectra. After extensive search we were able to find model combinations with modified generalized Lorentzian (MGLO) E1 PSF, which match the experimental spectra as well as the total radiative widths.

Microstructural stability of ODS steel after very long-term creep test

岡 弘; 丹野 敬嗣; 矢野 康英; 大塚 智史; 皆藤 威二; 舘 義昭

Journal of Nuclear Materials, 547, p.152833_1 - 152833_7, 2021/04

https://doi.org/10.1016/j.jnucmat.2021.152833

本研究では、ODS鋼被覆管の強度決定因子であるナノサイズ酸化物粒子及び母相組織の高温・応力負荷下での安定性を評価するため、700Cで45,000時間を超える内圧クリープ試験に供して破断したODS鋼被覆管の微細組織観察を行った。観察したODS鋼は、焼き戻しマルテンサイトを母相とする9Cr-ODS鋼及び再結晶フェライトを母相とする12Cr-ODS鋼の製造まま材及びクリープ破断材である。破断後の内圧クリープ試験片から切り出した板片を電解研磨にて薄膜化し、透過電子顕微鏡JEOL 2010Fにて観察した。観察の結果、ナノ粒子のサイズ及び数密度は700Cにて45,000時間を超えるクリープ試験後においてもほぼ変化なく、高温長時間試験中に安定に存在していたことを確認した。また、9Cr-ODS鋼の強度決定因子の一つである焼き戻しマルテンサイト組織についても、製造まま材とクリープ破断材の間に大きな違いはなく、母相組織は安定であることがわかった。

Effect of nitrogen concentration on nano-structure and high-temperature strength of 9Cr-ODS steel

岡 弘; 丹野 敬嗣; 大塚 智史; 矢野 康英; 皆藤 威二

Nuclear Materials and Energy (Internet), 16, p.230 - 237, 2018/08

https://doi.org/10.1016/j.nme.2018.05.010

In determining the nitrogen concentration specifications, nano-structure and high-temperature strength of 9Cr-ODS steel have been investigated as a function of the nitrogen content with the aim of obtaining technical knowledge that makes the specification reasonable. The hardness and tensile strength showed degradation with increasing nitrogen content. For a microstructure, the decrement of residual ferrite phase was confirmed. Since the nitrogen is an austenite stabilizer, the increment of nitrogen enhanced an alpha to transformation, resulted in the decrease of the residual ferrite phase. It is considered that the reduction of the strength is due to the decrease of the residual ferrite phase.

Overview of Japanese development of accident tolerant FeCrAl-ODS fuel claddings for BWRs

坂本 寛*; 平井 睦*; 鵜飼 重治*; 木村 晃彦*; 山路 哲史*; 草ヶ谷 和幸*; 近藤 貴夫*; 山下 真一郎

Proceedings of 2017 Water Reactor Fuel Performance Meeting (WRFPM 2017) (USB Flash Drive), 7 Pages, 2017/09

http://www.wrfpm2017.org/upload/draft_file/D_033-PD1.pdf

本論文では、現在、経済産業省のプログラムにおいて進められている沸騰水型原子炉(BWR)用事故耐性FeCrAl-ODS燃料被覆管の開発の状況について概要を述べる。本プログラムでは、多種多様な内容の研究により、軽水炉において事故耐性燃料等を実用化するために必要な技術基盤を整備することが目的である。FeCrAl-ODS燃料被覆管の開発においては、実験研究と解析研究の両方を実施してきており、FeCrAl-ODS燃料被覆管の主要な材料特性に関しては、解析研究における評価を実験的にもサポートするために、本事業で製作した各種形状の試験片を用いてデータ取得やデータ拡充を行う。本事業では、機械的な特性に及ぼす中性子照射の影響を調べるために、米国オークリッジ国立研究所の高照射束炉(HFIR)を用いた中性子照射試験も実施している。

Effect of thermo-mechanical treatments on nano-structure of 9Cr-ODS steel

岡 弘; 丹野 敬嗣; 大塚 智史; 矢野 康英; 上羽 智之; 皆藤 威二; 大沼 正人*

Nuclear Materials and Energy (Internet), 9, p.346 - 352, 2016/12

https://doi.org/10.1016/j.nme.2016.10.007

The effect of thermo-mechanical treatments (TMTs) on the evolution of nano-structure in an oxide dispersion strengthened (ODS) ferritic/martensitic steel (Fe-9Cr-2W-0.22Ti-0.36YO) was investigated. TMTs involve hot extruding and subsequent forging, which are expected to be part of a future industrial-scale manufacturing process of the ODS steel. It was shown that the ODS steel was composed of two phases - a fine-grained residual ferrite phase and a transformable martensite phase. The number density of the nano-sized particles in the residual ferrite phase was significantly higher than that in the martensite phase. The TMTs did not significantly affect the number density, but slightly affected the size distribution of the nano-sized particles in both ferrite phase and martensite phase. Moreover, the volume fraction of the residual ferrite phase decreased after TMTs. In summary, the TMT conditions could be a parameter which affects the nano-structure of the ODS steel.

Measurement of the Se(, n) cross section and uncertainty evaluation of the Se(n, ) cross section

北谷 文人; 原田 秀郎; 後神 進史*; 岩本 信之; 宇都宮 弘章*; 秋宗 秀俊*; 豊川 弘之*; 山田 家和勝*; 井頭 政之*

Journal of Nuclear Science and Technology, 53(4), p.475 - 485, 2016/04

https://doi.org/10.1080/00223131.2015.1056760

We precisely measured the (, n) cross section for Se by developing a spectroscopic method utilizing Laser Compton-Scattering -rays. Moreover, the Se(n, ) Se cross section was deduced using the statistical model calculation code CCONE with -ray strength functions adjusted to reproduce the (, n) cross sections for Se and the even Se isotopes Se, Se and Se. The reliability of the Se(n, ) Se cross section calculated by CCONE with the adjusted -ray strength function was evaluated by comparing available experimental (n, ) cross sections for stable Se isotopes and those calculated by CCONE with the adjusted -ray strength function. The result provides fundamental data for the study of nuclear transmutation for the long-lived fission product of Se.

Applicability study of nuclear graphite material IG-430 to VHTR

大崎 弘貴; 島崎 洋祐; 角田 淳弥; 柴田 大受; 小西 隆志; 石原 正博

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 8 Pages, 2015/05

超高温ガス炉(VHTR)黒鉛構造物の設計では、高強度で、かつ耐酸化性の高い黒鉛材の使用が望まれる。IG-430(黒鉛材)は、VHTR黒鉛構造物の有望な候補材のひとつであるが、高温ガス炉の設計のための十分なデータベースが存在しない。そこで、本研究では、IG-430の設計データとして最も重要な強度の一つである圧縮強度を測定結果を統計的に評価した。また、IG-430黒鉛構造物の信頼性をHTTRの黒鉛設計基準で用いられている安全率をもとに評価し、VHTR黒鉛構造物としての適用性を検討した。その結果、IG-430は、高温ガス炉で使われている従来の黒鉛材の一つであるIG-110よりも高強度(約11%)で、かつ、低い標準偏差(約27%)を持つことが示された。これは、IG-430中のき裂の伝播が、IG-110中と比較して容易でないためと推定される。また、評価したIG-430の破壊確率が低いことから、IG-430を用いることで黒鉛構造物の信頼性の向上が達成できることが分かった。以上より、IG-430がVHTRの黒鉛構造物に適用できる見通しを得た。