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Neutron resonance fission neutron analysis for nondestructive fissile material assay

弘中 浩太; Lee, J.; 小泉 光生; 伊藤 史哲*; 堀 順一*; 寺田 和司*; 佐野 忠史*

Nuclear Instruments and Methods in Physics Research A, 1054, p.168467_1 - 168467_5, 2023/09

We propose neutron resonance fission neutron analysis (NRFNA), an active nondestructive assay (NDA) technique, to improve the capability to identify and quantify a small amount of fissile material in a sample. NRFNA uses pulsed neutrons to induce fission reactions in the sample. Fission neutrons are detected by a neutron-gamma pulse shape discrimination (PSD) scintillation detector with time-of-flight (TOF) technique. The obtained nuclide-specific resonance peaks in the neutron energy spectrum provide information to identify and quantify a fissile material in the sample. The possibility of using PSD for NRFNA was confirmed through a test experiment using a natural uranium sample. We successfully observed the resonance peaks from $$^{235}$$U(n,f) reaction and showed that NRFNA would be useful for measuring a small amount of fissile material in a sample.


Data report of ROSA/LSTF experiment IB-HL-01; 17% hot leg intermediate break LOCA with totally-failed high pressure injection system

竹田 武司

JAEA-Data/Code 2023-007, 72 Pages, 2023/07


ROSA-V計画において、大型非定常実験装置(LSTF)を用いた実験(実験番号:IB-HL-01)が2009年11月19日に行われた。ROSA/LSTF IB-HL-01実験では、加圧水型原子炉(PWR)の加圧器サージラインの両端ギロチン破断による17%高温側配管中破断冷却材喪失事故を模擬した。このとき、高温側配管内面に接する様に、長いノズルを上向きに取り付けることにより破断口を模擬した。また、非常用炉心冷却系(ECCS)である高圧注入系の全故障と補助給水系の全故障を仮定した。実験では、比較的大きいサイズの破断が早い過渡現象を引き起こした。破断後一次系圧力が急激に低下し、蒸気発生器(SG)二次側圧力よりも低くなった。破断流は、破断直後に水単相から二相流に変化した。炉心露出は、ループシールクリアリング(LSC)前に、クロスオーバーレグの下降流側の水位低下と同時に開始した。低温側配管に注入されたECCSの蓄圧注入系(ACC)冷却水の蒸気凝縮により両ループのLSCが誘発された。LSC後の炉心水位の急速な回復により、全炉心はクエンチした。模擬燃料棒被覆管最高温度は、LSCとほぼ同時に検出された。ACC冷却水注入時、高速蒸気流による高温側配管からSG入口プレナムへの液体のエントレインメントにより、高温側配管とSG入口プレナムの水位が回復した。ECCSである低圧注入系の作動を通じた継続的な炉心冷却を確認後、実験を終了した。本報告書は、ROSA/LSTF IB-HL-01実験の手順、条件および実験で観察された主な結果をまとめたものである。


Impact of MOX fuel use in light-water reactors; Long-term radiological consequences of disposal of high-level waste in a geological repository

三成 映理子*; 樺沢 さつき; 三原 守弘; 牧野 仁史; 朝野 英一*; 中瀬 正彦*; 竹下 健二*

Journal of Nuclear Science and Technology, 60(7), p.793 - 803, 2023/07

 被引用回数:1 パーセンタイル:45.11(Nuclear Science & Technology)

As a series of studies to evaluate impact of mixed-oxide (MOX) fuel in light-water reactors (LWRs), post-closure long-term safety for various vitrified high-level radioactive waste (HLW) arising from the different fuel cycle intends to recycle Pu are examined. In this study, four fuel cycle scenarios with different ratio of spent MOX generated and two reprocessing options for each fuel cycle scenario are considered. One reprocessing option considers disposal of vitrified HLW generated separately from the reprocessing of spent UO$$_{2}$$ fuel and MOX fuel (separated HLW), and the other is blended vitrified UO$$_{2}$$-MOX HLW (blended HLW) generated during reprocessing whereby MOX spent fuel is diluted by UO$$_{2}$$ spent fuel. First, the radionuclide inventories of those vitrified HLWs are discussed. Next, radionuclide migration analyses for geological disposal of those vitrified HLWs are evaluated. It has revealed that the disposal of blended HLW will not have an adverse effect on the long-term radiological impact compared to separated HLW. Results of this study can be used as a basis for considering the blending option as a viable alternative approach in the future for managing MOX fuel used in light-water reactors.


日本原子力学会「2023年春の年会」、「シグマ」調査専門委員会、核データ部会合同セッション; シグマ委員会設立60周年記念; 核データ研究へのオールジャパンでの取り組み,1; シグマ委員会60年の歩み

深堀 智生

核データニュース(インターネット), (135), p.19 - 25, 2023/06



Study on borehole sealing corresponding to hydrogeological structures by groundwater flow analysis

澤口 拓磨; 高井 静霞; 笹川 剛; 打越 絵美子*; 嶋 洋佑*; 武田 聖司

MRS Advances (Internet), 8(6), p.243 - 249, 2023/06




青野 竜士; 水飼 秋菜; 土田 大貴; 今田 未来; 原賀 智子; 石森 健一郎; 亀尾 裕

JAEA-Data/Code 2023-002, 81 Pages, 2023/05


日本原子力研究開発機構の研究施設等から発生する放射性廃棄物は、放射能レベルに応じて将来的にトレンチとピットに分けて浅地中処分される予定であり、埋設処分を開始するまでに、廃棄体の放射能濃度を評価する方法を構築する必要がある。そこで、原子力科学研究所バックエンド技術部では、研究施設等廃棄物に対する放射能濃度評価方法の検討に資するため、原子力科学研究所内に保管されているJRR-2、JRR-3及びホットラボから発生した放射性廃棄物より分析試料を採取し、放射化学分析を実施した。本報告書は、令和2年度に取得した20核種($$^{3}$$H、$$^{14}$$C、$$^{36}$$Cl、$$^{60}$$Co、$$^{63}$$Ni、$$^{90}$$Sr、$$^{94}$$Nb、$$^{99}$$Tc、$$^{rm 108m}$$Ag、$$^{129}$$I、$$^{137}$$Cs、$$^{152}$$Eu、$$^{154}$$Eu、$$^{234}$$U、$$^{238}$$U、$$^{238}$$Pu、$$^{239}$$Pu、$$^{240}$$Pu、$$^{241}$$Am、$$^{244}$$Cm)の放射能濃度データについて整理し、放射能濃度評価方法の検討のための基礎資料としてまとめたものである。



坂井 章浩

デコミッショニング技報, (64), p.24 - 33, 2023/05



Design and characterization of the fission signature assay instrument for nuclear safeguards

Rossi, F.; 小泉 光生; Rodriguez, D.; 高橋 時音

Proceedings of INMM & ESARDA Joint Annual Meeting 2023 (Internet), 5 Pages, 2023/05

Since 2015, the Integrated Support Center for Nuclear Nonproliferation and Nuclear Security (ISCN) of the Japan Atomic Energy Agency has been working on the development of the Delayed Gamma-ray Spectroscopy non-destructive assay technique for the quantification of fissile-nuclide content in mixed nuclear materials. Thanks to the efforts and lessons learned from past experiments, the ISCN has successfully designed and fabricated a final integrated instrument. The instrument is composed of a moderator and dose shield where different neutron sources, like Cf-252 and neutron generators, can be inserted to irradiate the sample. Within the moderator, a series of neutron detectors are installed for perform prompt neutron analysis and continuous monitoring of the neutron source emission. Thanks to an innovative transfer system, the sample is then moved to the gamma-ray detector in less than 1.5s providing a fast and reliable movement while being safe from possible contamination. In this work, we will describe the design details of this new instrument. This work is supported by the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT) under the subsidy for the "promotion for strengthening nuclear security and the like".


Efforts for appropriate responses to safeguards activities, 1; Overview

青木 里英; 白藤 雅也; 野崎 天生; 阿久津 成美*; 宮地 紀子; 中村 仁宣

Proceedings of INMM & ESARDA Joint Annual Meeting 2023 (Internet), 7 Pages, 2023/05

In order to ensure transparency in the peaceful use of nuclear materials in Japan, it is important to appropriately respond to safeguards activities conducted by the IAEA/Japan. In order to strengthen activities to appropriately respond to safeguards activities, JAEA has started the following one activity of (1) for all employees in JAEA to promote understanding and raise awareness of safeguards and three activities of (2) for the employees involved in safeguards activities to appropriately respond on-site to the activities since FY2020: (1) Education on the basis of safeguards, (2-1) Lectures, (2-2) Case studies and (2-3) Standardization of procedures related to safeguards response. In Activity (1), the employees were required to understand Safeguards framework, safeguards activities and provisions of information to Nuclear Regulation Authority in Japan with developed education material, and to pass a confirmation test in FY2022. Accordingly, it was confirmed that understanding for safeguards was successfully promoted since 100% employees passed the test. In Activity (2-1), lectures were provided by experts of safeguards to make the employees reacknowledged the importance of transparency in the peaceful use of nuclear materials and the effect of inappropriate response to safeguards activities. In Activity (2-2), a material for case studies was developed including examples of inappropriate response to safeguards activities and the case studies were conducted by the employees based on the material for recognizing familiar risks of safeguards. The result of questionnaire in FY2022 indicated participants tended to become deeply understanding of familiar risk in each site through the case studies. In Activity (2-3), standard safeguards procedure for whole JAEA was developed to improve the procedures in each site based on the standard procedure and to standardize the response to safeguards throughout JAEA.


Applicability of differential die-away self-interrogation technique for quantification of spontaneous fission nuclides for fuel debris at Fukushima Daiichi Nuclear Power Plants

長谷 竹晃; 相樂 洋*; 小菅 義広*; 能見 貴佳; 奥村 啓介

Journal of Nuclear Science and Technology, 60(4), p.460 - 472, 2023/04

 被引用回数:0 パーセンタイル:0.01(Nuclear Science & Technology)

This paper provides an overview of the applicability of the Differential Die-Away Self-Interrogation (DDSI) technique for quantification of spontaneous fissile nuclides in fuel debris at the Fukushima Daiichi Nuclear Power Plants. In this research, massive fuel debris stored in a canister was evaluated, and the void space of the canister was assumed to be filled with water for wet storage and air for dry storage. The composition of fuel debris was estimated based on elements such as the inventory in the reactor core and operation history. The simulation results show that for wet storage, the DDSI technique can properly evaluate the neutron leakage multiplication and quantify spontaneous fissile nuclides with a total measurement uncertainty (TMU) of approximately 8%. For dry storage, the known-alpha technique, which was previously established, can be applied to quantify spontaneous fissile nuclides with a TMU of approximately 4%. In both cases, the largest uncertainty factor is the variation in water content in the canister. In the case of wet storage, the uncertainty could be significantly increased in cases where the fuel debris is extremely unevenly distributed in the canister.


Attention-based time series analysis for data-driven anomaly detection in nuclear power plants

Dong, F.*; Chen, S.*; 出町 和之*; 吉川 雅紀; 関 暁之; 高屋 茂

Nuclear Engineering and Design, 404, p.112161_1 - 112161_15, 2023/04

 被引用回数:0 パーセンタイル:0.02(Nuclear Science & Technology)

To ensure nuclear safety, timely and accurate anomaly detection is of utmost importance in the daily condition monitoring of Nuclear Power Plants (NPPs), as any slight anomaly in a plant may result in an irreversible and serious accident, as well as high costs of maintenance and management. Nevertheless, due to the unique inherent attributes of anomalies, the difficulty of automatic detection in NPPs is increased. Previous model-driven anomaly detection approaches required skilled priori knowledge, leading to their limited usability. Commonly adopted deep learning-based data-driven anomaly detection approaches may not easily acquire the most relevant features when dealing with sensor data containing redundant information with uneven distribution of anomalies. To alleviate these issues, this paper propose an attention-based time series model for anomaly detection to ensure safety in NPPs. First, we employ one-dimension convolutional neural network (1D-CNN) backbone for feature extraction to preserve original inherent features of time series inputs. Subsequently, we originally adopt soft-attention mechanism to automatically extract the most relevant temporal features considering the specificity of anomaly detection in NPPs. The performance of the proposed model was experimentally validated on the High Temperature Gas-cooled Reactor (HTGR) anomaly case dataset simulated using the analytical code. The experimental results indicate that the proposed model was capable of detecting anomalies in NPPs with superior performance to the baseline model, while ensuring fast detection at short time steps.


Study on safety characteristics of a sodium-cooled fast reactor with negative void reactivity during initiating phase in severe accident

石田 真也; 深野 義隆; 飛田 吉春; 岡野 靖

Proceedings of 2023 International Congress on Advanced in Nuclear Power Plants (ICAPP 2023) (Internet), 8 Pages, 2023/04

One of the effective design measures against core disruptive accident (CDA) is to decrease void reactivity, and a sodium-cooled fast reactor (SFR) with low void reactivity has been developed to improve reactor safety for future SFR. The evaluation of small SFRs, which can have a negative void reactivity coefficient, is useful to examine the reactor characteristics for future research and development. The event progression of unprotected loss of flow (ULOF), which is a typical initiating event of CDA, was analyzed by the SAS4A code. In comparison with a general behaviour of large SFR with relatively higher positive void reactivity, it was confirmed that the low void reactivity reactor has the following characteristics: (1) Event progression becomes slow and mild. (2) Positive reactivity insertion by a cladding melting and relocation has larger importance. (3) Generating mechanical energy during the initiating phase becomes less likely to occur.


福島原子力発電所事故由来の難固定核種の新規ハイブリッド固化への挑戦と合理的な処分概念の構築・安全評価(委託研究); 令和3年度英知を結集した原子力科学技術・人材育成推進事業

廃炉環境国際共同研究センター; 東京工業大学*

JAEA-Review 2022-072, 116 Pages, 2023/03




革新的水質浄化剤の開発による環境問題低減化技術の開拓(委託研究); 令和3年度英知を結集した原子力科学技術・人材育成推進事業

廃炉環境国際共同研究センター; 信州大学*

JAEA-Review 2022-067, 98 Pages, 2023/03




Pore connectivity influences mass transport in natural rocks; Pore structure, gas diffusion and batch sorption studies

Yuan, X.*; Hu, Q.*; Lin, X.*; Zhao, C.*; Wang, Q.*; 舘 幸男; 深津 勇太; 濱本 昌一郎*; Siitari-Kauppi, M.*; Li, X.*

Journal of Hydrology, 618, p.129172_1 - 129172_15, 2023/03

 被引用回数:0 パーセンタイル:0.01(Engineering, Civil)

Mass transport in geomedia as influenced by the pore structure is an important phenomenon. Six rocks (granodiorite, limestone, two chalks, mudstone, and dolostone) with different extents of heterogeneity at six different particle sizes were studied to describe the effects of pore connectivity on mass transport. The multiple methods applied were porosity measurement, gas diffusion test, and batch sorption test of multiple ions. Porosity measurement results reveal that with decreasing particle sizes, the effective porosities for the "heterogenous" group (granodiorite and limestone) increase, whereas the porosities of "homogeneous" group (chalks, mudstone, and dolostone) roughly remain constant. Gas diffusion results show that the intraparticle gas diffusion coefficient among these two groups, varying in the magnitude of 10$$^{-8}$$ to 10$$^{-6}$$ m$$^{2}$$/s. The batch sorption work displays a different affinity of these rocks for tracers, which are related to their mineral components. For granodiorite, mudstone, and dolostone, the adsorption capacity increases as the particle size decreases, due to higher specific surface area in smaller particle-size. In general, this integrated research of grain size distribution, rock porosity, intraparticle diffusivity, and ionic sorption capacity gives insights into the pore connectivity effect on both gas diffusion and chemical transport behaviors for different lithologies and/or different particle sizes.



坂井 章浩

第33回原子力施設デコミッショニング技術講座テキスト, p.31 - 63, 2023/02



Study on cesium compound formation by chemical interaction of CsOH and concrete at elevated temperatures

Luu, V. N.; 中島 邦久

Journal of Nuclear Science and Technology, 60(2), p.153 - 164, 2023/02

 被引用回数:3 パーセンタイル:81.34(Nuclear Science & Technology)

Recently, extremely high dose rates were detected in the three-layer concrete plugs of Units 2 and 3 at the Fukushima Daiichi Nuclear Power Plant. The high dose rates suggest that there are some trapping effects of radioactive materials on shield plugs when gas species and aerosols (e.g., CsOH, CsI) are released from reactor through the plug layers. To determine the trapping mechanism, concrete and commonly used aggregate and minerals are pulverized and mixed with CsOH, followed by heating at different temperatures to clarify the chemical interaction. The results showed that interactions of CsOH and CaCO$$_{3}$$ in concrete occurred even at room temperature to form Cs$$_{2}$$CO$$_{3}$$(H$$_{2}$$O)$$_{3}$$. The interaction with aggregates occurred above 100$$^{circ}$$C and resulted in the formation of CsAlSiO$$_{4}$$. Additionally, amorphous and crystalline SiO$$_{2}$$ interacted with CsOH, forming a glass-like product above 200$$^{circ}$$C. These results suggest that formation of Cs$$_{2}$$CO$$_{3}$$(H$$_{2}$$O)$$_{3}$$ would be one of the main trapping mechanism at shield plugs because CaCO$$_{3}$$ is commonly formed on concrete surface and reacts with CsOH at room temperature.


シグマ委員会60周年にあたって; シグマ委員会60年の物語

深堀 智生

核データニュース(インターネット), (134), p.34 - 45, 2023/02




友常 祐介; 矢嶋 まゆみ; 奥野 浩; 山本 一也

労働安全衛生研究, 16(1), p.29 - 43, 2023/02




外川 織彦; 大倉 毅史; 木村 仁宣

JAEA-Review 2022-049, 76 Pages, 2023/01



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