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Scalability of inertial particle deposition in bubbles with internal circulation

茂木 孝介; 柴本 泰照; 久木田 豊

Annals of Nuclear Energy, 184, p.109679_1 - 109679_10, 2023/05

Inertial deposition of small (less than a few $$mu$$ m in diameter) aerosol particles in mm-scale bubbles is an old but unsettled issue in modeling of pool scrubbing phenomenon. Whereas existing practical models give no specific consideration to the bubble-internal transport, some studies have shown that inertial transport affects considerably the particle deposition rate. We show, on the basis of Lagrangian simulations of particles advected by steady internal circulation in a spherical bubble, that particle centrifugal velocity becomes scale invariant for low- Stokes numbers (St $$le$$ $$10^{-2}$$) when the characteristic timescale is chosen to be that for transversal particle motion at the Stokes terminal velocity corresponding to the local fluid acceleration. Because a scaling law can be derived by running simulations with a small number of particles, it can provide a practical tool for considering the influence of inertial particle transport within the bubble on the decontamination factor.


Some considerations on the dependence to numerical schemes of Lagrangian radionuclide transport models for the aquatic environment

Peri$'a$$~n$ez, R.*; Brovchenko, I.*; Jung, K. T.*; Kim, K. O.*; Liptak, L.*; Little, A.*; 小林 卓也; Maderich, V.*; Min, B. I.*; Suh, K. S.*

Journal of Environmental Radioactivity, 261, p.107138_1 - 107138_8, 2023/05



Atmospheric ammonia deposition and its role in a cool-temperate fragmented deciduous broad-leaved forest

堅田 元喜*; 山口 高志*; 渡辺 誠*; 福島 慶太郎*; 中山 理智*; 永野 博彦*; 小嵐 淳; 舘野 隆之輔*; 久保田 智大

Atmospheric Environment, 298, p.119640_1 - 119640_12, 2023/04

Moderately elevated reactive nitrogen (Nr) deposition due to anthropogenic activities can have an impact on forest production via throughfall and canopy retention processes. Forest fragmentation can increase dry deposition of atmospheric ammonia volatilized from agricultural areas, and consequently increase spatial variability of Nr deposition even within the same forest (edge effect). However, little is known about the edge effect and its impact on forest production in a deciduous broad-leaved forest in Asian countries. Here, we performed the field observations of atmospheric concentration and deposition of inorganic Nr gases and particles in a Japanese fragmented forest from May 2018 to April 2019. The results demonstrated that annual dry deposition of ammonia was dominant in the annual total dissolved inorganic Nr deposition at the forest edge, including the edge effect. Additionally, agricultural activities such as fertilization in the area surrounding the forest likely enhanced the potential of canopy retention of NH$$_{4}$$$$^{+}$$, known as Nr species readily absorbed by tree canopy.


Experimental study on local damage to reinforced concrete panels subjected to oblique impact by projectiles

奥田 幸彦; 西田 明美; Kang, Z.; 坪田 張二; Li, Y.

Journal of Nuclear Engineering and Radiation Science, 9(2), p.021801_1 - 021801_12, 2023/04



ARKADIA; For the innovation of advanced nuclear reactor design

大島 宏之; 浅山 泰; 古川 智弘; 田中 正暁; 内堀 昭寛; 高田 孝; 関 暁之; 江沼 康弘

Journal of Nuclear Engineering and Radiation Science, 9(2), p.025001_1 - 025001_12, 2023/04



Validation of feedback reactivity evaluation models for plant dynamics analysis code during unprotected loss of heat sink event in sodium-cooled fast reactors

吉村 一夫; 堂田 哲広; 井川 健一*; 田中 正暁; 山野 秀将

Journal of Nuclear Engineering and Radiation Science, 9(2), p.021601_1 - 021601_9, 2023/04



Aging of fuel-containing materials (fuel debris) in the Chornobyl (Chernobyl) Nuclear Power Plant and its implication for the decommissioning of the Fukushima Daiichi Nuclear Power Station

北垣 徹; Krasnov, V.*; 池田 篤史

Journal of Nuclear Materials, 576, p.154224_1 - 154224_14, 2023/04


Nuclear fuel debris is a complex material containing a wide range of elements, compounds, and radiation. This complexity renders all the stages of the treatment of nuclear fuel debris extremely difficult and troublesome in the technical context. The whole treatment of nuclear fuel debris is also an extremely long-term process for tens of thousands of years, during which the aging of nuclear fuel debris is an unavoidable but critical issue. This applies to the decommissioning of the damaged reactors of the Fukushima Daiichi Nuclear Power Station (1F). This review article aims at collecting and summarizing the knowledge and information about the aging of materials containing nuclear fuels (fuel-containing materials) formed as a result of the accident at ChNPP-4 in the light of the decommissioning of 1F and assessing the potential effects of aging on the nuclear fuel debris remaining in the damaged 1F reactors.


Photocatalytic unification of iodine species using platinum-loaded titanium dioxide

杉田 剛; 森 勝伸*; 香西 直文

Journal of Photochemistry and Photobiology A; Chemistry, 438, p.114548_1 - 114548_6, 2023/04

原子力事故や放射性廃棄物の放出によって汚染された水からヨウ素を除去することは、水中に様々な形でヨウ素が存在するため、複雑でコストがかかる。そこで、水中の放射性ヨウ素を除去するための前処理として、光触媒によるヨウ素種の統一を検討した。ヨウ化物(I$$^{-}$$), ヨウ素酸(IO$$_3^{-}$$), o-ヨード安息香酸の光触媒酸化還元反応に及ぼすPt-TiO$$_{2}$$結晶相と溶液pHの影響を評価した。TiO$$_{2}$$結晶相とpHの選択により、混合されたヨウ素種をI$$^{-}$$またはIO$$_3^{-}$$のみに統一することができた。Pt-TiO$$_{2}$$の種類に関係なく、アルカリ性条件下でo-ヨード安息香酸中のヨウ素はI$$^{-}$$に無機化された。光触媒と溶液のpHを選択することでヨウ素種を単一化できるため、この光触媒処理は高効率でヨウ素種を除去するために適用できると考えられる。


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


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.


MAAP code analysis focusing on the fuel debris condition in the lower head of the pressure vessel in Fukushima-Daiichi Nuclear Power Station Unit 2

佐藤 一憲; 吉川 信治; 山下 拓哉; Cibula, M.*; 溝上 伸也*

Nuclear Engineering and Design, 404, p.112205_1 - 112205_21, 2023/04



A New application technique of a position-sensitive liquid light guide Cerenkov counter for the simultaneous position detection of $$^{90}$$Sr/$$^{90}$$Y and $$^{137}$$Cs radioactivity

寺阪 祐太; 瓜谷 章*

Nuclear Instruments and Methods in Physics Research A, 1049, p.168071_1 - 168071_7, 2023/04

A new application of a position-sensitive liquid light guide Cerenkov counter for the simultaneous position detection of $$^{90}$$Sr/$$^{90}$$Y and $$^{137}$$Cs radioactivity in a gamma-ray-dominant environment is proposed. $$beta$$-emitting $$^{90}$$Sr/$$^{90}$$Y and $$gamma$$-emitting $$^{137}$$Cs radioactive point sources were measured using a position-sensitive liquid light guide based on the time-of-flight (TOF) method. We found a clear difference in the count rate ratio between the source position peak and reflection peak of the position histogram. Moreover, simultaneous measurements of the radioactive point sources were performed. The results suggest that the source position and activity of $$^{90}$$Sr/$$^{90}$$Y and $$^{137}$$Cs can be simultaneously determined based on the count rate ratio of the source position peak and the reflection peak.


Elastic properties of nuclear pasta in a fully three-dimensional geometry

Xia, C.-J.*; 丸山 敏毅; 安武 伸俊*; 巽 敏隆*; Zhang, Y.-X.*

Physics Letters B, 839, p.137769_1 - 137769_5, 2023/04

Realistic estimations on the elastic properties of neutron star matter are carried out with a large strain ($$varepsilon$$ $$_sim^{<}$$ 0.5) in the framework of relativistic-mean-field model with Thomas-Fermi approximation, where various crystalline configurations are considered in a fully three-dimensional geometry with reflection symmetry. Our calculation confirms the validity of assuming Coulomb crystals for the droplet phase above neutron drip density, which nonetheless does not work at large densities since the elastic constants are found to be decreasing after reaching their peaks. Similarly, the analytic formulae derived in the incompressible liquid-drop model give excellent description for the rod phase at small densities, which overestimates the elastic constants at larger densities. For slabs, due to the negligence on the variations of their thicknesses, the analytic formulae from liquid-drop model agree qualitatively but not quantitatively with our numerical estimations. By fitting to the numerical results, these analytic formulae are improved by introducing dampening factors. The impacts of nuclear symmetry energy are examined adopting two parameter sets, corresponding to the slope of symmetry energy L = 41.34 and 89.39 MeV. Even with the uncertainties caused by the anisotropy in polycrystallines, the elastic properties of neutron star matter obtained with L = 41.34 and 89.39 MeV are distinctively different, results in detectable differences in various neutron star activities.


炉内ソースターム解析コードTRACER Version 2.4.1(マニュアル)

大野 雅広*; 内堀 昭寛; 岡野 靖; 高田 孝*

JAEA-Testing 2022-004, 193 Pages, 2023/03

高速炉の燃料破損時にナトリウム中に放出される放射性物質の挙動は、燃料破損の速やかな検出によるプラント異常事象の拡大防止、保守時の被曝線量の低減、及び事故時に放出される放射性物質量評価等に関して重要である。このため、燃料破損時に冷却材中に放出され、一次冷却材を経由してカバーガス空間へ至る核分裂生成物(以下、FPと略す)の種類とその量(炉内ソースターム)をより現実的に評価することを目的として、これらの FP 移行過程で起こる物理的・化学的挙動を機構論的に取り扱う解析コードTRACER (Transport phenomena of Radionuclides for Accident Consequence Evaluation of Reactor)が開発されている。TRACERコードは、燃料ピンの破損に伴う冷却材へのFP放出から始まる、一連のFP移行挙動を解析する。解析は燃料ピン、一次冷却材及びカバーガスと炉内の範囲でのFP挙動を対象としている。具体的には、燃料ピンから放出されるFP、1次系冷却材中を移行するFP、冷却材中を輸送されるFPを含む希ガス気泡、カバーガスへ放出されるFP、カバーガスから炉外へ漏洩するFPといった一連の挙動である。本マニュアルはTRACER Version 2.3のマニュアルに対し、数式等の参考文献の追加、インプットファイル作成方法の解説の改善、TRACERコードへ加えたNUREG-0772モデルの改良に関して追記、Appendixで行ったサンプル解析の図の修正、サンプル解析の追加といった変更を加えたものである。


海外炉を用いた中性子照射試験,1; キャプセル温度制御システムを用いた照射試験の検討(共同研究)

高部 湧吾; 大塚 紀彰; 冬島 拓実; 佐谷戸 夏紀; 井上 修一; 森田 寿; Jaroszewicz, J.*; Migdal, M.*; 小沼 勇一; 飛田 正浩*; et al.

JAEA-Technology 2022-040, 45 Pages, 2023/03


中性子照射場として中核を担ってきた材料試験炉(Japan Materials Testing Reactor: JMTR)の廃止に伴い、軽水炉の一層の安全性、信頼性・効率性向上のための技術開発や革新的な原子炉開発に必要な国内照射場が喪失され、照射試験炉の運転技術や照射技術の継承や人材育成も困難な状況となった。こうした課題に対処するため、代替手段として中性子照射場を海外炉に求めた照射試験の実施に係る検討を行った。「ポーランド国立原子力研究センターと日本原子力研究開発機構との間の試験研究炉の研究開発のための共同研究取決め」に基づきポーランド国立原子力研究センター(NCBJ)が所有するMARIA炉(出力30MW)を中性子照射場として、JMTRの有する照射技術の一つである温度制御システムを導入した照射試験の実施可否を検討した。その結果、JMTRの設計・製作基準に則って製作済であったキャプセルに対し改造を施すことで照射試験の実現が可能である見通しが得られた。改造後に浸透探傷検査、絶縁導通試験及びキャプセルの使用温度である室温$$sim$$300$$^{circ}$$Cの範囲における動作試験等を実施し、良好な結果が得られ、MARIA炉への輸送前準備を完了した。



濱口 拓; 山田 純也; 小松崎 直也*; 畠山 巧; 瀬谷 夏美; 武藤 保信; 宮内 英明; 橋本 周

JAEA-Technology 2022-038, 65 Pages, 2023/03





乙川 義憲; 松田 誠; 阿部 信市

JAEA-Technology 2022-037, 23 Pages, 2023/03





小野 礼人; 高柳 智弘; 杉田 萌; 植野 智晶*; 堀野 光喜*; 山本 風海; 金正 倫計

JAEA-Technology 2022-036, 31 Pages, 2023/03





山下 直輝; 入澤 恵理子; 加藤 千明; 佐野 成人; 田上 進

JAEA-Technology 2022-035, 29 Pages, 2023/03





佐野 成人; 山下 直輝; 星野 一豊*; 塚田 学*; 澤口 迪弥*; 大竹 良徳*; 市瀬 健一; 田上 進

JAEA-Technology 2022-034, 47 Pages, 2023/03





影山 十三男; 出沼 昭生; 小泉 仁*; 小田倉 学*; 萩野谷 雅浩*; 井坂 信一*; 門脇 弘幸*; 小林 真悟*; 森元 大成*; 加藤 芳章*; et al.

JAEA-Technology 2022-033, 130 Pages, 2023/03



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