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相馬 秀; 石垣 将宏*; 安部 諭; 柴本 泰照
Nuclear Engineering and Technology, 10 Pages, 2024/00
When analyzing containment thermal-hydraulics, computational fluid dynamics (CFD) is a powerful tool because multi-dimensional and local analysis is required for some accident scenarios. According to the previous study, neglecting steam bulk condensation in the CFD analysis leads to a significant error in boundary layer profiles. Validating the condensation model requires the experimental data near the condensing surface, however, available boundary layer data is quite limited. It is also important to confirm whether the heat and mass transfer analogy (HMTA) is still valid in the presence of bulk condensation. In this study, the boundary layer measurements on the vertical condensing surface in the presence of air were performed with the rectangular channel facility WINCS, which was designed to measure the velocity, temperature, and concentration boundary layers. We set the laminar flow condition and varied the Richardson number (1.0-23) and the steam volume fraction (0.35-0.57). The experimental results were used to validate CFD analysis and HMTA models. For the former, we implemented a bulk condensation model assuming local thermal equilibrium into the CFD code and confirmed its validity. For the latter, we validated the HMTA-based correlations, confirming that the mixed convection correlation reasonably predicted the sum of wall and bulk condensation rates.
和田 有希*; 鴨川 仁*; 久保 守*; 榎戸 輝揚*; 林 省吾*; 澤野 達也*; 米徳 大輔*; 土屋 晴文
Journal of Geophysical Research; Atmospheres, 128(21), p.e2023JD039354_1 - e2023JD039354_20, 2023/11
被引用回数：0During the 2020-2021 winter season, we detected 6 gamma-ray glows at Kanazawa University, Japan. Negative surface electric fields (E-fields) were observed by a field mill during all the glow cases. In five of the six cases, the maximum E-field reached 
12 
, and the E-field during the glow detection was the strongest in 3 hours before and after the detection time. Therefore, negative charges should have been dominant in the thunderclouds that produced the gamma-ray glows, and electrons were probably accelerated and multiplied by the E-fields between a predominantly negative charge layer and a localized positive charge layer below. In addition, we extracted 8 non-detection cases in the 2020-2021 winter season, in which surface E-fields were stronger than 12 . In 5 of the 8 cases, radar echoes were inadequately developed, suggesting insufficient charge accumulation. On the other hand, the remaining 3 cases had well-developed radar echoes, and there was no significant difference from the detection cases.
和田 有希*; Wu, T.*; Wang, D.*; 榎戸 輝揚*; 中澤 知洋*; 森本 健志*; 中村 佳敬*; 篠田 太郎*; 土屋 晴文
Journal of Geophysical Research; Atmospheres, 128(15), p.e2023JD038606_1 - e2023JD038606_9, 2023/08
被引用回数：2 パーセンタイル：58.15(Meteorology & Atmospheric Sciences)A gamma-ray glow, a minute-lasting burst of high-energy photons from a thundercloud, was detected by ground-based apparatus at Kanazawa University, Japan, in a winter thunderstorm on 18 December 2018. The gamma-ray glow was quenched by a lightning flash within a brief time window of 40 ms. The lightning flash produced several low-frequency (LF) E-change pulses that were temporally coincident withthe termination of the gamma-ray glow, and that were located within 0.5 km from the observation site by the Fast Antenna Lightning Mapping Array. The LF pulses had the same polarity as a positive cloud-to-ground current and a normal-polarity in-cloud current. Since this polarity is against the upward electric field for producing the gamma-ray glow (accelerating electrons to the ground), we infer that the glow was terminated by a normal-polarity in-cloud discharge activity between a middle negative layer and an upper positive layer.
鶴見 美和*; 榎戸 輝掲*; 一方井 祐子*; Wu, T.*; Wang, D.*; 篠田 太郎*; 中澤 知洋*; 辻 直樹*; Diniz, G.*; 片岡 淳*; et al.
Geophysical Research Letters, 50(13), p.e2023GL103612_1 - e2023GL103612_9, 2023/07
被引用回数：0 パーセンタイル：0(Geosciences, Multidisciplinary)Gamma-ray glows are observational evidence of relativistic electron acceleration due to the electric field in thunderclouds. However, it is yet to be understood whether such relativistic electrons contribute to the initiation of lightning discharges. To tackle this question, we started the citizen science "Thundercloud Project," where we map radiation measurements of glows from winter thunderclouds along Japan's sea coast area. We developed and deployed 58 compact gamma-ray monitors at the end of 2021. On 30 December 2021, five monitors simultaneously detected a glow with its radiation distribution horizontally extending for 2 km. The glow terminated coinciding with a lightning flash at 04:08:34 JST, which was recorded by the two radio-band lightning mapping systems, FALMA and DALMA. The initial discharges during the preliminary breakdown started above the glow, that is, in vicinity of the electron acceleration site. This result provides one example of possible connections between electron acceleration and lightning initiation.
田中 正暁; 三宅 康洋*; 江連 俊樹; 浜瀬 枝里菜
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 9 Pages, 2023/05
浸漬型直接冷却器(D-DHX)を用いた崩壊熱除去時に生じる炉心プレナム相互作用時の炉心熱流動を評価できる設計検討用の数値流体力学コードを用いた数値解析モデルの開発を行っている。ナトリウム試験装置PLANDTL-2での試験結果を用いた妥当性確認での妥当性を判断するため、AVM法及びその修正方法を用い、解析と実験結果との差を定量的に計測することを試み、これら手法の適用性を確認することができた。
Pacio, J.*; Van Tichelen, K.*; Eckert, S.*; Wondrak, T.*; Di Piazza, I.*; Lorusso, P.*; Tarantino, M.*; Daubner, M.*; Litfin, K.*; 有吉 玄; et al.
Nuclear Engineering and Design, 399, p.112010_1 - 112010_15, 2022/12
被引用回数：5 パーセンタイル：84.97(Nuclear Science & Technology)加速器駆動システムや次世代高速炉の一次冷却材として、鉛や鉛ビスマス共晶合金(LBE)などの重液体金属(HLM)が提案されており、欧州では、MYRRHA(LBE)とALFRED(鉛)がHLMを用いたリファレンスシステムとして使用されている。本論文では、プール型とループ型のHLM実験に関するこれまでの経験と現在進行中の活動の概要について述べる。プール実験では、いくつかのシナリオにおける強制循環と自然循環のフローパターンの測定を実施しており、ループ試験では燃料集合体,制御棒,熱交換器のモックアップのような特定の構成要素の評価に重点を置いた試験を実施している。これらの試験では、流量や圧力差などの変数と、温度や速度、振動などのローカルな数量の測定を行っている。測定技術に関してはコンパクトな形状で正確な測定を行うために高温と腐食に耐えることができる高度な計測器が必要であり、従来の技術に加え、光ファイバーに基づく計測器、超音波や電磁力を利用した測定方法について説明する。
長谷 竹晃; 相楽 洋*; 小菅 義広*; 中岫 翔; 能見 貴佳; 奥村 啓介
第43回日本核物質管理学会年次大会会議論文集(インターネット), 3 Pages, 2022/11
Neutrons emitted from fuel debris are dominated by Cm-244, and plutonium cannot be quantified only by nondestructive measurements based on the neutron measurements. In this paper, focusing on the difference in half-lives of Cm-244 and plutonium, we devised a method to quantify the Pu-240 effective mass in fuel debris by measuring it two times and evaluated numerically its applicability. As the results, it was confirmed that long time interval, more than five years, will be required to evaluate the Pu-240 effective mass accurately. It was also confirmed that for fuel debris with high burnup, the Pu-240 effective mass will be overestimated by Cm-246, and we devised a method to correct for this.
荒 邦章; 平林 勝*
CROSS T&T, (71), p.10 - 14, 2022/07
原子炉施設の過酷事故時に適用可能な超音波技術の応用による水素濃度モニターの開発を行なった。本報では超音波応用の原理や特徴の紹介から、開発成果として試作体の性能(測定精度,時間応答性など)や耐環境性能について解説する。併せて、開発技術の応用について紹介する。
呉田 昌俊
流体計測法; 改訂版, p.367 - 371, 2022/04
日本機械学会が流体計測法をまとめた技術資料の改定版を刊行する。本稿は、その応用編の一部であり、進展が著しい先進的な熱流体計測技術を用いた応用事例の紹介が主な内容となっている。「ボイド率分布計測」の章では、機器の内部を流れる気液二相流を対象として、ボイド率分布を中性子線で可視化や計測する技術について解説した。前半は、ボイド率の定義、中性子透過法による計測やCT撮像技術の基本原理について解説した。後半は、様々な混相流の2次元、2次元の時間変化、3次元、3次元の時間変化の順に、可視化・計測結果を示した。
雨森 道紘*; 土屋 晴文; Tibet AS
Collaboration*; 他111名*
Physical Review Letters, 127(3), p.031102_1 - 031102_6, 2021/07
被引用回数：18 パーセンタイル：87.51(Physics, Multidisciplinary)We report observations of gamma-ray emissions with energies in the 100-TeV energy region from the Cygnus region in our Galaxy. Two sources are significantly detected in the directions of the Cygnus OB1 and OB2 associations. Based on their positional coincidences, we associate one with a pulsar PSR J2032 + 4127 and the other mainly with a pulsar wind nebula PWN G75.2 + 0.1, with the pulsar moving away from its original birthplace situated around the centroid of the observed gamma-ray emission. This work would stimulate further studies of particle acceleration mechanisms at these gamma-ray sources.
雨森 道紘*; 土屋 晴文; Tibet AS Collaboration*; 他93名*
Nature Astronomy (Internet), 5(5), p.460 - 464, 2021/05
被引用回数：64 パーセンタイル：98.97(Astronomy & Astrophysics)Cosmic rays (protons and other atomic nuclei) are believed to gain energies of petaelectronvolts (PeV) and beyond at astrophysical particle accelerators called "PeVatrons" inside our Galaxy. Although a characteristic feature of a PeVatron is expected to be a hard gamma-ray energy spectrum that extends beyond 100 teraelectronvolts (TeV) without a cut-off, none of the currently known sources exhibit such a spectrum owing to the low maximum energy of accelerated cosmic rays or owing to insufficient detector sensitivity around 100 TeV. Here, we report the observation of gamma-ray emission from the supernova remnant G106.3+2.7 above 10 TeV. This work provides flux data points up to and above 100 TeV and indicates that the very-high-energy gamma-ray emission above 10 TeV is well correlated with a molecular cloud rather than with the pulsar PSR J2229+6114. Regarding the gamma-ray emission mechanism of G106.3+2.7, this morphological feature appears to favour a hadronic origin via the 
decay caused by accelerated relativistic protons over a leptonic origin via the inverse Compton scattering by relativistic electrons. Furthermore, we point out that an X-ray flux upper limit on the synchrotron spectrum would provide important information to firmly establish the hadronic scenario as the mechanism of particle acceleration at the source.
和田 有希*; 榎戸 輝揚*; 久保 守*; 中澤 知洋*; 篠田 太郎*; 米徳 大輔*; 澤野 達哉*; 湯浅 孝行*; 牛尾 知雄*; 佐藤 陽祐*; et al.
Geophysical Research Letters, 48(7), 11 Pages, 2021/04
被引用回数：20 パーセンタイル：90.11(Geosciences, Multidisciplinary)graupels
雨森 道紘*; 土屋 晴文; Tibet AS Collaboration*; 他93名*
Physical Review Letters, 126(14), p.141101_1 - 141101_7, 2021/04
被引用回数：112 パーセンタイル：99.57(Physics, Multidisciplinary)We report, for the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk. Particularly, all gamma rays above 398 TeV are observed apart from known TeV gamma-ray sources and compatible with expectations from the hadronic emission scenario in which gamma rays originate from the decay of 
's produced through the interaction of protons with the interstellar medium in the Galaxy. This is strong evidence that cosmic rays are accelerated beyond PeV energies in our Galaxy and spread over the Galactic disk.
阿部 雄太; 土川 雄介; 甲斐 哲也; 松本 吉弘*; Parker, J. D.*; 篠原 武尚; 大石 佑治*; 加美山 隆*; 永江 勇二; 佐藤 一憲
JPS Conference Proceedings (Internet), 33, p.011075_1 - 011075_6, 2021/03
Since the hardness of fuel debris containing boride from B
C pellet in control rod is estimated to be two times higher as that of oxide, such as UO
and ZrO, distribution of such boride in the fuel debris formed in the Fukushima-Daiichi Nuclear Power Plants may affect the process of debris cutting and removal. The high neutron absorption of boron may affect the possibility of re-criticality during the process of debris removal. Therefore, boride distribution in fuel debris is regarded as an important issue to be addressed. However, boron tends to have difficult in quantification with conventionally applied methods like EPMA and XPS. In this study, accelerator-driven neutron-imaging system was applied. Since boron is the material for neutron absorption, its sensitivity in terms of neutron penetration through specimens is concerned. To adjust neutron attenuation of a specimen to suit a particular measurement by selecting the neutron energy range, we focused on the energy resolved neutron imaging system RADEN, which utilizes wide energy range from meV to keV. Development of a method to visualize boron distribution using energy-resolved neutrons has been started. In this presentation the authors show the status of the development of a method utilizing energy-resolved neutrons and provide some outcome from its application to the Core Material Melting and Relocation (CMMR)-0 and -2 specimens.
豊田 智史*; 山本 知樹*; 吉村 真史*; 住田 弘祐*; 三根生 晋*; 町田 雅武*; 吉越 章隆; 鈴木 哲*; 横山 和司*; 大橋 雄二*; et al.
Vacuum and Surface Science, 64(2), p.86 - 91, 2021/02
X線光電子分光法における時空間的な測定・解析技術を開発した。はじめに、NAP-HARPES (Near Ambient Pressure Hard X-ray Angle-Resolved Photo Emission Spectroscopy)データにより、ゲート積層膜界面の時分割深さプロファイル法を開発した。この手法を用いて時分割ARPESデータからピークフィッティングとデプスプロファイリングを迅速に行う手法を確立し、4D-XPS解析を実現した。その結果、従来の最大エントロピー法(MEM)とスパースモデリングのジャックナイフ平均法を組み合わせることで、深さ方向プロファイルを高精度に実現できることがわかった。
孫 昊旻; Porcheron, E.*; Magne, S.*; Leroy, M.*; Dhote, J.*; Ruffien Ciszak, A.*; Bentaib, A.*
Proceedings of OECD/NEA Specialist Workshop on Advanced Measurement Method and Instrumentation for enhancing Severe Accident Management in an NPP addressing Emergency, Stabilization and Long-term Recovery Phases (SAMMI 2020) (Internet), 10 Pages, 2020/12
During a severe accident (SA), hydrogen may be generated. To avoid a hydrogen explosion, it is important to monitor gas concentrations of e.g. H, O, N, HO, CO and CO in the containment during a SA. A spontaneous Raman spectrometry (SRS) associated with a fiber-coupled probe had been developed. Since the probe had been designed to be implemented in the reactor containment, the SRS was qualified experimentally with the probe being surrounded by aerosols. Particles attached on the probe optical components (contamination) due to a continuous aerosol exposure as well as those in the atmosphere (aerosol) can cause photon-particle interactions such as light scattering (Mie) and fluorescence which may influence the Raman spectrum (RS). In our experiment, the contamination effect and the aerosol effect on the RS were investigated separately. It was found both effects increase the spectrum counts in whole wavelength range. Elementary criterion for the onset of each effect was suggested.
Bentaib, A.*; Janin, T.*; Porcheron, E.*; Magne, S.*; Leroy, M.*; Dhote, J.*; Ruffien Ciszak, A.*; 孫 昊旻
Proceedings of OECD/NEA Specialist Workshop on Advanced Measurement Method and Instrumentation for enhancing Severe Accident Management in an NPP addressing Emergency, Stabilization and Long-term Recovery Phases (SAMMI 2020) (Internet), 6 Pages, 2020/12
To prevent hydrogen explosion hazard during a severe accident, dedicated mitigation strategies were adopted according to plants design and improved as results of stress tests after the Fukushima accident. The strategies commonly used combine the implementation of safety components, as the passive autocatalytic recombiners (PARs), and the definition of adequate SAMGs (Severe Accident Management Guidelines). Concerning French PWRs, SAMGs procedure relies on information provided by limited monitoring systems as pressure, core exit temperature and dose rate sensors. The containment atmosphere gaseous composition is not monitored and only PARs are equipped with thermocouples to detect hydrogen through the heat release of the exothermic recombination reaction. In the framework of the MITHYGENE project, a prototypic device had been developed based on Raman probes connected by optical fibers to a transportable unit. Several qualification campaigns had been conducted to check the effect of severe accident representative conditions, including radiation, on the device response. This paper aims to present an overview of the device development and qualification and presents its potential implementation inside the containment.
尾上 博則; 竹内 竜史
JAEA-Data/Code 2020-015, 22 Pages, 2020/11
JAEA-Data-Code-2020-015.pdf:2.3MB
JAEA-Data-Code-2020-015-appendix(DVD-ROM).zip:2.42MB
日本原子力研究開発機構では、「地層処分技術に関する研究開発」のうち深地層の科学的研究(地層科学研究)の一環として、結晶質岩(花崗岩)を対象とした超深地層研究所計画を進めている。本計画は、「第1段階; 地表からの調査予測研究段階」、「第2段階; 研究坑道の掘削を伴う研究段階」、「第3段階; 研究坑道を利用した研究段階」の3段階からなる。超深地層研究所計画は、「深部地質環境の調査・解析・評価技術の基盤の整備」および「深地層における工学技術の基盤の整備」を第1段階から第3段階までを通した全体目標としている。研究坑道内に湧出する地下水については、超深地層研究所計画の「研究坑道の掘削を伴う研究段階(第2段階)」における岩盤の水理に関する調査研究の一環として計測体制が整備されて計測を開始し、「研究坑道を利用した研究段階(第3段階)」においても、湧水量計測を継続してきたが、2019年度末をもって超深地層研究所計画における研究開発を終了することに伴い、超深地層研究所計画における湧水量計測を終了する。本データ集は、2019年度に実施した研究坑道内での湧水量計測で取得したデータを取りまとめたものである。
岡 壽崇; 高橋 温*
放射線化学(インターネット), (110), p.13 - 19, 2020/10
東京電力福島第一原子力発電所によって野生動物が受けた外部被ばくを、電子スピン共鳴(ESR)法を用いてどのように計測するかを解説した。ニホンザルのエナメル質を用いて、炭酸ラジカル強度と吸収線量の関係、いわゆる検量線を作成した。検量線から推定された検出限界は33.5mGyであり、ヒト臼歯を用いた際の検出限界とほぼ同等であった。この検量線を用いて福島県で捕獲された野生ニホンザルの外部被ばく線量を推定したところ、45mGyから300mGyの被ばくをしているサルが見つかった。確立した方法により、ニホンザルだけでなく、アライグマやアカネズミなどの野生動物の外部被ばく線量推定が可能になった。
湯浅 孝行*; 和田 有希*; 榎戸 輝揚*; 古田 禄大; 土屋 晴文; 久富 章平*; 辻 結菜*; 奥田 和史*; 松元 崇弘*; 中澤 知洋*; et al.
Progress of Theoretical and Experimental Physics (Internet), 2020(10), p.103H01_1 - 103H01_27, 2020/10
被引用回数：15 パーセンタイル：74.18(Physics, Multidisciplinary)We designed, developed, and deployed a distributed sensor network aiming at observing high-energy ionizing radiation, primarily gamma rays, from winter thunderclouds and lightning in coastal areas of Japan. Starting in 2015, we have installed, in total, more than 15 units of ground-based detector system in Ishikawa Prefecture and Niigata Prefecture, and accumulated 551 days of observation time in four winter seasons from late 2015 to early 2019. In this period, our system recorded 51 gamma-ray radiation events from thundercloud and lightning. Highlights of science results obtained from this unprecedented amount of data include the discovery of photonuclear reaction in lightning which produces neutrons and positrons along with gamma rays, and deeper insights into the life cycle of a particle-acceleration and gamma-ray-emitting region in a thunder-cloud. The present paper reviews objective, methodology, and results of our experiment, with a stress on its instrumentation.
