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佐藤 優樹
Radiation Protection Dosimetry, p.ncaf046_1 - ncaf046_11, 2025/05
被引用回数：0Radioactive substances released during the Fukushima Daiichi Nuclear Power Station accident were deposited on various equipment and building structures within the plant site. To minimize worker exposure and plan effective remediation strategies, accurately identifying the locations of these deposits is crucial. In response to this need, the current study presents a method to accurately determine the locations of multiple radiation sources in three dimensions and quantify their radioactivity levels. In particular, the method involves the application of an inverse estimation technique to data captured using a Compton camera. Here, the target region is first divided into multiple regions of interest. Image data are then acquired by placing a radiation source of known radioactivity in each region of interest. The resulting images are subsequently multiplied by each coefficient and summed to reproduce the image data of multiple unknown radiation sources. The radioactivity of each unknown radiation source is then derived based on the coefficients determined through inverse estimation.
冠城 雅晃; 宮本 勇太; 森 教匡; 岩井 紘基; 手塚 将志; 黒澤 俊介*; 田川 明広; 高崎 浩司
Journal of Nuclear Science and Technology, 62(3), p.308 - 316, 2025/03
被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)Nuclear decommissioning has recently accelerated, particularly following the accident at Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Holdings. 
-ray/X-ray (radiation photon) spectroscopy provides information on the types of radionuclides with radiation photon emissions. Radiation photon spectroscopy in a control rod guide tube positioned at the center of Fugen was conducted. Fugen is a prototype advanced thermal reactor with 165 MWe electric power generation that is being decommissioned. The dose rates measured in a control rod guide tube positioned at the center of the reactor were 4.1 - 9.1 Gy/h. The dose rate considerably increased at a position close to a tank that contained 
Co caused by the radioactivation of stainless steel. Radiation photon spectroscopy was performed without radiation shielding, identifying Co with an energy resolution better than 5.4% at 1333 keV and 
Nb with an energy resolution better than 5.9% at 871 keV.
佐藤 優樹; 峯本 浩二郎*; 根本 誠*
Proceedings of Waste Management Conference 2025 (WM2025) (Internet)), 9 Pages, 2025/03
We have been developing software to visualize the location of radiation sources in three dimensions by importing output data from Compton cameras, survey meters, and SLAM (Simultaneous Localization and Mapping) devices. The software, named COMRIS (COMpton camera for Radiation Imaging System), is GUI-based and visualizes the location of radiation sources by capturing the output data of the above multiple measuring instruments. The authors previously presented an overview of COMRIS and reported the results of visualizing a 
Cs test source in the laboratory by combining a Compton camera and a 3D-Light Detection and Ranging (LiDAR)-based SLAM. However, we have not been able to report how this software is operated on a GUI screen. In addition, an new attempt was made this time to expand the effective field of view (FoV) to both front and rear by preparing two Compton cameras, each of which is sensitive only to the front of the device, and placing them back-to-back. In this work, we report once again on the integration method of output data from SLAM devices and Compton cameras using COMRIS, based on the GUI screen. In addition, data output from two back-to-back Compton cameras and SLAM devices were imported into COMRIS to demonstrate visualization of radiation sources.
宮崎 康典; 佐野 雄一; 石神 龍哉*
EPJ Web of Conferences, 317, p.01006_1 - 01006_7, 2025/01
被引用回数：0 パーセンタイル：0.00(Chemistry, Inorganic & Nuclear)TEHDGA吸着材にガンマ線及びHe
イオンビーム(例えば
Amからのアルファ線を模擬したもの)を照射し、水素ガス発生量、浸漬3M硝酸
溶液中の有機物の溶出量、熱特性及び分解生成物の化学種を評価した。これらを組み合わせて、1kGy/hの線量率のラフィネートからMAを分離回収プロセスの運転安全性を評価した。
伊藤 辰也; 永石 隆二; 桑野 涼*; 神戸 正雄*; 吉田 陽一*
Radiation Physics and Chemistry, 226, p.112198_1 - 112198_5, 2025/01
被引用回数：0 パーセンタイル：0.00(Chemistry, Physical)近年、放射線照射実験や非密封放射性同位元素実験用の容器として、ポリイミドやポリエーテルエーテルケトンなどの耐放射線性樹脂の使用が増えている。しかし、水の分解生成物と樹脂との相互作用の可能性が見つかり、樹脂が放射線場における水中の反応に影響を及ぼすことが懸念された。その相互作用を明らかにするために、線による水の放射線分解における重クロム酸イオン(Cr
O
)の還元と過酸化水素(HO)の生成を樹脂の有無で比較した。同一線量で樹脂ありの水溶液中のCrO還元量は樹脂なしの場合よりも大きくなり、樹脂によってCrO還元が促進されることを示した。一方、電子捕捉剤の有無にかかわらず、純水中のHO生成は樹脂の有無にほとんど依存しなかった。これらは、放射線場において水と接触した樹脂とヒドロキシルラジカルとの相互作用を示唆している。
佐藤 優樹; 角藤 壮*; 田中 孝幸*; 嶋野 寛之*
European Physical Journal; Special Topics, 10 Pages, 2025/00
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)In decommissioning the Fukushima Daiichi Nuclear Power Station, understanding the distribution of radioactive substances is crucial to developing detailed decontamination plans and minimizing worker exposure. In this study, an autonomous mobile radiation source detection system based on a mecanum wheel robot equipped with a Compton camera was constructed. The Compton camera visualizes the radiation source, and software embedded in the robot system reads the results to recognize the radiation source and move the robot toward it. If the robot's depth camera detects an obstacle while moving, it changes direction, visualizes the radiation source again using the Compton camera, and repeats moving the robot toward the radiation source. Furthermore, two demonstration tests were conducted in the laboratory using a Cs radiation source to confirm that the robot can reach it where there are obstacles or a narrow region. We have also summarized issues that must be identified to apply this system to actual decommissioning sites.
廃炉環境国際共同研究センター; 東北大学*
JAEA-Review 2024-016, 61 Pages, 2024/12
JAEA-Review-2024-016.pdf:2.88MB
日本原子力研究開発機構(JAEA)廃炉環境国際共同研究センター(CLADS)では、令和4年度英知を結集した原子力科学技術・人材育成推進事業(以下、「本事業」という。)を実施している。本事業は、東京電力ホールディングス株式会社福島第一原子力発電所の廃炉等をはじめとした原子力分野の課題解決に貢献するため、国内外の英知を結集し、様々な分野の知見や経験を、従前の機関や分野の壁を越えて緊密に融合・連携させた基礎的・基盤的研究および人材育成を推進することを目的としている。平成30年度の新規採択課題から実施主体を文部科学省からJAEAに移行することで、JAEAとアカデミアとの連携を強化し、廃炉に資する中長期的な研究開発・人材育成をより安定的かつ継続的に実施する体制を構築した。本研究は、令和4年度に採択された研究課題のうち、「革新的アルファダスト撮像装置と高線量率場モニタの実用化とその応用」の令和4年度分の研究成果について取りまとめたものである。ここでは、2つの検出器の開発を実施している。1つ目は、作業員の安全の確保のための
線核種の炉内の分布を明らかにする技術の実現を目指し、スミヤろ紙上に付着するより細かい線核種を含む微細なダストの詳細な分布を可視化することを可能にする技術の開発である。初年度にあたることから研究開始時は資材等の準備から始まり優れた位置分解能、高感度化を目指した検出素子などの材料開発、光検出器などのハードおよびソフトウェアといった準備を順調に行うことができた。令和4年度末までに発光波長が500-800nmの目標値の中に入る材料の開発などを実施することができた。2つ目の検出器は、光ファイバーを用いた超高線量率場での線量率モニタの開発である。こちらについても、高感度化を目指した検出素子などの材料開発およびシミュレーション体系の構築といった準備を順調に行うことができた。そして目標発光波長である650-1,000nmを満たす当該材料の開発を行うことができた。加えて、モニタとしての実証試験も実施して、80mSv/h未満から1kSv/h以上までの線量のダイナミックレンジを有することが分かり、現場適用に対応可能な検出器の開発が進められた。
墨田 岳大*; 大澤 崇人; Chiu, I.-H.; 池田 篤史
Analytica Chimica Acta, 1329, p.343256_1 - 343256_10, 2024/11
被引用回数：1 パーセンタイル：40.01(Chemistry, Analytical)The uncertainty including accuracy and precision is the most vital factor that determines the overall quality of quantitative analysis. The objectives of this study are (1) to investigate the analytical uncertainty of a prompt gamma-ray analysis (PGA), a chemical interference-free method in principle, on the quantitative analysis of boron and (2) to evaluate the applicability of inductively coupled plasma optical emission spectrometry (ICP-OES), a common technique for quantitative elemental analysis including boron. PGA provided analytical quantity that is equivalent to the true quantity. The analytical uncertainty in both methods was adequately evaluated by comparing the results from PGA and ICP-OES for a series of boron-containing materials with different physical/chemical properties and the major sources of uncertainty in both methods are specified. The evaluation concept demonstrated in this study could be beneficial to a wide range of analytical chemistry.
佐藤 優樹
Applied Radiation and Isotopes, 212, p.111421_1 - 111421_8, 2024/10
被引用回数：1 パーセンタイル：0.00(Chemistry, Inorganic & Nuclear)At the Fukushima Daiichi Nuclear Power Station, radiation sources released in the accident were deposited on various equipment and building structures. During decommissioning, it is crucial to understand the distribution of radiation sources and ambient dose equivalent rates to reduce worker exposure and implement detailed work planning. In this study, the author introduces a method for visualizing radiation sources, estimates their radioactivity using a Compton camera, and derives the dose rate around the radiation sources. In the demonstration test, the Compton camera was used to visualize radioactive hotspots caused by Cs radiation sources deposited in the outdoor environment and estimated the radioactivity. Furthermore, the dose rate around the hotspots was calculated from the estimated radioactivity, which confirmed that the calculated dose rate correlated with the dose rate measured using a survey meter. This approach is novel, where a series of analyses were conducted using the Compton camera to visualize radioactive hotspots, estimate the radioactivity, and derive the dose rate in the surrounding environment.
石井 隼也*; 清水 森人*; 加藤 昌弘*; 黒澤 忠弘*; 辻 智也; 吉富 寛; 谷村 嘉彦; 渡部 浩司*
Journal of Radiological Protection, 44(3), p.031516_1 - 031516_8, 2024/09
被引用回数：0 パーセンタイル：0.00(Environmental Sciences)The dosimeter response should be calibrated in a reference field near the user's radiation environment. Environments around nuclear reactors and radiation therapy facilities have high-energy photons with energies exceeding that of Co gamma rays, and controlling exposure to these photons is important. The Japan Atomic Energy Agency (JAEA) and National Metrology Institute of Japan (NMIJ) have high-energy reference fields with energies above several MeV for different types of accelerators. Their reference fields have different fluence-energy distributions. In this study, the energy dependencies of the two-cavity ionization chambers, which are often used by secondary laboratories, were experimentally and computationally evaluated for each high-energy field. These results agreed well with relative expanded uncertainties (
= 2), and their capabilities for air kerma measurements in each high-energy reference field were confirmed. Therefore, the capabilities of the air-kerma measurements can be verified in the two high-energy reference fields.
Li-glass detector to gamma rays by a coincidence method伊藤 史哲*; Lee, J.; 弘中 浩太; 高橋 時音; 鈴木 敏*; 持丸 貴則*; 堀 順一*; 寺田 和司*; 小泉 光生
Nuclear Instruments and Methods in Physics Research A, 1064, p.169465_1 - 169465_9, 2024/07
被引用回数：0 パーセンタイル：0.00(Instruments & Instrumentation)The response of a gamma-ray spectrometer is generally determined by analyzing full-energy peaks. However, full-energy peaks cannot be measured easily in the case of scintillation detectors that consist of light elements, such as glass scintillators. Only a strong Compton plateau appears in the spectrum of such detectors. Therefore, Compton edgers were used to evaluate the response of these detectors. The response of a low-resolution Li-glass detector to gamma rays was measured for the first time by a coincidence method with a high-resolution LaBr
:Ce detector using cascade gamma rays (2.75 and 1.37 MeV) from a 
Na source. Coincidence gates were applied at the peaks of the spectrum of the LaBr:Ce detector at the 0.51 MeV annihilation peak, and the sum peaks of a gamma ray and a backscattered gamma ray. By analyzing the gated spectra of the Li-glass detector, the energy-dependent detector response (i.e., the output strength and its dispersion) was determined.
Rodriguez, D.; 赤松 駿介*; Rossi, F.; 鈴木 敏*; 高橋 時音
Proceedings of 65th Annual Meeting of the Institute of Nuclear Materials Management (Internet), 9 Pages, 2024/07
Under the MEXT subsidy to promote nuclear security related activities, we will present the preliminary results from the new Fission Signature Assay Instrument that was fabricated and fully installed in November 2023. We will describe the instrument within the context of the JAEA-JRC collaboration development and the experimental activities planned with it in the larger context of finishing off Phase-III development.
Hu, X.*; 藤田 善貴; 土谷 邦彦; 福谷 哲*; 堀 順一*; 鈴木 達也*
Journal of Radioanalytical and Nuclear Chemistry, 333(11), p.6057 - 6063, 2024/05
被引用回数：0 パーセンタイル：0.00(Chemistry, Analytical)難溶性である多孔質MoOターゲットを使用した新しい
Mo/
Tcジェネレータの製造方法を開発している。本方法では、水への溶解度の違いを利用してMoOからTcを抽出する。まず、作製した多孔質MoOペレットをKUR(京都大学研究用原子炉)を用いて中性子照射した。照射した多孔質MoOを水へ浸漬させ、Tcの抽出率を調べた。この結果、MoOから比較的低いMo/Tc比でTcが抽出され、MoOの水への溶解度は極めて低かった。さらに、Moの溶解度はその他のモリブデンの安定同位体よりも高く、(n,)反応により生成されたMoの溶解におけるホットアトム効果を明らかにした。本方法は、MoOターゲットの再利用も可能で、製造プロセスの持続可能性を有するものであり、(n,)反応で生成されたMoを利用した水抽出によるMo/Tcジェネレータの実現が期待できる。
越智 康太郎; Barker, E.*; 中間 茂雄; Gleizes, M.*; Manach, E.*; Vincent, F.*; 眞田 幸尚
Journal of Disaster Research, 19(2), p.429 - 445, 2024/04
周辺線量当量率(空間線量率)分布のマッピング技術は、各国で統一された明確な基準はない。本研究では、日本原子力研究開発機構とフランス放射線防護・原子力安全研究所が共同で、福島第一原子力発電所周辺において、歩行サーベイ、車両サーベイ、無人ヘリコプターサーベイを実施し、各機関のモニタリング手法の有効性を確認した。例えば、歩行サーベイでは、検出器で得られた計数率を空間線量率に換算する際に、ガンマ線エネルギーの異なる放射性核種からの寄与を考慮するかどうかで、両機関が測定した空間線量率の間にずれが生じることが確認された。本研究のように、各国のマッピング技術を比較し、相互にフィードバックすることで、原子力発電所事故後のゾーニングシナリオの精度を向上させることができると思われる。
Cantarel, V.; Chupin, F.; Ortega-Charlot, M.*; 山岸 功; 上野 文義
Journal of Nuclear Materials, 592, p.154969_1 - 154969_9, 2024/04
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)When nuclear waste is immobilized in cement or geopolymer, gases may be generated by corrosion and radiolysis. This production must be accurately predicted, and waste loading and countermeasures selected accordingly to avoid overpressure and limit the risk of explosion in the case of dihydrogen (H). We measured and simulated H generation and release from water-saturated geopolymer confined in a glass bottle under Co gamma irradiation. It was observed that confinement of H in the pores of a high pH geopolymer could lead to recombination of more than 99.9% of the hydrogen generated by radiolysis. Shrinkage can allow hydrogen to diffuse between the geopolymer and the vessel, reducing the fraction of recombined H to 90% at our experimental scale. We then used a model to scale up the results of our experiments. The hydrogen release of a saturated geopolymer in a standard 200 L drum is expected to be equivalent to that of a hydraulic binder containing approximately 2% moisture. Harnessing the effects of recombination would make it possible to preserve the capacity of countermeasures such as H absorbers, increase the loading capacity of waste packages, and reduce the cost of nuclear waste immobilization.
) cross-section measurements at n_TOF EAR2Alcayne, V.*; 木村 敦; 他134名*
Radiation Physics and Chemistry, 217, p.111525_1 - 111525_11, 2024/04
被引用回数：6 パーセンタイル：95.86(Chemistry, Physical)The neutron time-of-flight facility n_TOF at CERN is a spallation source dedicated to measurements of neutron induced reaction cross-sections of interest in nuclear technologies, astrophysics, and other applications. Since 2014, Experimental ARea 2 (EAR2) is operational and delivers a neutron fluence of 
neutrons per nominal proton pulse, which is 50 times higher than the one of the other experimental area. The high neutron flux at EAR2 results in high counting rates in the detectors that challenged the previously existing capture detection systems. For this reason, a Segmented Total Energy Detector (sTED) has been developed to overcome the limitations in the detector's response, by reducing the active volume and by using a photo-multiplier (PMT) optimized for high counting rates. This paper presents the main characteristics of the sTED, including energy and time resolution, response to -rays, and provides details for the Pulse Height Weighting Technique (PHWT). The sTED has been validated to perform neutron-capture cross-section measurements in EAR2 in the neutron energy range from thermal up to at least 400 keV.
廃炉環境国際共同研究センター; 東北大学*
JAEA-Review 2023-030, 80 Pages, 2024/03
JAEA-Review-2023-030.pdf:4.96MB
日本原子力研究開発機構(JAEA)廃炉環境国際共同研究センター(CLADS)では、令和4年度英知を結集した原子力科学技術・人材育成推進事業(以下、「本事業」という)を実施している。本事業は、東京電力ホールディングス株式会社福島第一原子力発電所の廃炉等をはじめとした原子力分野の課題解決に貢献するため、国内外の英知を結集し、様々な分野の知見や経験を、従前の機関や分野の壁を越えて緊密に融合・連携させた基礎的・基盤的研究及び人材育成を推進することを目的としている。平成30年度の新規採択課題から実施主体を文部科学省からJAEAに移行することで、JAEAとアカデミアとの連携を強化し、廃炉に資する中長期的な研究開発・人材育成をより安定的かつ継続的に実施する体制を構築した。本研究は、令和3年度に採択された研究課題のうち、「連携計測による線源探査ロボットシステムの開発研究」の令和4年度分の研究成果について取りまとめたものである。本研究は、ガンマ線の飛来方向を検出可能な検出器を開発し、これを搭載した複数のロボットの連携により、単一センサーでは得られない広視野・迅速・安価な放射線源探査を実現するロボットシステム(Cooperative Operation Robot system for RAdiation Source Exploration: CORRASE、コラッセ)を開発することを目的とする。東京電力ホールディングス(株)福島第一原子力発電所の現場への投入に資することを目的として、線源探査を行う小型ロボットに放射線計測機器を搭載したシステムを3年間の計画終了時に完成させるための研究を行う。令和4年度は以下の成果を得た。多面体型とコーデットキューブ型のガンマ線イメージャーの製作を行い、点線源の位置推定に成功した。LiDARを用いた周囲環境測定結果に基づく環境地図作成システムの開発および環境地図上に放射線源分布推定結果を融合して表示するシステムの開発を行った。環境地図と粗い放射線源分布推定結果に基づき、検出器の特性に応じて複数台のロボットが指定した箇所の詳細な測定を行うための観測地点計画手法の開発を行った。小型ロボットに搭載する放射線測定器の評価のために検出器姿勢自動制御システムを製作した。また、多面体型検出器による線源探査のシミュレーションを行った。複数の線源がある場合でもほぼ線源位置を特定することができた。
-rays from slow neutron-induced fission of 
U with STEFFWright, T.*; 原田 秀郎; 木村 敦; 他121名*
European Physical Journal A, 60(3), p.70_1 - 70_11, 2024/03
被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)The average energy and multiplicity of prompt -rays from slow neutron-induced fission of U have been measured using the STEFF spectrometer at the neutron time-of-flight facility n_TOF. The individual responses from 11 NaI scintillators were corrected for multiple -ray interactions, prompt fission neutrons and background counts before being deconvolved to estimate the emitted spectrum of prompt fission -rays. The results give an average -ray energy 
of 1.71(5) MeV and multiplicity 
of 2.66(18) considering -rays emitted within the energy range from 0.8 to 6.8 MeV. The n_TOF data has a slightly larger and smaller than other recent measurements, however the product of the two is in agreement within the quoted uncertainties.
Rodriguez, D.; Rossi, F.; 高橋 時音
IEEE Transactions on Nuclear Science, 71(3), p.255 - 268, 2024/03
被引用回数：0 パーセンタイル：0.00(Engineering, Electrical & Electronic)Under the MEXT subsidy to improve nuclear security related capabilities, we are developing the delayed gamma-ray spectroscopic analysis technique. One goal is to develop an inverse Monte Carlo analysis method using spectra from simulations of the interrogation instrument for comparison to the actual measured spectra. This work presents the validity of the Monte Carlo foundation of the analysis compared to experimental results and other simulation codes.
Ho, H. Q.; 石井 俊晃; 長住 達; 小野 正人; 島崎 洋祐; 石塚 悦男; 澤畑 洋明; 後藤 実; Simanullang, I. L.*; 藤本 望*; et al.
Nuclear Engineering and Design, 417, p.112795_1 - 112795_6, 2024/02
被引用回数：1 パーセンタイル：0.00(Nuclear Science & Technology)External sources of neutron provide stable and sufficient neutron for initial startup of a nuclear reactor. They also provide signals for neutron detectors to monitor the safety of reactor during shutdown. In the high temperature engineering test reactor, 
Cf is used as the external neutron source. However, the Cf sources must be renewed every approximately 7 years because of its relatively short half-life of 2.6 years. The renewal of Cf sources requires a high cost and a very complicated procedure. This study investigated the feasibility of using BeO rods as the secondary neutron sources to avoid renewing the Cf neutron sources periodically. The BeO rods could exist in the reactor for a long time so that if the reactor operates long enough, the neutron flux at the wide-range monitoring detectors remains significant even if the reactor is shutdown for as long as 5 years. The results of this study indicated that using BeO rods as the secondary neutron sources would be an attractive option for the future HTGR design with a long-life fuel cycle.
