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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.
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
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08
Boron carbide is used as a neutron-absorbing material in Fukushima-Daiichi Nuclear Power Station (1F), producing borides that are twice as hard as oxides (such as UO and ZrO). The high neutron absorption of boron affects the evaluation of re-criticality during the process of debris retrieval. Therefore, it is important not only to determine the presence of boron but also to investigate the distribution of boron inside the material in a non-destructive manner during decommissioning. To address the uncertainties in the core material relocation behavior of boiling water reactor (BWR) during a severe accident (SA), solidified melt specimens of a simulated fuel assembly were prepared by plasma heating. If core material melting and relocation (CMMR) specimens can be used to estimate the B distribution in 1F Unit-3, that will provide valuable information in the decommissioning of 1F. To address this, the authors focused on the energy-resolved neutron imaging system, RADEN, which utilizes a wide energy range, from meV to keV. This is an innovative three-dimensional analysis technology for boride distribution that affects the evaluation of hardness and re-criticality. In the calibration standard samples (Zr
B
and FeB), there was a good correlation between boron concentration and the energy-dependence of the cross sections of cold and epi-thermal neutrons. In the CMMR specimens, boron distribution was confirmed from the contrast difference between cold and epi-thermal neutrons. In the future, the results of calibration standard samples will be applied to the results of CMMR specimens. With this method, three-dimensional boron distribution will be measured, and the understanding of boride distribution 1F Unit-3 will be improved, which may be reflected in an improved SA code.
甲斐 哲也; 廣井 孝介; Su, Y. H.; 篠原 武尚; Parker, J. D.*; 松本 吉弘*; 林田 洋寿*; 瀬川 麻里子; 中谷 健; 及川 健一; et al.
Physics Procedia, 88, p.306 - 313, 2017/06
被引用回数：4 パーセンタイル：85.09(Instruments & Instrumentation)Neutron resonance thermometry, which measures material temperature by analyzing the Doppler broadening of a neutron resonance peak, is one of the applications of energy-resolved neutron imaging at RADEN of J-PARC. Although this technique is promising, advantages and disadvantages have not been discussed in practical applications. The authors measured neutron transmission rates of tantalum and tungsten foils in a heater chamber up to 300 degrees Celsius at RADEN. The energy-dependent neutron transmission rates with different statistics were obtained after the measurements by selecting arbitrary measuring intervals from one measurement, and the temperatures of the foils were estimated from those transmission rates with different statistics. The reliability of the neutron resonance thermometry with statistical accuracy, irradiation time and spatial resolution are discussed.
廣井 孝介; 篠原 武尚; 林田 洋寿*; Su, Y. H.; 甲斐 哲也; 及川 健一
JAEA-Technology 2016-021, 14 Pages, 2016/10
JAEA-Technology-2016-021.pdf:16.4MB
J-PARCの物質・生命科学実験施設(MLF)BL22に設置されたパルス中性子イメージング用ビームライン「螺鈿」では、偏極中性子を利用した磁気イメージング手法の技術開発が精力的に行われている。「螺鈿」では、偏極中性子による磁気イメージングを実施するための偏極度解析装置が整備されたが、機器間の磁場接続を改善し、ビーム経路中で中性子偏極度の低下を防ぐことにより、偏極中性子輸送性能を向上させる余地があった。そこで「螺鈿」の偏極度解析装置内の磁場分布をシミュレーションにより評価し、偏極度低下の原因を特定するとともに、磁場接続の最適化を行い、ビーム経路中の中性子偏極度を高く保つことができる機器配置を決定した。さらに計算により求めた最適条件について中性子ビームを利用した実験を行った結果、波長や場所の違いによる偏極度の変動が改善され、約4cm角の視野範囲全体に渡って均一な偏極度を得ることができた。本報告ではシミュレーションに基づく磁場環境評価と最適化の結果および、シミュレーション結果の妥当性を実験的に検証した研究成果に関して報告する。
甲斐 哲也; 松本 吉弘*; Parker, J. D.*; 瀬川 麻里子; 篠原 武尚; 廣井 孝介; Su, Y. H.; Zhang, S.*; 林田 洋寿*; 及川 健一; et al.
no journal, ,
The first neutron beam was provided to the energy-resolved neutron imaging system, RADEN, of J-PARC in November 2014. Test/demonstration measurements of the resonance absorption imaging carried out so far will be presented. Element enhanced images of copper and zinc in 1- and 2- euro coins, cobalt, manganese and tungsten in a commercially available lithium-ion battery were obtained by the neutron resonance absorption imaging by using a gas electron multiplication (GEM) neutron detector. A test measurement of neutron thermometry was also carried out. Neutron resonances of copper, manganese and platinum were measured at different temperatures by using the GEM neutron detector. Doppler broadenings of the resonances were recognized.
甲斐 哲也
no journal, ,
中性子ラジオグラフィ技術の解説に続いて、中性子透過率のエネルギーによる変化を解析し、対象物の結晶情報を得る「ブラッグエッジイメージング」、元素情報や温度情報を測定する「共鳴吸収イメージング」、偏極中性子を使って磁場の空間分布を取得する「磁気イメージング」について説明を行う。また、J-PARCで運用を開始したパルス中性子イメージング装置「螺鈿」の概要と利用例について紹介する。
甲斐 哲也; 阿部 雄太; 松本 吉弘*; Parker, J. D.*; 篠原 武尚; 大石 佑治*; 永江 勇二; 佐藤 一憲
no journal, ,
The energy resolved neutron imaging system RADEN, installed at the Japan Proton Accelerator Complex (J-PARC), utilizes short-pulsed neutrons in the energy range from meV to keV by means of the time-of-flight method. The wide neutron energy range makes it possible to adjust neutron attenuation of a sample to suit a particular measurement by selecting the neutron energy range. The Core Material Melting and Relocation (CMMR) experiments have been performed to investigate core melt accidents in the Fukushima-Daiichi (1F) Nuclear Power Plant. Some amount of boride was found to be contained in simulated melted core material. The authors show the status of the development of a method utilizing energy-resolved neutrons, and demonstrate some measurements of boron-containing samples, including simulated melted core material.
阿部 雄太; 甲斐 哲也; 土川 雄介; 松本 吉弘*; Parker, J. D.*; 篠原 武尚; 加美山 隆*; 大石 佑治*; 永江 勇二; 佐藤 一憲
no journal, ,
福島第一原子力発電所事故(1F)における炉内状況の把握に重要な要素として、粒子状の炭化ホウ素を内包した制御棒ブレードの炉心溶融時の振舞いが挙げられる。BWR炉心溶融時の挙動解明に資する目的で行われたCMMR試験(基本構成要素を模擬した模擬燃料集合体による破損試験)では、1F2号機の温度履歴を模擬し、超高温(最高温度部分で2,300
C内外)まで加熱・保持した条件においても、試験体の一部にはホウ素含有物が存在することが確認されており、1Fの燃料デブリにもある程度のホウ素が含まれている可能性がある。炉内のホウ素含有物の分布は、燃料デブリの臨界性評価や取出し時の超高硬度物質への対処等の観点から重要課題であり、前記したCMMR試験体のホウ素含有物分布を精度良く測定することができれば、1F2号機等の推定精度を高めることに繋がる。本講演では、J-PARCのエネルギー分析型中性子イメージング装置(RADEN)で撮像した、CMMR試験体のホウ素含有物分布結果を紹介する。
