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Niu, X.*; Elakneswaran, Y.*; Li, A.*; Seralathan, S.*; 菊池 亮佑*; 平木 義久; 佐藤 淳也; 大杉 武史; Walkley, B.*
Cement and Concrete Research, 190, p.107814_1 - 107814_17, 2025/04
被引用回数：0 パーセンタイル：0.00(Construction & Building Technology)Metakaolin-based geopolymers have attracted significant interest in decontaminating radioactive debris from the Fukushima nuclear accident. This study explored the incorporation of boron (B) into geopolymers using boric acid as the source, with the goal of developing B-enriched geopolymers for enhanced radionuclide immobilisation and neutron capture potential.
C alloy measured in the electrostatic levitation furnace onboard the international space station石川 毅彦*; 織田 裕久*; 小山 千尋*; 下西 里奈*; 池内 留美子*; Paradis, P.-F.*; 岡田 純平*; 福山 博之*; 山野 秀将
International Journal of Microgravity Science and Application, 42(2), p.420202_1 - 420202_10, 2025/04
Samples of stainless steel (SS) - boron carbide (BC) alloys were levitated in the Electrostatic Levitation Furnace onboard the International Space Station (ISS-ELF) to measure the thermophysical properties of their melts. Melting of samples of two different compositions (SS-12.3, and 28 mass% BC) were attempted in the furnace. Even though only one sample (SS-12.3 mass% BC) could be melted, its density was successfully obtained.
石川 諒尚; 田中 浩基*; 中村 哲志*; 熊田 博明*; 櫻井 良憲*; 渡辺 賢一*; 吉橋 幸子*; 棚上 裕生*; 瓜谷 章*; 鬼柳 善明*
Journal of Radiation Research (Internet), 65(6), p.765 - 775, 2024/11
被引用回数：0 パーセンタイル：0.00(Biology)From the viewpoints of the advantage depths (ADs), peak tumor dose, and skin dose, we evaluated the effect of neutron beam properties, namely, the ratio between thermal and epithermal neutron fluxes (thermal/epithermal ratio), fast neutron component, and 
-ray component on the dose distribution. Several parameter surveys were conducted with respect to the beam properties of neutron sources for boron neutron capture therapy assuming boronophenylalanine as the boron agent using our dose calculation tool, called SiDE. The ADs decreased by 3% at a thermal/epithermal ratio of 20% - 30% compared with the current recommendation of 
. The skin dose increased with the increasing thermal/epithermal ratio, reaching a restricted value of 14 Gy-eq at a thermal/epithermal ratio of 
. The fast neutron component was modified using two different models, namely, the "linear model," in which the fast neutron intensity decreases log-linearly with the increasing neutron energy, and the "moderator thickness (MT) model," in which the fast neutron component is varied by adjusting the moderator thickness in a virtual beam shaping assembly. Although a higher fast neutron component indicated a higher skin dose, the increment was 
at a fast neutron component of 
Gy cm
for both models. Furthermore, in the MT model, the epithermal neutron intensity was 
higher at a fast neutron component of 
Gy cm compared with the current recommendation of 
Gy cm. The -ray component also caused no significant disadvantages up to several times larger compared with the current recommendation.
江村 優軌; 松場 賢一; 菊地 晋; 山野 秀将
Proceedings of 13th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS13) (Internet), 8 Pages, 2024/11
Assuming the CDA of SFRs, the eutectic melting between BC as a control rod material and stainless steel (SS) as a structural material could occur below their melting points. After that, the mixture produced by eutectic melting between BC and SS (BC-SS mixture) would relocate inside or outside of the original core region. From the viewpoint of core reactivity changes, the relocation behavior of BC-SS mixture induced by its melting/freezing behavior, is one of the key elements to evaluate the CDA consequences. Many experimental studies on freezing behavior using core materials and its simulants, including molten UO
, SS, tin, wood's metal have been reported in the past. Based on these experimental findings, the freezing/blockage model for the severe accident simulation code was established and discussed through analyses of freezing process. Specifically, it has been considered that the experimental correlation of melt-penetration length was a key indicator to quantitatively describe freezing behavior. However, there was no experimental data for the freezing behavior of actual BC-SS mixture. Therefore, the freezing experiments of BC-SS mixture were conducted to investigate the freezing and blockage behavior inside a flow path such as fuel pin bundle. In the freezing experiments, BC powder and SS block were heated up to around 1,750 K using a graphite heating furnace, then BC-SS mixture flowed down into an SS pipe for cooling below 750 K. The experimental results showed that the BC-SS mixture solidified and resulted in the blockage in the SS pipe with 4 mm or 6.7 mm in inner diameter, respectively. Furthermore, the observations for cross section of SS pipe suggested that the BC-SS mixture penetrated deeper than molten SS. This difference is considered to be influenced by decrease of the melting point.
江村 優軌; 高井 俊秀; 菊地 晋; 神山 健司; 山野 秀将; 横山 博紀*; 坂本 寛*
Journal of Nuclear Science and Technology, 61(7), p.911 - 920, 2024/07
被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)Boron carbide (B
C)- stainless steel (SS) eutectic reaction behavior is one of the most important issues in the core disruptive accidents (CDAs) of sodium-cooled fast reactors (SFRs). In this study, the immersion experiments using BC pellets with molten SS were conducted to evaluate the CDA sequences such as contact event of solid BC with degraded core materials including SS at very high temperature. The immersion experiment aims at understanding the kinetic behavior of solid BC-liquid SS reaction based on the reduced thickness of BC pellet after the experiment in the temperature ranges from 1763 to 1943 K, which is higher than the temperature of solid BC-solid SS reaction. Based on the kinetic consideration of the reaction rate constants for solid BC-liquid SS reaction, it was found that similar temperature dependency was identified between solid BC-liquid SS and solid BC-solid SS. Besides, the reaction rate constants of solid BC-liquid SS were smaller than those of solid BC-solid SS extrapolated in higher temperature region by two or more orders of magnitude due to two different evaluation method for BC side/SS side. It was confirmed that this difference was reasonable through the consideration of previous reaction tests in solid-solid contact for BC side/SS side.
林 好一*; Lederer, M.*; 福本 陽平*; 後藤 雅司*; 山本 裕太*; 八方 直久*; 原田 正英; 稲村 泰弘; 及川 健一; 大山 研司*; et al.
Applied Physics Letters, 120(13), p.132101_1 - 132101_6, 2022/03
被引用回数：4 パーセンタイル：34.41(Physics, Applied)The local structure around boron doped in a 6H-type silicon carbide (SiC) was investigated using neutron holography. Three dimensional atomic images reconstructed from multiple-wavelength holograms revealed the boron substitution for both silicon and carbon. To determine the boron locations accurately, we calculated holograms with varying occupancies of six different sites and fitted the image intensities with those obtained from the experimental holograms by the steepest descent method. As a result, it was found that boron atoms were selectively located at the Si-C-cubic site layer. Furthermore, boundaries right above the boron locations were suggested from the absence of atomic images in the upper region of the reconstruction.
濱本 真平; Ho, H. Q.; 飯垣 和彦; 後藤 実; 島崎 洋祐; 澤畑 洋明; 石塚 悦男
Nuclear Engineering and Design, 386, p.111564_1 - 111564_8, 2022/01
被引用回数：1 パーセンタイル：14.76(Nuclear Science & Technology)2011年に発生した東日本大震災による福島第一原子力発電所事故の経験から、安全機能の機能喪失に備えることの重要性が明らかになった。事故時であっても機能を失わないように機器の堅牢性を高めることは有効であるが、機能喪失の可能性は残るため、事故を早期に収束させるためには、機能喪失に備えて代替手段を用意しておくことが重要となる。そこで本研究では、高温ガス炉の経済性を損なうことなく、停止機能喪失時の対策をより強固なものにするために、既設の停止装置の代替として可搬型予備停止装置を設計した。本装置は、電力が完全に失われた状態でも動作するように、可搬型で手動で設置することが可能である。また、技術的および費用対効果の観点から、本装置のための様々な中性子吸収材を検討した結果、他の材料と比較して、良好な中性子特性と高い入手性を示す窒化ホウ素を選択した。
三輪 周平; 宮原 直哉*; 中島 邦久; 井元 純平; 鈴木 恵理子
日本原子力学会誌ATOMO
, 63(12), p.825 - 829, 2021/12
沸騰水型原子炉のシビアアクシデント時において、制御材ホウ素は、被ばく低減等の観点で重要なセシウム等の化学挙動や移行挙動に大きな影響を与えることが示唆されており、環境放出量や炉内分布の予測に内在する大きな不確かさの要因であった。そこで、シビアアクシデント解析で考慮すべき重要な化学挙動を解明するため、炉内移行時の化学挙動評価を可能とする装置を開発して、セシウムの化学挙動を評価した。その結果を基に、シビアアクシデント解析コードで化学挙動を評価できるように化学反応解析の基盤となるデータセットやモデルから構成されるデータベースECUMEを整備した。
高井 俊秀; 古川 智弘; 山野 秀将
Mechanical Engineering Journal (Internet), 8(4), p.20-00540_1 - 20-00540_11, 2021/08
炉心損傷事故時には、制御棒材である炭化ホウ素と構造材であるステンレス鋼が共晶反応を起こし、ステンレス鋼の融点より低い温度で溶融(液化)すると考えられる。こうして生成された制御棒溶解材は流動性があるため、崩壊炉心内を広範に移行し、崩壊炉心物質に混ざり込むことで、崩壊炉心物質の反応度抑制に顕著な効果をもたらすと考えられる。しかしながら、このような制御棒溶解材の共晶溶融反応やその移行挙動については、これまでの重大事故解析では何ら考慮されていない。本研究では、シビアアクシデント解析コードの高度化に資するため、炭化ほう素溶解量の異なる制御棒溶解材について固相物性測定を実施し、温度(及び炭化ホウ素濃度)依存性を示す物性評価式として整備した結果について報告する。
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 BC 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.
池部 友理恵*; 大島 真澄*; 伴場 滋*; 浅井 雅人; 塚田 和明; 佐藤 哲也; 豊嶋 厚史*; Bi, C.*; 瀬戸 博文*; 天野 光*; et al.
Applied Radiation and Isotopes, 164, p.109106_1 - 109106_7, 2020/10
被引用回数：2 パーセンタイル：17.88(Chemistry, Inorganic & Nuclear)ホウ素中性子捕捉療法(BNCT)は難治性がんの治療に有効な放射線療法である。BNCTでは、中性子照射時間や中性子被曝量のコントロールのために、全血試料中の
B濃度の正確な定量が不可欠である。我々は荷電粒子誘起放射化分析法(CPAA)を全血試料中B濃度の非破壊・精密測定に適用した。実験は原子力機構(JAEA)タンデム加速器にて8MeVの陽子ビームを用いて実施した。B(p,
)
Be反応で生成するBeからの478keV 線を用いてBを定量した。また血液中の鉄との核反応で生成する
Coの線を用いて線強度を規格化した。実験の結果、開発したCPAA法は血液中のB濃度の定量に適用できることが明らかとなった。
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.
高井 俊秀; 古川 智弘; 山野 秀将
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08
Eutectic melting behavior between boron carbide (BC) as control rod material and stainless steel (SS) as structural material and subsequent relocation behavior plays an important role to achieve an in-vessel retention concept which ensures long-term coolability of degraded core under core disruptive accident, because these behaviors are expected to reduce the neutronic reactivity significantly. However, these behaviors have never been simulated in severe accident computer codes before. Since 2016, JAEA has been conducting a research project to develop physical models that describe these behaviors. For the physical models' development, it is necessary to obtain thermophysical properties of SS-BC eutectic mixture with various BC concentration and maintain them as a database. In this work, the density and specific heat of SS-17 mass%BC in a solid state are obtained and compared with these of stainless steel containing 0 and 5 mass%BC.
Si single crystals林 慶*; 齋藤 亘*; 杉本 和哉*; 大山 研司*; 林 好一*; 八方 直久*; 原田 正英; 及川 健一; 稲村 泰弘; 宮崎 譲*
AIP Advances (Internet), 10(3), p.035115_1 - 035115_7, 2020/03
被引用回数：19 パーセンタイル：69.37(Nanoscience & Nanotechnology)MgSi is a potential thermoelectric (TE) material that can directly convert waste energy into electricity. In expectation of improving its TE performance by increasing electron carrier concentration, the element boron (B) is doped in MgSi single crystals (SCs). Their detailed crystal structures are definitely determined by using white neutron holography and single-crystal X-ray diffraction (SC-XRD) measurements. The white neutron holography measurement proves that the doped B atom successfully substitutes for the Mg site. The SC-XRD measurement confirms the B-doping site and also reveals the presence of the defect of Si vacancy (VSi) in the B-doped MgSi SCs. Regarding TE properties, the electrical conductivity, 
, and the Seebeck coefficient, S, decreases and increases, respectively, due to the decrease in the electron carrier concentration, contrary to the expectation. The power factor of the B-doped MgSi SCs evaluated from and S does not increase but rather decreases by the B-doping.
三輪 周平; 高瀬 学; 井元 純平; 西岡 俊一郎; 宮原 直哉; 逢坂 正彦
Journal of Nuclear Science and Technology, 57(3), p.291 - 300, 2020/03
被引用回数：10 パーセンタイル：66.83(Nuclear Science & Technology)BWR重大事故における制御材ホウ素の移行挙動を、セシウム及びヨウ素に与える化学的影響の観点から評価するため、高温領域を移行するホウ素の化学挙動を実験的に調べた。核分裂生成物放出移行再現実験装置を用いて水蒸気雰囲気にて酸化ホウ素試料の加熱実験を実施した。放出した酸化ホウ素蒸気は1,000K以上においてステンレス鋼への凝集により多量に沈着した。さらに、この酸化ホウ素の沈着物、もしくはホウ素蒸気種とステンレス鋼が1,000K以上において反応することで、安定な鉄-ホウ素の複合酸化物(FeO)BO
化合物を形成することが分かった。この結果は、重大事故時において、破損したBWR制御ブレードから放出されるホウ素は圧力容器内等の高温領域に保持されることを示している。このことから、セシウム蒸気がホウ素の沈着物と反応することで低揮発性のホウ酸セシウム化合物を形成し、圧力容器から低温領域に移行するセシウム蒸気が減少することなどが可能性として考えられる。
C in the solid phase高井 俊秀; 古川 智弘; 山野 秀将
Nuclear Technology, 205(9), p.1164 - 1174, 2019/09
被引用回数：12 パーセンタイル：70.03(Nuclear Science & Technology)This paper describes evaluation results of thermophysical properties of stainless steel (SS) containing 5 mass% boron carbide (BC) in its solid phase. First, the authors have synthesized SS-BC samples with emphasis on 5 mass%-BC and SS using a hot press method and then evaluated its homogeneity in several ways such as chemical composition analysis, metallographic structure observation, and micro X-ray diffraction (XRD). This study also evaluated the density, specific heat and thermal conductivity of the SS-BC sample and found that the density becomes lower and the temperature dependence of the density decreased as the temperature rose compared to that of grade type 316L stainless steel (SS316L) used as a reactor material. The specific heat became slightly higher than that of SS316L and showed similar temperature dependence up to 1073 K. Unexpectedly, the thermal conductivity became lower than that of SS316L and showed similar temperature dependence up to 1273 K.
C addition on thermophysical properties of austenitic stainless steel in a solid state高井 俊秀; 古川 智弘; 山野 秀将
Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.847 - 852, 2019/09
In a core disruptive accident scenario, boron carbide (BC) in control-rod will be predicted to react with stainless steel (SS) as structural material. Produced eutectic material of SS-BC is assumed to relocate widely in the core. To add a function of evaluating this liquefaction and relocation behavior to CDA analysis codes, it is indispensable to maintain the thermophysical properties database of SS-BC. In this report, density and specific heat of SS-7mass%BC in a solid state were obtained, and compared them with those of SS-5mass%BC obtained so far and literature value of SS. It is found that the density decreased while the specific heat increased, as BC concentration in the austenitic stainless steel increased. By addition of 7mass%-BC to 316L SS, the density was decreased by approximately 7% at 294K. On the other hand, specific heat was increased by approximately 21% at 294K.
宮原 直哉; 三輪 周平; 堀口 直樹; 佐藤 勇*; 逢坂 正彦
Journal of Nuclear Science and Technology, 56(2), p.228 - 240, 2019/02
被引用回数：9 パーセンタイル：63.15(Nuclear Science & Technology)軽水炉シビアアクシデント時のソースターム評価における核分裂生成物(FP)化学挙動評価モデルを高度化するため、FP化学データベース「ECUME」の初版を構築した。ECUMEには、代表的な事故シーケンスにおける主要な化学反応と、その実効的な化学反応速度定数を実装する計画である。初版においては、300-3000Kの温度領域におけるCs-I-B-Mo-O-H系の主要化学種に対し、それらの生成に係る化学反応の速度定数を文献調査または第一原理に基づく理論計算によって整備した。構築した化学反応データセットを用いた解析の一例として化学反応解析を実施した結果、1000Kにおいて有意な化学反応速度の効果が見られた。また、平衡に至った後の化学組成を化学平衡計算の結果と比較したところ、代表的なCs-I-B-Mo-O-H系化学種に対して良く整合する結果が得られた。これらの結果から、構築したデータセットは、速度論の考慮が必要なシビアアクシデント時のCs-I-B-Mo-O-H系FP化学挙動評価のために有用であるとの結論を得た。
Ochs, M.*; Vriens, B.*; 舘 幸男
Progress in Nuclear Science and Technology (Internet), 5, p.208 - 212, 2018/11
福島第一原子力発電所の事故に関連したクリーンアップ活動によって、コンクリートなどのセメント系材料を含む様々な種類の放射性廃棄物が発生している。さらに、放射性核種の収着や取り込み能力を含む、その好ましく安定した化学特性のために、セメント系バリア材の利用が検討されている。福島で生じている廃棄物には、特に、有機物,ホウ素,塩分といった、収着遅延に擾乱影響をもたらす共存物質が含まれる。本研究では、異なる劣化条件と、有機物,ホウ素,塩分といった共存物質が存在する条件でのセメント系材料へのU(VI)及びU(IV)の収着遅延を、既存の文献情報をもとに、定量評価する手法を構築することを目的とする。段階的なアプローチを提案し、U(VI)及びU(IV)の収着遅延を例示的に評価した。
C in the solid phase高井 俊秀; 古川 智弘; 山野 秀将
Proceedings of 2018 International Congress on Advances in Nuclear Power Plants (ICAPP 2018) (CD-ROM), p.1007 - 1013, 2018/04
This study describes estimation results of thermophysical properties of stainless steel containing 5mass% boron carbide (5mass%BC-SS) in the solid state. 5mass%BC-SS eutectic sample was synthesized using a hot press method. Homogeneity of the sample was evaluated by chemical composition analysis, metal structure observation, and micro X-ray diffraction (XRD). Specific gravity and specific heat were evaluated up to 1000
C. These measurements proved that the specific gravity in our sample was lowered and the temperature dependence of the specific gravity, along with the elevation of temperature, became gradual compared to that of grade type 316L stainless steel (SUS316L) used as a reactor material by addition of BC. The specific heat became slightly higher than that of SUS316L by addition of BC and showed similar temperature dependence up to 800C.
