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蓬田 匠; 大内 和希; 岡 壽崇; 北辻 章浩; 駒 義和; 今野 勝弘*
Scientific Reports (Internet), 12(1), p.7191_1 - 7191_10, 2022/05
被引用回数：1 パーセンタイル：0(Multidisciplinary Sciences)福島第一原子力発電所2号機トーラス室滞留水に含まれる
線放出核種の存在形態を、走査型電子顕微鏡X線検出(SEM-EDX)やアルファトラック法により分析した。SEM-EDXによる観察の結果、Uを主成分とするサブ
m
数mサイズの粒子を複数同定できた。これらの粒子はZrなどの燃料被覆管や構造材を構成する元素を含んでいる。また、同じ粒径フラクションの固形分に含まれるU同位体比(235/238)は、原子炉燃料のそれと一致した。このことから、U粒子は原子炉に由来し、これが微細化したものであることを示している。アルファトラック分析により同定した核種含有粒子は、粒径数10m~数100mのサイズであり、SEM-EDXの元素分析の結果、鉄を主成分としていた。核種の物質量は極わずかであることから、Pu, Am, Cm等が鉄粒子上に付着する形態であると考えられる。分析した滞留水中の固形分試料では、Uと他の核種の存在形態が異なる場合があることが明らかになった。
Grambow, B.; 二田 郁子; 柴田 淳広; 駒 義和; 宇都宮 聡*; 高見 龍*; 笛田 和希*; 大貫 敏彦*; Jegou, C.*; Laffolley, H.*; et al.
Journal of Nuclear Science and Technology, 59(1), p.1 - 24, 2022/01
被引用回数：8 パーセンタイル：57.65(Nuclear Science & Technology)Following the NPP accident, some hundred tons of nuclear fuel elements of 3 damaged nuclear reactor units were partly molten with even larger masses of steel and concrete structures, creating a big mass of corium and fuels debris. Since ten years, this heat generating mass has been cooled permanently by millions of m
of water flowing over them. Knowledge on the interaction of this solid mass with water is crucial for any decommissioning planning. Starting from analyses of the evolutions of the accident in the 3 reactor cores and associated fuel debris formations and some additional isotopic and physiochemical information of debris fragments collected in soils of Fukushima, we review the temporal evolution of the chemistry and leached radionuclide contents of the cooling water. Measured concentration ratios of the actinides and fission products in the water where compared to reported results of laboratory leaching studies with either spent nuclear fuel or simulated fuel debris under a variety of simulated environmental conditions.
五十嵐 豪*; 芳賀 和子*; 山田 一夫*; 粟飯原 はるか; 柴田 淳広; 駒 義和; 丸山 一平*
Journal of Advanced Concrete Technology, 19(9), p.950 - 976, 2021/09
被引用回数：5 パーセンタイル：64.78(Construction & Building Technology)Decommissioning of the Fukushima Daiichi Nuclear Power Station (F1NPS) in a proper manner requires assessment of the contamination levels and mechanisms for contamination in the concrete structures. Between January 2018 and March 2020, Japan's Ministry of Education Ministry of Education, Culture, Sports, Science and Technology (MEXT) conducted a project called "The Analysis of Radionuclide Contamination Mechanisms of Concrete and the Estimation of Contamination Distribution at the Fukushima Daiichi Nuclear Power Station". In this review, we outline the results of this study. The experimental results from the first project indicate that concrete carbonation, Ca leaching, and drying conditions affected the adsorption behaviors of Cs and Sr and therefore, their penetration depths. Additionally, the studies showed that -nuclides precipitated on the surface of the samples because concrete causes a high pH. A reaction transport model was developed to assess further the adsorption characteristics of Cs and Sr in carbonated cement paste and on concrete aggregates. The model used real concrete characteristics from the materials used at F1NPS and historical boundary conditions at the site, including radionuclide concentrations and penetration profiles within the turbine pit wall. Capillary water suction resulting from dried concrete was evaluated by considering structural changes in cement hydrates using X-ray CR and 
H-NMR relaxometry.
杉山 大輔*; 中林 亮*; 田中 真悟*; 駒 義和; 高畠 容子
Journal of Nuclear Science and Technology, 58(4), p.493 - 506, 2021/04
被引用回数：1 パーセンタイル：30.57(Nuclear Science & Technology)A modeling calculation methodology for estimating the radionuclide composition in the wastes generated at the Fukushima Daiichi nuclear power station has been upgraded by introducing an approach using Bayesian inference. The developed stochastic method describes the credible interval of the regression curve for the log-normal distribution of the measured transport ratio, which is used to calibrate the radionuclide transport parameters included in the modeling calculation. Consequently, the method can predict the robability distribution of the radionuclide composition in the Fukushima Daiichi wastes. The notable feature of the developed method is that it can explicitly investigate the improvement in the accuracy and confidence (degree of belief) of the estimation of the waste inventory using Bayesian inference. Specifically, the developed method can update and improve the degree of belief of the estimation of the radionuclide composition by visualizing the reduction in the width of uncertainty in the radionuclide transport parameters in the modeling calculation in accordance with the accumulation of analytically measured data. Further investigation is expected to improve the credibility of waste inventory estimation through iteration between modeling calculations and analytical measurements and to reduce excessive conservativeness in the estimated waste inventory dataset.
山田 一夫*; 丸山 一平*; 芳賀 和子*; 五十嵐 豪*; 粟飯原 はるか; 富田 さゆり*; Kiran, R.*; 大澤 紀久*; 柴田 淳広; 渋谷 和俊*; et al.
Proceedings of International Waste Management Symposia 2021 (WM 2021) (CD-ROM), 10 Pages, 2021/03
To properly decommission the Fukushima Daiichi Nuclear Power Plant, the contamination levels and mechanisms for the concrete structures must be assessed. In this review, we outline the results of this study and present the objectives of a future study called "Quantitative Evaluation of Contamination in Reinforced Concrete Members of Fukushima Daiichi NPP Buildings Considering the Actual Environment Histories for Legitimate Treatments", which will run from October 2020 to March 2023. The experimental results from the first project indicate that concrete carbonation, Ca leaching, and drying conditions affected the adsorption of Cs and Sr and their penetration depths. Additionally, the studies showed that -nuclides precipitated on the surface of the samples because of the high pH of concrete. A reaction transfer model was developed to further assess the adsorption characteristics of Cs and Sr in carbonated cement paste and concrete aggregates. The model used real concrete characteristics from the FDNPP materials and historical boundary conditions at the site, including radionuclide concentrations and penetration profiles within the turbine pit wall. The water suction by dried concrete was evaluated with the consideration of the structure change of cement hydrates by X-ray CR and H-NMR relaxometry. In the new project, the studies will also include concrete cracks for more realistic contamination estimations.
Yin, X.; Zhang, L.*; Meng, C.*; 稲葉 優介*; Wang, X.*; 二田 郁子; 駒 義和; 竹下 健二*
Journal of Hazardous Materials, 387, p.121677_1 - 121677_10, 2020/04
被引用回数：10 パーセンタイル：61.89(Engineering, Environmental)The effective and efficient removal of radioactive Cs from contaminated soil is highly urgent for the nuclear post-accident remediation. In present study, we achieved rapid Cs desorption from both a typical micaceous clay (i.e., vermiculitized biotite, VB) and actually contaminated soil by high-speed ion exchange through temperature-controlled continuous leaching with Mg-solutions in a column reactor. Cs-sorbed VB was firstly employed as a soil surrogate to explore the macro-Cs desorption process and micro-mechanism in detail.
駒 義和
原子力バックエンド研究(CD-ROM), 26(2), p.133 - 136, 2019/12
福島第一原子力発電所では廃炉工程の進展に伴い廃棄物が発生している。廃棄物管理技術の研究開発のために実施している分析の概要を報告する。
駒 義和; 新堀 雄一*
日本機械学会誌, 122(1211), p.21 - 23, 2019/10
2019年5月に日本機械学会と日本原子力学会が国際会議International Topical Workshop on Fukushima Decommissioning Researchを共催した。会議は5つのトラックから構成され、うち廃棄物管理技術に関する概要を報告する。
杉山 大輔*; 中林 亮*; 駒 義和; 高畠 容子; 塚本 政樹*
Journal of Nuclear Science and Technology, 56(9-10), p.881 - 890, 2019/09
被引用回数：3 パーセンタイル：39.69(Nuclear Science & Technology)A calculation methodology for estimating the radionuclide composition in the wastes generated at the F1NPS has been developed by constructing a skeleton overview of the distribution of radionuclides considering the material balance in the system and calculation flowcharts of the transportation of radionuclides into the wastes. The wastes have a distinctive feature that their level of contamination includes considerable uncertainties. The developed method can explicitly specify the intrinsic uncertainties as a band to be included in the estimated radionuclide composition and can quantitatively describe the uncertainties by calibration using data on actual waste samples. Further studies to improve the quality of the calculation method, and acquiring a quantitative understanding of the spatial distribution of radionuclides inside the reactor building are suggested to be important steps toward reasonable and sustainable waste management as an integral part of the decommissioning.
駒 義和; 村上 絵理奈
Radiochimica Acta, 107(9-11), p.965 - 977, 2019/09
被引用回数：1 パーセンタイル：14.17(Chemistry, Inorganic & Nuclear)東京電力福島第一原子力発電所は、2011年3月11日に発生した地震と津波に被災し、放射性物質による重大な汚染を引き起こした。将来、廃棄物の処理や処分を行うために汚染した物質が分析されており、それにより得られたアクチニド核種の分析データを概観した。汚染水からアクチニド核種が検出されている。汚染水は化学的に除染されているが、アクチニド核種の濃度は時間とともには低下しておらず、損傷した燃料から冷却水へゆっくりと溶出しているとみられる。土壌に検出されるPu, Am, Cmは損傷した燃料に由来するが、Uは天然が支配的である。TRU核種は深部へのゆっくりとした移行が示唆される。瓦礫類の汚染は不均一であり、核分裂生成物とともにアクチニド核種も検出される。植物は、原子炉建屋に近い場所の落葉からTRU核種が検出された。
高畠 容子; 駒 義和
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05
Radioactive nuclides contaminated F1NPS on the severe accident. It is necessary to discuss about radioactive waste processing and disposal. To investigate contamination process for the waste is important to establish methodologies for their management. Operation floor of unit 2 reactor building was highly contaminated, and boring cores of floor and ceiling were radiochemicaly analyzed. Comparing with distribution of 
Cs and dose rate indicated the difference of degree of contamination between the floor and ceiling. Contamination with 
Pu, 
Am and 
Cm was higher at the floor above the reactor shield plug, where is considered that the contaminated gas leaked. Degree of contamination of H, 
Co, 
Tc, Am and Cm were highest at the point of the opposite side of the blow out panel among several sampling point of the ceiling. From the activity ratio of 
U to U with samples, the origin of uranium was the damaged fuel.
山田 一夫*; 丸山 一平*; 駒 義和; 芳賀 和子*; 五十嵐 豪*; 渋谷 和俊*; 粟飯原 はるか
Proceedings of International Waste Management Symposia 2019 (WM 2019) (CD-ROM), 6 Pages, 2019/03
For the decommissioning of a Nuclear Power Station (NPS) after a severe accident, estimation of contamination depth and radioactivity level in concrete is essential. This paper outlines a recently begun project on the analysis of the contamination mechanisms of concrete in the Fukushima Daiichi NPS. For this analysis, data on various parameters are required, such as the materials used in the NPS, the environmental conditions of the exposed concrete, the conditions of exposure during the accident and until decommissioning, and the fundamental transport characteristics of nuclides in concrete. These aspects of this project are illustrated with some examples.
三枝 純; 駒 義和; 芦田 敬
JAEA-Review 2018-017, 259 Pages, 2018/12
JAEA-Review-2018-017.pdf:53.88MB
廃炉国際共同研究センター(CLADS)は、福島第一原子力発電所の廃止措置の加速化や人材育成に資するため、国内外の研究協力を進めている。CLADSは、「廃棄物の分析技術開発に関する研究カンファレンス(FRCWM2018)」を2018年6月19日20日に開催した。本報告書は上記研究カンファレンスの講演要旨と発表資料を収録したものである。
渡部 創; 後藤 一郎; 佐野 雄一; 野村 和則; 駒 義和
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04
Clogging of the extraction chromatography column caused by inflow of insoluble residue into the bed possible to lead accumulation of decay heat and explosive gas inside the bed. Behavior of small particle is necessary to be investigated to prevent hazardous events. In this study, influence of fine particles contained in the feed solution on the clogging and on separation performance of the bed were evaluated by laboratory scale experiments. Discharging operation of the simulated particles from the bed was experimentally demonstrated using an engineering scale system. The particles were accumulated on top of the bed and hardly come inside the bed. Backwashing operation was effective to discharge a part of the accumulated powder. Supplying water into the column with normal flow rate condition was possible after the short time backwashing operation. Backwashing with cold water as a normal operation must be one of the most appropriate countermeasures for preventing from the clogging.
浅見 誠*; 高畠 容子; 明道 栄人; 飛田 剛志; 小林 究; 早川 美彩; 薄井 由香; 綿引 博美; 柴田 淳広; 野村 和則; et al.
JAEA-Data/Code 2017-001, 78 Pages, 2017/03
JAEA-Data-Code-2017-001.pdf:4.92MB
JAEA-Data-Code-2017-001-appendix(DVD-ROM).zip:818.06MB
東京電力ホールディングス(東京電力)福島第一原子力発電所において採取された汚染水(滞留水, 処理水)、汚染水処理二次廃棄物、瓦礫、土壌が分析され、放射性核種濃度等の分析データが報告されている。そこで、東京電力, 日本原子力研究開発機構, 国際廃炉研究開発機構により2016年3月末までに公開されたデータを収集し、データ集としてとりまとめた。また分析試料についての情報、分析により得られた放射性核種濃度等の値を表としてまとめるとともに、主な放射性核種濃度の時間変化を表す図を作成して収録した。電子情報として英訳と収録した分析データを提供する。
駒 義和; 柴田 淳広; 芦田 敬
Nuclear Materials and Energy (Internet), 10, p.35 - 41, 2017/01
被引用回数：20 パーセンタイル：90.77(Nuclear Science & Technology)2011年に発生した東京電力福島第一原子力発電所の事故により、放射性核種が環境に拡散し、種々の物を汚染した。発電所サイト内の汚染物,滞留水,瓦礫,土壌と植物に関して公開されている分析データを基にして、放射性核種の汚染ふるまいを検討した。放射性核種の濃度のCsに対する比を損傷燃料の組成により規格化して考察に用いた。瓦礫や土壌へのSrの移行はCsに比べて10
から10
であり、このような空気を経由した汚染に比べて、滞留水への移行が大きく、Csと同等である。Pu, AmとCmの移行は、Csに比べてごく小さい。ヨウ素、セレンやテルルの移行は、空気と水を経由するいずれについてもCsと同等以上である。Hと
Cの汚染は、Cs, 
SrやTRU核種と独立しており、異なる移行過程による可能性がある。
柴田 淳広; 駒 義和; 大井 貴夫
Journal of Nuclear Science and Technology, 53(12), p.1933 - 1942, 2016/12
被引用回数：17 パーセンタイル：82.69(Nuclear Science & Technology)For planning and investigating on treatment and disposal of the wastes on Fukushima Daiichi NPS, it is necessary to quantify the radioactivity inventory of them. The secondary wastes from the water treatment system are one of the major wastes and the analysis of the water of the treatment system holds the promise of giving the useful information on the inventory of damaged fuel. Therefore, the inventories of the secondary wastes and damaged fuel were estimated with a radionuclide transport model in the contaminated water. The model was developed based on unknown factors that are initial concentration in the hypothetical volume assuming the instantaneous homogeneous mixing and continuous release rate from damaged fuels. In the numerical analysis using this model, the key parameters, initial concentration C
, continuous release rate F and inventory of source of continuous release I
were given by fitting the model with analysis data of the contaminated water. By using these parameter values, the nuclides inventories in the damaged fuel and secondary waste were calculated.
駒 義和; 杉山 大輔*; 芦田 敬
Proceedings of International Conference on the Safety of Radioactive Waste Management (Internet), p.153_1 - 153_4, 2016/11
東京電力福島第一原子力発電所の事故廃棄物に関するインベントリ推定方法を議論する。事故廃棄物管理の方法を検討する上で、廃止措置に伴い発生する廃棄物を含めてインベントリを推定するために、解析的モデルが不可欠である。分析データが少ない初期の段階では、文献を利用してモデルを設定する。分析データが得られてからは、これを利用して不確実性の低減を図る。
佐藤 隆博; 横山 彰人; 喜多村 茜; 大久保 猛; 石井 保行; 高畠 容子; 渡部 創; 駒 義和; 加田 渉*
Nuclear Instruments and Methods in Physics Research B, 371, p.419 - 423, 2016/03
被引用回数：5 パーセンタイル：47.19(Instruments & Instrumentation)The cross-sectional distribution of neodymium (Nd) simulating minor actinides (MA) in a minute globular adsorbent of less than 50 m in diameter was measured using PIXE (particle induced X-ray emission)-CT (computed tomography) with a 3-MeV proton microbeam for the investigation of residual MA in extraction chromatography of spent fast reactor fuel. The measurement area was 100 
100 m
corresponding to 128 128 pixels of projection images. The adsorbent target was placed on an automatic rotation stage with 9
step. Forty projections of the adsorbent were finally measured, and image reconstruction was carried out by the modified ML-EM (maximum likelihood expectation maximization) method. As a result, the cross-sectional distribution of Nd in the adsorbent was successfully observed, and it was first revealed that Nd remained in the region corresponding to internal cavities of the adsorbent even after an elution process. This fact implies that the internal structure of the adsorbent must be modified for the improvement of the recovery rate of MA.
渡部 創; 佐野 雄一; 野村 和則; 駒 義和; 岡本 芳浩
EPJ Nuclear Sciences & Technologies (Internet), 1, p.9_1 - 9_8, 2015/12
In the extraction chromatography system, accumulation of hydrogen gas in the chromatography column is suspected to lead to fire or explosion. In order to prevent the hazardous accidents, it is necessary to evaluate behaviors of gas radiolytically generated inside the column. In this study, behaviors of gas inside the extraction chromatography column were investigated through experiments and Computation Fluid Dynamics (CFD) simulation. N
gas once accumulated as bubbles in the packed bed was hardly discharged by the flow of mobile phase. However, the CFD simulation and X-ray imaging on 
-ray irradiated column revealed that during operation the hydrogen gas generated in the column was dissolved into the mobile phase without accumulation and discharged.
