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Radiocesium interaction with clay minerals; Theory and simulation advances Post-Fukushima

奥村 雅彦; Kerisit, S.*; Bourg, I. C.*; Lammers, L. N.*; 池田 隆司*; Sassi, M.*; Rosso, K. M.*; 町田 昌彦

Journal of Environmental Radioactivity, 189, p.135 - 145, 2018/09



Characterizing regional-scale temporal evolution of air dose rates after the Fukushima Daiichi Nuclear Power Plant accident

Wainwright, H. M.*; 関 暁之; 三上 智; 斎藤 公明

Journal of Environmental Radioactivity, 189, p.213 - 220, 2018/09

本研究では、福島第一原子力発電所周辺の特定の区域における空間線量率の時間的な変化を定量化し、将来の空間的な線量の分布を予測した。我々は、まず、異なる規模・解像度・範囲・精度を持つ線量測定のデータセット(歩行サーベイ, 車両サーベイ, 航空機サーベイ)の統合のため、Wainwright等によって開発された地理統計的なベイズ手法を使った。そして、この手法を3年間(2014年から2016年)のデータに適用した。これによって作成した3つの統合マップからわかる時間的変化から、放射性物質による線量の空間的・時間的なダイナミクスが特徴付けられた。


Radiocesium distribution in aggregate-size fractions of cropland and forest soils affected by the Fukushima nuclear accident

小嵐 淳; 西村 周作; 安藤 麻里子; 松永 武*; 佐藤 努*; 長尾 誠也*

Chemosphere, 205, p.147 - 155, 2018/08



原子力発電所の廃炉技術最前線; 福島第一原発の廃止措置に向けた取り組み,1; 現状と課題、求められる技術

小川 徹

電気学会誌, 138(8), p.518 - 521, 2018/08



Reduction of water content in calcium aluminate cement with/out phosphate modification for alternative cementation technique

Garcia-Lodeiro, I.*; 入澤 啓太; Jin, F.*; 目黒 義弘; 木下 肇*

Cement and Concrete Research, 109, p.243 - 253, 2018/07

Cementation of the secondary aqueous wastes from TEPCO Fukushima Daiichi Nuclear Power Plant is challenging due to the significant strontium content and radioactivity, leading to a potential risk of hydrogen gas generation via radiolysis of water content. The present study investigates the reduction of water content in calcium aluminate cement (CAC) with/out phosphate modification by a heat-treatment during the solidification. The reduction of water in the CAC was found restricted by the rapid formation of crystalline hydration phases, whereas the phosphate-modified system allowed the gradual reduction of water, achieving the reduction of 60% water content at 95$$^{circ}$$C. Curing at 60-95$$^{circ}$$C also eliminated the significant cracks found at 35$$^{circ}$$C in the phosphate system. The possible difference in the amorphous products, NaCaPO$$_{4}$$.nH$$_{2}$$O type at 35$$^{circ}$$C and Ca(HPO$$_{4}$$).xH$$_{2}$$O type at 60-95$$^{circ}$$C, may have contributed to the improvement in the microstructure together with the change in the pore size distribution.


Evaluation of physicochemical properties of radioactive cesium in municipal solid waste incineration fly ash by particle size classification and leaching tests

藤井 健悟*; 越智 康太郎; 大渕 敦司*; 小池 裕也*

Journal of Environmental Management, 217, p.157 - 163, 2018/07



Review of reduction factors by buildings for gamma radiation from radiocaesium deposited on the ground due to fallout

吉田 浩子*; 松田 規宏; 斎藤 公明

Journal of Environmental Radioactivity, 187, p.32 - 39, 2018/07

In order to estimate residents' external dose due to radionuclide exposure resulting from fallout deposit on the ground, the shielding and dose reduction effects provided by structures such as houses and workplaces are taken into account as most individuals spend a large portion of their time indoors. Soon after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, several measurements and calculations were performed to obtain specific reduction factors for Japanese settlements due to this lack of data. This research reviews previous studies that determined factors such as, shielding factors, protection factors, reduction factors, and location factors and summarizes specific results for Japan. We discuss the issues in determining these factors and in applying them to estimate indoor dose. The contribution of surface contamination to the indoor ambient dose equivalent rate is also discussed.


Mechanical properties of cubic (U,Zr)O$$_{2}$$

北垣 徹; 星野 貴紀; 矢野 公彦; 岡村 信生; 小原 宏*; 深澤 哲生*; 小泉 健治

Journal of Nuclear Engineering and Radiation Science, 4(3), p.031011_1 - 031011_7, 2018/07

Evaluation of fuel debris properties is required to develop fuel debris removal tools for the decommissioning of Fukushima Daiichi Nuclear Power Plant (1F). In this research, the mechanical properties of cubic (U,Zr)O$$_{2}$$ samples containing 10-65% ZrO$$_{2}$$ are evaluated. In case of the (U,Zr)O$$_{2}$$ samples containing less than 50% ZrO$$_{2}$$, Vickers hardness and fracture toughness increased, and the elastic modulus decreased slightly with increasing ZrO$$_{2}$$ content. Moreover, all of those values of the (U,Zr)O$$_{2}$$ samples containing 65% ZrO$$_{2}$$ increased slightly compared to (U,Zr)O$$_{2}$$ samples containing 55% ZrO$$_{2}$$. However, higher Zr content (exceeding 50%) has little effect on the mechanical properties. This result indicates that the wear of core-boring bits in the 1F drilling operation will accelerate slightly compared to that in the TMI-2 drilling operation.


Development of experimental technology for simulated fuel-assembly heating to address core-material-relocation behavior during severe accident

阿部 雄太; 山下 拓哉; 佐藤 一憲; 中桐 俊男; 石見 明洋; 永江 勇二

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 9 Pages, 2018/07

Authors are developing an experimental technology to realize experiments simulating Severe Accident (SA) conditions using simulant fuel material (ZrO$$_{2}$$ with slight addition of MgO for stabilization) that would contribute not only to Fukushima Daiichi (1F) decommissioning but also to enhance the safety of worldwide existing and future nuclear power plants through clarification of the accident progression behavior. Based on the results of the prototype test, improvement of plasma heating technology was conducted. The Core Material Melting and Relocation (CMMR)-1/-2 experiments were carried out in 2017 with the large-scale simulated fuel assembly (1 m $$times$$ 0.3 m $$phi$$) applying the improved technology (higher heating power and controlled oxygen concentration). In these two tests, heating history was different resulting basically in similar physical responses with more pronounced material melting and relocation in the CMMR-2 experiment. The CMMR-2 experiment is selected here from the viewpoint of establishing an experimental technology. The CMMR-2 experiment adopted 30-min heating period, the power was increased up to a level so that a large temperature gradient ($$>$$ 2,000 K/m) expected at the lower part of the core in the actual 1F accident conditions. Most of the control blade and the channel box migrated from the original position. After the heating, the simulated fuel assembly was measured by the X-ray Computed Tomography (CT) technology and by Electron Probe Micro Analyzer (EPMA). CT pictures and elemental mapping demonstrated its excellent performance with rather good precision. Based on these results, an excellent perspective in terms of applicability of the non-transfer type plasma heating technology to the SA experimental study was obtained.


Three-dimensional numerical study on pool stratification behavior in molten corium-concrete interaction (MCCI) with MPS method

Li, X.; 佐藤 一憲; 山路 哲史*; Duan, G.*

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07




佐藤 優樹; 鳥居 建男

Isotope News, (757), p.44 - 47, 2018/06



The CMMR program; BWR core degradation in the CMMR-1 and the CMMR-2 tests

山下 拓哉; 佐藤 一憲; 阿部 雄太; 中桐 俊男; 石見 明洋; 永江 勇二

Proceedings of 12th International Conference of the Croatian Nuclear Society; Nuclear Option for CO$$_{2}$$ Free Energy Generation (USB Flash Drive), p.109_1 - 109_15, 2018/06




坂本 浩幸*; 赤木 洋介*; 山田 一夫*; 舘 幸男; 福田 大祐*; 石松 宏一*; 松田 樹也*; 齋藤 希*; 上村 実也*; 浪平 隆男*; et al.

日本原子力学会和文論文誌, 17(2), p.57 - 66, 2018/05




堀口 賢一

技術士, 30(4), p.8 - 11, 2018/04



Applicability of $$K_{d}$$ for modelling dissolved $$^{137}$$Cs concentrations in Fukushima river water; Case study of the upstream Ota River

佐久間 一幸; 辻 英樹*; 林 誠二*; 舟木 泰智; Malins, A.; 吉村 和也; 操上 広志; 北村 哲浩; 飯島 和毅; 細見 正明*

Journal of Environmental Radioactivity, 184-185, p.53 - 62, 2018/04

福島河川水中の溶存態$$^{137}$$Cs濃度を数値計算するにあたって、分配係数($$K_{d}$$)を用いた吸脱着モデルの適用可能性を評価した。数値計算結果は平水時および出水時の水と浮遊砂の流出フラックス、懸濁態$$^{137}$$Cs濃度を再現した。一方、河川水中の溶存態$$^{137}$$Cs濃度の実測値の再現性は低かった。粗い粒径区分の$$K_{d}$$をチューニングした結果、平水時の溶存態$$^{137}$$Cs平均濃度を再現することが可能であった(実測値:0.32Bq/L、計算値: 0.36Bq/L)。しかし、平水時の溶存態$$^{137}$$Cs濃度の季節変動(0.14-0.53Bq/L)や出水時の濃度上昇(0.18-0.88Bq/L, mean: 0.55Bq/L)は現実的な数値計算パラメータでは再現することはできなかった。


Submesoscale mixing on initial dilution of radionuclides released from the Fukushima Daiichi Nuclear Power Plant

上平 雄基; 内山 雄介*; 川村 英之; 小林 卓也; 古野 朗子

Journal of Geophysical Research; Oceans (Internet), 123(4), p.2808 - 2828, 2018/04



Application of nontransfer type plasma heating technology for core-material-relocation tests in boiling water reactor severe accident conditions

阿部 雄太; 佐藤 一憲; 中桐 俊男; 石見 明洋; 永江 勇二

Journal of Nuclear Engineering and Radiation Science, 4(2), p.020901_1 - 020901_8, 2018/04

原子力機構では非移行型プラズマ加熱を用いたBWR体系での炉心物質の下部プレナムへの移行挙動(CMR)に着目した試験を検討している。この技術の適用性を確認するために、我々は小規模試験体(107mm$$times$$107mm$$times$$222mm (height))を用いたプラズマ加熱の予備実験を行った。これらの予備実験の結果から、SA(シビアアクシデント)研究への非移行型プラズマ加熱の優れた適用性が確認できた。また我々は、中規模の模擬燃料集合体(燃料ピン50ロッド規模)を準備し、まだ技術的な適用性が確認できていない制御ブレードやCMR事体に関する試験を実施予定である。


Safety assessment for recycling of soil generated from decontamination activities

武田 聖司

Str${aa}$levern Rappot 2018:4 (Internet), p.62 - 64, 2018/04



A Three-dimensional radiation image display on a real space image created via photogrammetry

佐藤 優樹; 小澤 慎吾*; 谷藤 祐太; 鳥居 建男

Journal of Instrumentation, 13(3), p.P03001_1 - P03001_8, 2018/03

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown after the large tsunami caused by the Great East Japan Earthquake of March 11, 2011. Radiation distribution measurements inside FDNPS buildings are indispensable to execute decommissioning tasks in the reactor buildings. We have developed a method of three-dimensional (3-D) image reconstruction for radioactive substances using a compact Compton camera. We also succeeded in visually recognize the position of the radioactive substances on the real space by integration of the 3D radiation image and the 3D photo-model created by photogrammetry.



長洲 亮佑*; 田邉 大次郎*; 横塚 享*; 熊沢 紀之*; 安食 貴也*; 相澤 雄介*; 長縄 弘親; 永野 哲志; 柳瀬 信之*; 三田村 久吉*; et al.

環境浄化技術, 17(2), p.58 - 61, 2018/03

原子力機構は、茨城大学, 熊谷組およびグループ会社であるテクノスとともに、森林からのセシウムの移行を抑制する新技術を開発した。この新技術では、ポリイオンと呼ばれるイオン性高分子と鉱物である粘土を併用し、降雨や雨水の流れといった自然の力を利用して、セシウムの移行を抑制する。福島県飯舘村で新規技術の実証試験を行い、森林から森林に隣接する牧草地へのセシウム移行に対する抑制効果を証明した。

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