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論文

Anisotropic magnetic fluctuations in ferromagnetic superconductor UGe$$_2$$; $$^{73}$$Ge-NQR study at ambient pressure

野間 雄一郎*; 小手川 恒*; 久保 徹郎*; 藤 秀樹*; 播磨 尚朝*; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*; 伊藤 公平*; Haller, E. E.*; et al.

Journal of the Physical Society of Japan, 87(3), p.033704_1 - 033704_5, 2018/03

 被引用回数:1 パーセンタイル:49.95(Physics, Multidisciplinary)

$$^{73}$$Ge nuclear quadrupole resonance study of ferromagnetic superconductor UGe$$_2$$ is reported. Detailed analyses successfully assigned crystallographic sites of Ge atoms. The measurement of the nuclear spin-lattice relaxation rate revealed highly anisotropic magnetic fluctuations.

論文

Effect of topsoil removal and selective countermeasures on radiocesium accumulation in rice plants in Fukushima paddy field

Yang, B.*; 恩田 裕一*; 大森 良弘*; 関本 均*; 藤原 徹*; 脇山 義史*; 吉村 和也; 高橋 純子*; Sun, X.*

Science of the Total Environment, 603-604, p.49 - 56, 2017/12

 被引用回数:1 パーセンタイル:83.76(Environmental Sciences)

In this study, the effect of topsoil removal measure and fertilizer application on radiocesium uptake by rice plants was investigated over a four-year period. The results indicate that the effect of topsoil removal measure on the accumulation of radiocesium in rice plants was effective. We summarized four year's data to further confirm that potassium and nitrogen fertilizers had an opposite effect on the accumulation of radiocesium in rice plants. Increasing potassium and reducing nitrogen fertilizer conditions tended to inhibit the radiocesium uptake by rice plants.

論文

台風201326号出水に伴う新田川起源懸濁態放射性核種の沿岸域でのインベントリ解析

内山 雄介*; 東 晃平*; 小谷 瑳千花*; 岩崎 理樹*; 津旨 大輔*; 上平 雄基; 清水 康行*; 恩田 裕一*

土木学会論文集,B2(海岸工学)(インターネット), 73(2), p.I_685 - I_690, 2017/10

福島新田川流域には原子力発電所事故直後に大量の放射性セシウム137($$^{137}$$Cs)が大気経由で沈着し、高濃度の懸濁態$$^{137}$$Csとして河道に集積したのち、出水毎に間欠的に海域へ供給され、沿岸域の底質環境に影響を与え続けている。本研究では、4段ネストJCOPE2-ROMS海洋モデル、波浪推算モデルSWAN、河川土砂流出モデルiRIC-Nays2DH、混合粒径土砂3次元海洋輸送モデル、放射性核種吸着モデルを連成させた超高解像度広域での土砂およびそれらに吸着した懸濁態$$^{137}$$Csの海洋移流分散モデリングを行い、台風201326号出水イベントに伴う新田川起源土砂の河口・沿岸域における輸送、再懸濁、堆積、浸食過程の時空間特性を評価した。その結果、台風通過直後に新田川から海域へ流入した懸濁態$$^{137}$$Csの総量の約45.3%は河口1km圏内に堆積していた。さらに、浅海域における沿岸漂砂の輸送には南方向への偏りがみられた。以上の結果は現地調査結果とも整合的であった。

論文

Time dependence of the $$^{137}$$Cs concentration in particles discharged from rice paddies to freshwater bodies after the Fukushima Daiichi NPP accident

吉村 和也; 恩田 裕一*; 若原 妙子*

Environmental Science & Technology, 50(8), p.4186 - 4193, 2016/04

 被引用回数:7 パーセンタイル:42.78(Engineering, Environmental)

Particulate radiocesium concentration in paddy fields was studied for its parameterization and temporal changes over an extensive area covering various deposition levels of radiocesium after the FDNPP accident. The particulate radiocesium concentration in the paddy field correlated with the deposition amounts, indicating that the entrainment coefficient, defined as the ratio of concentration and deposition amounts, is useful for estimating the particulate radiocesium concentration in a paddy field. Variability of the entrainment coefficient was reduced by correcting the particle size dependency of particulate radiocesium concentration. The entrainment coefficient decreased with time according to a double exponential function. The decrease rate constant of the entrainment coefficient was higher than those of other land uses, thus demonstrating a rapid decrease in the particulate radiocesium concentration in the tested paddy field.

論文

Temporal changes of radiocesium in irrigated paddy fields and its accumulation in rice plants in Fukushima

Yang, B.*; 恩田 裕一*; 脇山 義史*; 吉村 和也; 関本 均*; Ha, Y.*

Environmental Pollution, 208(Part B), p.562 - 570, 2016/01

 被引用回数:5 パーセンタイル:55.17(Environmental Sciences)

In this study, we investigated the temporal changes of radiocesium in soil, irrigation water, and rice plant in two adjacent rice paddies, with and without surface-soil-removal practice, in Fukushima Prefecture for over three years (2012 to 2014). Our results showed that radiocesium migrated into 24-28 cm soil layers and that the concentration and inventory of radiocesium in paddy soils generally decreased. The newly added radiocesium to paddies through irrigation water contributed only the maximum values of 0.15% and 0.75% of the total amount present in normal and decontaminated paddies, respectively, throughout the study period. The change trend of radiocesium concentration in suspended sediment in irrigation water exponentially decreased. Radiocesium accumulation in rice plant also decreased with time in both paddies. However, the transfer factor of radiocesium for rice plant in the decontaminated paddy increased compared with normal paddy.

論文

Behavior of accidentally released radiocesium in soil-water environment; Looking at Fukushima from a Chernobyl perspective

Konoplev, A.*; Golosov, V.*; Laptev, G.*; 難波 謙二*; 恩田 裕一*; 高瀬 つぎ子*; 脇山 義史*; 吉村 和也

Journal of Environmental Radioactivity, 151(Part 3), p.568 - 578, 2016/01

 被引用回数:27 パーセンタイル:6.18(Environmental Sciences)

Comparative analysis is provided for radiocesium wash-off parameters and Kd between suspended matter and water in rivers and surface runoff on Fukushima and Chernobyl contaminated areas for the first years after the accidents. It was found that radiocesium distribution coefficient in Fukushima rivers is essentially higher than those in Chernobyl. This can be associated with two factors: a higher RIP of samples in Fukushima and the presence of water insoluble glassy particles. It was found also that dissolved wash-off coefficients for Fukushima catchments are lower than those in Chernobyl. Particulate wash-off coefficients are comparable for Fukushima and Chernobyl. The radiocesium migration in undisturbed forest and grassland soils at Fukushima has been shown to be faster than those in Chernobyl. Investigation and analysis of radiocesium distribution in soils of Niida river catchment revealed accumulation of contaminated sediments on its floodplain.

論文

Detailed deposition density maps constructed by large-scale soil sampling for $$gamma$$-ray emitting radioactive nuclides from the Fukushima Dai-ichi Nuclear Power Plant accident

斎藤 公明; 谷畑 勇夫*; 藤原 守; 齊藤 敬*; 下浦 享*; 大塚 孝治*; 恩田 裕一*; 星 正治*; 池内 嘉宏*; 高橋 史明; et al.

Journal of Environmental Radioactivity, 139, p.308 - 319, 2015/01

 被引用回数:121 パーセンタイル:0.45(Environmental Sciences)

The soil deposition density maps of $$gamma$$-ray emitting radioactive nuclides from the Fukushima Daiichi Nuclear Power Plant (NPP) accident were constructed on the basis of the results from large-scale soil sampling. The 10,915 soil samples were collected at 2,168 locations. $$gamma$$-rays emitted from the samples were measured by Ge detectors and analyzed using a reliable unified method. The determined radioactivity was corrected to that as of June 14, 2011 by taking into account the intrinsic decay constant of each nuclide. Finally the maps were created for $$^{134}$$Cs, $$^{137}$$Cs, $$^{131}$$I, $$^{129m}$$Te and $$^{110m}$$Ag. The radioactivity ratio of $$^{134}$$Cs to $$^{137}$$Cs was almost constant as 0.91 irrelevant to the soil sampling location. Effective doses for 50 years after the accident were evaluated for external and inhalation exposures due to the observed radioactive nuclides. The radiation doses from radioactive cesium were found to be much higher than those from other radioactive nuclides.

論文

Evaluation of radiocaesium wash-off by soil erosion from various land uses using USLE plots

吉村 和也; 恩田 裕一*; 加藤 弘亮*

Journal of Environmental Radioactivity, 139, p.362 - 369, 2015/01

 被引用回数:30 パーセンタイル:9.39(Environmental Sciences)

Radiocaesium wash-off associated with soil erosion in different land use was monitored using USLE plots in Kawamata, Fukushima Prefecture, Japan after the Fukushima Dai-ichi Nuclear Power Plant accident. Parameters and factors relating to soil erosion and $$^{137}$$Cs concentration in the eroded soil were evaluated based on the field monitoring and presented. The erosion of fine soil, which is defined as the fraction of soil overflowed along with discharged water from a sediment-trap tank, constituted a large proportion of the discharged radiocaesium. This indicated that the quantitative monitoring of fine soil erosion is greatly important for the accurate evaluation of radiocaesium wash-off. An exponential relationship was found between vegetation cover and the amount of eroded soil. Moreover, the radiocaesium concentrations in the discharged soil were greatly affected by the land use. These results indicate that radiocaesium wash-off related to vegetation cover and land use is crucially important in modelling radiocaesium migration.

論文

An Extensive study of the concentrations of particulate/dissolved radiocaesium derived from the Fukushima Dai-ichi Nuclear Power Plant accident in various river systems and their relationship with catchment inventory

吉村 和也; 恩田 裕一*; 坂口 綾*; 山本 政儀*; 松浦 裕樹*

Journal of Environmental Radioactivity, 139, p.370 - 378, 2015/01

 被引用回数:36 パーセンタイル:6.65(Environmental Sciences)

An extensive investigation of particulate radiocaesium in suspended solids and dissolved radiocaesium in river water was undertaken at 30 sites in Fukushima and Miyagi Prefectures in December 2012, and their relationships with catchment inventory and the solid/liquid distribution coefficient ($$K_{rm d}$$) were evaluated. Rivers located in the coastal region on the north side of the Fukushima Dai-ichi Nuclear Power Plant exhibited relatively higher particulate radiocaesium concentrations. Significant correlations were found between concentrations of particulate/dissolved radiocaesium and average catchment inventories, indicating that the concentrations of particulate/dissolved radiocaesium could be approximated from the catchment inventory. Particulate radiocaesium concentration was significantly correlated with dissolved radiocaesium concentration (with the exception of concentrations measured in estuaries), and the geometric mean $$K_{rm d}$$ was calculated.

論文

Outline of the national mapping projects implemented after the Fukushima accident

斎藤 公明; 恩田 裕一*

Journal of Environmental Radioactivity, 139, p.240 - 249, 2015/01

 被引用回数:20 パーセンタイル:7.39(Environmental Sciences)

福島第一原子力発電所事故の後、国からの委託を受け原子力機構は多くの機関と協力しながらマップ事業を実施してきた。この中で、広域にわたる大規模放射線モニタリングと放射線量率等のマップ作成、環境中における放射線セシウムの移行調査とモデル化等を行なってきた。平成24年度までにマップ事業の中で得られた成果を17編の論文としてまとめ、学術雑誌Journal of Environmental Radioactivityの特集号として発刊する。本稿では、この特集号の序論として、マップ事業の全体計画、スケジュール、各調査項目の位置付け及び主要な成果について紹介する。

論文

Unique Fermi surface and emergence of charge density wave in EuGa$$_4$$ and EuAl$$_4$$

仲村 愛*; 平仲 裕一*; 辺土 正人*; 仲間 隆男*; 三浦 泰直*; 堤 泰樹*; 森 晶宣*; 石田 一裕*; 三田村 勝哉*; 広瀬 雄介*; et al.

JPS Conference Proceedings (Internet), 3, p.011012_1 - 011012_6, 2014/06

Two europium compounds with the same structure EuGa$$_4$$ and EuAl$$_4$$ have been investigated. The Fermi surfaces revealed experimentally show a peculiar feature: flat Fermi surface sheets appear parallel to the tetragonal [110] planes. Reflecting this, a charge density wave transition due to the nesting of Fermi surface sheets has been observed in EuAl$$_4$$.

論文

Sediment particle size and initial radiocesium accumulation in ponds following the Fukushima DNPP accident

吉村 和也; 恩田 裕一*; 福島 武彦*

Scientific Reports (Internet), 4, p.4514_1 - 4514_6, 2014/03

 被引用回数:14 パーセンタイル:36.38(Multidisciplinary Sciences)

This study used particle size analysis to investigate the initial accumulation and trap efficiency of radiocesium ($$^{137}$$Cs) in four irrigation ponds, 4-5 months after the Fukushima Dai-ichi Nuclear Power Plant (DNPP) accident. Trap efficiency, represented by the inventory of $$^{137}$$Cs in pond sediment to the inventory of radiocesium in soil surrounding the pond (i.e., total $$^{137}$$Cs inventory), was less than 100% for all but one pond. Trap efficiency decreased as sediment particle size increased, indicating that sediments with a smaller particle size accumulate more $$^{137}$$Cs. In ponds showing low trap efficiency, fine sediment containing high concentrations of $$^{137}$$Cs appeared to be removed from the system by hydraulic flushing, leaving behind mostly coarse sediment.

論文

Fermi surface and magnetic properties of antiferromagnet EuBi$$_3$$

仲村 愛*; 平仲 裕一*; 辺土 正人*; 仲間 隆男*; 立津 慶幸*; 眞榮平 孝裕*; 三浦 泰直*; 森 晶宣*; 堤 泰樹*; 広瀬 雄介*; et al.

Journal of the Physical Society of Japan, 82(12), p.124708_1 - 124708_6, 2013/12

 被引用回数:13 パーセンタイル:28.22(Physics, Multidisciplinary)

Fermi surfaces and magnetic properties of an antiferromagnet EuBi$$_3$$ were investigated on a flux-grown single crystal. A critical magnetic field of 225 kOe where the magnetic moments are forced to align ferromagnetically was well explained by the magnetic exchange interaction based on a two-sublattice model. The Fermi surface characteristics are in agreement with the theoretical prediction indicating a fully magnetic divalent state in Eu atoms.

論文

Magnetic and Fermi surface properties of EuGa$$_4$$

仲村 愛*; 平仲 裕一*; 辺土 正人*; 仲間 隆男*; 三浦 泰直*; 堤 泰樹*; 森 晶宣*; 石田 一裕*; 三田村 勝哉*; 広瀬 雄介*; et al.

Journal of the Physical Society of Japan, 82(10), p.104703_1 - 104703_10, 2013/10

 被引用回数:23 パーセンタイル:16.99(Physics, Multidisciplinary)

High quality single crystals of EuGa$$_4$$ have been grown from Ga flux. Electrical resistivity, magnetic susceptibility, high-field magnetization, specific heat, thermoelectric power and de Haas-van Alphen effect were investigated. Antiferromagnetic transition due to divalent Eu atoms were observed at 16.5 K. A charge density wave transition was also found under high pressure accompanied by a Fermi surface reconstruction. These observations were fully accounted for by the Fermi surface topology and corresponding band calculations.

報告書

JMTR照射イナートマトリクス窒化物燃料の照射後試験

岩井 孝; 中島 邦久; 菊地 啓修; 本田 順一; 畠山 祐一; 小野 勝人; 松井 寛樹; 荒井 康夫

JAEA-Research 2007-026, 75 Pages, 2007/03

JAEA-Research-2007-026.pdf:13.6MB

マイナーアクチノイドをプルトニウムで模擬し、ZrN及びTiNを母材としたイナートマトリクス窒化物ペレットを燃料ピンに封入したうえで、01F-51Aキャプセルに組み込み、JMTRで照射した。(Zr,Pu)N及び(TiN,PuN)ペレットの平均線出力及び燃焼度は、それぞれ、408W/cm, 約30000MWd/t(Zr+Pu)(約132000MWd/t-Pu)並びに355W/cm, 約38000MWd/t(Ti+Pu)(約153000MWd/t-Pu)に達した。照射キャプセルを燃料試験施設に搬入して、非破壊及び破壊試験を実施した。照射後の燃料ピンに有害な欠陥はなく、健全性が確認された。FPガス放出率は約1.6%と極めて低い値であった。ステンレス鋼被覆管内面に有意な腐食は観察されなかった。

口頭

粒子分散型U-ROX燃料の照射後試験,3; セラモグラフィー

白数 訓子; 蔵本 賢一*; 山下 利之; 本田 順一; 畠山 祐一; 市瀬 健一

no journal, , 

JRR-3にて照射した粒子分散型岩石型燃料について、XRDによる相状態の確認,SEM及びEPMAによる燃料ペレットの表面観察を行った。1400K以下の低い照射温度では照射によるスピネルの分解は起こらないことが確認された。また安定化ジルコニア単相燃料は、低熱伝導率による高い照射温度にもかかわらず、最も低いFPガス放出率を示し、その高い照射安定性が確認された。

口頭

イナートマトリックス窒化物燃料の照射後破壊試験,2; X線微小分析

松井 寛樹; 岩井 孝; 本田 順一; 畠山 祐一; 三田 尚亮; 荒井 康夫

no journal, , 

マイナーアクチノイド核変換用燃料の候補であるイナートマトリクス窒化物燃料を模擬した、(Zr,Pu)N及び(TiN,PuN)の照射後破壊試験のうち、X線微小分析等を報告する。X線微小分析では、燃料ペレットの構成元素であるPu, Ti, Zrのほか、FP元素としてNd, Xe, Pd, Mo, Cs及びTeを選択した。両試料とも、外周部の燃焼度が若干高いことを反映したPu及びFPの存在を示す結果となった。Xeの線分析結果は燃焼度に応じた分布であり、外周部への移行は生じていないと結論できる。(Zr,Pu)Nでは、外周部の一部でCsの析出が見られ、該当箇所の面分析を実施したが、ほかの元素の共存等を判別するに至らなかった。

口頭

新クロスオーバ研究「照射・高線量領域の材料挙動制御のための新しいエンジニアリング」,6; 実燃料の照射後歪の観察

中村 仁一; 天谷 政樹; 本田 順一; 畠山 祐一; 更田 豊志; 木下 幹康*

no journal, , 

高燃焼度燃料ペレット(燃焼度40$$sim$$60GWd/t)の結晶格子歪,結晶子径(結晶子の粒径)及び結晶粒間に生じる不均一歪を測定することにより、燃焼に伴うペレット内部の結晶組織変化状態を調べ、組織変化に及ぼす照射の影響を検討した。

口頭

高速炉用水素化物の照射後試験結果,2; 重量測定,X線回折

原田 晃男; 畠山 祐一; 本田 順一; 松井 寛樹; 黒崎 健*; 小無 健司*

no journal, , 

「水素化物中性子吸収材を用いた革新的高速炉炉心に関する研究開発」の一環として、高速実験炉「常陽」で照射された水素化物に関し、原子力科学研究所燃料試験施設に受け入れ、照射後試験を実施した。本報告では、当施設で実施した照射後試験の概要,重量測定,X線回折結果を報告する。

口頭

福島第一原子力発電所事故に伴う放射性物質の長期的影響把握手法の確立,13; 福島県の試験水田における$$^{137}$$Csの濃度経時変化とフラックスの観測

吉村 和也; 恩田 裕一*

no journal, , 

水田において灌漑水に伴う$$^{137}$$Cs移行フラックスと浮遊砂中の$$^{137}$$Cs濃度の経時変化を観測した。灌漑水中の浮遊土砂の流入出を介した、$$^{137}$$Cs量の年間収支は-1.1$$sim$$0.1%であった。田面水、および流出水に含まれる浮遊土砂中の$$^{137}$$Cs濃度は、事故後初期(一年以内)の速やかな減少から緩やかな減少へと移っていることが示唆された。

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