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論文

Summary of temporal changes in air dose rates and radionuclide deposition densities in the 80 km zone over five years after the Fukushima Nuclear Power Plant accident

斎藤 公明; 三上 智; 安藤 真樹; 松田 規宏; 木名瀬 栄; 津田 修一; 吉田 忠義; 佐藤 哲朗*; 関 暁之; 山本 英明*; et al.

Journal of Environmental Radioactivity, 210, p.105878_1 - 105878_12, 2019/12

 被引用回数:5 パーセンタイル:29.47(Environmental Sciences)

We summarized temporal changes in air dose rates and radionuclide deposition densities over five years in the 80 km zone based on large-scale environmental monitoring data obtained continuously after the Fukushima Nuclear Power Plant (NPP) accident. The air dose rates in environments associated with human lives decreased at a considerably faster rate than expected for radioactive decay. The average air dose rate originating from the radiocesium deposited in the 80 km zone was lower than that predicted from radioactive decay by a factor of 2-3 at five years after the accident. The causes of this rapid reduction were discussed quantitatively considering the characteristics of radiocesium migration in the environment.

論文

Temporal change in radiological environments on land after the Fukushima Daiichi Nuclear Power Plant accident

斎藤 公明; 三上 智; 安藤 真樹; 松田 規宏; 木名瀬 栄; 津田 修一; 佐藤 哲朗*; 関 暁之; 眞田 幸尚; Wainwright-Murakami, Haruko*; et al.

Journal of Radiation Protection and Research, 44(4), p.128 - 148, 2019/12

Massive environmental monitoring has been conducted continuously after the Fukushima accident with different monitoring methods having different features together with migration studies of radiocesium in diverse environments. At three months after the accident, multiple radionuclides were detected at many places; while it was confirmed that radiocesium was most important from the viewpoint of long-term exposures. The air dose rates in environments related to human living have decreased faster than expected from radioactive decay by a factor of 2-3 on average. An empirical model for predicting air dose rate distribution was developed based on statistical analysis of massive car-borne survey data. Some trials were performed to integrate different types of contamination maps to obtain an integrated map of better quantity. Annual external exposure doses for residents who would return to their home were estimated to less than a few mSv as a whole. The environmental data and knowledge have been provided for diverse-spectrum of people in different ways.

論文

Overview of computational frog models

木名瀬 栄; Mohammadi, A.*; G$'o$mez-Ros, J.-M.*

Computational Anatomical Animal Models; Methodological Developments and Research Applications, p.5_1 - 5_9, 2018/12

 被引用回数:0 パーセンタイル:100

There are limited investigations on the computational frog models and the organ dose evaluations for frogs in environmental protection. In this article, computational frog models and their applications are reviewed to share some perspectives of frog model development in the near future. The authors hope that 3D printing frog phantoms with adequate tissue substitutes should be developed for the validation of the dosimetric quantities by the Monte Carlo simulations.

論文

Overview of computational mouse models

Mohammadi, A.*; 木名瀬 栄; Safavi-Naeini, M.*

Computational Anatomical Animal Models; Methodological Developments and Research Applications, p.3_1 - 3_27, 2018/12

 被引用回数:0 パーセンタイル:100

The review summarizes the history of development of the computational models during the last 24 years with some provision about what to expect in the near future for their application in preclinical research, radiation dosimetry calculations and imaging physics research. Around 26 computational mouse models have been constructed for various researches in ionizing and nonionizing radiation dosimetry, preclinical imaging including multimodality imaging and instrumentation, image processing and analysis. The approach of using the computational mouse models and simulation tools are very useful comparing the experimental approach using physical phantoms or real mice due to high cost and complexity of organizing an experimental research.

論文

Long-term predictions of ambient dose equivalent rates after the Fukushima Daiichi Nuclear Power Plant accident

木名瀬 栄; 高橋 知之*; 斎藤 公明

Journal of Nuclear Science and Technology, 54(12), p.1345 - 1354, 2017/12

 被引用回数:15 パーセンタイル:3.74(Nuclear Science & Technology)

To predict how exposure situations might change in the future and to analyze radiation protection strategies and rehabilitation programmes in Fukushima, prediction models were developed for ambient dose equivalent rate distributions within the 80 km-radius around the Fukushima Daiichi Nuclear Power Plant. Model parameters such as the ecological half-lives for the short-/long-term components and the fractional distribution of short-term component were evaluated using ambient dose equivalent rates through car-borne surveys. It was found that the ecological half-lives among land-use differ only slightly, whereas the fractional distributions of the short-term component are dependent on land-use. Distribution maps of ambient dose equivalent rates for the next 30 years after the accident, created by the prediction models were found to be useful for follow-up of the radiological situation since they provide information on the space variation of the ambient dose equivalent rates in inhabited areas.

論文

福島の環境回復に向けた取り組み,2; 事故進展と放射性物質の放出・沈着分布の特徴

斎藤 公明; 永井 晴康; 木名瀬 栄; 武宮 博

日本原子力学会誌, 59(6), p.40 - 44, 2017/06

福島の環境回復に関してまとめた連載記事の一つである。福島第一原子力発電所事故の進展と放射線物質の放出・大気拡散・沈着過程の解明が、シミュレーションおよび環境測定データの解析により進められている。大規模環境調査により福島周辺における放射線環境の経時変化等の特徴が明らかになりつつあり、この知見に基づいて空間線量率の分布状況変化モデルが開発され将来予測に活用されてきた。事故後に測定された種々の環境測定データは集約され、データベースを通して簡単な解析ツールとともに継続的に公開されている。これら一連の取り組みについて概説している。

論文

特異値分解を用いた放射性核種の摂取量推定

波戸 真治*; 木名瀬 栄

日本原子力学会和文論文誌, 15(3), p.146 - 150, 2016/09

It is significant to accurately estimate the intake quantity for the reliable internal exposure assessments. The intake quantity has been estimated by using least squares method. However, to conduct the least squares method, the number of radioactivity measurements must be more than the number of intakes. To remedy this restriction, this study suggests the estimation method using a singular value decomposition that is available regardless the relation of numbers between measurements and intakes. Moreover, this study introduces the procedure to calculate the intake quantity from the measurements with uncertainty.

論文

30年後の福島の環境放射線レベル推定とその技術開発

木名瀬 栄

日本原子力学会誌, 58(6), p.362 - 366, 2016/06

日本原子力研究開発機構では、福島第一原子力発電所(福島第一原発)から80km圏内を対象に、空間線量率の分布状況変化モデルを開発するとともに、福島第一原発事故後30年までの空間線量率分布を予測した。事故30年後の年間20mSv(3.8$$mu$$Sv/h)を超えるエリアは、事故5年後に較べ、約20分の1程度に減少することが示唆された。空間線量率の分布状況変化モデルは、環境半減期などのモデルパラメータを用いた計算により、避難指示区域内外それぞれの生活圏において空間線量率分布を簡便に推定することが可能であるため、福島復興に役立つと考える。

論文

Uncertainty in predictions of the ambient dose equivalent rates for 30 years following the Fukushima Daiichi Nuclear Power Plant accident

木名瀬 栄; 高橋 知之*; 佐藤 仁士; 山本 英明; 斎藤 公明

Proceedings of 17th NSFS Conference (Internet), p.27 - 33, 2016/02

At the Japan Atomic Energy Agency, long-term prediction models have been developed to assess how ambient dose equivalent rates might change in the future and to analyze radiological situations within the 80 km radius of the Fukushima Daiichi Nuclear Power Plant. In the present study, uncertain predictions of future ambient dose equivalent rates arising from variability in model parameters were assessed using Monte Carlo simulations. It was found that ambient dose equivalent rates for the next 5-30 years after the accident would be predicted within a factor of approximately 2. The long-term prediction models would be useful for a better understanding of the radiological situation since they provide information on the time variation of the ambient dose equivalent rates in inhabited areas.

論文

Changes in ambient dose equivalent rates around roads at Kawamata town after the Fukushima accident

木名瀬 栄; 佐藤 仁士; 坂本 隆一*; 山本 英明; 斎藤 公明

Radiation Protection Dosimetry, 167(1-3), p.340 - 343, 2015/11

 被引用回数:5 パーセンタイル:45.16(Environmental Sciences)

Changes in ambient dose equivalent rates through the vehicle-borne surveys have elucidated ecological half-lives of radioactive caesium in the environment. To confirm that the ecological half-lives are appropriate for predicting ambient dose equivalent rates within living areas, it is important to ascertain ambient dose equivalent rates on/around roads. In this present study, radiation monitoring on/around roads at Kawamata town located about 37km northwest of the Fukushima Daiichi Nuclear Power Plant was performed using monitoring vehicles and survey meters. It was found that the ambient dose equivalent rates around roads were higher than those on roads as of October of 2012. And withal the ecological half-lives on roads were essentially consistent with those around roads. As basis of dose predictions using ecological half-lives on roads, it is necessary to make corrections to ambient dose equivalent rates through the vehicle-borne surveys against those within living areas.

論文

福島周辺における空間線量率の測定と評価,5; 福島周辺における空間線量率分布の特徴

三上 智; 松田 規宏; 安藤 真樹; 木名瀬 栄; 北野 光昭; 川瀬 啓一; 松元 愼一郎; 山本 英明; 斎藤 公明

Radioisotopes, 64(9), p.589 - 607, 2015/09

福島周辺における空間線量率や放射性核種沈着量の地域的分布及び経時変化の特徴について、様々な手法による大規模環境調査の解析結果に基づいて紹介する。また、除染モデル実証事業後の継続的な環境測定結果を基に、除染効果の継続性に関する議論を行う。さらに、土地利用状況ごとの環境半減期の解析結果、及びこれをベースにした空間線量率の将来予測の例について紹介する。

論文

Prediction of ambient dose equivalent rates for the next 30 years after the accident

木名瀬 栄; 高橋 知之*; 佐藤 仁士*; 山本 英明; 斎藤 公明

Proceedings of International Symposium on Radiological Issues for Fukushima's Revitalized Future, p.40 - 43, 2015/00

原子力機構では、福島の復興に資するため、福島第一原子力発電所から80km圏内を対象に、環境中に放出された放射性セシウムを起因とする空間線量率の長期的予測手法を開発している。長期的予測手法は、土地利用形態ごとの環境半減期を用いた2成分1コンパートメントからなる二重指数関数モデルを基盤とし、事故30年後までの生活圏の空間線量率を予測する。2014年までに実施された第8次走行サーベイなどによる空間線量率測定データを用いて、減衰が速い成分の環境半減期や減衰が速い成分の割合などのモデルパラメータを導出した。落葉樹や常緑樹のような森林に分類されたエリアにおける減衰が速い成分の環境半減期や減衰が速い成分の割合は、森林以外に分類されたエリアでの値と相違があることが示唆された。また、モデルの不確かさ解析により、事故5年後から30年後のバックグラウンド空間線量率を含む空間線量率を予測する場合、係数2程度の不確かさで推定できることが示唆された。

論文

内部被ばくの評価法

木名瀬 栄

Isotope News, (724), p.82 - 85, 2014/08

放射線取扱主任者の復習のきっかけになるよう、これまで一般的に実施してきた内部被ばくの評価法について概要を述べるとともに、福島第一原子力発電所事故後の内部被ばくの評価法に関する課題を紹介する。内部被ばくモニタリングである直接法, 間接法ともに、体内負荷量、排泄(率)、空気中濃度で表現される放射能について、信頼性高く測定評価することが日常的な課題であり、特に、直接法には被検者の測定条件と同一条件となる人体形状ファントムを用いた校正法が、間接法には十分な量の試料採取と迅速かつ高感度な組成分析法が極めて重要になると考えられる。評価対象核種によっては、直接法、間接法ともに、長所と短所があり、いずれがよいかを選択することは困難になるが、最終的には測定結果の不確かさなどを考慮して、預託実効線量を評価しなければならない。

論文

Evaluation of averted doses to members of the public by tap water restrictions after the Fukushima Daiichi Nuclear Power Plant Accident

木名瀬 栄; 木村 仁宣; 波戸 真治*

Progress in Nuclear Science and Technology (Internet), 4, p.5 - 8, 2014/04

After the Fukushima Daiichi Nuclear Power Plant Accident, temporal changes in the concentration of the iodine 131 in tap water were studied using published data from several authorities in Fukushima, Ibaraki and Tokyo. Averted doses to members of the public due to intake of iodine 131 through tap water restrictions were also evaluated using an internal dose calculation code, DSYS-chronic. Consequently, it was found that the apparent half-life of iodine 131 in tap water was 2.8 days. The averted equivalent doses to the thyroids of members of the public-1-year-old children- were found to be a maximum value of 13.0 mSv in a local area of Fukushima. In comparison with Fukushima, the bottled water supplies might be a large sum of money regardless of the low doses in Tokyo. In conclusion, apart from the bottled water supplies, the tap water restrictions implemented by the authorities would be effective in the early phase of the emergency exposure situation.

論文

Development of internal dosimetry evaluation code for chronic exposure after intake of radionuclides

木村 仁宣; 木名瀬 栄; 波戸 真治*

Progress in Nuclear Science and Technology (Internet), 4, p.60 - 63, 2014/04

The Fukushima Daiichi Nuclear Power Plant accident resulted in a wide range of radioactive contamination. The national government and local governments implemented food restrictions to reduce internal exposure from the intake of foodstuffs. It is important that the averted doses to the public are calculated and the effect of these protective actions is evaluated to improve the protective action strategy. Therefore, the assessment of internal doses for chronic exposures is needed because the public takes foodstuffs in daily life. In the present study, we develop the DSYS-chronic code to evaluate internal doses for the chronic exposures. The code has GI-tract model, respiratory tract model, and biokinetic and bioassay models for the ICRP. In the DSYS-chronic, internal doses can be evaluated for continuous or discontinuous intake. The present study shows the outline of the DSYS-chronic and the example of evaluation results of internal doses for the chronic exposures.

論文

Evaluation of retention and excretion function to members of the public for chronic intake of radionuclides

波戸 真治*; 木名瀬 栄; 木村 仁宣

Progress in Nuclear Science and Technology (Internet), 4, p.36 - 38, 2014/04

After the Fukushima Daiichi Nuclear Power Plant accident, the daily diet is of concern to expose internally through foodstuffs. To dispel the concern, it is important to measure the radiation in the bodies and to estimate internal doses. The radiation in the bodies of the Fukushima residents is measured by using whole body counting scanners. Predicted values of measured quantities (whole-body content and daily urinary excretion) are given as retention and excretion functions of time following a single intake in the ICRP's Publ.78. However, since the evaluation for internal doses due to chronic intake is required, these retention and excretion functions cannot apply. We developed the DSYS-Chronic code that can evaluate retention and excretion functions following a continuous inhalation or ingestion. The present study evaluates retention and excretion to members of the public for chronic intake using the DSYS-Chronic and examines the impact.

論文

Development of prediction models for radioactive caesium distribution within the 80-km radius of the Fukushima Daiichi Nuclear Power Plant

木名瀬 栄; 高橋 知之*; 佐藤 仁士; 坂本 隆一*; 斎藤 公明

Radiation Protection Dosimetry, 160(4), p.318 - 321, 2014/00

 被引用回数:25 パーセンタイル:5.83(Environmental Sciences)

Preliminary prediction models have been studied for radioactive caesium distribution within the 80 km radius of the Fukushima Daiichi Nuclear Power Plant to follow up radiological situations after the accident. The models were represented by exponential functions using ecological half-life of radioactive caesium in the environment. The ecological half-lives were derived from the changes in ambient dose equivalent rates through vehicle-borne surveys. It was found that ecological half-lives of radioactive caesium were not constant within the 80 km radius of the Fukushima Daiichi Nuclear Power Plant. The ecological half-life for forest areas was found to be much larger than that for urban and water areas.

報告書

慢性摂取による内部被ばく線量評価コードの開発

木村 仁宣; 木名瀬 栄; 波戸 真治*

JAEA-Data/Code 2012-027, 27 Pages, 2013/02

JAEA-Data-Code-2012-027.pdf:2.33MB

福島第一原子力発電所事故が発生し、環境中に放出された放射性物質を長期間にわたり摂取し続ける、いわゆる慢性摂取による公衆の内部被ばくが懸念されたことから、慢性摂取に対し、最新知見に基づく信頼性の高い内部被ばく線量評価手法の確立が重要となった。内部被ばく線量係数計算システムDSYSは、原子力機構が開発したレベル3PSAコードOSCAARで公衆の内部被ばく線量を計算するために必要な線量係数を整備する支援コードであり、ICRPが規定した呼吸気道モデル(Publ.66)、胃腸管モデル(Publ.30)、代謝・体内動態モデル(Publ.30, 56, 67, 69, 71, 72)、膀胱モデル(Publ.67)及び線量評価モデル(Publ.56)に準拠したものである。しかし、DSYSは、急性摂取を仮定した上記のICRPの線量評価手法に基づく計算コードであるため、慢性摂取による体内の残留放射能、預託実効/等価線量などを評価するには適切なものではなかった。そこで、慢性摂取による線量評価手法を検討するとともにDSYSの機能を拡張することで、慢性摂取による内部被ばく線量評価コードDSYS-Chronicを開発した。本報告書では、DSYS-Chronicの概要とその評価例を示す。

論文

Assessment of olfactory nerve by SPECT-MRI image with nasal thallium-201 administration in patients with olfactory impairments in comparison to healthy volunteers

志賀 英明*; 滝 淳一*; 鷲山 幸信*; 山本 純平*; 木名瀬 栄; 奥田 光一*; 絹谷 清剛*; 渡邉 直人*; 利波 久雄*; 越田 吉郎*; et al.

PLOS ONE (Internet), 8(2), p.e57671_1 - e57671_8, 2013/02

 被引用回数:12 パーセンタイル:34.86(Multidisciplinary Sciences)

Current olfactory function tests are useful for the analysis of olfactory thresholds in olfaction-impaired patients. However, a decrease in olfactory thresholds has not been used as an index for olfactory nerve damage in patients. The authors assessed peripheral olfactory nerve viability by performing combined SPECT-CT after nasal administration of Tl-201 to determine whether olfactory nerve was damaged in patients with olfactory impairments in comparison to healthy volunteers. It was found that nasal Tl-201 migration to the olfactory bulb was significantly lower in the patients with head trauma, respiratory infection, and chronic rhinosinusitis than in healthy volunteers.

論文

Internal dosimetry for continuous chronic intake of caesium-137 in cedar pollen after the Fukushima Daiichi Nuclear Power Plant accident

木名瀬 栄; 木村 仁宣; 波戸 真治*

Proceedings of International Symposium on Environmental monitoring and dose estimation of residents after accident of TEPCO's Fukushima Daiichi Nuclear Power Station, 4 Pages, 2012/12

Internal dose assessments for chronic intake of caesium-137 in cedar pollen were carried out for adult residents in Fukushima, Ibaraki and Tokyo. Committed effective doses, retention and excretion functions for caesium-137 were evaluated using DSYS-chronic code. The observation period was from early February to the end of May 2012. Consequently, it was found that the committed effective doses for adults in Fukushima, Ibaraki and Tokyo were 1.6-1.8$$times$$10$$^{-9}$$ Sv, 4.5$$times$$10$$^{-10}$$ Sv and 3.0$$times$$10$$^{-10}$$ Sv, respectively. Retention and excretion functions for caesium-137 were found to be dependence on the times of intakes.

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