- 著者
- 町田 昌彦 岩田 亜矢子 山田 進 乙坂 重嘉 小林 卓也 船坂 英之 森田 貴己
- 出版者
- 一般社団法人 日本原子力学会
- 雑誌
- 日本原子力学会和文論文誌 (ISSN:13472879)
- 巻号頁・発行日
- vol.21, no.1, pp.33-49, 2022 (Released:2022-02-15)
- 参考文献数
- 53
- 被引用文献数
- 4
We estimate the monthly discharge inventory of tritium from the port of Fukushima Daiichi Nuclear Power Plant (1F) from Jun. 2013 to Mar. 2020 using the Voronoi tessellation scheme, following the tritium monitoring inside the port that started in Jun. 2013. As for the missing period from the initial month, Apr. 2011 to May 2013, we calculate the tritium discharge by utilizing the ratio of tritium concentration to 137Cs concentration in stagnant contaminant water during the initial direct run-off period to Jun. 2011 and the discharge inventory correlation between tritium and 137Cs for the next-unknown continuous-discharge period up to May 2013. From all the estimated results over 9 years, we found that the monthly discharge inventory sharply dropped immediately after closing the seaside impermeable wall in Oct. 2015 and subsequently coincided well with the sum of those of drainage and subdrain etc. By comparing the estimated results with those in the normal operation period before the accident, we point out that the discharge inventory from the 1F port after the accident is not very large. Even the estimation for the year 2011 is found to be comparable to the maximum of operating pressurized water reactors releasing relatively large inventories in the number of digits. In the national level, the total domestic release inventory in Japan significantly decreased after the accident owing to the operational shutdown of most plants. Furthermore, 1F and even the total Japanese discharge inventory are found to be minor compared with those of nuclear reprocessing plants and heavy-water reactors on a worldwide level. From the above, we suggest that various scenarios can be openly discussed regarding the management of tritium stored inside 1F with the help of the present estimated data and its comparison with the past discharge inventory.
- 著者
- 町田 昌彦 岩田 亜矢子 山田 進 乙坂 重嘉 小林 卓也 船坂 英之 森田 貴己
- 出版者
- 一般社団法人 日本原子力学会
- 雑誌
- 日本原子力学会和文論文誌 (ISSN:13472879)
- 巻号頁・発行日
- pp.J20.036, (Released:2022-01-26)
- 参考文献数
- 53
- 被引用文献数
- 4
We estimate the monthly discharge inventory of tritium from the port of Fukushima Daiichi Nuclear Power Plant (1F) from Jun. 2013 to Mar. 2020 using the Voronoi tessellation scheme, following the tritium monitoring inside the port that started in Jun. 2013. As for the missing period from the initial month, Apr. 2011 to May 2013, we calculate the tritium discharge by utilizing the ratio of tritium concentration to 137Cs concentration in stagnant contaminant water during the initial direct run-off period to Jun. 2011 and the discharge inventory correlation between tritium and 137Cs for the next-unknown continuous-discharge period up to May 2013. From all the estimated results over 9 years, we found that the monthly discharge inventory sharply dropped immediately after closing the seaside impermeable wall in Oct. 2015 and subsequently coincided well with the sum of those of drainage and subdrain etc. By comparing the estimated results with those in the normal operation period before the accident, we point out that the discharge inventory from the 1F port after the accident is not very large. Even the estimation for the year 2011 is found to be comparable to the maximum of operating pressurized water reactors releasing relatively large inventories in the number of digits. In the national level, the total domestic release inventory in Japan significantly decreased after the accident owing to the operational shutdown of most plants. Furthermore, 1F and even the total Japanese discharge inventory are found to be minor compared with those of nuclear reprocessing plants and heavy-water reactors on a worldwide level. From the above, we suggest that various scenarios can be openly discussed regarding the management of tritium stored inside 1F with the help of the present estimated data and its comparison with the past discharge inventory.
- 著者
- 町田 昌彦 岩田 亜矢子 山田 進 乙坂 重嘉 小林 卓也 船坂 英之 森田 貴己
- 出版者
- 一般社団法人 日本原子力学会
- 雑誌
- 日本原子力学会和文論文誌 (ISSN:13472879)
- 巻号頁・発行日
- vol.22, no.1, pp.12-24, 2023 (Released:2023-01-18)
- 参考文献数
- 54
We estimate the inventory of tritium in two sea areas corresponding to coastal and offshore ones around Fukushima Daiichi Nuclear Power Plant (1F) on the basis of the measured seawater tritium concentrations monitored constantly from 2013 to Jan. 2021 by using the Voronoi tessellation scheme. The obtained results show that the offshore area inventory and its temporal variation amount correspond to approximately 1/5 and 1/50 of that of the treated water accumulated inside 1F, respectively. These results suggest that the amount of tritium included in seawater as the background is non-negligible in evaluating the environmental impact of releasing the accumulated treated water into the sea area. We also estimate the offshore area inventory before the 1F accident and find that it had exceeded the 1F stored inventory over 30 years from 1960s to 1980s, being approximately 4 times larger in the peak decade 1960s. This finding means that we had already experienced more contaminated situations over 30 years in the past compared with the conservative case emerged by just releasing whole the present 1F inventory. Here, it should also be emphasized that the past contamination situation was shared by the entire world. We further extend the estimation area to include the offshore area from Miyagi to Chiba Prefectures and find that the average area inventory is now comparable to half the present 1F inventory. Finally, we estimate the internal dose per year by ingesting fishes caught inside the area when the 1F inventory is added only inside the area and kept there for one year. The result indicates that it approximately corresponds to 1.0 × 10−6 of the dose from natural radiation sources. From these estimation results, we find that all the tritium inventories stored inside 1F never contribute to significant dose increment even when it is instantly released into the area.
3 0 0 0 OA 福島第一原発港湾からの放射性セシウム137の推定流出量の変遷
- 著者
- 町田 昌彦 山田 進 岩田 亜矢子 乙坂 重嘉 小林 卓也 渡辺 将久 船坂 英之 森田 貴己
- 出版者
- 一般社団法人 日本原子力学会
- 雑誌
- 日本原子力学会和文論文誌 (ISSN:13472879)
- 巻号頁・発行日
- vol.18, no.4, pp.226-236, 2019 (Released:2019-11-20)
- 参考文献数
- 34
- 被引用文献数
- 9
After direct discharges of highly contaminated water from Units 2 and 3 of the Fukushima Daiichi Nuclear Power Plant (1F) from April to May 2011, Kanda suggested that relatively small amounts of run-off of radionuclides from the 1F port into the Fukushima coastal region subsequently continued, on the basis of his estimation method. However, the estimation period was limited to up to September 2012, and there has been no report on the issue since that work. Therefore, this paper focuses on the discharge inventory from the 1F port up to June 2018. In the missing period, the Japanese government and Tokyo Electric Power Company Holdings have continued efforts to stop the discharge, and consequently, the radionuclide concentration in seawater inside the 1F port has gradually diminished. We show the monthly discharge inventory of 137Cs up to June 2018 by two methods, i.e., Kanda’s method partially improved by the authors and a more sophisticated method using Voronoi tessellation reflecting the increase in the number of monitoring points inside the 1F port. The results show that the former always yields overestimated results compared with the latter, but the ratio of the former to the latter is less than one order of magnitnde. Using these results, we evaluate the impact of the discharge inventory from the 1F port into the coastal area and the radiation dose upon fish digestion.
3 0 0 0 トリチウム水の取扱い
2 0 0 0 OA 深海魚筋肉タンパク質の高水圧適応
- 著者
- 森田 貴己
- 出版者
- 日本高圧力学会
- 雑誌
- 高圧力の科学と技術 (ISSN:0917639X)
- 巻号頁・発行日
- vol.20, no.4, pp.339-346, 2010 (Released:2010-12-11)
- 参考文献数
- 29
Deep-sea fish distributes to abyssal depths of several thousand meters, the pressures of which shallower-living fish cannot tolerate. Tolerance to abyssal pressures by deep-sea fish is likely to depend at least in part on adaptive modifications of proteins. However, structural modifications that allow proteins to function at high pressures have not been well understood. To elucidate the mechanisms of protein adaptation to high pressures, we cloned α-actin and myosin heavy chain cDNAs from skeletal muscles of two deep-sea fishes, Coryphaenoides yaquinae and C. armatus, and two non deep-sea fishes, C. acrolepis and C. cinereus. The comparison of the α-actins from deep-sea fishes with those of non deep-sea fishes identified three amino acid substitutions, which would make the deep-sea fish actin function even at 60 MPa. The myosin heavy chains from deep-sea fishes have a Pro residue in the loop-1 region and have a shorter loop-2 region than non deep-sea fishes. Additionally, the myosin heavy chains from deep-sea fishes have the biased amino acid substitutions at core positions in the coiled-coil structure of the rod region. The roles of these characteristic sequences in myosin heavy chain from deep-sea fish, however, have remained unclear.
- 著者
- 森田 貴己
- 出版者
- 一般社団法人 日本原子力学会
- 雑誌
- 日本原子力学会誌ATOMOΣ (ISSN:18822606)
- 巻号頁・発行日
- vol.58, no.7, pp.408-412, 2016 (Released:2020-02-19)
- 参考文献数
- 10
東京電力福島第一原子力発電所の事故により,大量の放射性物質が海洋に流出した。このため,日本の水産業は甚大な被害を被り,その被害は現在も継続している。事故後しばらくは水産物から比較的高い濃度の放射性セシウムが検出されていたが,2015年度の福島県のモニタリング検査において国の出荷制限基準である100 Bq/kg-wetを超過した海産物は1検体もない。本報告では,福島県海域での水産物汚染の現状を紹介するとともに,その汚染が減少した仕組みや汚染が比較的長期化した一部の魚種についてその理由を解説する。また,報告例の少ない水産物中のストロンチウム-90についても述べる。
1 0 0 0 深海魚α-アクチンの高水圧適応の分子機構に関する研究
- 著者
- 森田 貴己
- 出版者
- 水産総合研究センター
- 雑誌
- 水産総合研究センター研究報告 (ISSN:13469894)
- 巻号頁・発行日
- no.13, pp.35-77, 2004-12
ある種の深海魚は水圧が600気圧にも及ぶ深海に生息している。その高水圧適応機構については古くから関心が持たれてきたが、タンパク質構造と高水圧下での機能との関係を明らかにした報告はこれまでにない。本研究では、深海性ソコダラ類のヨロイダラCoryphaenoides armatusおよびシンカイヨロイダラC. yaquinaeの骨格筋α-アクチンを対象に高水圧適応機構を分子レベルで解明した。本論文の構成は次の通りである。第1章では、ホカケダラ属(Coryphaenoides)の分子系統樹の作成を行った。ホカケダラ属のソコダラ類は、浅海から深海と幅広い水深に生息する同属種が存在することから、深海魚の特性を探る様々な研究に用いられている。比較生化学研究を行う対象魚を選択することを目的として、ミトコンドリア12S rRNAおよびcytochrome oxidase subunit I(COI)遺伝子の部分配列を決定し、本属の分子系統樹を作成した。本系統樹から深海性および浅海性ソコダラ類がホカケダラ属の進化の初期の段階で分岐したことが示された。得られた系統樹を参考に、深海性ソコダラ類であるヨロイダラおよびシンカイヨロイダラの比較対象魚として、浅海性ソコダラ類からイバラヒゲおよびカラフトソコダラを選択した。第2章では、深海性ソコダラ類α-アクチンの高水圧下での性状変化を検討した。深海性ソコダラ類2種、浅海性のソコダラ類イバラヒゲ、淡水魚のコイおよび陸上動物のニワトリの骨格筋からα-アクチンを精製し、高水圧下で重合に要する時間、臨界濃度及び重合に伴う体積増加量を調べた。いずれの分析においても深海性ソコダラ類のα-アクチンは、大気圧下とほぼ変わらぬ性状を示した。第3章では、深海性ソコダラ類α-アクチンのcDNAクローニング及び高水圧適応に必須のアミノ酸の同定を行った。深海性ソコダラ類と浅海性ソコダラ類の骨格筋からα-アクチンのcDNAクローニングを行った結果、それぞれ2タイプずつのα-アクチンcDNAが単離された。ノザンブロット解析、定量RT-PCR法及び2次元電気泳動法から、これらα-アクチンmRNA及びタンパク質のいずれも骨格筋中に存在していること、その存在量は高水圧に適応しているタイプがいずれの形態でも多く存在していることが示された。演繹アミノ酸配列において、深海性ソコダラ類に特異的なアクチンのタイプは、浅海性ソコダラ類に特異的なタイプと比べてQ137K、A155SおよびV54AまたはL67Pの計3カ所にアミノ酸置換を示した。幾つかの生化学的実験から、Q137KおよびA155Sの両置換はα-アクチン分子内にCa2+とATPが高圧によって押し込まれるのを防ぎ、深海性ソコダラ類に高水圧適応を付与していることが示唆された。さらにdeoxyribonuclease I(DNase I)とアクチンの結合実験から、深海性ソコダラ類のα-アクチンが高水圧下で重合するためには、V54AまたはL67Pの置換が重要であることが推測された。第4章では、高水圧適応と低水温適応との関連などを含む総合的考察を行った。