著者

山本 政儀 Yamamoto Masayoshi

出版者

金沢大学自然計測応用研究センター

雑誌

平成15(2003)年度科学研究費補助金 基盤研究(C) 研究成果報告書 = 2003 Fiscal Year Final Research Report

巻号頁・発行日

vol.2002-2003, pp.7p., 2004-03-01

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本研究は、陸上環境における放射性物質の最大のリザーバーである大地、すなわち土壌中でのPuのスピシエーション(存在状態、存在形態)を重点的に行なった。フィールドとして国内のPu汚染レベルの数〜数百倍高い旧ソ連核実験場セミパラチンスク内外の表層土壌を用いた。土壌の粒径分画、磁気分画とバイオイメージングアナライザー法を組み合わせて、種々の粒径の放射性物質を含む粒子Hot-particle(放射能の強い粒子)を定量的に探査する手法をまず確立し、それら粒子の特性を走査型電子顕微鏡(SEM)、エネルギー分散型蛍光X線分液装置(SEM-EDX)等で観察し、全体及び個々の粒子のPu測定も実施して、粒子特性とPuの関係、全体としての粒子Puの存在割合を明らかにする。また、微粒子に対しては、アルファー・トラック法を併用してPuの存在特性を考察することを目的に研究を進めてきた。 セミパラチンスク核実験場周辺のドロン村で採取した高濃度Pu汚染土壌を用いた。この地域の^<239,240>Pu及び^<137>Cs蓄積量はそれぞれ530-14,320Bq/m^2,790-10,310Bq/m^2であった。その後、試料をサイズ別に<0.45,0.45-32,32-88,88-125,125-250,250-500,500-2000μmに分画し、それぞれの分画中のPu濃度の測定を測定し、アルファー・トラック法でHot-particleの存在を確かめた。その結果、土壌の125μmを境にして<125μmで^<239,240>Pu濃度が高く更にHot-particle数が多いことが解り、土壌の再浮游からの吸入被曝経路の重要性が示唆された。Hot-particleの探査については、数-数十μmの勢多くのHot-particleの存在を確認(Pu由来)したが、定量的評価には更なる検討が必要で有り、顕微鏡下での自動測定を放医研の研究者と共同で研究を進めている。

著者

Stepanenko Valeriy F. Hoshi Masaharu Dubasov Yuriy V. SAKAGUCHI Aya YAMAMOTO Masayoshi ORLOV Mark Y. BAILIFF Ian K. IVANNIKOV Alexander I. SKVORTSOV Valeriy G. IASKOVA Elena K. KRYUKOVA Irina G. ZHUMADILOV Kassym S. ENDO Satoru TANAKA Kenichi APSALIKOV Kazbek N. GUSEV Boris I.

出版者

放射線影響学会 = Japan Radiation Research Society

雑誌

Journal of radiation research (ISSN:04493060)

巻号頁・発行日

vol.47, pp.A149-A158, 2006-02-28

参考文献数

27

被引用文献数

10 21

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金沢大学環日本海域環境研究センター地球環境計測研究部門Spatial distributions of soil contamination by 137Cs (89 sampling points) and 239+240pu (76 points) near and within Dolon village were analyzed. An essential exponential decrease of contamination was found in Dolon village: the distance of a half reduction in contamination is about 0.87-1.25 km (in a northwest-southeast direction from the supposed centerline of the radioactive trace). This fact is in agreement with the available exposure rate measurements near Dolon (September 1949 archive data): on the basis of a few measurements the pattern of the trace was estimated to comprise a narrow 2 km corridor of maximum exposure rate. To compare computed external doses in air with local dose estimates by retrospective luminescence dosimetry (RLD) the gradient of radioactive soil contamination within the village was accounted for. The computed dose associated with the central axis of the trace was found to be equal to 2260 mGy (calculations based on archive exposure rate data). Local doses near the RLD sampling points (southeast of the village) were calculated to be in the range 466-780 mGy (averaged value: 645+/-70 mGy), which is comparable with RLD data (averaged value 460+/-92 mGy with range 380-618 mGy). A comparison of the computed mean dose in the settlement with dose estimates by ESR tooth enamel dosimetry makes it possible to estimate the "upper level" of the "shielding and behavior" factor in dose reduction for inhabitants of Dolon village which was found to be 0.28+/-0.068.

著者

Shichijo Kazuko Takatsuji Toshihiro Yamamoto Masayoshi Nakashima Masahiro

出版者

広島大学平和科学研究センター

雑誌

IPSHU English Research Report Series

巻号頁・発行日

no.28, pp.70-73, 2012-03

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The explosion of a plutonium Atomic bomb over Nagasaki city in Japan took place at 1102h on August 9, 1945. Radiation dose of A-bomb survivor is practically estimated from external radiation. The alpha particles can be disregarded science they travel only a short distance through air. Plutonium remaining in the soil at Nagasaki after 24yr has been determined in 1971. In the patients subjected to the Atomic bomb there was no evidence of the introduction of radioactive material. We have already studied the preserved body cells of seven A-bombed victims in 1945, and became the first one to prove that plutonium is continuing to emit radiations after more than 60 years since the A-bomb attack. In this study, the nuclide identification of alpha-emitters in environmental samples and calibration standards has been attempted by the measurement of the alpha track length using autoradiography. Alpha track length in Nagasaki soil; Ground surface soil collected in 1979 from the Nishiyama area in Nagasaki City, 210Po, 241Am and 243Am fitted the relation curve between energy and track length of alpha-particles in the photo emulsion. Moreover, the alpha track length in Nagasaki soil was consisted with that in paraffin-embedded specimen of A-bomb cases. Therefore, the nuclide of alpha-emitters in specimen of atomic victims at Nagasaki was identified with 239,240Pu by autoradiography.

著者

TAKADA JUN HOSHI MASAHARU NAGATOMO TSUNETO YAMAMOTO MASAYOSHI ENDO SATORU TAKATSUJI TOSHIHIRO YOSHIKAWA ISAO GUSEV BORIS I. SAKERBAEV ALEXANDER K. TCHAIJUNUSOVA NAILYA.J.

出版者

日本放射線影響学会

雑誌

Journal of radiation research (ISSN:04493060)

巻号頁・発行日

vol.40, no.4, pp.337-344, 1999-12

被引用文献数

13 33 44

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Accumulated external radiation doses of residents near the Semipalatinsk nuclear test site of the former USSR are presented as a results of study by the thermoluminescence technique for bricks sampled at several settlements in 1995 and 1996. The external doses that we evaluated from exposed bricks were up to about 100 cGy for resident. The external doses at several points in the center of Semipalatinsk City ranged from a background level to 60 cGy, which was remarkably high compared with the previously reported values based on military data. INTRODUCTION A total of 459 nuclear tests were conducted by the former Union of Soviet Socialist Republics (USSR) between 1949 and 1989 at the Semipalatinsk nuclear test site (SNTS) of Kazakhstan, including 87 atmospheric, 26 on the ground, and 346 underground explosions1). The total release of the energy equivalent of trinitrotoluene (TNT) of about 18 Mt was eleven hundred times that of the Hiroshima atomic bomb. However, previous reports concerning the effects of radiation on residents near the SNTS based on data provided by the Defense Department of the former USSR2, 3) did not involve direct experimental data concerning the effective equivalent dose. They just measured some doses for particular settlements after some nuclear explosions. These did not indicate an integrated dose of the residents of all the explosions. The technique of thermoluminescence dosimetry (TLD), which had been successfully applied in dosimetry for the Hiroshima and Nagasaki atomic bombs4, 5), enabled us to evaluate the accumulated external gamma ray doses of all the nuclear explosions at specific places in the Semipalatinsk test site. The TLD technique is well-established not only for instantaneous exposure as in A-bombs (Hiroshima and Nagasaki)6) but also in prolonged exposure to natural radiation, which is used in dating7). Moreover, this technique was applicable for dosimetry studies of radioactive fallout as shown in studies of the Chernobyl accident8,9).

著者

Imanaka Tetsuji Fukutani Satoshi Yamamoto Masayoshi SAKAGUCHI Aya HOSHI Masaharu

出版者

日本放射線影響学会

雑誌

Journal of radiation research (ISSN:04493060)

巻号頁・発行日

vol.47, pp.A121-A127, 2006-02

被引用文献数

3 15

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Dolon village, located about 60 km from the border of the Semipalatinsk Nuclear Test Site, is known to be heavily contaminated by local fallout from the first USSR atomic bomb test in 1949. External radiation in Dolon was evaluated based on recent 137Cs data in soil and calculation of temporal change in the fission product composition. After fitting a log-normal distribution to the soil data, a 137Cs deposition of 32 kBq m-2, which corresponds to the 90th-percentile of the distribution, was tentatively chosen as a value to evaluate the radiation situation in 1949. Our calculation indicated that more than 95% of the cumulative dose for 50 y had been delivered within 1 y after the deposition. The resulting cumulative dose for 1 y after the deposition, normalized to the initial contamination containing 1 kBq m-2 of 137Cs, was 15.6 mGy, assuming a fallout arrival time of 3 h and a medium level of fractionation. Finally, 0.50 Gy of absorbed dose in air was derived as our tentative estimate for 1-year cumulative external dose in Dolon due to local fallout from the first USSR test in 1949.

著者

Yamamoto Masayoshi 山本 政儀

巻号頁・発行日

1986

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Thesis--University of Tsukuba, D.Sc.(B), no. 311, 1986. 3. 25