Refine your search:     
Report No.
 - 
Search Results: Records 1-7 displayed on this page of 7
  • 1

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Current state of atmospheric and oceanic environmental researches on the Fukushima Daiichi nuclear accident; What is known about/from the accident

Aoyama, Michio*; Yamazawa, Hiromi*; Nagai, Haruyasu

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 60(1), p.46 - 50, 2018/01

no abstracts in English

Journal Articles

Factors controlling the spatiotemporal variation of $$^{137}$$Cs in seabed sediment off the Fukushima coast; Implications from numerical simulations

Misumi, Kazuhiro*; Tsumune, Daisuke*; Tsubono, Takaki*; Tateda, Yutaka*; Aoyama, Michio*; Kobayashi, Takuya; Hirose, Katsumi*

Journal of Environmental Radioactivity, 136, p.218 - 228, 2014/10

 Times Cited Count:22 Percentile:54.4(Environmental Sciences)

Major controls on spatiotemporal variations of $$^{137}$$Cs activity in seabed sediments derived from the Fukushima Dai-ichi Nuclear Power Plant accident during the first year after the accident were investigated by using numerical simulations. The model successfully reproduced major features of the observed spatiotemporal variations of $$^{137}$$Cs activity in sediments. The spatial pattern of $$^{137}$$Cs in sediments, which mainly reflected the history of $$^{137}$$Cs activity in the bottom water overlying the sediment and the sediment particle size distribution, became established during the first several months after the accident. Taking $$^{137}$$Cs activities in sediments in the coastal area and in the vicinity of the power plant into account, increased the simulated total inventory of $$^{137}$$Cs in sediments off the Fukushima coast to a value on the order of 10$$^{14}$$ Bq.

Journal Articles

Cesium, iodine and tritium in NW Pacific waters; A Comparison of the Fukushima impact with global fallout

Povinec, P. P.*; Aoyama, Michio*; Biddulph, D.*; Breier, R.*; Buesseler, K. O.*; Chang, C. C.*; Golser, R.*; Hou, X. L.*; Je$v{s}$kovsk$'y$, M.*; Jull, A. J. T.*; et al.

Biogeosciences, 10(8), p.5481 - 5496, 2013/08

 Times Cited Count:99 Percentile:94.68(Ecology)

Radionuclide impact of the Fukushima Dai-ichi Nuclear Power Plant accident on the distribution of radionuclides in seawater of the NW Pacific Ocean is compared with global fallout from atmospheric tests of nuclear weapons. Surface and water column seawater samples collected during the international expedition in June 2011 were analyzed for $$^{134}$$Cs, $$^{137}$$Cs, $$^{129}$$I and $$^{3}$$H. The $$^{137}$$Cs, $$^{129}$$I and $$^{3}$$H levels in surface seawater offshore Fukushima varied between 0.002-3.5 Bq/L, 0.01-0.8 $$mu$$Bq/L, and 0.05-0.15 Bq/L, respectively. At the sampling site about 40 km from the coast, where all three radionuclides were analyzed, the Fukushima impact on the levels of these three radionuclides represent an increase above the global fallout background by factors of about 1000, 30 and 3, respectively. The water column data indicate that the transport of Fukushima-derived radionuclides downward to the depth of 300 m has already occurred. The observed $$^{137}$$Cs levels in surface waters and in the water column are in reasonable agreement with predictions obtained from the Ocean General Circulation Model, which indicates that the radionuclides have been transported from the Fukushima coast eastward. Due to a suitable residence time in the ocean, Fukushima-derived radionuclides will provide useful tracers for isotope oceanography studies on the transport of water masses in the NW Pacific Ocean.

Journal Articles

Reconstruction of the atmospheric releases of $$^{131}$$I and $$^{137}$$Cs resulting from the Fukushima Daiichi Nuclear Power Plant accident

Chino, Masamichi; Terada, Hiroaki; Katata, Genki; Nagai, Haruyasu; Nakayama, Hiromasa; Yamazawa, Hiromi*; Hirao, Shigekazu*; Ohara, Toshimasa*; Takigawa, Masayuki*; Hayami, Hiroshi*; et al.

NIRS-M-252, p.127 - 135, 2013/03

We estimated the release rates and total amounts of $$^{131}$$I and $$^{137}$$Cs discharged into the atmosphere from March 12 to April 5, 2011. The applied method is a reverse estimation by coupling environmental monitoring data with atmospheric dispersion simulations under the assumption of unit release rate (1 Bq/h). It calculates release rates of radionuclides (Bq/h) by dividing measured air concentrations of $$^{131}$$I and $$^{137}$$Cs into calculated ones at sampling points. The estimated temporal variation of releases indicates that the significant release, over 10$$^{15}$$ Bq/h of $$^{131}$$I, occurred on March 15, following to relatively small releases, 10$$^{13}$$ $$sim$$ 10$$^{14}$$ Bq/h, but the release rates from March 16 are estimated to be rather constant on the order 10$$^{14}$$ Bq/h until March 24. The release rates have decreased with small day-to-day variations to the order of 10$$^{11}$$ $$sim$$ 10$$^{12}$$ Bq/h of $$^{131}$$I on the beginning of April. The estimated source term was examined on the point of the time trend, total releases and the ground depositions of $$^{137}$$Cs by using different atmospheric dispersion models with above source term and compared them with observed $$^{137}$$Cs deposition distribution. These examinations showed that the estimated source term was reasonably accurate during the period when the plume flowed over land in Japan.

Journal Articles

IAEA'97 expedition to the NW Pacific Ocean; Results of oceanographic and radionuclide investigations of the water column

Povinec, P. P.*; Livingston, H. D.*; Shima, Shigeki*; Aoyama, Michio*; Gastaud, J.*; Goroncy, I.*; Hirose, Katsumi*; Huynh-Ngoc, L.*; Ikeuchi, Yoshihiro*; Ito, Toshimichi; et al.

Deep Sea Research Part 2: Topical Studies in Oceanography, 50(17-21), p.2607 - 2637, 2003/09

 Times Cited Count:97 Percentile:88.84(Oceanography)

An international sampling cruise, IAEA'97, was carried out in 1997 in the NW Pacif1c Ocean. The main results of this study are following: (1) The levels of oceanographic parameter showed differences from the historical data, (2) Transuranics water profiles showed typical sub-surface concentration maxima with decrease in concentration by about a factor of 4 from the historical results, deepening their positions by about a factor of 2 and declining the water column inventory by about 20% over 24 years, (3) Sr-90 and Cs-137 data confirmed that the observed changes in concentration profiles have been resulting from the regional water masses circulation, and (4) The concentrations of these radionuclides in surface water after 40 years of their main introduction to the NW Pacific are still showing a latitudinal dependence. The results present the most comprehensive recent study on the distribution of radionuclides in the NW Pacific Ocean with the implications for behaviour of these radionuclides in the water column and physical forcing of water mass circulation over the last 24 years.

Oral presentation

Intercomparison of $$gamma$$ ray analysis softwares using reference spectra

Aoyama, Michio*; Akiyama, Masakazu*; Asai, Masato; Abe, Takaaki*; Sato, Yasushi*; Takano, Naoto*; Takamiya, Koichi*; Hamajima, Yasunori*; Muto, Giichi*; Yamada, Takashi*; et al.

no journal, , 

Performance of $$gamma$$-ray spectrum analysis softwares is significantly important because it directly affects the results of nuclide identification and radioactivity measurement. The Expert Committee on Next-generation Gamma-ray Spectrometry, Science and Engineering Committee, Japan Radioisotope Association, performed intercomparison of $$gamma$$-ray analysis software by analyzing the same reference spectra with several softwares used in Japan, to know and to improve their performance. It was found that the number of peaks detected by the peak search analysis and deduced peak areas were different among each of the softwares. The reasons why such differences occur are investigated in detail.

Oral presentation

Estimation of particulate and dissolved $$^{137}$$Cs discharge from rivers to the ocean near the Fukushima Dai-ichi Nuclear Power Plant using a simple model

Sakuma, Kazuyuki; Aoyama, Michio*; Nakanishi, Takahiro; Kurikami, Hiroshi; Machida, Masahiko; Yamada, Susumu; Iwata, Ayako

no journal, , 

MERCURY is one of the models developed to simply predict $$^{137}$$Cs discharge from rivers to the ocean for understanding of $$^{137}$$Cs migration from seawater and sediment to the ecosystem and for estimating $$^{137}$$Cs discharge under heavy rainfall immediately. It is composed of a tank model, relationships between water discharge and suspended solids load, and two-component exponential models for river water $$^{137}$$Cs concentration. Using the MERCURY, $$^{137}$$Cs discharge to the ocean from five rivers near the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in 2018 and 2019 was estimated to be 0.23 and 0.81 TBq. $$^{137}$$Cs discharge in 2019 was larger than in 2018 due to the two huge typhoons in October 2019, Hagibis and Bualoi. Although the model has some limitations such as underestimating the $$^{137}$$Cs discharge during a heavy rainfall due to lack of modeling dependence of $$^{137}$$Cs concentration on sediment size, it can quickly evaluate the effect of $$^{137}$$Cs discharge from rivers to the coastal area near FDNPP.

7 (Records 1-7 displayed on this page)
  • 1