- 著者
- 平山 英夫 松村 宏 波戸 芳仁 佐波 俊哉
- 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.14, no.1, pp.1-11, 2015 (Released:2015-02-15)
- 参考文献数
- 13
- 被引用文献数
- 2 9
Time histories of the I-131 concentration in air at monitoring posts in Fukushima prefecture in March 2011 were estimated using the pulse height distribution of a NaI(Tl) detector, which was opened to the public. Several corrections to the pulse height distribution were necessary owing to high count rates. The contribution to the count rates from I-131 accumulated around the monitoring post was estimated on the basis of the time history of the peak count rate by the method proposed by the authors. The concentrations of I-131 in air were converted from the peak count rates using the calculated response of the NaI(Tl) detector with egs5 for a model of a plume containing I-131 uniformly. The obtained time histories of the I-131 concentration in air at a fixed point in March 2011 were the first ones for Fukushima prefecture. The results at 3 monitoring posts, Naraha Town Shoukan, Hirono Town Futatunuma and Fukushima City Momijiyama, which can be analyzed during almost all of March, show that a plume including I-131 arrived after March 15. The results at other monitoring posts near Fukushima Daiichi Nuclear Power Station are used to characterize plume diffusion at the early period of the accident before March 15. The I-131 time-integrated concentrations in air at several monitoring posts were compared with those given in UNSCEAR 2013 ANNEX A, which were obtained using estimated time-dependent rates of release to the atmosphere. The agreement between the two results varies depending on the places compared, owing to the large uncertainties in the estimated release rate used in UNSCEAR. The results obtained in this study can be used to increase the accuracy of the time-dependent release rate estimation.
- 著者
- 平山 英夫 松村 宏 波戸 芳仁 佐波 俊哉
- 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.16, no.1, pp.1-14, 2017 (Released:2017-02-15)
- 参考文献数
- 11
- 被引用文献数
- 3 5
The Xe-135, I-131, I-132, I-133 and Te-132 concentrations in plumes at the monitoring posts in Fukushima prefecture in March 2011 were estimated using the pulse height distribution obtained from a NaI(Tl) detector, which were available to the public. Several corrections to the pulse height distribution were necessary owing to high count rates. The contribution to the count rates from each radionuclide except Xe-135 accumulated around each monitoring post was estimated using a method based on the time history of the peak count rate proposed by the authors. The concentration of each radionuclide in the plume was converted from the peak count rate using the response of the NaI(Tl) detector calculated with the egs5 code for a model of a plume containing a uniform distribution of radionuclides. The obtained time histories of Xe-135, I-131, I-132, I-133 and Te-132 concentrations in air at a fixed point in March 2011 were the first ones for Fukushima prefecture. The results at five monitoring posts near Fukushima Daiichi Nuclear Power Station were used to characterize radionuclides in the plume before March 15, soon after the accident. The results at three monitoring posts, Naraha-town Shoukan, Hirono-town Futatsunuma and Fukushima-city Momijiyama, which were analyzed during almost all of March, were used to characterize radionuclides in the plume in the period after March 14. It was fourd that Xe-135 was dominant on March 12 and Te-132 increased from March 13. For the radionuclides of iodine, I-131, I-132 and I-133 were detected with almost the same concentration for the first few days after the reactor shutdown.
- 著者
- 平山 英夫 松村 宏 波戸 芳仁 佐波 俊哉
- 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.J14.027, (Released:2015-01-28)
- 参考文献数
- 13
- 被引用文献数
- 9 9
Time histories of the I-131 concentration in air at monitoring posts in Fukushima prefecture in March 2011 were estimated using the pulse height distribution of a NaI(Tl) detector, which was opened to the public. Several corrections to the pulse height distribution were necessary owing to high count rates. The contribution to the count rates from I-131 accumulated around the monitoring post was estimated on the basis of the time history of the peak count rate by the method proposed by the authors. The concentrations of I-131 in air were converted from the peak count rates using the calculated response of the NaI(Tl) detector with egs5 for a model of a plume containing I-131 uniformly. The obtained time histories of the I-131 concentration in air at a fixed point in March 2011 were the first ones for Fukushima prefecture. The results at 3 monitoring posts, Naraha Town Shoukan, Hirono Town Futatunuma and Fukushima City Momijiyama, which can be analyzed during almost all of March, show that a plume including I-131 arrived after March 15. The results at other monitoring posts near Fukushima Daiichi Nuclear Power Station are used to characterize plume diffusion at the early period of the accident before March 15. The I-131 time-integrated concentrations in air at several monitoring posts were compared with those given in UNSCEAR 2013 ANNEX A, which were obtained using estimated time-dependent rates of release to the atmosphere. The agreement between the two results varies depending on the places compared, owing to the large uncertainties in the estimated release rate used in UNSCEAR. The results obtained in this study can be used to increase the accuracy of the time-dependent release rate estimation.
- 著者
- 平山 英夫 佐波 俊哉 波戸 芳仁
- 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.J12.043, (Released:2013-06-27)
- 参考文献数
- 4
- 被引用文献数
- 4 6
Gamma-ray pulse-height distributions from widely distributed Cs-134 and Cs-137 calculated using the EGS5 Monte Carlo code with the transformation of a system consisting of a plane isotropic source and a unit sphere detector into a system consisting of a point isotropic source and a plane detector were compared with measured ones. Results agree well in terms of both spectrum shape and absolute value. Spectra at a height of 1 m from widely distributed I-131, Cs-134 and Cs-137 were studied by EGS5 calculation. It was clarified that the contribution of scattered gamma rays is dominant within the total gamma-ray flux. The contributions of the scattered gamma rays to ambient dose equivalents and effective dose were also studied.
- 著者
- 平山 英夫 松村 宏 波戸 芳仁 佐波 俊哉
- 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.12, no.4, pp.304-310, 2013 (Released:2013-11-15)
- 参考文献数
- 4
- 被引用文献数
- 1 3
A method was presented to estimate radionuclide concentration in plume using the pulse height distribution measured by a LaBr3 scintillation detector and its calculated response to radionuclides in plume with egs5. Radionuclide concentration was estimated from the ratio between the peak count rates corresponding to each radionuclide in the measured pulse height distribution on an expressway on March 15 and in the calculated one from each radionuclide in plume using the egs5 Monte Carlo code. The pulse height distribution reconstructed based on the estimated concentrations agrees well with the measured one at the time that the contribution from radionuclides deposited on a ground surface is negligible.
- 著者
- 平山 英夫 川崎 将亜 松村 宏 大倉 毅史 波戸 芳仁 佐波 俊哉 滝 光成 大石 哲也 吉澤 道夫
- 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.13, no.3, pp.119-126, 2014 (Released:2014-08-15)
- 参考文献数
- 4
- 被引用文献数
- 3 6
A method of deducing the I-131 concentration in a radioactive plume from the time history of peak count rates determined from pulse height spectra obtained from an NaI(Tl) scintillation detector employed as a detector of a monitoring post was presented. The contribution to the count rates from I-131 accumulated around the monitoring post was subtracted in accordance with the time history, taking into consideration the cumulative attachment and its decay. The concentrations of I-131 in the plumes were estimated from the count rates using the calculated response of the NaI(Tl) detector with egs5 for a model of a plume uniformly containing I-131. This method was applied to the data from the monitoring posts at Nuclear Science Research Institutes of Japan Atomic Energy Agency (JAEA). The estimated time history variation of I-131 concentrations in plumes was in fair agreement with those measured directly by an air sampling method. The difference was less than a factor of 4 for plumes that arrived on March 15 and March 21, indicating relatively high I-131 concentrations among the plumes studied in this work.