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 近藤 健次郎 海野 泰裕 松村 宏 岩瀬 広 柚木 彰 佐々木 慎一

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.J14.048, (Released:2015-06-30)

参考文献数

16

被引用文献数

1

---

A rapid and simple method to measure the concentration of 90Sr in water by measuring β-rays from 90Y was presented. Under the situation that 90Sr/90Y, 134Cs and 137Cs are the main radionuclides included in the water sample, only β-rays from 90Y can transmit through 1.5-mm-thick polyethylene. From this fact, it is possible to measure β-rays from 90Y using a β-ray detector, such as the GM-counter, set beneath the 1.5-mm-thick bottom of the water bottle containing the sample with 90Sr/90Y. The acrylic resin collimator having 0 cm, 1.00 cm, 1.50 cm or 3.00 cm diameter was made to detect β-rays at the fixed region of the GM-counter used. Contributions from bremsstrahlung produced by β-rays and γ-rays from radionuclides such as 134Cs and 137Cs/137mBa are removed by subtracting the count rate measured with a 1.00 cm acrylic resin collimator without a hole as the background count rate. The developed method was studied using the bottle routinely used at the Fukushima Daiichi Nuclear Power Station. It was confirmed that the developed method can be applied to measure the 90Sr concentration in water to the order of several Bq/cm3 if 134Cs and 137Cs concentrations are less than or equal to the 90Sr/90Y concentration.

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

近藤 健次郎 平山 英夫 平 雅文 松村 宏 岩瀬 広 佐々木 慎一

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.J14.034, (Released:2015-06-30)

参考文献数

16

---

Strontium-90/Y-90 are major radionuclides observed in the water samples tested recently at the site of the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company. A simple method of evaluating Sr-90 concentration in these water samples by measuring β rays from Y-90 with a GM-detector setup was developed. By applying the precipitation method, Sr-90 and Y-90 were separated and quantitatively collected with a filter. β rays from Y-90 in the filter were measured two times at appropriate intervals by inserting a polyethylene plate of 2 mm thickness as a β-ray absorber. The contribution of γ rays from Cs-134 and Cs-137 to the Y-90 count rates was quantitatively evaluated using a 10-mm-thick acrylic resin plate. From the parent-daughter relationship between Sr-90 and Y-90, the Sr-90 concentration was evaluated using the conversion coefficient of Y-90 count rate (cps) to Sr-90 concentration (Bq/cm3). It was verified that Sr-90 concentration of below 0.01 Bq/cm3 in water samples can be correctly measured by this simple method.

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

出版者

公益社団法人 日本アイソトープ協会

雑誌

RADIOISOTOPES (ISSN:00338303)

巻号頁・発行日

vol.62, no.6, pp.335-345, 2013 (Released:2013-06-28)

参考文献数

9

被引用文献数

12 21

---

本論文では,福島県等で地表に広く分布した134Cs及び137Cs環境において着用された個人線量計により測定される線量について,モンテカルロ計算コードEGS5で評価を行ったのでその結果を報告する。個人線量計は,実用量である個人線量当量Hp(10)を測定することを目的とした線量計であるが,広く地表に分布した線源による被ばくの場合は,線量計を着用している前面だけでなく若干下向きの角度を中心に様々な角度から光子が入射するため,数値的には実効線量に相当する線量を結果的に測定していることになるという結果が得られた。

著者

平山 英夫 松村 宏 波戸 芳仁 佐波 俊哉

雑誌

2016年秋の大会

巻号頁・発行日

2016-07-22

著者

谷村 嘉彦 平山 英夫 近藤 健次郎 永田 寛 岩永 宏平 鈴木 征四郎

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.15, no.3, pp.129-132, 2016 (Released:2016-08-15)

参考文献数

6

---

Photon energy spectra were measured above the operating floor of unit 3 reactor at the Fukushima Daiichi Nuclear Power Station by using a CdZnTe semiconductor spectrometer. The spectrometer was installed in a lead collimator to measure the photons from the area directly below the detector. The collimator and spectrometer were lifted up by a huge crane and set above the operating floor. The photon spectra were derived by unfolding the pulse height spectra measured using the spectrometer. The response function of the spectrometer was calculated with the MCNP-4C code and was used as an input parameter of the unfolding code MAXED. It was found from the photon energy spectra that low-energy photons with energy below 0.4 MeV were dominant above the operating floor. These spectra are fundamental data for evaluating the dose reduction effect by setting up shields on the operating floor.

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 近藤 健次郎 海野 泰裕 松村 宏 岩瀬 広 柚木 彰 佐々木 慎一

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.3, pp.141-150, 2015 (Released:2015-08-15)

参考文献数

16

被引用文献数

1

---

A rapid and simple method to measure the concentration of 90Sr in water by measuring β-rays from 90Y was presented. Under the situation that 90Sr/90Y, 134Cs and 137Cs are the main radionuclides included in the water sample, only β-rays from 90Y can transmit through 1.5-mm-thick polyethylene. From this fact, it is possible to measure β-rays from 90Y using a β-ray detector, such as the GM-counter, set beneath the 1.5-mm-thick bottom of the water bottle containing the sample with 90Sr/90Y. The acrylic resin collimator having 0 cm, 1.00 cm, 1.50 cm or 3.00 cm diameter was made to detect β-rays at the fixed region of the GM-counter used. Contributions from bremsstrahlung produced by β-rays and γ-rays from radionuclides such as 134Cs and 137Cs/137mBa are removed by subtracting the count rate measured with a 1.00 cm acrylic resin collimator without a hole as the background count rate. The developed method was studied using the bottle routinely used at the Fukushima Daiichi Nuclear Power Station. It was confirmed that the developed method can be applied to measure the 90Sr concentration in water to the order of several Bq/cm3 if 134Cs and 137Cs concentrations are less than or equal to the 90Sr/90Y concentration.

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.