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JAEA Reports

Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2020 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2021-025, 159 Pages, 2022/01

JAEA-Technology-2021-025.pdf:46.66MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances owing to TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS) conducted in FY2020. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data. Air dose rate distribution maps were created and temporal changes of the air dose rates were analyzed. Regarding radiocesium deposition into the ground, surveys on depth profile of radiocesium and in-situ measurements were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. In the examination of scoring for classifying the importance of measurement points, a score map was created for Fukushima Prefecture and the 80 km zone from the FDNPS, and the factors causing changes in the score when monitoring data from multiple years were used were discussed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated the air dose rate distribution data obtained from aircraft monitoring, car-borne surveys, and walk surveys with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2020 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out.

JAEA Reports

Investigations on distribution of radioactive substances owing to the Fukushima Dai-ichi Nuclear Power Station Accident in the fiscal year 2019 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2020-014, 158 Pages, 2020/12

JAEA-Technology-2020-014.pdf:23.82MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances owing to TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS) conducted in FY2019. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data. Air dose rate distribution maps were created and temporal changes of the air dose rates were analyzed. Regarding radiocesium deposition into the ground, surveys on depth profile of radiocesium and in-situ measurements were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. In the examination of scoring to classify the importance of measurement points, we created a score map of Fukushima Prefecture and that within 80 km from the FDNPS based on the "score" method developed in 2018. The way of monitoring radioactive materials in land area was examined and the representativeness of monitoring points was proposed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated the air dose rate distribution data obtained from aircraft monitoring, car-borne surveys, and walk surveys with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2019 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out.

JAEA Reports

Investigations on distribution of radioactive substances owing to the FDNPP accident in the fiscal year 2018 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2019-019, 135 Pages, 2020/03

JAEA-Technology-2019-019.pdf:22.01MB

After the accident at TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS), distribution situation survey on radioactive materials have been conducted with financially supported by the Ministry of Education, Culture, Sports, Science and Technology (later the Nuclear Regulatory Agency) from June 2011 to FY2018. Results obtained in the project in FY2018 are presented in this report. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data. Air dose rate distribution maps were created and temporal changes of air dose rate were analyzed. Regarding radiocesium deposition in the soil, depth profile survey in the soil and in-situ measurement were performed. Based on these measurement results, effective half-life of the air dose rate and the deposition were evaluated. Considering radiation monitoring data obtained in previous surveys and the installation positions of existing monitoring posts, we tried to make the "score" of the importance of measurement points. Using the Bayesian hierarchical modeling approach, we obtained a map that integrated the air dose rate distribution data obtained from aircraft monitoring, car-borne surveys, and walk surveys for the entire region within 80 km from the FDNPS. The measurement results for FY2018 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and environmental sample analysis owing to the comprehensive radiation monitoring plan were carried out.

Journal Articles

Study of the screening survey using an ambient dose equivalent rate survey meter in criticality accidentsy

Hoshi, Katsuya; Tsujimura, Norio; Yoshida, Tadayoshi; Kurihara, Osamu*; Kim, E.*; Yajima, Kazuaki*

Progress in Nuclear Science and Technology (Internet), 6, p.152 - 155, 2019/01

Journal Articles

Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant using KURAMA-II until 2016

Ando, Masaki; Yamamoto, Hideaki*; Kanno, Takashi*; Saito, Kimiaki

Journal of Environmental Radioactivity, 190-191, p.111 - 121, 2018/10

 Times Cited Count:11 Percentile:59.27(Environmental Sciences)

Ambient dose equivalent rates in various environments related to human lives were measured by walk surveys using the KURAMA-II systems from 2013 to 2016 around the Fukushima Dai-ichi Nuclear Power Plant. The dose rate of the locations where the walk survey was performed decreased to about 38% of its initial value in the 42 months, which was beyond that attributable to the physical decay. The air dose rates decreased depending on the level of the evacuation areas, and the decrease was slightly larger in populated areas where humans are active. The comparison of walk survey data with car-borne survey data indicated that the air dose rate varies largely even within a 100 m square area. The dose rates measured by the walk surveys were estimated to be medial of those along roads and those of undisturbed flat ground. The air dose rates measured by the walk surveys decreased quickly compared with the air dose rate from the flat ground measurement.

Journal Articles

Improvement of estimation of $$^{131}$$I concentrations in the air using data measured by monitoring posts applied by determination of passing-through time of plume using noble gas counts

Yamada, Junya; Hashimoto, Makoto; Seya, Natsumi; Haba, Risa; Muto, Yasunobu; Shimizu, Takehiko; Takasaki, Koji; Yokoyama, Sumi*; Shimo, Michikuni*

Hoken Butsuri, 52(1), p.5 - 12, 2017/03

The purpose of this study is to improve a quick method for estimation of $$^{131}$$I concentrations in the air using data measured by monitoring posts in case that a nuclear disaster occurs. In this method, $$^{131}$$I concentrations were estimated by multiplying $$^{131}$$I count rates of cloud-shine measured with NaI (Tl) detector by concentration conversion factor. A previous study suggested that it was difficult to determine passing-through time of plume from temporal change of $$^{131}$$I count rates or dose rate. Our study applies the method for estimating passing-through time of plume from temporal change of noble gas counts. The $$^{131}$$I concentrations in the air at Oarai center, Japan Atomic Energy Agency resulting from the accident at the Fukushima Daiichi Nuclear Power Plant were estimated by proposal technique. The result of comparison of this method with sampling method for $$^{131}$$I concentrations in the air were within factor 3.

Journal Articles

LaCl$$_{3}$$(Ce) scintillation detector applications for environmental $$gamma$$-ray measurements of low to high dose rates

Tsutsumi, Masahiro; Tanimura, Yoshihiko

Nuclear Instruments and Methods in Physics Research A, 557(2), p.554 - 560, 2006/02

 Times Cited Count:12 Percentile:65.95(Instruments & Instrumentation)

A new cerium-doped LaCl$$_{3}$$(Ce) scintillator is evaluated with respect to the application in environmental $$gamma$$-ray dosimetry and spectrometry. The scintillator is very attractive for $$gamma$$-ray spectrometry in the case of high count rate, because it has excellent energy resolution and fast decay time. The performance characteristics of a scintillator with a 25.4 mm $$times$$ 25.4 mm LaCl$$_{3}$$(Ce) crystal are studied and compared to those of a NaI(Tl) scintillator with the same size crystal. Acquired pulse-height spectra are converted to dose rates by using the G(E) function method. Though the LaCl$$_{3}$$(Ce) crystal itself produces a rather high background in the crystal itself, the scintillator provides good energy information and dose-rate readings from low to high-level (several mGy/h) by subtracting the self-background. The properties of LaCl$$_{3}$$(Ce) scintillator suggest that the scintillator could be a promising candidate for monitoring at high-dose levels as in emergencies, as well as at ordinary levels of background radiation.

JAEA Reports

Development of elemental components in NDA systems for certifying radioactive wastes with the clearance level

Tsutsumi, Masahiro; Oishi, Tetsuya*; Yamasoto, Kotaro; Yoshida, Makoto

JAERI-Research 2004-021, 43 Pages, 2004/12

JAERI-Research-2004-021.pdf:8.55MB

We have designed and developed a $$gamma$$ measurement system to certify radioactive wastes below the clearance level. By advancing non-destructive $$gamma$$-ray assay technology, it aims at quantitative determination of radionuclides contained in 200 litter drum/container wastes. Unlike the waste from a nuclear power plant, you have to assume that the waste originating from radioisotope usage and nuclear research laboratory have a variety of contents and a complex mixture of radionuclides, and furthermore the uniformity of activity concentration is unknown. To cope with the problems, we have developed the $$gamma$$-ray measuring instruments (units) with effective improvement of capability against each problem. They are (1) germanium $$gamma$$ spectrometry unit for enhanced peak identification, (2) positioning detection unit for positioning of $$gamma$$ interactions and (3)high-efficiency detection unit for separation of low-energy component. This report summarizes the direction of the clearance level measuring system and the three developed measuring units with their performances.

Journal Articles

Design of an anti-compton spectrometer for low-level radioactive wastes using Monte Carlo techniques

Tsutsumi, Masahiro; Oishi, Tetsuya; Kinouchi, Nobuyuki; Sakamoto, Ryuichi; Yoshida, Makoto

Journal of Nuclear Science and Technology, 39(9), p.957 - 963, 2002/09

 Times Cited Count:3 Percentile:24.34(Nuclear Science & Technology)

An anti-Compton spectrometer with semi-2$$pi$$ Compton suppression is designed to identify the photons emitted from low-level radioactive wastes from radioisotope usage and nuclear research laboratory. Since the objective sample is massive and large, the system has a full opening towards the sample position. The characteristics and features of the system concerning Compton suppression and reduction of the background component due to natural radioactive source are estimated by the Monte Carlo simulations. The anti-Compton technique is shown to be quite advantageous for the reduction of the surrounding natural background radiation, as well as the suppression of the background for the higher energy photons.

Journal Articles

Sea bottom $$gamma$$ ray measurement by NaI(Tl) scintillation spectrometers installed on manned submersibles, ROV and sea bottom long term observatory

Hattori, Mutsuo*; Okano, Masaharu*; Togawa, Orihiko

Proceedings of 2000 International Symposium on Underwater Technology, p.212 - 217, 2000/05

no abstracts in English

Journal Articles

Development of a detector for measuring effective dose (equivalent) for external photon exposures in natural environment

Tsutsumi, Masahiro; Saito, Kimiaki; Moriuchi, Shigeru*

Journal of Nuclear Science and Technology, 37(3), p.300 - 306, 2000/03

no abstracts in English

Journal Articles

Measurement of air dose; G(E) function method

Nagaoka, Toshi

JCAC, (32), p.28 - 34, 1998/00

no abstracts in English

JAEA Reports

Estimation of photon energy distribution in gamma calibration field

Takahashi, Fumiaki; ; Yamaguchi, Yasuhiro

JAERI-Tech 97-006, 36 Pages, 1997/03

JAERI-Tech-97-006.pdf:1.25MB

no abstracts in English

Journal Articles

Detection efficiency of a total energy absorption peak for a Ge detector in water using water tank experiment

Yanase, Nobuyuki; Sekine, Keiichi

Nihon Genshiryoku Gakkai-Shi, 37(8), p.704 - 709, 1995/00

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Procedure of data treatment for measurement of environmental gamma ray dose ratewith high accuracy

Nagaoka, Toshi; Moriuchi, Shigeru

Hoken Butsuri, 29, p.315 - 320, 1994/00

no abstracts in English

Journal Articles

Simultaneous counting of $$alpha$$,$$beta$$ and $$gamma$$ rays with phoswich detectors

Usuda, Shigekazu; Abe, Hitoshi; Mihara, Akira

Journal of Alloys and Compounds, 213-214, p.437 - 439, 1994/00

 Times Cited Count:11 Percentile:65.71(Chemistry, Physical)

no abstracts in English

Journal Articles

Phoswich detectors combining doubly or triply ZnS(Ag), NE102A, BGO and/or NaI(Tl) scintillators for simultaneous counting of $$alpha$$, $$beta$$ and $$gamma$$ rays

Usuda, Shigekazu; Abe, Hitoshi; Mihara, Akira

Nuclear Instruments and Methods in Physics Research A, 340, p.540 - 545, 1994/00

 Times Cited Count:26 Percentile:88.77(Instruments & Instrumentation)

no abstracts in English

JAEA Reports

Experimental assessment of cosmic ray ionizing component at ground level by means of HPGe and NaI(Tl) spectrometry

J-S.Jun*; Nagaoka, Toshi; Moriuchi, Shigeru

JAERI-M 92-101, 25 Pages, 1992/07

JAERI-M-92-101.pdf:0.95MB

no abstracts in English

Journal Articles

Development of an effective dose equivalent detector having angular response of human bodies

Tsutsumi, Masahiro; Saito, Kimiaki; Moriuchi, Shigeru

Proc. of the Int. Radiation Protection Association,Vol. 1, p.616 - 619, 1992/00

no abstracts in English

JAEA Reports

Spectrum-dose conversion operators, G(E) functions of NaI(Tl) scintillators adapted for effective dose equivalent quantities

Tsutsumi, Masahiro; Saito, Kimiaki; Moriuchi, Shigeru

JAERI-M 91-204, 152 Pages, 1991/12

JAERI-M-91-204.pdf:11.3MB

no abstracts in English

60 (Records 1-20 displayed on this page)