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Journal Articles

Review of the performance of a car-borne survey system, KURAMA-II, used to measure the dose rate after the Fukushima Dai-ichi Nuclear Power Plant accident

Tsuda, Shuichi; Tanigaki, Minoru*; Yoshida, Tadayoshi; Saito, Kimiaki

Hoshasen, 44(3), p.109 - 118, 2018/11

JAEA has started to perform dose rate monitoring using a car-borne survey system KURAMA to rapidly produce the dose rate mappings of the deposited radionuclides in the environment after the Fukushima Dai-ichi Nuclear Power Plant accident. KURAMA is a car-borne survey system developed by Kyoto University to perform dose rate monitoring in a wide area in detail with rapidity. By improving KURAMA with continuous dose rate monitoring, the 2nd generation of KURAMA (KURAMA-II) succeeded in downsizing, durability and automated transmission of data so that enable detailed dose rate mapping in wide area in shorter period of time. This paper reports the radiation characteristics and the simulation analysis of KURAMA-II on the special issue of Hoshasen, the journal of Ionization Radiation Division in the Japan society of applied physics.

Journal Articles

Dependence of dose rate measurement in the environment on crystal configuration of scintillation detectors

Tsuda, Shuichi; Tanigaki, Minoru*; Yoshida, Tadayoshi; Okumura, Ryo*; Saito, Kimiaki

Nippon Genshiryoku Gakkai Wabun Rombunshi, 17(1), p.11 - 17, 2018/03

Environmental dose rate monitoring has been performed using scintillation detectors since the Fukushima Dai-ichi Nuclear Power Plant accident happened. After the accident, various scintillation detectors with directional dependence are used in the measurement, though detectors with superior directional dependence are needed because photons come from various direction in the environment. To investigate the influence of crystal configurations on indicated values of dose rates, pulse height spectra were measured using scintillation-based detectors with different crystal configurations and ambient dose rates were obtained using a spectrum - dose conversion operator (G(E) function). It is found that the dose rate for a rectangular-parallelepiped crystal is $$sim$$ 40% than that for a cylindrical one at the maximum. However, the values agreed within 10% among all the detectors irrespective of the crystal shapes, using G(E) functions determined in a rotational irradiation geometry.

Journal Articles

Measurements and evaluations of air dose rates around Fukushima, 4; Practical aspects of air dose rate measurements in the environment

Tsuda, Shuichi; Yoshida, Tadayoshi; Ando, Masaki; Matsuda, Norihiro; Mikami, Satoshi; Tanigaki, Minoru*; Okumura, Ryo*; Takamiya, Koichi*; Sato, Nobuhiro*; Seki, Akiyuki; et al.

Radioisotopes, 64(4), p.275 - 289, 2015/04

This article provides practically useful information on air dose rate measurements in the environments. The basic requirements for the accurate measurements are described giving actual data. The characteristics and some measured results are shown for reliable methods which are widely used in the environmental radiation measurements. Further, information is given on internet sites where air dose rates and related data obtained by official organizations can be browsed.

Journal Articles

Measurement of air dose rates over a wide area around the Fukushima Dai-ichi Nuclear Power Plant through a series of car-borne surveys

Ando, Masaki; Nakahara, Yukio; Tsuda, Shuichi; Yoshida, Tadayoshi; Matsuda, Norihiro; Takahashi, Fumiaki; Mikami, Satoshi; Kinouchi, Nobuyuki; Sato, Tetsuro*; Tanigaki, Minoru*; et al.

Journal of Environmental Radioactivity, 139, p.266 - 280, 2015/01

 Times Cited Count:24 Percentile:14.05(Environmental Sciences)

A series of car-borne surveys using the KURAMA and KURAMA-II systems was conducted in a wide area in eastern Japan from June 2011 to December 2012 to evaluate the distribution of air dose rates around the Fukushima Dai-ichi Nuclear Power Plant, and to determine the time-dependent trend of decrease in air dose rates. An automated data processing system was established, which enables analyses of large amounts of data obtained with the use of about 100 units of the measurement system in a short time. The initial data for studying the migration status of radioactive cesium was obtained in the first survey, followed by the other car-borne surveys having wider measurement ranges. Comparing the measured air dose rates obtained in each survey, it was found that the decreasing trend of air dose rates measured through car-borne surveys was larger than that expected from the physical decay of radioactive cesium and that measured using NaI (Tl) survey meters around the road.

JAEA Reports

Construction of a car-borne survey system for measurement of dose rates in air; KURAMA-II, and its application

Tsuda, Shuichi; Yoshida, Tadayoshi; Nakahara, Yukio; Sato, Tetsuro; Seki, Akiyuki; Matsuda, Norihiro; Ando, Masaki; Takemiya, Hiroshi; Tanigaki, Minoru*; Takamiya, Koichi*; et al.

JAEA-Technology 2013-037, 54 Pages, 2013/10

JAEA-Technology-2013-037.pdf:4.94MB

JAEA has been performing dose rate mapping in air using a car-borne survey system KURAMA-II. The KURAMA system is a GPS-aided mobile radiation monitoring system that has been newly developed by Kyoto University Research Reactor Institute in response to the nuclear disaster. The KURAMA system is composed of an energy-compensated scintillation survey meter for measuring dose rate, electric device for controlling both the dose rates and the position data from a GPS module, a computer server for processing and analyzing data from KURAMA, and client PCs for providing for end users. The KURAMA-II has been improved in small-packaging, durability, and automated data transmission. In consequence, dose rate mapping in wide area has become possible in shorter period of time. This report describes the construction of KURAMA-II, its application and a suggestion of how to manage a large number of KURAMA-II.

Oral presentation

Study on distribution and migration of radioactive substances around the Fukushima Daiichi Nuclear Power Plant; Development of real-time visualization system for air dose rate data in Fukushima district measured by car-borne surveys

Takemiya, Hiroshi; Saito, Kimiaki; Mizuno, Satoshi*; Tanigaki, Minoru*

no journal, , 

Visualization system for immediately publishing detailed time variation data on the distribution of radioactive substances in Fukushima district is presented. The system visualizes and provides continuous and consecutive air dose rate data measured by devices mounted on buses. It automatically generates scripts for both displaying intuitive distribution data with the help of networked GIS systems and providing graphs on the time variation data in cooperation with web-services. In this presentation, we introduce an outline of the Fukushima air dose measurement project in which the system is utilized, and report elemental technologies for the development of the system.

Oral presentation

Oral presentation

Mapping project in Fukushima and related researches, 7; Dose estimation of artificial / natural radioisotopes by an analysis of photon energy spectrum

Tsuda, Shuichi; Tanigaki, Minoru*; Saito, Kimiaki

no journal, , 

A GPS-aided radiation monitoring system KURAMA and the KURAMA-II developed by Kyoto University has been utilized after the Fukushima Dai-ichi Nuclear Power Plant accident in a mapping project of radionuclides deposited in the environment and monitoring of dose rates in air. KURAMA-II has a function of precisely evaluating dose rates in air based on measured pulse-height spectra from the incorporated CsI(Tl) scintillation detector. In this study, to evaluate dose contribution of the radionuclides in the environment, photon energy spectra was estimated by an unfolding method, using the measured pulse-height spectra and the dataset of the calculated response functions of the CsI(Tl) scintillation detector in a simulative environment. The results of dose contributions of artificial and natural radionuclides based on the estimation method will be reported in the session, "Mapping project in Fukushima and related researches".

Oral presentation

Intercomparison of dose rates obtained from scintillation detectors with different shape in the environmental monitoring, 1; Experiments

Yoshida, Tadayoshi; Tsuda, Shuichi; Tanigaki, Minoru*; Okumura, Ryo*; Saito, Kimiaki

no journal, , 

no abstracts in English

Oral presentation

Intercomparison of dose rates obtained from scintillation detectors with different shape in the environmental monitoring, 2; Simulation

Tsuda, Shuichi; Yoshida, Tadayoshi; Tanigaki, Minoru*; Okumura, Ryo*; Saito, Kimiaki

no journal, , 

Environmental dose rate monitoring has been performed using scintillation detectors since the Fukushima Dai-ichi Nuclear Power Plant accident happened. It is necessary to evaluate the influence of directional dependence on indicated values, because scintillation detectors with such dependence are used, though photons come from various direction in the environment. In this study, pulse height spectra were measured using scintillation detectors with different crystal configurations and ambient dose equivalent rates were obtained using spectrum - dose conversion operators. The ratio of dose rates calculated in a simulated environmental radiation field agrees with the measurement fairly well. The calculated dose rates of CsI(Tl) cylindrical crystals with varying height-to-diameter ratios indicated that the environmental dose rates can be estimated by a simple calibration using a unidirectional beam, provided that a crystal configuration and an irradiation surface are properly selected.

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