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Journal Articles

Trends in radiation standard; Current status of secondary standards at JAEA

Tanimura, Yoshihiko; Yoshitomi, Hiroshi

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 66(1), p.42 - 45, 2024/01

no abstracts in English

Journal Articles

Radiation exposure to the lens of the eye for Japanese nuclear power plant workers

Yokoyama, Sumi*; Tatsuzaki, Hideo*; Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Hirao, Shigekazu*; Aoki, Katsunori; Tachiki, Shuichi*; Ezaki, Iwao*; Hoshi, Katsuya; Tsujimura, Norio

Journal of Radiological Protection, 42(3), p.031504_1 - 031504_17, 2022/09

 Times Cited Count:1 Percentile:33.72(Environmental Sciences)

In Japan, the radiation-dose limit for the lens of the eye was revised in April 2021. Consequently, for workers, the numerical values of the equivalent dose to the lens of the eye are equal to those of the effective dose. Radiation workers, radiation safety officers and licensees must comply with regulations related to radiation protection and optimize protection. The new guidelines on dose monitoring of the lens of the eye developed by the Japan Health Physics Society recommend for the dose to be estimated near the eye for accurate estimation, when the dose to the lens approaches or exceeds the management criteria. However, there is limited information regarding the non-uniform exposure of nuclear power plant workers. In this study, the dose equivalents of high-dose-rate workplaces and the personal doses of 88 workers were estimated at four Japanese commercial nuclear power plant sites (RWR: 3 units and BWR: 3 units) and the dose to the lens of the eye and the exposure situations of the workers were analyzed.

Journal Articles

Development of portable thyroid monitoring system with detector shields

Tanimura, Yoshihiko

FBNews, (548), p.1 - 5, 2022/08

In the situation of a severe nuclear accident, radioiodine monitoring in thyroid should be performed for a large number of people immediately after accident. The portable thyroid dose monitoring system with the radiation shield which can be used in a high dose rate condition has been developed. In this paper, the outline of the monitoring system and the performance test results using the system will be described.

Journal Articles

Study on method for simultaneous determination of ambient dose equivalent rates and activity concentration in air for environmental radiation monitoring

Kowatari, Munehiko; Tanimura, Yoshihiko; Kessler, P.*; Neumaier, S.*; R$"o$ttger, A.*

Radioisotopes, 70(1), p.1 - 18, 2021/01

Journal Articles

Lens dosimetry study in $$^{90}$$Sr+$$^{90}$$Y beta field; Full-face mask respirator shielding and dosemeter positioning

Tsujimura, Norio; Hoshi, Katsuya; Yamazaki, Takumi; Momose, Takumaro; Aoki, Katsunori; Yoshitomi, Hiroshi; Tanimura, Yoshihiko; Yokoyama, Sumi*

KEK Proceedings 2020-5, p.21 - 28, 2020/11

Journal Articles

Measurements of the doses of eye lens for the workers of Fukushima Daiichi Nuclear Power Plant

Yokoyama, Sumi*; Ezaki, Iwao*; Tatsuzaki, Hideo*; Tachiki, Shuichi*; Hirao, Shigekazu*; Aoki, Katsunori; Tanimura, Yoshihiko; Hoshi, Katsuya; Yoshitomi, Hiroshi; Tsujimura, Norio

Radiation Measurements, 138, p.106399_1 - 106399_5, 2020/11

 Times Cited Count:2 Percentile:24.76(Nuclear Science & Technology)

Journal Articles

Attempt to estimate the background pulse height spectrum of the CeBr$$_{3}$$ scintillation spectrometer due to terrestrial gamma ray components; Application in environmental radiation monitoring

Kowatari, Munehiko; Tanimura, Yoshihiko; Kessler, P.*; R$"o$ttger, A.*

Radiation Measurements, 138, p.106431_1 - 106431_6, 2020/11

 Times Cited Count:1 Percentile:12.47(Nuclear Science & Technology)

Journal Articles

Background correction method for portable thyroid dose monitor using gamma-ray spectrometer developed at JAEA in high dose rate environment

Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Nishino, Sho; Takahashi, Masa

Radiation Measurements, 137, p.106389_1 - 106389_5, 2020/09

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

A portable thyroid dose monitoring system has been developed at the Japan Atomic Energy Agency (JAEA) to assess the thyroid equivalent dose for workers and members of the public in a high dose rate environment. The background (B.G.) photon correction is required for an accurate measurement in a high dose rate environment at an early stage after a nuclear accident. We developed the B.G. photon correction method using cylindrical PMMA phantoms.

Journal Articles

Eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Plant, 2; Field study using humanoid phantoms

Tsujimura, Norio; Hoshi, Katsuya; Aoki, Katsunori; Yoshitomi, Hiroshi; Tanimura, Yoshihiko; Yokoyama, Sumi*

Radiation Measurements, 134, p.106305_1 - 106305_5, 2020/06

 Times Cited Count:3 Percentile:36.29(Nuclear Science & Technology)

Journal Articles

Prototype test of a portable thyroid dose monitoring system using gamma-ray spectrometers

Nishino, Sho; Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Takahashi, Masa

Radiation Measurements, 134, p.106292_1 - 106292_5, 2020/06

 Times Cited Count:4 Percentile:46.37(Nuclear Science & Technology)

In the situation of a severe nuclear accident, radioiodine monitoring in thyroid should be performed for a large number of people immediately after accident. The portable thyroid dose monitoring system which can be used in a high dose rate condition is in development. In this presentation, the result of performance test using prototype model will be described.

Journal Articles

Eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Plant, 1; Laboratory study on the dosemeter position and the shielding effect of full face mask respirators

Hoshi, Katsuya; Yoshitomi, Hiroshi; Aoki, Katsunori; Tanimura, Yoshihiko; Tsujimura, Norio; Yokoyama, Sumi*

Radiation Measurements, 134, p.106304_1 - 106304_5, 2020/06

 Times Cited Count:4 Percentile:46.37(Nuclear Science & Technology)

In FY 2017, the Japanese Nuclear Regulatory Agency (NRA) established the Radiation Safety Research Promotion Fund for funding projects on nuclear safety regulation, and adopted the two-year research project entitled "Study on standard eye lens monitoring, suitable dose management and radiation protection for nuclear and medical workers". The study is a two-phase study: a laboratory study on the eye lens dosemeter's characteristics to photons, and a field study executed at actual workplaces at Fukushima Daiichi Nuclear Power Station. This paper summarizes the results of the first-phase study, which was designed to clarify the eye lens dosemeter positioning and the shielding effect of full face mask respirators used at the station. No marked difference was observed in readings of the dosemeters attached on the different positions on the head phantom. Two types of full face mask respirators provided insignificant shielding effect for photons of 83 keV to 662 keV.

Journal Articles

Experimental determination of anisotropic emission of neutrons from $$^{252}$$Cf neutron source with the spherical protection case

Kowatari, Munehiko; Nishino, Sho; Romallosa, K. M. D.*; Yoshitomi, Hiroshi; Tanimura, Yoshihiko; Oishi, Tetsuya

Radiation Protection Dosimetry, 189(4), p.436 - 443, 2020/05

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

The anisotropic emission of neutrons from a cylindrical X1 $$^{252}$$Cf source with the spherical external casing was experimentally determined. The influence of metal materials and shapes of the external casing to the anisotropy factor, $$F_{I}$$($$theta$$) was assessed by the Monte Carlo calculation, before performing the measurement. The results of the calculation result implied that light and spherical-shaped external casing decreases the anisotropic emission of neutrons from a cylindrical source and the nature of the material does not affect the anisotropic emission to a large extent. The experimental results obtained when a spherical-shaped aluminum protection case was employed also revealed that the anisotropy factor was close to 1.0 with a wide zenith angle range.

Journal Articles

A Study of a calibration technique for a newly developed thyroid monitor and its uncertainties due to body size for radioiodine measurements

Yoshitomi, Hiroshi; Nishino, Sho; Tanimura, Yoshihiko; Takahashi, Masa

Radiation Measurements, 133, p.106279_1 - 106279_6, 2020/04

 Times Cited Count:4 Percentile:54.54(Nuclear Science & Technology)

Uncertainty of the body size on the counting efficiency of a newly developed thyroid monitor was estimated by Monte Carlo simulations using several voxel phantoms. Overlying tissue thickness was a major impact factor on the counting efficiency. As a result, uncertainty related to the body size of the monitored subject was found to be 25%.

Journal Articles

Establishment of a low dose rate gamma ray calibration field for environmental radiation monitoring devices

Kowatari, Munehiko; Yoshitomi, Hiroshi; Nishino, Sho; Tanimura, Yoshihiko; Oishi, Tetsuya; Kessler, P.*; Neumaier, S.*; R$"o$ttger, A.*

Radiation Protection Dosimetry, 187(1), p.61 - 68, 2019/12

 Times Cited Count:1 Percentile:21.95(Environmental Sciences)

Journal Articles

Corrigendum; Establishment of a low dose rate gamma ray calibration field for environmental radiation monitoring devices

Kowatari, Munehiko; Yoshitomi, Hiroshi; Nishino, Sho; Tanimura, Yoshihiko; Oishi, Tetsuya; Kessler, P.*; Neumaier, S.*; R$"o$ttger, A.*

Radiation Protection Dosimetry, 186(4), P. 538, 2019/12

 Times Cited Count:0 Percentile:1.45(Environmental Sciences)

In the original version of this article an error occurred in Table 5. In section (b), the unit $$mu$$Sv h$$^{-1}$$ has been amended to nSv h$$^{-1}$$. The corrected table appears below. The author apologises for this error.

Journal Articles

Journal Articles

Characteristics of commercially available CdZnTe detector as gamma-ray spectrometer under severe nuclear accident

Tanimura, Yoshihiko; Nishino, Sho; Yoshitomi, Hiroshi; Kowatari, Munehiko; Oishi, Tetsuya

Progress in Nuclear Science and Technology (Internet), 6, p.134 - 138, 2019/01

At the severe nuclear accidents like the Fukushima Daiichi Nuclear Power Plant, various radionuclides will be dispersed into the environment and raise the dose rate. The $$in$$-$$situ$$ measurements of $$gamma$$ ray spectra and identifying radionuclides using the results are important for the radiological protection from both external and internal exposure. For this application a commercially available CdZnTe spectrometer (Kromek GR-1) was characterized at the calibration fields of FRS/JAEA. The angular dependence of the detection efficiency was studied and the efficiency was kept within 15 % degradation in $$pm$$135 degree incident angle, which covers 85 % of all. The usable dose range was evaluated and the spectrometer could correctly measure the $$gamma$$ ray spectra below 200 $$mu$$Gy/h.

Journal Articles

Development of a simultaneous evaluation method of radioactivity in soil and dose rate using CeBr$$_{3}$$ and SrI$$_{2}$$(Eu) scintillation detectors for environmental monitoring

Kowatari, Munehiko; Tanimura, Yoshihiko; Kessler, P.*; Neumaier, S.*; Roettger, A.*

Progress in Nuclear Science and Technology (Internet), 6, p.81 - 85, 2019/01

Journal Articles

Development of a high-efficiency proton recoil telescope for D-T neutron fluence measurement

Tanimura, Yoshihiko; Yoshizawa, Michio

Radiation Protection Dosimetry, 180(1-4), p.417 - 421, 2018/08

BB2016-1356.pdf:0.59MB

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

A high efficiency proton recoil telescope (PRT), which consists of a radiator, a $$Delta$$E detector and an E detector, was developed to determine the neutron fluence in the 14.8 MeV mono-energetic neutron field at the FRS. A 2 mm thick plastic scintillation detector was employed as the radiator to increase the detection efficiency and compensate the energy loss of the recoil proton in the radiator. A thin and a thick silicon detectors with 150 $$mu$$m and 3 mm thick sensitive layers were employed as the $$Delta$$E and E detectors, respectively. The detection efficiency was evaluated by the neutron measurements in the 14.8 MeV field for the distances from the radiator to E detector of 50 mm, 100 mm and 150 mm. The detection efficiency increases up to 3.7 $$times$$ 10$$^{-3}$$ with the decrease in the distance, which is roughly a few orders of magnitude greater than those of common PRTs. These detection efficiencies are high enough to determine the neutron fluence at the 14.8 MeV field within a few hours.

Journal Articles

The Facility of radiation standards in Japan Atomic Energy Agency, present status and its research works on dosimetry

Kowatari, Munehiko; Yoshitomi, Hiroshi; Nishino, Sho; Tanimura, Yoshihiko; Oishi, Tetsuya; Yoshizawa, Michio

Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1230 - 1238, 2017/11

The Facility of Radiation Standards (FRS) of the Japan Atomic Energy Agency (JAEA) offers various kinds of radiation calibration fields for calibration and testing for over three decades. The FRS-JAEA offers reliable X-ray, $$gamma$$-ray, beta-ray and neutron calibration fields with a vast range of variety. The quality and a set of neutron calibration fields are particularly mentioned. Neutron calibration fields with energies ranging between 0.025 eV and 19 MeV enable users to check the whole items for performance test. Two different sets of beta-ray calibration fields were established and served for regular calibration of dosimeters mainly used in nuclear industries. Resent research accomplishments on $$gamma$$-ray calibration fields can extend the upper limit of the energy up to 6 MeV. In addition to them, a simulated workplace neutron calibration field has been newly established for calibration of neutron dosimeters used inside the nuclear reactors.

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