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

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

 Times Cited Count:0 Percentile:0.01(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:0 Percentile:0.01(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:1 Percentile:39.17(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:2 Percentile:62.87(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:2 Percentile:39.17(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:2 Percentile:62.87(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:23.13(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

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 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


 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

Investigation of main radiation source above shield plug of Unit 3 at Fukushima Daiichi Nuclear Power Station

Hirayama, Hideo*; Kondo, Kenjiro*; Suzuki, Seishiro*; Tanimura, Yoshihiko; Iwanaga, Kohei*; Nagata, Hiroshi*

EPJ Web of Conferences, 153, p.08010_1 - 08010_3, 2017/09

 Times Cited Count:0 Percentile:0.03

Pulse height distributions were measured using a CdZnTe detector inside a lead collimator to investigate main source producing high dose rates above the shield plugs of Unit 3 at Fukushima Daiichi Nuclear Power Station. It was confirmed that low energy photons are dominant. Concentrations of Cs-137 under 60 cm concrete of the shield plug were estimated to be between 8.1$$times$$10$$^9$$ and 5.7$$times$$10$$^{10}$$ Bq/cm$$^2$$ from the measured peak count rate of 0.662 MeV photons. If Cs-137 was distributed on the surfaces of the gaps of the shied plugs with radius 6 m and with the averaged concentration of 5 points, 2.6$$times$$10$$^{10}$$ Bq/cm$$^2$$, total amount of Cs-137 is estimated to be 30 PBq.

Journal Articles

Evaluation of $$gamma$$-ray spectra measured inside and outside a house in Fukushima

Tanimura, Yoshihiko; Tomita, Jumpei; Yoshitomi, Hiroshi; Yoshizawa, Michio; Hakozaki, Ryozo*; Takahashi, Sohei*

Hoken Butsuri, 51(3), p.141 - 146, 2016/09

Photon spectra were measured inside and outside a house in Minami-Soma city by using a NaI(Tl) scintillation spectrometer. The photons were categorized into three groups according to their energy. The groups were (1) scattered photons, which include low energy photons, (2) direct photons from $$^{134}$$Cs and $$^{137}$$Cs sources and (3) the other photons. Then the ratios of the ambient dose equivalents H$$^*$$(10) of the scattered photons to those of the direct photons from the $$^{134}$$Cs and $$^{137}$$Cs sources have been evaluated from the measured photon spectra. The ratios are high inside the house compared with those out of the house. It was found that the scattered photons contribute to the H$$^*$$(10) by more than 50$$%$$ inside the house. The ambient dose equivalent average energies of the scattered photons are around 0.25 MeV both inside and outside the house. These data is worthwhile to design the optimum shielding for the protection against the public radiation exposure.

Journal Articles

Development of the graphite-moderated neutron calibration fields using $$^{241}$$Am-Be sources in JAEA-FRS

Nishino, Sho; Tanimura, Yoshihiko; Ebata, Yoshiaki*; Yoshizawa, Michio

Journal of Radiation Protection and Research, 41(3), p.211 - 215, 2016/09

We developed the graphite-moderated neutron calibration fields using $$^{241}$$Am-Be sources at the Facility of Radiation Standard in the Japan Atomic Energy Agency. The neutron spectra of the fields were evaluated by Monte-Carlo calculation and measurements using the Bonner Multi-sphere Spectrometer. Reference values of fluence rates and dose equivalent rates of H$$^{*}$$(10) and H$$_{rm p}$$(10) were determined from neutron spectra by measurements. Currently, our fields are available for calibration or performance test of neutron measuring instruments.

Journal Articles

Determination of low-level radiostrontium, with emphasis on ${it in situ}$ pre-concentration of Sr from large volume of freshwater sample using Powdex resin

Tomita, Jumpei; Yamamoto, Masayoshi*; Nozaki, Teo; Tanimura, Yoshihiko*; Oishi, Tetsuya

Journal of Environmental Radioactivity, 146, p.88 - 93, 2015/08

 Times Cited Count:10 Percentile:38.89(Environmental Sciences)

Journal Articles

Series studies on inter-comparison of radiation calibration fields and calibration techniques between KAERI and JAEA

Yoshitomi, Hiroshi; Tanimura, Yoshihiko*; Tatebe, Yosuke; Tsutsumi, Masahiro; Kawasaki, Katsuya; Kowatari, Munehiko; Yoshizawa, Michio; Shimizu, Shigeru*; Kim, J.-S.*; Lee, J.-G.*; et al.

Proceedings of 4th Asian and Oceanic Congress on Radiation Protection (AOCRP-4) (CD-ROM), 4 Pages, 2015/07

Journal Articles

Measurement of air kerma rates for 6- to 7-MeV high-energy $$gamma$$-ray field by ionisation chamber and build-up plate

Kowatari, Munehiko; Tanimura, Yoshihiko; Tsutsumi, Masahiro

Radiation Protection Dosimetry, 162(4), p.446 - 458, 2014/12

 Times Cited Count:3 Percentile:28.59(Environmental Sciences)

no abstracts in English

Journal Articles

Photon dose mixed in monoenergetic neutron calibration fields using $$^7$$Li(p,n)$$^7$$Be reaction

Tanimura, Yoshihiko; Tsutsumi, Masahiro; Yoshizawa, Michio

Radiation Protection Dosimetry, 161(1-4), p.149 - 152, 2014/10

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

Mono-energetic neutron calibration fields have been established in the energy range from 8 keV to 19 MeV using an accelerator at FRS. In the 144, 250 and 565 keV fields, mono-energetic neutrons are produced by bombarding a LiF target with accelerated protons in order to cause $$^7$$Li(p,n)$$^7$$Be reactions. Photons mixed in these neutron fields, which are produced by other nuclear reactions, can affect the calibration results. These mixed photon dose should be evaluated. In this paper the photons produced by the nuclear reactions between neutrons and target, its supporting materials and the constructional materials of the irradiation room such as the walls, floor and ceiling. were calculated using the MCNP-ANT code. Then the ambient dose equivalent H*(10) of the photons were evaluated and compared with that of the mono-energetic neutrons.

116 (Records 1-20 displayed on this page)