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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

Evaluation of an ultra-thin plastic scintillator to detect alpha and beta particle contamination

Morishita, Yuki; Hoshi, Katsuya; Torii, Tatsuo

Nuclear Instruments and Methods in Physics Research A, 966, p.163795_1 - 163795_8, 2020/06

To date, alpha and high beta particle emitters have been detected in the reactor buildings of the Fukushima Daiichi Nuclear Power Station (FDNPS). Since the beta radiation levels in the FDNPS buildings are extremely high, a commercial beta survey meter, such as a Geiger-Muller (GM) counter, would no longer have the ability to measure the beta contamination levels. In order to solve this issue, we utilized ultra-thin plastic scintillators to increase the detection rate of alpha and beta contamination. In this study, ultra-thin plastic scintillators with varied thicknesses of 7, 22, 24, 31, 39, and 55 um were prepared. To test their sensitivity, each scintillator was optically coupled to a glass plate and a 2-in square position-sensitive photomultiplier tube, and exposed to either an alpha, beta, or gamma source. Results from alpha spectrometry show that only the 55 um-thick plastic scintillator fully absorbed the alpha particles (5.5 MeV) with a 16.7% Full Width at Half Maximum. For alpha imaging under a high beta background, the 7 um-thick plastic scintillator was found to be the best choice, with an alpha to beta ratio of 652. This plastic scintillator also had the lowest sensitivity to beta particles, measuring only 41.74 cps when exposed to a 1 MBq $$^{90}$$Sr/$$^{90}$$Y source in contact. It would therefore be possible to use the 7 um-thick plastic scintillator, to directly measure the surface contamination levels at the FDNPS site in real-time, where previous methods have fallen short. Thus, the developed detector would be a useful tool for the detection of alpha and beta contamination in the FDNPS.

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

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

A Remote continuous air monitoring system for measuring airborne alpha contamination

Morishita, Yuki; Usami, Hiroshi; Furuta, Yoshihiro; Aoki, Katsunori; Tsurudome, Koji; Hoshi, Katsuya; Torii, Tatsuo

Radiation Protection Dosimetry, 189(2), p.172 - 181, 2020/04

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

We developed a remote continuous air monitoring (RCAM) system. The RCAM system consisted of a personal air monitor and a robot. The personal air monitor (poCAMon, SARAD, Germany) had a 400 mm$$^{2}$$ ion-injected silicon detector and a membrane air filter with 25 mm-diameter. The personal air monitor provides the alpha energy spectra for any measurement time interval. Demonstration measurements were taken underground at the Mizunami Underground Research Laboratory (MIU) and at a poorly ventilated concrete building. The RCAM system was remotely operated and successfully measured the $$^{222}$$Rn progeny even though the relative humidity (RH) was almost 100%. In the measured alpha spectra, the peaks of $$^{218}$$Po (6.0 MeV alpha) and $$^{214}$$Po (7.7 MeV alpha) were clearly identified. Our developed monitor is promising for alpha dust monitoring in a high gamma-ray environment or contaminated areas where a worker cannot safely physically enter.

Journal Articles

Determination of emission rates and spectra of neutrons from $$^{241}$$Am-Li sources

Hoshi, Katsuya; Nishino, Sho; Yoshida, Tadayoshi; Tsujimura, Norio

JPS Conference Proceedings (Internet), 24, p.011020_1 - 011020_6, 2019/01

We studied the application of AmLi interrogation neutron sources, which originally deployed in non-destructive assay apparatus for nuclear safeguard, to calibration work. To determine the emission rate, the angular distribution of neutron fluence was measured by a potable long counter. The emission rate at the date of measurement (October 23rd, 2015) was determined to be 1.00$$times$$10$$^{6}$$ n/s ($$pm$$4.1% (${it k}$ = 2)).

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

Optimization of thickness of GAGG scintillator for detecting an alpha particle emitter in a field of high beta and gamma background

Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Hoshi, Katsuya; Torii, Tatsuo

Radiation Measurements, 112, p.1 - 5, 2018/05

 Times Cited Count:7 Percentile:77.16(Nuclear Science & Technology)

To detect plutonium isotopes ($$^{238}$$Pu, $$^{239}$$Pu, and $$^{240}$$Pu) in a field of high beta and $$gamma$$ background, an alpha particle detector with low beta and $$gamma$$-ray sensitivity is required. Therefore, we optimized the thickness of the GAGG scintillator for alpha particle detection in a field of high beta and $$gamma$$ background. We prepared three GAGG scintillators with thicknesses of 0.05 mm, 0.07 mm, and 0.1 mm. Each of the GAGG scintillators was coupled optically to the SiPM array, which was used as the photodetector. Alpha, beta, and $$gamma$$ rays were irradiated onto the developed alpha particle detector, and their spectra were obtained. All GAGG scintillators used in this study were not sensitive to $$gamma$$ rays with a dose rate of 1 mSv/h. The beta count of the 0.05-mm-thick GAGG was only 1/100 that of the 0.1-mm-thick GAGG. Therefore, the 0.05-mm-thick GAGG scintillator is promising from the viewpoint of detecting plutonium contamination in a field with high beta and $$gamma$$ background.

Journal Articles

Comprehensive study on the response of neutron dosimeters in various simulated workplace neutron calibration fields

Nishino, Sho; Hoshi, Katsuya; Tsujimura, Norio; Kowatari, Munehiko; Yoshida, Tadayoshi

Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1258 - 1263, 2017/11

In order to investigate how neutron dosimeters respond in the continuous neutron fields in workplaces, we performed performance tests of four widely-used neutron survey meters in various simulated workplace neutron calibration fields established in two calibration facilities (FRS and ICF) in JAEA. As a result, we found that survey meters significantly over or underestimate neutron dose in the fields which have spectral components only in the energy range below 1 MeV, while those show good performance in the fields which have spectral components in the energy range above 1 MeV.

Journal Articles

Performance of Panasonic ZP-1460 electronic personal dosemeter under exposure conditions likely to be found at Fukushima Daiichi Nuclear Power Plant

Tsujimura, Norio; Yoshida, Tadayoshi; Hoshi, Katsuya; Momose, Takumaro

JPS Conference Proceedings (Internet), 11, p.070008_1 - 070008_6, 2016/11

Journal Articles

The Evaluation of the 0.07 mm and 3 mm dose equivalent with a portable beta spectrometer

Hoshi, Katsuya; Yoshida, Tadayoshi; Tsujimura, Norio; Okada, Kazuhiko

JPS Conference Proceedings (Internet), 11, p.070009_1 - 070009_6, 2016/11

Beta spectra of various nuclide species were measured by commercially available compact spectrometer. The shape of spectra obtained from the spectrometer approximately agreed with that of theoretical spectra. The beta dose equivalent at any depths has been able to be obtained as a product of measured pulse height spectra and appropriate conversion coefficients of ICRP Publ. 74. The dose rates evaluated from the spectra were comparable to the reference dose rates of standard beta calibration sources. And, we were able to determine the dose equivalent with relative error of indication of 10% without the complicated correction.

Journal Articles

Measurement of radioactive contamination on work clothing of workers engaged in decontamination operations

Tsujimura, Norio; Yoshida, Tadayoshi; Hoshi, Katsuya

JPS Conference Proceedings (Internet), 11, p.070003_1 - 070003_7, 2016/11

Oral presentation

The Effect of room-scattered $$gamma$$ ray on the calibration of NaI(Tl) scintilation survey meter

Hoshi, Katsuya; Yoshida, Tadayoshi; Tsujimura, Norio; Ishikawa, Hisashi

no journal, , 

no abstracts in English

Oral presentation

The Effect of room-scattered $$gamma$$ ray on the calibration of survey meter

Hoshi, Katsuya; Yoshida, Tadayoshi; Tsujimura, Norio; Ishikawa, Hisashi

no journal, , 

no abstracts in English

Oral presentation

Establishment of the outdoor $$gamma$$-ray irradiation field with wide irradiation area

Yoshida, Tadayoshi; Hoshi, Katsuya; Tsuchiko, Yasuhiro*; Suto, Yudai*; Tsujimura, Norio

no journal, , 

no abstracts in English

Oral presentation

Investigations of personal dose characteristics involved Fukushima Daiichi reactor accident, 2; Desemeter characteristics

Kojima, Naomi; Hoshi, Katsuya; Yamazaki, Takumi; Takada, Chie; Takada, Masashi*

no journal, , 

no abstracts in English

Oral presentation

Investigations of personal dose characteristics involved Fukushima Daiichi reactor accident, 4; Field test, 2; Response of the personal dosemeter on the phantoms and result of a measurement of the ambient dose and the energy spectrum of $$gamma$$ rays

Yamazaki, Takumi; Takada, Chie; Nakamura, Keisuke; Sagawa, Naoki; Hoshi, Katsuya; Nakagawa, Takahiro; Takimoto, Misaki; Tanimura, Yoshihiko*; Takahashi, Fumiaki; Momose, Takumaro; et al.

no journal, , 

no abstracts in English

Oral presentation

The Effect of room-scattered $$gamma$$ ray on the calibration of survey meter

Hoshi, Katsuya

no journal, , 

no abstracts in English

Oral presentation

Estimation of radioactive surface contamination on work clothing due to soil adhesion during decontamination activities

Tsujimura, Norio; Yoshida, Tadayoshi; Hoshi, Katsuya

no journal, , 

no abstracts in English

64 (Records 1-20 displayed on this page)