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Journal Articles

A Phoswich alpha/beta detector for monitoring in the site of Fukushima Daiichi Nuclear Power Station

Morishita, Yuki; Takasaki, Koji; Kitayama, Yoshiharu; Tagawa, Akihiro; Shibata, Takuya; Hoshi, Katsuya; Kaneko, Junichi*; Higuchi, Mikio*; Oura, Masatoshi*

Radiation Measurements, 160, p.106896_1 - 106896_10, 2023/01

 Times Cited Count:0

This study proposes a newly developed phoswich alpha/beta detector that can discriminate alpha and beta particles emitted from the alpha and beta contaminations in the FDNPS site. The phoswich alpha/beta detector is made up of two layers of scintillators that detect alpha and beta particles. The pulse shape discrimination (PSD) method was used to detect alpha particles in high beta particle and high gamma-ray (comparable to gamma-ray dose rate near the FDNPS reactor building) environments. Due to a 23.3% full width at half maximum (FWHM) energy resolution for alpha particles, the detector can be used to distinguish between nuclear fuel materials such as plutonium and its radon progeny (Po-214). Moreover, the detector could distinguish alpha particles from $$^{137}$$Cs gamma rays with a dose rate background up to 9.0 mSv/h. It is the first to demonstrate that the developed phoswich detector can be used to discriminate and measure alpha and beta particles of the actual contaminated FDNPS samples.

Journal Articles

3D position and radioactivity estimation of radiation source by a simple directional radiation detector combined with structure from motion

Sato, Yuki; Minemoto, Kojiro*; Nemoto, Makoto*

Radiation Measurements, 142, p.106557_1 - 106557_6, 2021/03

 Times Cited Count:2 Percentile:53.86(Nuclear Science & Technology)

Journal Articles

Development of an alpha- and beta-imaging detector using a thin-stilbene plate for radon-222 progeny measurements

Morishita, Yuki

Radiation Measurements, 140, p.106511_1 - 106511_7, 2021/01

 Times Cited Count:1 Percentile:30.57(Nuclear Science & Technology)

Radon-222 ($$^{222}$$Rn) is a naturally-occurring radioactive gas, and the measurement of this isotope and its progeny is of interest from the viewpoint of protection against internal exposure. We have developed a new alpha beta-imaging detector combined with a waveform digitizer capable of imaging alpha- and beta-particle locations simultaneously. This detector is used for $$^{222}$$Rn -progeny measurements. The thin-stilbene plate was optically coupled to a position-sensitive photomultiplier tube (PSPMT), and the analog signals from the PSPMT were transferred in parallel to the waveform digitizer. For 5.5-MeV alpha particles, the detection efficiency was 97.2% for 2$$pi$$ steradians, and the energy resolution was 21.6% full width at half maximum (FWHM). The imaging detector was able to discriminate between alpha and beta particles via the pulse-shape-discrimination (PSD) technique, as well as being capable of alpha- and beta-particle imaging. When measuring the $$^{222}$$Rn progeny, both $$^{214}$$Bi and $$^{214}$$Po are imaged simultaneously, and a correlation is found between the positions of $$^{214}$$Bi and $$^{214}$$Po. The developed detector will be useful as a $$^{222}$$Rn detector and in alpha-continuous-air monitoring for nuclear-fuel facilities.

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:1 Percentile:17.77(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:17.77(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

Radon measurements with a compact, organic-scintillator-based alpha/beta spectrometer

Morishita, Yuki; Ye, Y.*; Mata, L.*; Pozzi, S. A.*; Kearfott, K. J.*

Radiation Measurements, 137, p.106428_1 - 106428_7, 2020/09

 Times Cited Count:4 Percentile:58.08(Nuclear Science & Technology)

We have developed a compact, organic-scintillator-based alpha/beta spectrometer for radon measurements and have characterized it using a unique, small radon chamber. The spectrometer is composed of a through-silicon via (TSV) silicon photomultiplier (or SiPM) and a 6 mm $$times$$ 6 mm $$times$$ 6 mm stilbene crystal cube. Analog signals from the SiPM are sent to a digitizer. The detector is housed in a light-tight box, with a stacked air filter installed in one side of the box to enable $$^{222}$$Rn gas to diffuse to the inside. We conducted one experiment with the spectrometer and an AlphaGUARD detector placed in a basement at the University of Michigan, and we conducted other experiments with both detectors placed in a small radon chamber together with $$^{226}$$Ra sources. By applying a pulse-shape-discrimination technique, we were able to separate the alpha and beta spectra simultaneously and clearly and to measure them quantitatively. We found two peaks in the measured alpha spectrum: a lower-energy peak due to $$^{218}$$Po and a higher-energy peak due to $$^{214}$$Po. We found a linear relation between the radon concentration y from AlphaGUARD and the counting rates from the stilbene-SiPM detector. The alpha/beta spectrometer is less than 10 mm thick, and we expect that it will be easy to increase the sensitivity with future device construction. Thus, this compact, organic-scintillator-based alpha/beta spectrometer shows promise for use in novel radon-detection systems.

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:47.69(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:3 Percentile:47.69(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:3 Percentile:47.69(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

Investigation of using a long-life electronic personal dosimeter for monitoring aviation doses of frequent flyers

Yasuda, Hiroshi*; Yajima, Kazuaki*; Sato, Tatsuhiko

Radiation Measurements, 134, p.106309_1 - 106309_4, 2020/06

 Times Cited Count:3 Percentile:47.69(Nuclear Science & Technology)

We have investigated an application of a recently developed electronic personal dosimeter (D-Shuttle) for aviation dosimetry. As results of measurements in four long-haul flights between Japan and Germany, the D-Shuttle indicated values were in the range of 25 to 30% of the total H$$^{*}$$(10) values estimated by a route-dose calculations program JISCARD EX. Though we need more measurements and analyses under different flight conditions to conclude, according to these results obtained so far, it would be possible to perform monitoring of the annual aviation doses of frequent flyers by using D-Shuttle on an individual basis.

Journal Articles

External exposure dose estimation by electron spin resonance technique for wild Japanese macaque captured in Fukushima Prefecture

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Mitsuyasu, Yusuke*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; Osaka, Ken*; et al.

Radiation Measurements, 134, p.106315_1 - 106315_4, 2020/06

 Times Cited Count:4 Percentile:33.86(Nuclear Science & Technology)

The relationship between the CO$$_{2}$$ radical intensity and the absorbed dose (dose response curve) of tooth enamel of Japanese macaque was observed by electron spin resonance and the detection limit of our system was estimated to be 33.5 mGy, which is comparable to the detection limit for human molar teeth. Using the dose response curve, external exposure dose for seven wild Japanese macaques captured in Fukushima prefecture were examined. The results suggest that the external exposure dose for the wild Japanese macaques were ranged between 45 mGy to 300 mGy.

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:58.08(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

Verification of dose estimation of Auger electrons emitted from Cu-64 using a combination of FNTD measurements and Monte Carlo simulations

Kusumoto, Tamon*; Matsuya, Yusuke; Baba, Kentaro*; Ogawara, Ryo*; Akselrod, M. S.*; Harrison, J.*; Fomenko, V.*; Kai, Takeshi; Ishikawa, Masayori*; Hasegawa, Sumitaka*; et al.

Radiation Measurements, 132, p.106256_1 - 106256_4, 2020/03

 Times Cited Count:4 Percentile:58.08(Nuclear Science & Technology)

Internal radiation therapy with Cu-64 concentrates energy deposition in tumor cells by virtue of released Auger electrons with low energy. In our previous study, we have attached the solutions at the surface of Fluorescent Nuclear Track Detector (FNTD) and succeeded in measuring the absorbed doses of Auger electrons registered in FNTD. However, because there are several types of radiation emitted from the source, i.e., beta rays, positron etc., the contribution degree of Auger electron to energy concentration remain uncertain. In this study, we quantitatively analyzed the spatial dose distribution in the FNTD based on Monte Carlo simulation with PHITS and GEANT4, and evaluated high dose deposited by Auger electrons. The dose distribution calculated by the PHITS code is exactly equivalent to that by Geant4. Also, the simulations are well agreement with experimental results. If the contribution of Auger electrons is ignored, the significantly high absorbed dose proximal to the source is not properly reduced. These findings demonstrate that Auger electrons work very effectively to kill cancer cells proximal to Cu-64 source while minimizing damage effects on normal cells distal to the source.

Journal Articles

Development of an alpha dust monitor using a GPS scintillator plate

Morishita, Yuki; Kaneko, Junichi*; Higuchi, Mikio*; Izaki, Kenji; Yajima, Tatsuo*; Matsuura, Mitsugu*; Tamura, Ken; Torii, Tatsuo

Radiation Measurements, 122, p.115 - 120, 2019/03

 Times Cited Count:7 Percentile:65.49(Nuclear Science & Technology)

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:12 Percentile:80.55(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

Flexible alpha camera for detecting plutonium contamination

Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Nemoto, Norio

Radiation Measurements, 103, p.33 - 38, 2017/08

 Times Cited Count:13 Percentile:82.55(Nuclear Science & Technology)

Nuclear fuel materials, such as uranium and plutonium (Pu), are handled at nuclear fuel facilities. There are a contamination source of Pu in tight spaces that cannot be directly measured by a ZnS(Ag) scintillation detector, such as interspace between a glovebox window and a platform, pipe flange, port cover of vinyl bag, and filter interspaces. Therefore, we developed a new imaging detector called a flexible alpha camera that enables to identify the Pu contamination for tight spaces at work sites. The thickness of the flexible alpha camera was only $$sim$$1/5 of the ZnS(Ag) scintillation detector, and its efficiency for 4-pi direction was 42.7% for 5.5-MeV alpha particles. Minimal detectable activity (MDA) was 0.014 Bq. Four types of PuO$$_{2}$$ sample, removed from a duct, Bag-In/Bag-Out port, glovebox glove, and vinyl sheet, were measured by the flexible alpha camera and the PuO$$_{2}$$ particle was automatically identified. Using the flexible alpha camera, the Pu contamination source can be quickly detected, preventing the spread of contamination.

Journal Articles

An Approach to discriminatively determine thoron and radon emanation rates for a granular material with a scintillation cell

Sakoda, Akihiro; Meisenberg, O.*; Tschiersch, J.*

Radiation Measurements, 89, p.8 - 13, 2016/06

 Times Cited Count:2 Percentile:21.88(Nuclear Science & Technology)

In the present study, the methodology for the discriminative determination of thoron and radon emanation rates from a granular material has been examined using a flow-through scintillation cell and so-called sandwich sample. The mathematical model was developed to differentiate total alpha counts into thoron- and radon-associated counts. This method was experimentally validated, and then the detection limits and uncertainties were evaluated to characterize this method. It was concluded that the present method is advantageous to a sample that has much higher $$^{226}$$Ra activity than $$^{224}$$Ra if the emanation fractions are similar between thoron and radon.

Journal Articles

Behavior of radon progeny produced in a scintillation cell in the flow-through condition

Sakoda, Akihiro; Meisenberg, O.*; Tschiersch, J.*

Radiation Measurements, 77, p.41 - 45, 2015/06

 Times Cited Count:6 Percentile:49.32(Nuclear Science & Technology)

When a scintillation cell is used for radon measurement, detection efficiencies for individual alpha emitters ($$^{222}$$Rn, $$^{218}$$Po and $$^{214}$$Po) are required depending on the methods of data analysis. The present study describes an attempt to obtain an empirical parameter which is necessary to calculate their individual detection efficiencies in the flow-through cell: the fraction of the progeny generated in the cell which is deposited onto the wall. As a result, an empirical formula was acquired to estimate the deposition fraction of $$^{218}$$Po as a function of flow rate. This result is helpful in understanding the characteristics of the scintillation cell. The empirical formula derived in this study can also be applied to predicting the behavior of thoron progeny ($$^{212}$$Pb and its progeny) in continuous thoron measurements with the flow-through scintillation cell.

Journal Articles

Comparison of Bonner Sphere responses calculated by different Monte Carlo codes at energies between 1 MeV and 1 GeV; Potential impact on neutron dosimetry at energies higher than 20 MeV

R$"u$hm, W.*; Mares, V.*; Pioch, C.*; Agosteo, S.*; Endo, Akira; Ferrarini, M.*; Rakhno, I.*; Rollet, S.*; Satoh, Daiki; Vincke, H.*

Radiation Measurements, 67, p.24 - 34, 2014/08

 Times Cited Count:15 Percentile:77.71(Nuclear Science & Technology)

In order to investigate the impact of the difference of the transport code on the response calculation of Bonner Sphere, EURADOS (European Radiation Dosimetry Group) initiated an exercise where six groups having experience in neutron transport calculations with the MC codes (MCNP, MCNPX, FLUKA, PHITS, MARS, or GEANT4) calculated the responses of a bare $$^{3}$$He proportional counter, a $$^{3}$$He proportional counter embedded in the middle of a 9 inch polyethylene sphere, and a $$^{3}$$He proportional counter centred in a 9 inch polyethylene sphere containing a lead shell, at neutron energies of 1, 10, 100, and 1,000 MeV.

44 (Records 1-20 displayed on this page)