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-ray dust monitor for highly-concentrated airborne contaminantsSagawa, Naoki; Fujisawa, Makoto; Hosomi, Kenji; Morishita, Yuki; Takada, Chie
Hoken Butsuri (Internet), 58(3), p.135 - 140, 2023/11
Radioactivity concentrations of airborne dust are important measurements because they are used to protect workers from intakes and to assess internal exposure doses. Therefore, we developed a portable -ray dust monitor by using an ultra-thin plastic scintillator, which is designed for continuous monitoring of highly-concentrated airborne contaminants (
10
Bq/cm
, equivalent to 30 times larger than the derived air concentration of 
Sr) such as a decommissioning work in the Fukushima Daiichi Nuclear Power Plant. From the performance test results, it is evaluated that the developed portable -ray dust monitor is functional in continuous monitoring with an airborne concentration of 1 Bq/cm.
particle diameters using an alpha-particle imaging detectorMorishita, Yuki; Sagawa, Naoki; Takada, Chie; Momose, Takumaro; Takasaki, Koji
Radiation Protection Dosimetry, 199(13), p.1376 - 1383, 2023/08
Times Cited Count：0 Percentile：0.01(Environmental Sciences)It is very important to evaluate the diameters (activity median aerodynamic diameter) of Plutonium dioxide (PuO) particles for internal exposure dose evaluation. In this study, a method of evaluating PuO particle diameters using an alpha-particle imaging detector was developed. PuO particles with different diameters were modeled by Monte Carlo simulation, and the change in the shape of the energy spectrum for each particle diameter was evaluated. Two different patterns were modeled, namely, the case of 
PuO and the case of PuO (including isotopic composition of Pu). Multiple regression analysis was performed to determine the PuO particle diameter from the obtained parameters. The simulated diameters and the diameters obtained with the regression model were in good agreement. The advantage of using the alpha-particle imaging detector is to measure the alpha energy spectrum for individual particle, and this allows accurate measurement of particle diameter distribution.
Sagawa, Naoki; Izaki, Kenji; Mizuniwa, Harumi*
JAEA-Technology 2013-029, 28 Pages, 2013/11
JAEA-Technology-2013-029.pdf:3.35MB
Developed in the Mixed Oxide fuel fabrication facility, Basic handling of IP, analysis method, detection of Pu and radioactivity quantification. These are the conditions that the exposure conditions and the analysis condition are constant. However, in the case of Contamination has occurred in the workplace, contaminated samples are not only Pu. It may contain a Pb or RnTn. Then, if other work is being carried out in a room that is the operation of IP, it's difficult to darken the room. PSL is reduced when light hits the IP. In this study, we have investigated in order to upgrade radiation protection, in the case of Containing the Pb or PSL reduction by light. Additionally, regarding change of analysis condition, the analysis method was examined when the resolution was changed to 50 micro, 100 micro and 200 micro.
Shinohara, Masanori; Yanagi, Shunki; Tochio, Daisuke; Shimazaki, Yosuke; Nojiri, Naoki; Owada, Hiroyuki; Sato, Nao; Sagawa, Hiroshi; Umeda, Masayuki
JAEA-Technology 2011-029, 39 Pages, 2011/12
JAEA-Technology-2011-029.pdf:3.03MB
JAEA plans and performs the safety demonstration test using the HTTR to develop High Temperature Gas Reactor technologies. Cold test of the loss of forced cooling was conducted prior to the safety demonstration test, to check test procedure and plant behavior. Cold test consists of two phases, Phase1, 1 or 2 Vessel Cooling System (VCS) terminates, in the Phase2, all 3 Gas circulators and 1 VCS terminates. Cold test could confirm test process, and obtain data necessary to analysis and 2-dimensional horizontal sectional model analysis was verified to simulate actual measurement value.
Takasaki, Koji; Sagawa, Naoki; Kurosawa, Shigeyuki; Mizuniwa, Harumi
Journal of Nuclear Science and Technology, 48(6), p.911 - 918, 2011/06
Times Cited Count：12 Percentile：66.68(Nuclear Science & Technology)An autoradiographical method using an imaging plate (IP) was developed to analyze the plutonium contamination in the plutonium handling facility and was applied to the monitoring of the workplace in a practical uranium-plutonium mixed oxide (MOX) fuel fabrication facility. A good relationship between the photo stimulated luminescence (PSL) intensities of IP and radioactivities measured by a radiation counter was obtained by the least-square fitting, taking the fading effect into consideration. The 
-radioactivities of plutonium contamination were derived from the PSL image in this IP method, and their relative errors were evaluated from exposure time.
Sagawa, Naoki; Yamazaki, Takumi; Kurosawa, Shigeyuki*; Izaki, Kenji; Mizuniwa, Harumi; Takasaki, Koji
JAEA-Technology 2010-051, 35 Pages, 2011/03
JAEA-Technology-2010-051.pdf:1.83MB
The image analysis method using a imaging plate (IP) is recent technique, and this method can get the information of radioactivity distribution by the unit of Photo Simulated Luminescence (PSL). We have investigated the PSL images obtained by measuring some plutonium samples which are radiation protection samples in order to apply imaging plate to the radiation protection at the MOX fuel facility. Plutonium spots were extracted from the PSL image extracted by the threshold, in which about 99% of the back ground was excluded, and identified by the additional requirement that the spot size is more than 40 pixels. The average background is subtracted from PSL strength of the spot area identified as Pu, and the radioactivity of the Pu spot was evaluated by multiplying the conversion calculation that is in consideration of fading.
Tsujimura, Norio; Yoshida, Tadayoshi; Sagawa, Naoki; Shoji, Shigeru
Progress in Nuclear Science and Technology (Internet), 1, p.154 - 157, 2011/02
Takasaki, Koji; Sagawa, Naoki; Kurosawa, Shigeyuki*; Shioya, Satoshi; Suzuki, Kazunori; Horikoshi, Yoshinori; Mizuniwa, Harumi
JAEA-Technology 2008-028, 73 Pages, 2008/03
JAEA-Technology-2008-028.pdf:5.88MB
Recently, an imaging plate (IP) was developed. Pu analysis by an IP was studied in the JAEA Cooperative Research Scheme on the Nuclear Fuel Cycle, and the availability about detection of Pu and discrimination with radon progenies was shown. In order to apply these results to the radiation control, this research aims at evaluation of radioactivity, discrimination with radon progenies, and evaluation of AMAD by an IP. In the conventional autoradiography (ARG) by a ZnS and Polaroid film, Contamination of Pu can only be grasped by viewing. Since the digital data of the radiation and location is obtained by an IP, Pu can be detected quantitatively and radioactivity can be evaluated. As a result of this research, the image of alpha emitter on an IP is the same as that of the conventional ARG, and can be applied also to the ARG of beta and 
emitter. In measurement of Pu, the function of Image J (image-analysis software) was very available. Pu radioactivity was evaluated by an IP.
Mizuniwa, Harumi; Takasaki, Koji; Horikoshi, Yoshinori; Suzuki, Kazunori; Shioya, Satoshi; Sagawa, Naoki; Kurosawa, Shigeyuki*
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Yoshida, Tadayoshi; Tsujimura, Norio; Sagawa, Naoki; Shoji, Shigeru
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Sagawa, Naoki; Kurosawa, Shigeyuki*; Takasaki, Koji; Mizuniwa, Harumi
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Yamazaki, Takumi; Sagawa, Naoki; Izaki, Kenji; Mizuniwa, Harumi
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Sagawa, Naoki; Odano, Takayuki*; Morifuji, Masayuki; Izaki, Kenji; Mizuniwa, Harumi
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Morishita, Yuki; Sagawa, Naoki; Tsubaki, Hirohiko; Izaki, Kenji; Mizuniwa, Harumi
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Morishita, Yuki; Sagawa, Naoki; Suga, Takumi; Tsujimura, Norio; Yoshida, Tadayoshi; Nagai, Hiroyuki
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raysYamazaki, Takumi; Takada, Chie; Nakamura, Keisuke; Sagawa, Naoki; Hoshi, Katsuya; Nakagawa, Takahiro; Takimoto, Misaki; Tanimura, Yoshihiko*; Takahashi, Fumiaki; Momose, Takumaro; et al.
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Morishita, Yuki; Sagawa, Naoki; Suga, Takumi; Yamazaki, Takumi; Tsujimura, Norio; Yoshida, Tadayoshi; Nagai, Hiroyuki
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Suga, Takumi; Morishita, Yuki; Sagawa, Naoki; Yamazaki, Takumi; Tsujimura, Norio; Yoshida, Tadayoshi; Nagai, Hiroyuki
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Sasaki, Kazuki; Okuyama, Shun; Sagawa, Naoki; Hosomi, Kenji; Takada, Chie
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-particle detector designed for monitoring of airborne dust with high radioactivityFujisawa, Makoto; Sagawa, Naoki; Hosomi, Kenji; Morishita, Yuki; Takada, Chie
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