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Yokoyama, Sumi*; Iwai, Satoshi*; Tsujimura, Norio; Hashimoto, Makoto; Yoshitomi, Hiroshi; Kato, Masahiro*; Kurosawa, Tadahiro*; Tatsuzaki, Hideo*; Sekiguchi, Hiroshi*; Koguchi, Yasuhiro*; et al.
Proceedings of 15th International Congress of the International Radiation Protection Association (IRPA-15) (Internet), 8 Pages, 2022/00
Ji, Y.-Y.*; Mikami, Satoshi; Hong, B. S.*; Sanada, Yukihisa; Jang, M.*; Ochi, Kotaro; Nakama, Shigeo
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Sanada, Yukihisa; Mikami, Satoshi
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Yoshimura, Kazuya
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Furuta, Takuya
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Recently polygon phantoms with tetrahedral-mesh became treatable in PHITS by implementation of a new function. Using this function, radiation transport simulation of external radiation exposure of the new ICRP mesh-type reference computational phantoms becomes possible. The function was introduced together with an original algorithm to limit number of elements and surfaces in search during the transport calculation to reduce the computational cost. Owing to this algorithm, efficient transport calculation in tetrahedral-mesh geometries was realized as good as in voxel-mesh geometries with the same number of meshes. The tetrahedral-mesh can represent complex structures such as human phantoms with a much smaller number of meshes compared to the voxel representation and thus the computational speeds of radiation transport simulation using human phantoms can be faster with tetrahedral-mesh representation. The performance of PHITS was demonstrated by a comparison of the computational time between the voxel and tetrahedral-mesh for radiation transport calculations in water and human phantoms. Benchmark studies using the ICRP mesh-type reference computational phantoms in comparison with other Monte Carlo codes such as MCNP and Geant4 were also performed.
Sato, Rina; Yoshimura, Kazuya; Sanada, Yukihisa; Sato, Tetsuro*
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Sakoda, Akihiro; Nomura, Naoki*; Naito, Wataru*; Kono, Takahiko; Kuroda, Yujiro*; Yoshida, Hiroko*
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The present study focused on radiation- or risk-associated academic societies in Japan, and collected data on experts' communication activities with the public and socially conscious activities within the societies to discuss how such experts should be in society.
Manabe, Kentaro; Matsumoto, Masaki*
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Insoluble particles containing high specific activity of cesium were found after the accident of TEPCO's Fukushima Daiichi Nuclear Power Station. It is expected that activities in the particle will not dissolve into blood or tissue fluid due to the insolubility and will move in the body as a single particulate material when the particle is inhaled. Therefore, internal doses due to the particle inhalation depend on the stochastic path of the particle in the body. An existing methodology for internal dose estimation is not designed for the case that the doses depend on the individual path. The authors developed a stochastic biokinetic method to estimate the internal doses due to the particle. This method enables to obtain a probability density function of the doses. This presentation reviews the outline of the SB method, and the topics and ongoing tasks regarding internal dose estimation for intake of insoluble particles.
Hirouchi, Jun; Takahara, Shogo; Komagamine, Hiroshi*; Kato, Nobuyuki*; Matsui, Yasuto*; Yoneda, Minoru*
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Sheltering is one of the countermeasures for protection against radiation exposures in nuclear accidents. The effectiveness of sheltering is often expressed by the reduction factor, that is the ratio of the indoor to the outdoor cumulative radioactivity concentrations or doses. The indoor concentration is mainly controlled by the air exchange rate, penetration factor, and indoor deposition rate. The penetration factor and indoor deposition rate depend on the surface and opening materials. We investigated experimentally these parameters of I
and particles. The experiment was performed in two apartment houses, three single-family houses, and chambers. The obtained penetration factor ranged 0.3 
1 for particles of 0.3 1 
m and 0.1 0.6 for I depending on the air exchange rate. The indoor deposition rate for a house room ranged 0.007 0.2 h
for particles of 0.31 m and 0.21.5 h for I depending on floor materials.
Morishita, Yuki; Izaki, Kenji; Kaneko, Junichi*; Higuchi, Mikio*; Tamura, Ken; Usami, Hiroshi; Kikuchi, Hiroyuki*; Utsugi, Wataru*; Takahira, Shiro*; Torii, Tatsuo
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We have developed new alpha particle detectors for detecting the alpha contaminations accurately and instantaneously: alpha imaging detectors and alpha dust monitors. For the development of the alpha imaging detector, we used a thin cerium-doped Gd
(Ga,Al)
O
(Ce: GAGG) scintillator and silicon photomultipliers (SiPMs). The thin GAGG scintillator was optically coupled to a light-guide and the SiPMs for the detector fabrication. The detector showed a good energy resolution for 5.5 MeV alpha particles (13 % at the full width at half maximum (FWHM)). The detector is capable of capturing two-dimensional alpha images. This detector also has the advantage of its compact size, which enables to measure the alpha contaminations in narrow spaces. We demonstrated the actual measurement of smear samples obtained from the Fukushima Daiichi Nuclear Power Station using the developed imaging detector. Commercial alpha dust monitors with a silicon surface barrier detector (SSBD) operating at some nuclear facilities frequently produced false alarms due to environmental conditions such as humidity. For the development of the alpha dust monitor, we used a cerium-doped GdSiO
(GPS) scintillator plate and a photomultiplier tube (PMT). The energy resolution for 5.5-MeV alpha particles was 12% FWHM. The count-rate of the radon progeny decreased by 77% with applying energy discrimination. The alpha dust monitor was capable of conducting alpha-particle spectroscopy even though the GPS scintillator got wet. The alpha dust monitor is an ideal choice for in places lacking temperature and humidity controls. In the presentation at the IRPA 15 conference, we will present the developments and measurement results of these alpha detectors.
Sato, Yuki
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