Quantitative estimation of exposure inhomogeneity in terms of eye lens and extremity monitoring for radiation workers in the nuclear industry

Yoshitomi, Hiroshi; Kowatari, Munehiko; Hagiwara, Masayuki*; Nagaguro, Seiji*; Nakamura, Hajime*

Radiation Protection Dosimetry, 184(2), p.179 - 188, 2019/08

https://doi.org/10.1093/rpd/ncy197

Assessment of equivalent dose of the lens of the eyes and the extremities to workers under nonhomogeneous exposure situation in nuclear and accelerator facilities by means of measurements using a phantom coupled with Monte Carlo simulation

Yoshitomi, Hiroshi; Hagiwara, Masayuki*; Kowatari, Munehiko; Nishino, Sho; Sanami, Toshiya*; Iwase, Hiroshi*

Proceedings of 14th International Congress of the International Radiation Protection Association (IRPA-14), Vol.3 (Internet), p.1188 - 1195, 2017/11

http://www.irpa.net/docs/IRPA14%20Proceedings%20Volume%203.pdf

The equivalent doses to the lens of the eye and extremities for radiation workers should be assessed properly to ensure that the dose limits are not exceeded. Recently, the following two issues has pressed demand on more appropriate evaluation of the equivalent doses of the lens of the eye and extremity. One is the new occupational dose limit for the lens of the eye the ICRP recommended. The other is growing demand on handling of highly activated materials in the maintenance works of an accelerator and contaminated materials during the decommissioning works of nuclear facility, which increases the potential exposure risk to the extremities to a wider variety of radio-nuclides. Since the points to be assessed for the exposures to the lens of the eye and the extremities are apart from the trunk, the homogeneity of the radiation fields would be significantly impact on the assessment of these equivalent doses. However, there has been no sufficient and available method to identify the nonhomogeneous situations systematically in terms of the eye lens or extremity monitoring. The goal of this study is to provide the framework to identify the nonhomogeneous exposure situations. In order to fulfil this purpose, newly proposed indices to represent the homogeneity were calculated by Monte Carlo simulation incorporated with mathematical phantom, verifying the benchmark measurements. Important parameters that significantly impact on these indices were also shown from the various trials of calculations of homogeneity indices.

Numerical analysis of organ doses delivered during computed tomography examinations using Japanese adult phantoms with the WAZA-ARI dosimetry system

Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ono, Koji*; Ban, Nobuhiko*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Yoshitake, Takayasu*; Kai, Michiaki*

Health Physics, 109(2), p.104 - 112, 2015/08

https://doi.org/10.1097/HP.0000000000000299

A dosimetry system, named WAZA-ARI, is developed to assess accurately radiation doses to persons from Computed Tomography (CT) examination patients in Japan. Organ doses were prepared to application to dose calculations in WAZA-ARI by numerical analyses using average adult Japanese human models with the Particle and Heavy Ion Transport code System (PHITS). Experimental studies clarified the radiation configuration on the table for some multi-detector row CT (MDCT) devices. Then, a source model in PHITS could specifically take into account for emissions of X-ray in each MDCT device based on the experiment results. Numerical analyses with PHITS revealed a concordance of organ doses with human body size. The organ doses by the JM phantoms were compared with data obtained using previously developed systems. In addition, the dose calculation in WAZA-ARI were verified with previously reported results by realistic NUBAS phantoms and radiation dose measurement using a physical Japanese model. The results implied that analyses using the Japanese phantoms and PHITS including source models can appropriately give organ dose data with consideration of the MDCT device and physiques of typical Japanese adults.

Development of computational dosimetry system "JCDS" for neutron capture therapy

Kumada, Hiroaki; Yamamoto, Kazuyoshi; Matsumura, Akira*; Nakagawa, Yoshinobu*

Hoshasen, 31(4), p.287 - 297, 2005/10

http://ci.nii.ac.jp/naid/10016952621

no abstracts in English

Dogleg duct streaming experiment with 14 MeV neutron source

Morimoto, Yuichi*; Ochiai, Kentaro; Nishio, Takashi*; Wada, Masayuki*; Yamauchi, Michinori*; Nishitani, Takeo

Journal of Nuclear Science and Technology, 41(Suppl.4), p.42 - 45, 2004/03

http://www.tandfonline.com/doi/abs/10.1080/00223131.2004.10875640

no abstracts in English

Evaluation of energy response of neutron rem monitor applied to high-energy accelerator facilities

Nakane, Yoshihiro; Harada, Yasunori; Sakamoto, Yukio; Oguri, Tomomi*; Yoshizawa, Michio; Takahashi, Fumiaki; Ishikura, Takeshi*; Fujimoto, Toshiaki*; Tanaka, Susumu; Sasamoto, Nobuo

JAERI-Tech 2003-011, 37 Pages, 2003/03

JAERI-Tech-2003-011.pdf:1.73MB

no abstracts in English

Conversion from tooth enamel dose to organ doses for ESR dosimetry

Takahashi, Fumiaki; Yamaguchi, Yasuhiro

Radiation Risk Assessment Workshop Proceedings, p.71 - 78, 2003/00

Conversion from tooth enamel dose to organ doses against external photon exposure were studied in order to develop a method that can retrospectively estimate organ doses by the Electron Spin Resonance (ESR) dosimetry using tooth samples. Monte Carlo calculations using EGS4 code were performed to obtain dose to tooth enamel and organ doses by using a modified MIRD-type phantom. The Electron Spin Resonance (ESR) dosimetry using tooth samples and dose measurements using thermo-luminescence dosimeters (TLDs) were also carried out to examine dose to teeth region with a realistic physical phantom. A Voxel-type phantom was constructed from CT images of the physical phantom. Monte Carlo calculations with the Voxel-type phantom were performed to verify the results of the experiments and enamel doses calculated by use of the modified MIRD-type phantom. The obtained data are to be useful for the retrospective assessment of individual dose in past exposure events by the ESR dosimetry with tooth enamel.

Analysis of absorbed dose to tooth enamel for ESR dosimetry

Takahashi, Fumiaki; Yamaguchi, Yasuhiro; Saito, Kimiaki; Iwasaki, Midori*; Miyazawa, Chuzo*; Hamada, Tatsuji*; Funabiki, Jun*

Journal of Nuclear Science and Technology, 39(Suppl.2), p.1314 - 1317, 2002/08

http://wwwndc.jaea.go.jp/nd2001/proc/pdf/2_1314.pdf

An analysis of dose to tooth enamel was carried out to develop a method that can predict the organdose and effective dose by the Electron Spin Resonance (ESR) dosimetry using teeth for external photon exposure. Absorbed dose to tooth enamel were obtained with Monte Carlo calculations using EGS4 code with a mathematical human model, which has a newly defined teeth-part. Experiments were also carried out to investigate the dose at the tooth area with a physical head phantom. The calculated doses to tooth enamel were, however, less than the measured doses with the TLDs for the case of photon incidence from the back of a human body. Then, a computational human model, called a “Voxel (Volume-pixel) type" phantom was constructed based upon a computed topography (CT) image of the physical head phantom used in the experiments.The additional Monte Carlo calculations were performed to verify the results in the experiments with the EGS4 in conjunction with user's code UCPIXEL and the Voxel type phantom.

Relations between tooth enamel dose and organ doses for the Electron Spin Resonance dosimetry against external photon exposure

Takahashi, Fumiaki; Yamaguchi, Yasuhiro; Iwasaki, Midori*; Miyazawa, Chuzo*; Hamada, Tatsuji*

Radiation Protection Dosimetry, 95(2), p.101 - 108, 2001/09

https://doi.org/10.1093/oxfordjournals.rpd.a006529

An analysis of doses to tooth enamel and to organs was carried out to develop a method that can predict the organ doses and the effective dose by the Electron Spin Resonance (ESR) dosimetry using tooth samples for external photon exposure. Absorbed dose to tooth enamel and organ doses were obtained by Monte Carlo calculations using EGS4 code in combination with a mathematical human model with a newly defined teeth-part. The calculations gave quantitative relations between tooth enamel dose and organ doses for some cases of external photon exposure. It was also found that tooth enamel dose depends more significantly on energy of incident photons than the other organ dose or the effective dose. The obtained data are to be useful for the assessment of individual dose in past exposure events by the ESR dosimetry with tooth enamel.

Analysis of dose in teeth for estimation of effective dose by the electron spin resonance (ESR) dosimetry using dental enamels

Takahashi, Fumiaki; Yamaguchi, Yasuhiro; Saito, Kimiaki; Iwasaki, Midori*; Miyazawa, Chuzo*; Hamada, Tatsuji*

KEK Proceedings 2000-20, p.48 - 55, 2000/12

no abstracts in English