Radiation exposure to the lens of the eye for Japanese nuclear power plant workers

Yokoyama, Sumi*; Tatsuzaki, Hideo*; Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Hirao, Shigekazu*; Aoki, Katsunori; Tachiki, Shuichi*; Ezaki, Iwao*; Hoshi, Katsuya; Tsujimura, Norio

Journal of Radiological Protection, 42(3), p.031504_1 - 031504_17, 2022/09

https://doi.org/10.1088/1361-6498/ac7913

In Japan, the radiation-dose limit for the lens of the eye was revised in April 2021. Consequently, for workers, the numerical values of the equivalent dose to the lens of the eye are equal to those of the effective dose. Radiation workers, radiation safety officers and licensees must comply with regulations related to radiation protection and optimize protection. The new guidelines on dose monitoring of the lens of the eye developed by the Japan Health Physics Society recommend for the dose to be estimated near the eye for accurate estimation, when the dose to the lens approaches or exceeds the management criteria. However, there is limited information regarding the non-uniform exposure of nuclear power plant workers. In this study, the dose equivalents of high-dose-rate workplaces and the personal doses of 88 workers were estimated at four Japanese commercial nuclear power plant sites (RWR: 3 units and BWR: 3 units) and the dose to the lens of the eye and the exposure situations of the workers were analyzed.

Data of radon measurement in underground facilities of Mizunami Underground Research Laboratory

Aoki, Katsunori; Yamanaka, Hiroki*; Watanabe, Kazuhiko*; Sugihara, Kozo

JAEA-Data/Code 2020-018, 45 Pages, 2021/02

JAEA-Data-Code-2020-018.pdf:4.54MB
JAEA-Data-Code-2020-018-appendix(DVD-ROM).zip:6.8MB

Mizunami Underground Research Laboratory (MIU) Project is pursued by Japan Atomic Energy Agency (JAEA) in the crystalline host rock (granite) as a part of geoscientific study of JAEA, and underground facilities of MIU are constructed down to 500m blow the ground surface. As small amount of Uranium is normally contained in granite, high concentration of radon is sometimes detected in the air of the underground facilities constructed in granitic rocks depending on their ventilation conditions. Radon concentrations in underground facilities of MIU have been measured according to the excavation progress of underground facilities or the change of ventilation system. It is recognized that the data obtained by the actual measurement of radon concentration in such underground facilities are rare and valuable. This repot summarizes the measured data from fiscal 2010 to fiscal 2020, together with the information of ventilation conditions and air temperature which affect radon concentrations in underground facilities. The variation of the equilibrium factors of radon is also examined with the actually measured data. As a result, it has been found that radon concentration in the drift is high in summer and low in winter according to the natural ventilation caused by the seasonal temperature difference between in and out of the underground facilities. Furthermore, the temporary increase in the equilibrium factor of radon in the drift at the start of ventilation is supposed to be due to the aerosol increase by the ventilation flow, such as the dust blown up.

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

https://doi.org/10.1016/j.radmeas.2020.106399

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

https://doi.org/10.1016/j.radmeas.2020.106304

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.

Calculation of equivalent dose for the lens of the eye in a positron field using EGS5

Yokoyama, Sumi*; Aoki, Katsunori

Progress in Nuclear Science and Technology (Internet), 4, p.788 - 792, 2014/04

https://doi.org/10.15669/pnst.4.788

The equivalent dose rate per positron fluence for the human eye lens is calculated using a Monte Carlo simulation code, EGS5, with two mathematical models (a computational head voxel phantom and a simple eye model). The eye lens doses for medical staff and carers as received from a radiopharmaceutical such as 18F-FDG, which is used in PET examinations, when spilled on the floor, and from positrons passing through a thin injection tube are calculated using a simple eye model. At energies less than 1 MeV, the equivalent dose for the eye lens per electron and positron fluence as calculated using the simple eye model was a maximum of three orders of magnitude lower than that for the head voxel phantom. These values for the simple eye model were equal to the calculation results obtained using the eye lens model in ICRP Publication 116 and those reported in past studies. The eye lens dose rates from the point and tube sources of 18F-FDG as calculated using our simple eye model are about 0.57 and 0.37 Sv min MBq at 5 cm, respectively. The doses at 10 cm were one-third to half of those at 5 cm.

The Spectroscopy of LX-rays emitted from transuranium element using transition edge sensor microcalorimeter

Nakamura, Keisuke; Maeda, Makoto*; Aoki, Katsunori; Yasumune, Takashi; Takasaki, Koji; Maehata, Keisuke*; Iyomoto, Naoko*; Ishibashi, Kenji*; Mitsuda, Kazuhisa*; Tanaka, Keiichi*

no journal, , 

no abstracts in English

Measurement of radon concentration and dose evaluation in the galleries at the Mizunami Underground Research Laboratory

Aoki, Katsunori; Ogura, Hideki; Kubota, Mitsuru; Tsurudome, Koji; Ikeda, Koki; Nagasaki, Yasushi; Ogata, Nobuhisa; Furuta, Sadaaki*

no journal, , 

no abstracts in English

Eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Station, 3; Evaluation of eye lens dose based on the -ray spectroscopy

Yoshitomi, Hiroshi; Tanimura, Yoshihiko; Hoshi, Katsuya; Aoki, Katsunori; Tsujimura, Norio; Yokoyama, Sumi*

no journal, , 

no abstracts in English

Eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Station, 4; Evaluation of eye lens dose based on the beta-ray spectrometry

Hoshi, Katsuya; Tsujimura, Norio; Aoki, Katsunori; Yoshitomi, Hiroshi; Tanimura, Yoshihiko; Yokoyama, Sumi*

no journal, , 

no abstracts in English

Eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Station, 2; Summary of personal dose measurement and dosimeter comparison

Ezaki, Iwao*; Aoki, Katsunori; Tatsuzaki, Hideo*; Tachiki, Shuichi*; Hirao, Shigekazu*; Yoshitomi, Hiroshi; Hoshi, Katsuya; Tanimura, Yoshihiko; Oguchi, Hiroyuki*; Tsujimura, Norio; et al.

no journal, , 

no abstracts in English