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.

Lens dosimetry study in Sr+Y beta field; Full-face mask respirator shielding and dosemeter positioning

Tsujimura, Norio; Hoshi, Katsuya; Yamazaki, Takumi; Momose, Takumaro; Aoki, Katsunori; Yoshitomi, Hiroshi; Tanimura, Yoshihiko; Yokoyama, Sumi*

KEK Proceedings 2020-5, p.21 - 28, 2020/11

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

https://doi.org/10.1016/j.radmeas.2020.106305

Study to improve recriticality evaluation methodology after severe accident (Joint research)

Kugo, Teruhiko; Ishikawa, Makoto; Nagaya, Yasunobu; Yokoyama, Kenji; Fukaya, Yuji; Maruyama, Hiromi*; Ishii, Yoshihiko*; Fujimura, Koji*; Kondo, Takao*; Minato, Hirokazu*; et al.

JAEA-Research 2013-046, 53 Pages, 2014/03

JAEA-Research-2013-046.pdf:4.42MB

The present report summarizes the results of a 2-year cooperative study between JAEA and Hitachi-GE in order to contribute to the settlement of the Fukushima-Daiichi Nuclear Power Plants which suffered from the severe accident on March 2011. In the present study, the possible scenarios to reach the recriticality events in Fukushima-Daiichi were investigated first. Then, the analytical methodology to evaluate the time-dependent recriticality events has been developed by modelling the reactivity insertion rate and the possible feedback according to the recriticality scenarios identified in the first step. The methodology developed here has been equipped as a transient simulation tool, PORCAS, which is operated on a multi-purpose platform for reactor analysis, MARBLE. Finally, the radiation exposure rates by the postulated recriticality events in Fukushima-Daiichi were approximately evaluated to estimate the impact to the public environment.

A Study of defects in electron- and ion-irradiated ZrCuAl bulk glassy alloy using positron annihilation techniques

Hori, Fuminobu*; Onodera, Naoto*; Fukumoto, Yuka*; Ishii, Akito*; Iwase, Akihiro*; Kawasuso, Atsuo; Yabuuchi, Atsushi; Maekawa, Masaki; Yokoyama, Yoshihiko*

Journal of Physics; Conference Series, 262, p.012025_1 - 012025_4, 2011/01

https://doi.org/10.1088/1742-6596/262/1/012025

Free volume changes in ZrCuAl bulk glassy alloys irradiated by 200 and 2.5 MeV Xe ions, 180 keV He ions, and 2 MeV electrons were investigated at room temperature using positron annihilation techniques. X-ray diffraction revealed that no crystallization took place in any of the irradiated sample. The positron lifetime increased only after electron and 180 keV He irradiation. This indicates that the radiation has increased the open volume size (free volume). On the other hand, the positron lifetime was decreased by irradiation with heavy Xe-ions at either energy of 2.5 or 200 MeV. It is conceivable that the difference in behavior can be attributed to the difference in displacements per radiation particle (dpp), because the dpp estimated for 2 MeV electrons and 180 keV He ions is three or more orders of magnitude less than that for heavy Xe ions. We found that the radiation effect in ZrCuAl bulk glassy alloy is dependent on the displacement per radiation particle.

Dynamics of ion internal transport barrier in LHD heliotron and JT-60U tokamak plasmas

Ida, Katsumi*; Sakamoto, Yoshiteru; Yoshinuma, Mikiro*; Takenaga, Hidenobu; Nagaoka, Kenichi*; Hayashi, Nobuhiko; Oyama, Naoyuki; Osakabe, Masaki*; Yokoyama, Masayuki*; Funaba, Hisamichi*; et al.

Nuclear Fusion, 49(9), p.095024_1 - 095024_9, 2009/09

https://doi.org/10.1088/0029-5515/49/9/095024

Dynamics of ion internal transport barrier (ITB) formation and impurity transport both in the Large Helical Device (LHD) heliotron and JT-60U tokamak are described. Significant differences between heliotron and tokamak plasmas are observed. The location of the ITB moves outward during the ITB formation regardless of the sign of magnetic shear in JT-60U and the ITB becomes more localized in the plasma with negative magnetic shear. In LHD, the low Te/Ti ratio ( 1) of the target plasma for the high power heating is found to be necessary condition to achieve the ITB plasma and the ITB location tends to expand outward or inward depending on the condition of the target plasmas. Associated with the formation of ITB, the carbon density tends to be peaked due to inward convection in JT-60U, while the carbon density becomes hollow due to outward convection in LHD. The outward convection observed in LHD contradicts the prediction by neoclassical theory.

Eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Station, 5; Photon response of eye lens dosemeters on head phantom

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

no journal, , 

no abstracts in English

Eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Station, 1; Outline of the research and results of dose measurement for the workers

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

no journal, , 

no abstracts in English

Study of eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Station, 2; Relationship of the personal dosimetry obtained from phantom experiments and workers

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

no journal, , 

no abstracts in English

Evaluation of eye lens dose in non-uniform scattered radiation fields

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

no journal, , 

no abstracts in English

Yakedake Nakao tephra; An Attempt to use the local tephra as a Late Holocene age marker for the southern part of the Northern Japan Alps

Nishio, Gaku*; Kagami, Saya; Yokoyama, Tatsunori; Kariya, Yoshihiko*; Kojima, Satoru*

no journal, , 

We attempt to use local tephra derived from nearby volcanoes as an age marker. The Kamikochi area in the southern part of the Northern Alps is strongly affected by the Yakedake volcano. We prepared distinctive tephras, (1) one sample of glassy volcanic ash in hand auger boring cores drilled at the near-shore Kinugasanoike Pond, about 4.7 km northeast of Mt. Yakedake and (2) two samples of glassy volcanic ash in the Nakao pyroclastic flow deposites, which is considered to be a product of the last magmatic eruption about 2,300 years ago, distributed about 1.5 km north-northwest of Mt. Yakedake. We investigated the clast composition of these tephras and the chemical composition and refractive index of volcanic glass. Approximately 70% of the clasts were volcanic glasses, and most of them were vesicular and blocky types. These glasses were characterized by high SiO, KO, NaO and low AlO, FeO, which were clearly distinguishable from the volcanic glasses in Quaternary widespread tephras. The refractive indices of 30 volcanic glasses for each tephra were 1.4958-1.5011 with a peak in the range of 1.497 to 1.499. The results of this study indicate the tephra from Kinugasanoike Pond were erupted from Mt. Yakedake about 2,300 years ago. Therefore, the tephra with the above characteristics can be used as a useful age marker for the southern part of the Northern Alps about 2,300 years ago.