40 years of TLD badge monitoring experience and operational dose quantities

Tsujimura, Norio

Hokeikyo Nyusu, (71), p.2 - 5, 2023/04

https://www.irm.or.jp/news71.pdf

The TLD badge, a personal dosimeter using a thermoluminescence dosemeter, currently in operation at the Nuclear Fuel Cycle Engineering Laboratories of the Japan Atomic Energy Agency (JAEA-NCL), was developed in collaboration with Matsushita Industrial Co., Ltd. (now Panasonic System Solutions Japan Co., Ltd.), and was put into operation in 1982. Since then, the TLD badge has been used not only at NCL but also in Japan and overseas for a long time. However, the TLD badge system will no longer be accepted for new production by the manufacturer in 2019, and maintenance and repair services for the TLD readers will cease in 2027. In addition, a performance accreditation system for personal dosimetry will be introduced in Japan, and accredited personal dosemeters will be required under the revised enforcement regulations of the RI Law (from October 2023). Given these changes in the circumstance, NCL has decided to abandon the in-house measurement service and switch to commercially available accredited personal dosemeters in the future. In this paper, the development history and design concept of the TLD badge are outlined along with the historical development of the operational quantities, and the findings obtained from more than 40 years of operational experience with the TLD badge are presented.

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.

Development of guidelines on radiation protection for the lens of the eye in Japan

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

https://irpa.net/irpa15/T3.1-O0124.pdf

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

Nuclear fallout encountered by oceanographic observation vessel Takuyo

Tsujimura, Norio

Radioisotopes, 69(8), p.253 - 261, 2020/08

https://doi.org/10.3769/radioisotopes.69.253

The Japan Coast Guard observation vessel Takuyo encountered nuclear fallout originating from a U.S. nuclear weapon test detonated at Bikini Atoll on July 12, 1958. The exposure occurred two days after the detonation when the vessel was sailing southbound, about 300 km west of the danger area set up around the test site. From a small amount of rain sampled at the beginning of a rainsquall, a gross beta radioactivity of 16 kBq/L was observed, but no total precipitation measurement was made at that time. Therefore, the total amount of gross beta activity surface deposition density was alternatively derived based on an indication of a NaI(Tl) scintillation detector placed 0.3-m above the after deck of the Takuyo. By combining the maximum measured dose rate of 3.1 Sv/h aboard with the results of Monte Carlo simulations, the surface deposition density on the Takuyo was estimated to be 2 PBq/km, about 10 times higher than the past maximum observed in Japan in 1966. The resultant effective dose to crew members was also estimated to be below 100 Sv over the entire period of the voyage.

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.

When was the maximum observation of nuclear weapon fallout?

Tsujimura, Norio

Isotope News, (768), p.38 - 39, 2020/04

https://www.jrias.or.jp/books/cat3/2020/768.html

no abstracts in English

Recent discussions toward regulatory implementation of the new occupational equivalent dose limit for the lens of the eye and related studies in Japan

Yokoyama, Sumi*; Hamada, Nobuyuki*; Tsujimura, Norio

International Journal of Radiation Biology, 95(8), p.1103 - 1112, 2019/08

https://doi.org/10.1080/09553002.2019.1605464

Review on the gross beta activity in rainwater observed throughout Japan in 1954

Tsujimura, Norio

Hoken Butsuri (Internet), 54(1), p.40 - 44, 2019/03

https://doi.org/10.5453/jhps.54.40

Rainwater containing radioactive materials originating from the USA's nuclear weapon test conducted at Bikini Atoll was observed throughout Japan in 1954. It has been reported that the maximum gross beta activity observed at that time in Kyoto was 523 pCi/mL (19,000 Bq/L). This measurement, however, focused on the gross beta activity contained in a small amount of rain sampled at the beginning of rainfall, which is different from present observations that are based on the average gross beta activity contained in rain collected during a 24-h period. As a result of reviewing and converting the 1954 data to be equivalent to current measurement, the maximum value was reduced to 50 pCi/mL (1,800 Bq/L), with a resultant surface deposition density of 310 mCi/km (11,000 MBq/km). These values are well below 1/10 of the past maximum observed a few days after China's fifth nuclear weapon test in 1966.

Testing of criticality accident alarm system detectors to pulsed radiation at TRACY

Tsujimura, Norio; Yoshida, Tadayoshi; Sanada, Yukihisa

JPS Conference Proceedings (Internet), 24, p.011013_1 - 011013_6, 2019/01

https://doi.org/10.7566/JPSCP.24.011013