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Tsujimura, Norio
JAEA-Review 2024-028, 19 Pages, 2024/07
The surface density limits currently set by Japan's regulations for radioactive surface contamination, 4 Bq/cm for -emitting radionuclides and 40 Bq/cm for /-emitting radionuclides, are based on the derived working limits studied by Dunster of the UKAEA in the 1950s and 1960s. This derived working limit was introduced into Japan's and the UK's legislation at about the same time. Since then, however, the regulatory content in Japan has remained almost unchanged, while in the UK it has been amended several times over the past few decades. The most recent UK legislation does not include specific numerical requirements for surface contamination density; therefore, nuclear operators are now taking voluntary measures such as setting their radiological control standards for surface contamination. This report provides primary reference material for discussing Japan's future regulatory framework for surface contamination density, including the historical evolution of the differences between Japan's and the UK's regulations.
Tsujimura, Norio
Hokeikyo Nyusu, (71), p.2 - 5, 2023/04
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.
Yokoyama, Sumi*; Hamada, Nobuyuki*; Tsujimura, Norio; Kunugita, Naoki*; Nishida, Kazutaka*; Ezaki, Iwao*; Kato, Masahiro*; Okubo, Hideki*
International Journal of Radiation Biology, 99(4), p.604 - 619, 2023/04
Times Cited Count:2 Percentile:25.26(Biology)In April 2011, the International Commission on Radiological Protection recommended reducing the occupational equivalent dose limit for the lens. Such a new occupational lens dose limit has thus far been implemented in many countries, and there are extensive discussions toward its regulatory implementation in other countries. In Japan, discussions in the Japan Health Physics Society (JHPS) began in April 2013 and in Radiation Council in July 2017, and the new occupational lens dose limit was implemented into regulation in April 2021. To share our experience, we have published a series of papers summarizing situations in Japan: the first paper based on information available by early 2017, and the second paper by early 2019. This paper (our third paper of this series) aims to review updated information available by mid-2022, such as regarding regulatory implementation of the new occupational lens dose limit, recent discussions by relevant ministries based on the opinion from the council, establishment process of safety and health management systems, the JHPS guidelines on lens dose monitoring and radiation safety, voluntary countermeasures of the licensees, development of lens dose calibration method, and recent studies on exposure of the lens in nuclear workers and biological effect on the lens.
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
Times Cited Count:1 Percentile:19.69(Environmental Sciences)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.
Yokoyama, Sumi*; Tsujimura, Norio; Hashimoto, Makoto; Yoshitomi, Hiroshi; Kato, Masahiro*; Kurosawa, Tadahiro*; Tatsuzaki, Hideo*; Sekiguchi, Hiroshi*; Koguchi, Yasuhiro*; Ono, Koji*; et al.
Journal of Radiation Protection and Research, 47(1), p.1 - 7, 2022/03
Background: In Japan, new regulations that revise the dose limit for the lens of the eye (the lens), operational quantities, and measurement positions for the lens dose were enforced in April 2021. Based on the international safety standards, national guidelines, the results of the Radiation Safety Research Promotion Fund of the Nuclear Regulatory Authority, and other studies, the Working Group of Radiation Protection Standardization Committee, the Japan Health Physics Society (JHPS) developed a guideline for radiation dose monitoring for the lens. Materials and Methods: The Working Group of the JHPS discussed the criteria of non-uniform exposure and the management criteria set to not exceed the dose limit for the lens. Results and Discussion: In July 2020, the JHPS guideline was published. The guideline consists of three parts: main text, explanations, and 26 questions. In the questions, the corresponding answers were prepared, and specific examples were provided to enable similar cases to be addressed. Conclusion: With the development of guideline on radiation dose monitoring of the lens, radiation managers and workers will be able to smoothly comply with revised regulations and optimise radiation protection.
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
Tsujimura, Norio; Yamazaki, Takumi; Takada, Chie
Journal of Nuclear Science and Technology, 58(1), p.40 - 44, 2021/01
Times Cited Count:3 Percentile:30.60(Nuclear Science & Technology)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
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
Times Cited Count:3 Percentile:30.60(Nuclear Science & Technology)Tsujimura, Norio
Radioisotopes, 69(8), p.253 - 261, 2020/08
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.
Hoshi, Katsuya; Yoshitomi, Hiroshi; Aoki, Katsunori; Tanimura, Yoshihiko; Tsujimura, Norio; Yokoyama, Sumi*
Radiation Measurements, 134, p.106304_1 - 106304_5, 2020/06
Times Cited Count:4 Percentile:39.72(Nuclear Science & Technology)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.
Tsujimura, Norio; Hoshi, Katsuya; Aoki, Katsunori; Yoshitomi, Hiroshi; Tanimura, Yoshihiko; Yokoyama, Sumi*
Radiation Measurements, 134, p.106305_1 - 106305_5, 2020/06
Times Cited Count:4 Percentile:39.72(Nuclear Science & Technology)Furuta, Hiroshige*; Tsujimura, Norio; Nishide, Akemi*; Kudo, Shinichi*; Saigusa, Shin*
Radiation Protection Dosimetry, 189(3), p.371 - 383, 2020/05
Times Cited Count:5 Percentile:47.80(Environmental Sciences)Tsujimura, Norio
Isotope News, (768), p.38 - 39, 2020/04
no abstracts in English
Tsujimura, Norio
Hoken Butsuri (Internet), 54(4), P. 205, 2019/12
no abstracts in English
Yokoyama, Sumi*; Hamada, Nobuyuki*; Tsujimura, Norio
International Journal of Radiation Biology, 95(8), p.1103 - 1112, 2019/08
Times Cited Count:10 Percentile:62.69(Biology)Tsujimura, Norio
Isotope News, (763), p.42 - 43, 2019/06
no abstracts in English
Tsujimura, Norio
Hoken Butsuri (Internet), 54(1), p.40 - 44, 2019/03
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.
Hoshi, Katsuya; Nishino, Sho; Yoshida, Tadayoshi; Tsujimura, Norio
JPS Conference Proceedings (Internet), 24, p.011020_1 - 011020_6, 2019/01
We studied the application of AmLi interrogation neutron sources, which originally deployed in non-destructive assay apparatus for nuclear safeguard, to calibration work. To determine the emission rate, the angular distribution of neutron fluence was measured by a potable long counter. The emission rate at the date of measurement (October 23rd, 2015) was determined to be 1.0010 n/s (4.1% ( = 2)).
Tsujimura, Norio; Yoshida, Tadayoshi; Sanada, Yukihisa
JPS Conference Proceedings (Internet), 24, p.011013_1 - 011013_6, 2019/01