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

Design and produce two sets of multi-joint manipulator (for opening a door) against nuclear disaster and a crawler robot for opening and closing manual valves

Nishiyama, Yutaka; Iwai, Masaki; Chiba, Yusuke; Tsubaki, Hirohiko; Ono, Hayato*; Hayasaka, Toshiro*; Hanyu, Toshinori*

JAEA-Technology 2020-007, 18 Pages, 2020/09

JAEA-Technology-2020-007.pdf:2.33MB

Maintenance and Operation Section for Remote Control Equipment in Naraha Center for Remote Control Technology Development is the main part of the nuclear emergency response team of Japan Atomic Energy Agency (JAEA) in full-scale operation starts on the 1st of April, 2020. The section needs to develop equipment for JAEA nuclear emergency. Because of dealing the full-scale operation, the section designed and produced two sets of Multi-joint Manipulator or (for Opening Doors) against Nuclear Disaster in order to put them on two crawler robots in 2018 fiscal year. And the section also designed and produced a Crawler Robot for Opening and Closing Manual Valves in 2019 fiscal year. This report shows two sets of Multi-Joint Manipulator (for Opening Doors) and a Crawler Robot for Opening and Closing Manual Valves designed and produced by Maintenance and Operation Section for Remote Control Equipment in 2018 and 2019 fiscal year.

Current situations and discussions in Japan in relation to the new occupational equivalent dose limit for the lens of the eye

Yokoyama, Sumi*; Hamada, Nobuyuki*; Hayashida, Toshiyuki*; Tsujimura, Norio; Tatsuzaki, Hideo*; Kurosawa, Tadahiro*; Nabatame, Kuniaki*; Oguchi, Hiroyuki*; Ono, Kazuko*; Kawaura, Chiyo*; et al.

Journal of Radiological Protection, 37(3), p.659 - 683, 2017/09

https://doi.org/10.1088/1361-6498/aa73e8

Since the International Commission on Radiological Protection recommended reducing the occupational equivalent dose limit for the lens of the eye in 2011, there have been extensive discussions in various countries. This paper reviews the current situations in radiation protection of the ocular lens and the discussions on the potential impact of the new lens dose limit in Japan. Topics include historical changes to the lens dose limit, the current situations in occupational lens exposures (e.g., in medical workers, nuclear workers, and Fukushima nuclear power plant workers) and measurements, and the current status of biological studies and epidemiological studies on radiation cataracts. Our focus is on the situations in Japan, but we believe such information sharing will be useful in many other countries.

R&D activities of tritium technologies on Broader Approach in Phase 2-2

Isobe, Kanetsugu; Kawamura, Yoshinori; Iwai, Yasunori; Oyaizu, Makoto; Nakamura, Hirofumi; Suzuki, Takumi; Yamada, Masayuki; Edao, Yuki; Kurata, Rie; Hayashi, Takumi; et al.

Fusion Engineering and Design, 98-99, p.1792 - 1795, 2015/10

https://doi.org/10.1016/j.fusengdes.2015.06.075

Activities on Broader Approach (BA) were started in 2007 on the basis of the Agreement between the Government of Japan and the EURATOM. The period of BA activities consist of Phase1 and Phase2 dividing into Phase 2-1 (2010-2011), Phase 2-2 (2012-2013) and Phase 2-3 (2014-2016). Tritium technology was chosen as one of important R&D issues to develop DEMO plant. R&D activities of tritium technology on BA consist of four tasks. Task-1 is to prepare and maintain the tritium handling facility in Rokkasho BA site in Japan. Task 2, 3 and 4 are main R&D activities for tritium and these are focused on: Task-2) Development of tritium accountancy technology, Task-3) Development of basic tritium safety research, Task-4) Tritium durability test. R&D activities of tritium technology in Phase 2-2 were underway successfully and closed in 2013.

Investigation on degradation mechanism of ion exchange membrane immersed in highly concentrated tritiated water under the Broader Approach activities

Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko

Fusion Engineering and Design, 89(7-8), p.1534 - 1538, 2014/10

https://doi.org/10.1016/j.fusengdes.2014.02.018

The ion exchange membrane such as Nafion is a key material for electrolysis cells of the Water Detritiation System. Long-term exposure of Nafion ion exchange membrane into 1.3810Bq/kg of tritiated water was conducted at room temperature for up to 2 years. The ionic conductivity of Nafion ion exchange membrane after immersed in tritiated water was changed. The change in color of membrane from colorless to yellowish was caused by active radical reactions. Infrared Fourier transform spectrum of the membrane immersed in tritiated water revealed a small peak for bending vibration of C-H situated at 1437 cm demonstrating the formation of hydrophobic functional group in the membrane. The high-resolution solid state F NMR spectrum of the membrane after immersed in tritiated water was similar to that of membrane irradiated with -rays. From the F NMR spectrum, any distinctive degradation in the membrane structure by interaction with tritium was not measured.

Interim report of the JHPS expert committee on radiation protection of the lens of the eye, 2; The Dosimetry method for the lens of the eye of workers in Japan

Akahane, Keiichi*; Iimoto, Takeshi*; Ichiji, Takeshi*; Iwai, Satoshi*; Oguchi, Hiroyuki*; Ono, Kazuko*; Kawaura, Chiyo*; Tatsuzaki, Hideo*; Tsujimura, Norio; Hamada, Nobuyuki*; et al.

Hoken Butsuri, 49(3), p.153 - 156, 2014/09

https://doi.org/10.5453/jhps.49.153

A brief review is given of the history and methodology of external dosimetry for the lens of the eye. Under the 1989 revision to domestic radiological protection regulations, the concept on the effective dose equivalent and the dose limit to the lens of the eye (150 mSv/y) both introduced in ICRP 1977 recommendations has changed nationwide the external monitoring methodology in non-uniform exposure situations to the trunk of a radiological worker. In such situations, often created by the presence of a protective apron, the worker is required to use at least two personal dosemeters, one worn on the trunk under the apron and the other, typically, at the collar over the apron. The latter dosemeter serves the dual purpose of providing the dose profile across the trunk for improved effective dose equivalent assessment and of estimating the dose to lens of the eye. The greater or appropriate value between (10) and (0.07), given by the dosemeter, is generally used as a surrogate of (3).

Effect of cation exchange on hydrogen adsorption property of mordenite for isotope separation

Kawamura, Yoshinori; Iwai, Yasunori; Munakata, Kenzo*; Yamanishi, Toshihiko

Journal of Nuclear Materials, 442(1-3), p.S455 - S460, 2013/11

https://doi.org/10.1016/j.jnucmat.2012.11.003

Zeolite easily exchanges its cation to another. In this work, synthetic mordenite type zeolite (Na-MOR) was used as start material. And, its cation (Na) has been exchanged by Li, K, Mg and Ca. Then, adsorption capacities of H and D on them were investigated at 77 K, 159 K, 175 K and 195 K. Adsorption capacities on Li-MOR and Ca-MOR became larger than that on Na-MOR at low pressure range. Oppositely, that on K-MOR became smaller. In case of alkaline metal, cation with small atomic number may lead to large adsorption capacity.

Recent results on tritium technology in JAEA under BA program

Yamanishi, Toshihiko; Kawamura, Yoshinori; Iwai, Yasunori; Isobe, Kanetsugu

Fusion Engineering and Design, 88(9-10), p.2272 - 2275, 2013/10

https://doi.org/10.1016/j.fusengdes.2013.04.046

The multi-purpose RI equipment has been constructed at Rokkasho site in DEMO R&D building until 2011. The equipment is the first and unique facility in Japan, where tritium, RI species, and beryllium can simultaneously be used. The amounts of tritium used and stored are 3.7 TBq per day and 7.4 TBq, respectively. The material of the column of the micro gas chromatograph has been studied. The calorimeter has also been studied as a possible tritium measurement method. A set of basic data on the interaction between materials and tritium has been measured especially for pure Fe. As for the tritium behavior in the blanket materials, the tritium release after neutron irradiation was studied. As a study for the tritium durability, the endurance of ion exchange membrane has been tested by using high concentration tritium water. The data of tritium water were well consistent with those obtained by irradiation.

Characteristic of tritium release from LiTiO under D-T neutron irradiation

Edao, Yuki; Kawamura, Yoshinori; Ochiai, Kentaro; Hoshino, Tsuyoshi; Takakura, Kosuke; Ota, Masayuki; Iwai, Yasunori; Yamanishi, Toshihiko; Konno, Chikara

JAEA-Research 2012-040, 15 Pages, 2013/02

JAEA-Research-2012-040.pdf:1.8MB

Tritium generation and recovery studies on LiTiO as a solid breeding material under neutron irradiation carried out in the Fusion Neutron Source (FNS) facility. A capsule with LiTiO packed bed was put in a system which simulated an actual blanket system which built in beryllium blocks and lithium titanate ones. Estimated values of the amount of tritium generation by a numerical calculation agreed closely with experimental values. The capsule was heated up to 300C, and helium, helium with water vapor, hydrogen or hydrogen/water vapor were selected as purge gas. In the case of purge by helium added water vapor, the ratio of HTO to total tritium release was 98%. In helium with hydrogen/water vapor purge, the ratio of HTO to total tritium release was 80%, which was confirmed that HTO released by isotope exchange reaction between water vapor and tritium. In helium with hydrogen purge, the ratio of HT to total tritium release was 6070%, which was shown that HT released by isotope exchange reaction between hydrogen gas and tritium. HTO released by water generation reaction between hydrogen in purge gas and oxygen in LiTiO although water vapor was not added in purge gas. The ratio of HTO release seemed to be small under the deoxidized condition of the LiTiO surface. Tritium release behavior in the LiTiO depended on the composition of purge gas, and its chemical form was affected by the surface conditions of LiTiO.

Change in activity of catalysts for the oxidation of tritium during a fire event

Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko

Fusion Engineering and Design, 87(7-8), p.946 - 950, 2012/08

https://doi.org/10.1016/j.fusengdes.2012.02.056

The catalytic performance should be maintained in any off normal events. Fire accident is the typical off normal event. In the fusion plant, typical combustibles are evaluated to be polymeric low-halogen cables. Produced gases from burned low-halogen cable may affect the activity of catalysts for the oxidation of tritium. We experimentally demonstrated the influence of produced gases from burned low-halogen cable on the activity of catalyst using tritium gas. Our analyzed result showed that ethylene, methane and benzene were major produced gases. The activity of catalysts for the oxidation of tritium during a fire event was evaluated using two types of commercial Pt catalysts which are the hydrophilic Pt/AlO and the new type hydrophobic catalyst named TKK-H1P especially developed for the room temperature conversion of tritium to tritiated vapor. The temperature of catalytic reactor was selected to be 423 or 293 K. At 423 K, no considerable decrease in catalytic activity was observed for both catalysts even in the presence of produced gases from burned low-halogen cable. At 293K, considerable increase in catalytic activity was initially observed for both catalysts due to the effect of produced hydrogen. Then the temporary decrease was observed, however the catalytic activity was gradually recovered to be the original activity. Consequently, the irreversible decrease in activity of the catalysts during a fire event was not observed.