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JAEA Reports

Decommissioning of the Plutonium Research Building No.1 (Plan and Present Status)

Komuro, Michiyasu; Kanazawa, Hiroyuki; Kokusen, Junya; Shimizu, Osamu; Honda, Junichi; Harada, Katsuya; Otobe, Haruyoshi; Nakada, Masami; Inagawa, Jun

JAEA-Technology 2021-042, 197 Pages, 2022/03

JAEA-Technology-2021-042.pdf:16.87MB

Plutonium Research Building No.1 was constructed in 1960 for the purpose of establishing plutonium handling technology and studying its basic physical properties. Radiochemical research, physicochemical research and analytical chemistry regarding solutions and solid plutonium compounds had been doing for the research program in Japan Atomic Energy Agency (JAEA). In 1964, the laboratory building was expanded and started the researching plutonium-uranium mixed fuel and reprocessing of plutonium-based fuel, playing an advanced role in plutonium-related research in Japan. Since then, the research target has been expanded to include transplutonium elements, and it has functioned as a basic research facility for actinides. The laboratory is constructed by concrete structure and it has the second floor, equipped with 15 glove boxes and 4 chemical hoods. Plutonium Research Building No.1 was decided as one of the facilities to be decommissioned by Japan Atomic Energy Agency Reform Plan in September 2014. So far, the contamination survey of the radioactive materials in the controlled area, the decontamination of glove boxes, and the consideration of the equipment dismantling procedure have been performed as planned. The radioisotope and nuclear fuel materials used in the facility have been transfer to the other facilities in JAEA. The decommissioning of the facility is proceeding with the goal of completing by decommissioning the radiation controlled area in 2026. In this report, the details of the decommissioning plan and the past achievements are reported with the several data.

JAEA Reports

Carrying-out of whole nuclear fuel materials in Plutonium Research Building No.1

Inagawa, Jun; Kitatsuji, Yoshihiro; Otobe, Haruyoshi; Nakada, Masami; Takano, Masahide; Akie, Hiroshi; Shimizu, Osamu; Komuro, Michiyasu; Oura, Hirofumi*; Nagai, Isao*; et al.

JAEA-Technology 2021-001, 144 Pages, 2021/08

JAEA-Technology-2021-001.pdf:12.98MB

Plutonium Research Building No.1 (Pu1) was qualified as a facility to decommission, and preparatory operations for decommission were worked by the research groups users and the facility managers of Pu1. The operation of transportation of whole nuclear materials in Pu1 to Back-end Cycle Key Element Research Facility (BECKY) completed at Dec. 2020. In the operation included evaluation of criticality safety for changing permission of the license for use nuclear fuel materials in BECKY, cask of the transportation, the registration request of the cask at the institute, the test transportation, formulation of plan for whole nuclear materials transportation, and the main transportation. This report circumstantially shows all of those process to help prospective decommission.

Journal Articles

Design loads and structural member modelling to shock-resistant design of buildings

Ikawa, Nozomu*; Mukai, Yoichi*; Nishida, Akemi; Hamamoto, Takuji*; Kano, Toshiya*; Ota, Toshiro*; Nakamura, Naohiro*; Komuro, Masato*; Takeuchi, Masato*

Proceedings of 12th International Conference on Shock and Impact Loads on Structures (SI 2017) (USB Flash Drive), p.259 - 268, 2017/06

Accidental actions on building structures involve impact and explosion loads. The design loads due to impact are determined by experiment data, impact simulation and energetics approach. These loads are presented in the form of load-time (F-t) curves caused by collision and explosion. It is assumed that the structure is rigid and immovable and that impacting body absorbs all the energy (i.e., hard impact condition is supposed), because this assumption gives conservative results in general. Responses of individual structural members directly-subjected to an impulsive load are evaluated. These responses are classified into three types; impulsive response, dynamic response, and quasi-static response. The maximum responses are basically estimated by direct integration method with a single-degree-of-freedom (SDOF) model. The procedure of the SDOF modelling based on the classification of types of members and failure modes is proposed in AIJ guideline.

Journal Articles

Criteria for performance evaluation and numerical verification to shock-resistant design of buildings

Nishida, Akemi; Mukai, Yoichi*; Hamamoto, Takuji*; Kushibe, Atsumichi*; Komuro, Masato*; Ohashi, Yasuhiro*; Obi, Hirotoshi*; Tsubota, Haruji

Proceedings of 12th International Conference on Shock and Impact Loads on Structures (SI 2017) (USB Flash Drive), p.379 - 388, 2017/06

Some design examples are presented to evaluate the shock-resistant performance of target buildings to confirm the applicability of the design criteria of AIJ guideline. Dynamic analyses are performed using SDOF model of an individual member on which an impulsive load is acting. Furthermore, analyses are performed using finite element model for the same member, and the results are compared to the results of the corresponding SDOF model for validation. Frame building structure model which is supposed to be located at the corner of a crossroad is investigated as an example. Dynamic responses and the corresponding damage states are illustrated for this building subjected to shock loads due to road vehicle crashes. As a non-structure member case, examples of window glass destruction subjected to internal and external gas explosions are presented.

Journal Articles

Design examples

Nishida, Akemi; Ohashi, Yasuhiro*; Obi, Hirotoshi*; Takeuchi, Yoshitaka*; Kano, Toshiya*; Ryuzaki, Hibiki*; Ota, Toshiro*; Kishi, Tokumitsu*; Komuro, Masato*; Nakamura, Naohiro*

Kenchikubutsu No Taishogeki Sekkei No Kangaekata, p.161 - 202, 2015/01

Though design guidelines for earthquake and wind loads are specified for buildings, the guideline for impulsive load as explosion and impact is not specified yet in architectural field. This document corresponds to Chapter 8 of the book titled "Introduction to Shock-Resistant Design of Buildings" which made towards the impact design guideline. Some design examples are presented to illustrate the applicability of the tentative guideline for impulsive loads. Two buildings - a steel frame and a reinforced concrete frame building structures - located at the corner of a crossroads are selected. Dynamic responses and the corresponding damage states are illustrated for the cases of two buildings subjected to impact loads due to road vehicle crashes, internal and external explosions. The idea has been shown in this document are those that can be applied to nuclear facilities.

JAEA Reports

Disassembly of JT-60 tokamak device and ancillary facilities for JT-60 tokamak

Okano, Fuminori; Ichige, Hisashi; Miyo, Yasuhiko; Kaminaga, Atsushi; Sasajima, Tadayuki; Nishiyama, Tomokazu; Yagyu, Junichi; Ishige, Yoichi; Suzuki, Hiroaki; Komuro, Kenichi; et al.

JAEA-Technology 2014-003, 125 Pages, 2014/03

JAEA-Technology-2014-003.pdf:13.32MB

The disassembly of JT-60 tokamak device and its peripheral equipments, where the total weight was about 5400 tons, started in 2009 and accomplished in October 2012. This disassembly was required process for JT-60SA project, which is the Satellite Tokamak project under Japan-EU international corroboration to modify the JT-60 to the superconducting tokamak. This work was the first experience of disassembling a large radioactive fusion device based on Radiation Hazard Prevention Act in Japan. The cutting was one of the main problems in this disassembly, such as to cut the wielded parts together with toroidal field coils, and to cut the vacuum vessel into two. After solving these problems, the disassembly completed without disaster and accident. This report presents the outline of the JT-60 disassembly, especially tokamak device and ancillary facilities for tokamak device.

JAEA Reports

Disassembly of JT-60 tokamak device

Okano, Fuminori; Ikeda, Yoshitaka; Sakasai, Akira; Hanada, Masaya; Ichige, Hisashi; Miyo, Yasuhiko; Kaminaga, Atsushi; Sasajima, Tadayuki; Nishiyama, Tomokazu; Yagyu, Junichi; et al.

JAEA-Technology 2013-031, 42 Pages, 2013/11

JAEA-Technology-2013-031.pdf:18.1MB

The disassembly of JT-60 tokamak device and its peripheral equipments, where the total weight was about 6200 tons, started in 2009 and accomplished in October 2012. This disassembly was required process for JT-60SA project, which is the Satellite Tokamak project under Japan-EU international corroboration to modify the JT-60 to the superconducting tokamak. This work was the first experience of disassembling a large radioactive fusion device based on Radiation Hazard Prevention Act in Japan. The cutting was one of the main problems in this disassembly, such as to cut the wielded parts together with toroidal field coils, and to cut the vacuum vessel into two. After solving these problems, the disassembly completed without disaster and accident. This report presents the outline of the JT-60 disassembly, especially tokamak device.

JAEA Reports

Data on plutonium sorption onto rock; Results of the experiment for data on plutonium sorption onto tuff under conditions of reducing and of presence of nitrate

Suguro, Toshiyasu; Nishikawa, Yoshiaki*; Komuro, Takashi*; Kagawa, Akio; Kashiwazaki, Hiroshi; Yamada, Kazuo

JAEA-Technology 2007-058, 20 Pages, 2007/11

JAEA-Technology-2007-058.pdf:3.26MB

For safety assessment of TRU waste disposal, data on sorption data of plutonium on Tuff have been obtained by a static batch-type experiment. Because the repository condition will be reducing and be affected by considerable amount of nitrate in waste, the authors carried out the experiments using Tuff under the reducing (Na $_{2}$ S $_{2}$ O $_{4}$ as added as reductant) and anoxic condition (O $_{2}$ 1 ppm) and solution of 0 to 0.5 M NaNO $_{3}$ . The experimental results suggest that distribution coefficient (Kd) ranges 0.2 to 0.7 m $^{3}$ kg $^{-1}$ in case of L/S=0.1 m $^{3}$ kg $^{-1}$ . Similarly the Kd ranges, 1 to 7 m $^{3}$ kg $^{-1}$ at L/S=1 m $^{3}$ kg $^{-1}$ . However, almost samples of the solution after experiments were plutonium solubility less than detection limit(10 $^{-13}$ mol/dm $^{3}$ ) of alpha spectrometer. The reason, it is guessed plutonium coprecipitation with calcium hydroxide, because experiments using saturated calcium hydroxide in the liquid.

Journal Articles

Positronium formation in fused quartz; Experimental evidence of delayed formation

Komuro, Yo; Hirade, Tetsuya; Suzuki, Ryoichi*; Odaira, Toshiyuki*; Muramatsu, Makoto*

Radiation Physics and Chemistry, 76(2), p.330 - 332, 2007/02

https://doi.org/10.1016/j.radphyschem.2006.03.062

Times Cited Count：3 Percentile：25.51(Chemistry, Physical)

Recently, positronium (Ps) formation mechanism in the spur is becoming clarified. Blob model, the modified Spur model, proposed by Stepanov can give information of Ps formation time. Dauwe et al. showed that S(t) curve of PMMA observed by AMOC measurement could be fitted by the blob model. The young-age broadening was found and explained with the delayed slowing down of Ps by Stuttgart group. The delayed Ps formation was shown by Suzuki et al. especially at low temperatures, because positrons can diffuse long distance to find trapped electrons. According to the blob model, Ps formation even after long diffusion of positrons might be possible even at the room temperature. Now we are trying to obtain the experimental evidence of delayed Ps formation in spur process.

Journal Articles

Statistics of individual doses of JAERI for the past 48 Years

Sekiguchi, Masato; Takahashi, Masa; Miyauchi, Hideaki; Tachibana, Haruo; Komuro, Yuji*; Nemoto, Kiyoko*; Okawa, Ikuko*; Yoshizawa, Michio

Proceedings of 2nd Asian and Oceanic Congress Radiological Protection (AOCRP-2) (CD-ROM), p.114 - 117, 2006/10

In the Japan Atomic Energy Research Institute (JAERI), which was merged with the Japan Nuclear Cycle Development Institute into the Japan Atomic Energy Agency in 2005, individual monitoring and dose record keeping for radiation workers have been conducted since 1957. This report outlines the statistics of the number of radiation workers and individual doses, such as annual collective doses, annual average doses, the maximum doses and dose distributions, over the past 48 years from 1957 to 2005. Individual doses were increased due to the augment of trouble and maintenance of new experimental facilities in 1960's. The collective doses and annual average doses in 1960's exceeded 1,200 man-mSv and 0.4mSv, respectively, in some years. Then, consecutive dose reduction efforts made the collective dose significantly decrease to less than 400 man-mSv (1/3 of the highest) and the average dose to 0.04 mSv (1/10 of the highest). The collective doses in recent years keep almost constant even though radiation works increase in some high-contaminated hot laboratories for the decontamination and maintenance of experimental equipments. It was found from the analysis of cumulative distributions that there was a specific work-group exposed to significantly high dose compared with other workers.

JAEA Reports

Statistics of individual doses of JAERI for the past 48 years

Shiraishi, Akemi; Sekiguchi, Masato; Tachibana, Haruo; Yoshizawa, Michio; Komuro, Yuji*; Nemoto, Kiyoko*; Okawa, Ikuko*

JAEA-Data/Code 2006-014, 36 Pages, 2006/06

JAEA-Data-Code-2006-014.pdf:2.46MB

In Japan Atomic Energy Research Institute (JAERI), individual monitoring and dose data recording for radiation workers have been conducted since 1957, the next year of which JAERI was established. This report compiles the statistics of individual doses, such as average doses, collective doses, the number of radiation workers and dose distributions, over the past 48 years from 1957 to 2005, when JAERI merged with Japan Nuclear Cycle Development Institute into Japan Atomic Energy Agency. Transition of the statistics showed the history of radiation works in JAERI and many efforts for dose reduction based on the ALARA principle recommended by ICRP. In addition, it was found from the analysis of cumulative distributions that, in recent years, there was a specific work-group exposed to significantly high dose compared with other workers.

JAEA Reports