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Journal Articles

Measurements of the doses of eye lens for the workers of Fukushima Daiichi Nuclear Power Plant

Yokoyama, Sumi*; Ezaki, Iwao*; Tatsuzaki, Hideo*; Tachiki, Shuichi*; Hirao, Kazushige*; Aoki, Katsunori; Tanimura, Yoshihiko; Hoshi, Katsuya; Yoshitomi, Hiroshi; Tsujimura, Norio

Radiation Measurements, 138, p.106399_1 - 106399_5, 2020/11

Journal Articles

Experimental investigation of density stratification behavior during outer surface cooling of a containment vessel with the CIGMA facility

Ishigaki, Masahiro; Abe, Satoshi; Shibamoto, Yasuteru; Yonomoto, Taisuke

Nuclear Engineering and Design, 367, p.110790_1 - 110790_15, 2020/10

no abstracts in English

JAEA Reports

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.

JAEA Reports

Registration and related activities of the Japan Atomic Energy Agency for the response and assistance network of the International Atomic Energy Agency

Togawa, Orihiko; Hayakawa, Tsuyoshi; Tanaka, Tadao; Yamamoto, Kazuya; Okuno, Hiroshi

JAEA-Review 2020-017, 36 Pages, 2020/09

JAEA-Review-2020-017.pdf:2.24MB

In 2010, the government of Japan joined the Response and Assistance Network (RANET) of the International Atomic Energy Agency (IAEA), in order to contribute to offering international assistance in the case of a nuclear accident or radiological emergency. At that occasion, the Japan Atomic Energy Agency (JAEA) was registered as the National Assistance Capability (NAC) having resources capable of the External Based Support (EBS) in the following seven areas: (1) aerial survey, (2) radiation monitoring, (3) environmental measurements, (4) assessment and advice, (5) internal dose assessment, (6) bioassay and (7) dose reconstruction. After the registration, three inquiries were directed to the JAEA about a possibility of its support. However, the JAEA's assistance has not eventually been realized. On the other hand, the JAEA participated almost every year in the international Convention Exercise (ConvEx) carried out by the IAEA in connection with RANET. This report describes an outline of the RANET and related activities of the JAEA for RANET registration and participation in the ConvEx.

JAEA Reports

Design and mounting advanced wireless communication equipment on the crawler-type robots for tasks and on the crawler-type scouting robot

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

JAEA-Technology 2020-006, 26 Pages, 2020/08

JAEA-Technology-2020-006.pdf:2.43MB

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 JAEA deal with Act on Special Measures Concerning Nuclear Emergency Preparedness. The section needs to remodel crawler-type robots for tasks, crawler-type scouting robots, and so on. About two crawler-type robots for tasks, the section designed and mounted advanced wireless communication equipment on manipulators mounted on the two robots. The crawler part of the robot has been able to be controlled by way of the new equipment, and when it is broken down, it can be changed by way of an original equipment. And the new equipment makes a single relay robot controllable both the crawler part and the manipulator part of the robot, in case of wireless relay robots being needed. And after checking the ability and characteristic about 5 wireless communication equipment, the section chose and mounted the best equipment on one crawler-type scouting robot. This report shows design and mounting advanced wireless communication equipment on the two crawler-type robots for tasks and on the one crawler-type scouting robot.

Journal Articles

A Linear Equation of characteristic time profile of power in subcritical quasi-steady state

Yamane, Yuichi

Journal of Nuclear Science and Technology, 57(8), p.926 - 931, 2020/08

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

An equation of power in subcritical quasi-steady state has been derived based on one-point kinetics equations for the purpose of utilizing it for the development of timely reactivity estimation from complicated time profile of neutron count rate. It linearly relates power, $$P$$, to a new variable $$q$$, which is a function of time differential of the power. It has been confirmed by using one-point kinetics code, AGNES, that the calculated points ($$q, P$$) are perfectly in a line described by the new equation and that points ($$q, P$$) calculated from transient subcritical experiments by using TRACY made a line with a slope indicated by the new equation.

Journal Articles

Fatigue crack growth for ferritic steel under negative stress ratio

Yamaguchi, Yoshihito; Hasegawa, Kunio; Li, Y.

Journal of Pressure Vessel Technology, 142(4), p.041507_1 - 041507_6, 2020/08

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

The phenomenon of crack closure is important in the prediction of fatigue crack growth. Several experimental data indicate the closing of fatigue cracks both under negative and positive loads at constant amplitude loading cycles, depending on the magnitude of stress amplitude and stress ratio. Appendix A-4300 of the ASME Code Section XI provides two equations of fatigue crack growth rates expressed by the stress intensity factor range for ferritic steels under negative stress ratio. The boundary of two fatigue crack growth rates is classified with the magnitude of applied stress intensity factor range, in consideration of the crack closure. The boundary value provided by the ASME Code Section XI is validated in this study through an investigation of the influence of the magnitude of the applied stress intensity factor range on crack closure, with the application of fatigue crack growth tests using ferritic steel specimens in air environment at room and high temperatures. Crack closures are obtained as a parameter of stress ratio, and herein, were found to occur at a smaller applied stress intensity factor range, as opposed to the definition given by Appendix A-4300.

Journal Articles

Unsteady natural convection in a cylindrical containment vessel (CIGMA) with external wall cooling; Numerical CFD simulation

Hamdani, A.; Abe, Satoshi; Ishigaki, Masahiro; Shibamoto, Yasuteru; Yonomoto, Taisuke

Energies (Internet), 13(14), p.3652_1 - 3652_22, 2020/07

 Times Cited Count:0

Journal Articles

Four-point-bend tests on high-burnup advanced fuel cladding tubes after exposure to simulated LOCA conditions

Narukawa, Takafumi; Amaya, Masaki

Journal of Nuclear Science and Technology, 57(7), p.782 - 791, 2020/07

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

JAEA Reports

Development of the vertically moveable dose rate meter for a nuclear emergency response robot

Iwai, Masaki

JAEA-Technology 2020-004, 14 Pages, 2020/06

JAEA-Technology-2020-004.pdf:2.88MB

Maintenance and Operation Section for Remote Control Equipment in Naraha Center for Remote Control Technology Development needs to develop equipment for JAEA nuclear emergency, and because of reasonably and effectively developing machines, the section members examined plants in JAEA must deal with the new low. Then, radiation rates detectors with an elevator on a crawler robot were found as a very useful system, and the system was designed and produced. This report shows radiation rates detectors with an elevator for a crawler robot designed and produced by Maintenance and Operation Section for Remote Control Equipment in 2018 fiscal year.

Journal Articles

Method for groundwater monitoring on the disposal of radioactive waste

Murakami, Hiroaki; Iwatsuki, Teruki; Takeuchi, Ryuji; Nishiyama, Nariaki*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(1), p.22 - 33, 2020/06

Geological disposal of radioactive waste requires the large amounts of fundamental technical knowledge throughout the project. Monitoring is carried out to collect site-relevant information for the creation of an environmental database, to assist in the decision-making process, etc. We summarized the current technical level and problems of the groundwater monitoring in the world. Through the research and technology development so far, the technologies have been developed for drilling borehole in the geological environment survey prior to monitoring and the selection of the monitoring site. However, the following technical developments are remaining issues: long-term operation method of monitoring equipment, retrieving method of monitoring equipment after long-term operation, transport method of backfill material for borehole sealing, technical basis for the sealing performance when the borehole-protective casing and strainer tube are left.

Journal Articles

Journal Articles

Assessment model of radiation doses from external exposure to the public after the Fukushima Daiichi Nuclear Power Plant accident

Takahara, Shogo; Iijima, Masashi*; Watanabe, Masatoshi*

Health Physics, 118(6), p.664 - 677, 2020/06

 Times Cited Count:0 Percentile:100(Environmental Sciences)

Assessment model of radiation doses from external exposures was developed based on the actual measurement of individual doses and ambient dose equivalent rate inside and outside of a house in Fukushima city. The survey on behavioral pattern was also carried out under the same purpose. In addition to the actual measurement and survey by ourselves, we also took into account the latest insights from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Comparisons between the assessed results and the measured ones revealed that the time dependences of doses obtained using the developed models were in good agreement with the results of actual measurements. In addition, we were able to reproduce the distribution of doses for indoor and outdoor workers. Therefore, our probabilistic approach was validated. According to our assessment and actual measurement, no participants received 1 mSv/y or higher in Fukushima city in eight years after the FDNPP accident.

Journal Articles

Concept of radiation protection for low-dose risks

Takahara, Shogo

Hoshasen Seibutsu Kenkyu, 55(2), p.162 - 172, 2020/06

no abstracts in English

Journal Articles

Fracture-mechanics-based evaluation of failure limit on pre-cracked and hydrided Zircaloy-4 cladding tube under biaxial stress states

Li, F.; Mihara, Takeshi; Udagawa, Yutaka; Amaya, Masaki

Journal of Nuclear Science and Technology, 57(6), p.633 - 645, 2020/06

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Journal Articles

Application scope of limit load criterion for ductile material pipes with circumferentially external cracks

Hasegawa, Kunio; Li, Y.; Lacroix, V.*; Mares, V.*

Journal of Pressure Vessel Technology, 142(3), p.031506_1 - 031506_7, 2020/06

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

Bending stress at plastic collapse for a circumferentially cracked pipe is predicted by limit load criterion provided by the Appendix C of the ASME Code Section XI. The equation of the Appendix C is applicable for pipes with both external and internal surface cracks. On the other hand, the authors have developed a more precise equation. From the comparison of Appendix C equation and the new equation, the plastic collapse stress estimated by the Appendix C equation gives less conservative bending capacity prediction for external cracked pipes with thick wall thickness and large crack angle. This paper discusses the limitation scope to use the limit load criterion of the Appendix C equation.

Journal Articles

Influence evaluation of sampling methods of the nondestructive examination on failure probability of piping based on probabilistic fracture mechanics analysis

Mano, Akihiro; Katsuyama, Jinya; Li, Y.

Mechanical Engineering Journal (Internet), 7(3), p.19-00567_1 - 19-00567_11, 2020/06

Non-destructive examinations (NDEs) have an important role in assurance of the structural integrity of nuclear components including pipe lines. In Japanese nuclear power plants, NDEs are performed for welds in piping in accordance with the rules such as the Rules on Fitness-for-Service for Nuclear Power Plants of the Japan Society of Mechanical Engineers. For the welds where stress corrosion cracking (SCC) is not postulated, NDEs are performed in each 10-year interval. For each interval, the extent of examination is specified in the rules. In general, there are two kinds of sampling method for selecting welds to be examined in each interval considering the specified extent of examination. The first method is the fixed location sampling method, in which welds for NDEs are same as those examined in the last interval. The second method is the random location sampling method, in which welds for NDEs are selected from those not examined in the last interval. The selection of the sampling method is important to assure the structural integrity of piping. Probabilistic fracture mechanics (PFM) analysis which is one of rational structural integrity assessment methods can quantitatively calculate failure probability of welds in piping considering aging degradation mechanisms such as SCC and fatigue as well as crack detections and repair of cracked welds through NDE. In this study, to clarify the influence of the sampling methods on structural integrity of piping, we evaluated the failure probability of a typical nuclear piping considering NDEs based on the two sampling methods through PFM analysis. From the results, we clarified the quantitative influence of two sampling methods on failure probability of piping.

Journal Articles

Recent verification activities on probabilistic fracture mechanics analysis code PASCAL4 for reactor pressure vessel

Lu, K.; Katsuyama, Jinya; Li, Y.; Miyamoto, Yuhei*; Hirota, Takatoshi*; Itabashi, Yu*; Nagai, Masaki*; Suzuki, Masahide*; Kanto, Yasuhiro*

Mechanical Engineering Journal (Internet), 7(3), p.19-00573_1 - 19-00573_14, 2020/06

Journal Articles

Impact simulations on local damage of reinforced concrete panel influenced by projectile nose shape

Kang, Z.; Nishida, Akemi; Okuda, Yukihiko; Tsubota, Haruji; Li, Y.

Mechanical Engineering Journal (Internet), 7(3), p.19-00566_1 - 19-00566_20, 2020/06

Most impact research has been presented on the basis of impact tests and numerical analysis performed by rigid projectile impact perpendicular to the target structure. On the other hand, there are only few reports on impacts at an oblique angle. To evaluate more realistic conditions regarding issues related to oblique impacts to reinforced concrete (RC) structures, we have proposed an analytical method to estimate the local damage to RC structures by an oblique impact and have validated the evaluation approach by comparison with experimental results. At present, we have finalized simulation analyses of oblique impact assessments on RC panels using rigid/soft projectiles with a flat nose shape utilizing the validated approach. Furthermore, in this study, we focus on impacts caused by rigid/soft projectiles with a hemispherical nose shape. The same analytical method is applied to simulate the structural damage caused by an RC panel due to a rigid/soft projectile with a hemispherical nose shape. Results on the penetration depth of the RC structure and the energy-contribution ratio are presented. By comparing the results of local damage to an RC structure caused by projectiles with flat and hemispherical nose shapes, the influence of the nose shape of the projectile on local damage of the RC panel has been investigated.

Journal Articles

Dose estimation in the recycling of removed soil for land reclamation

Shimada, Asako; Nemoto, Hiromi*; Sawaguchi, Takuma; Takeda, Seiji

Mechanical Engineering Journal (Internet), 7(3), p.19-00569_1 - 19-00569_17, 2020/06

After treatments such as sieve classification and washing of decontamination soil taken in Fukushima prefecture, recycling of the treated soil in which radioactivity concentration level is relatively low to public engineering works is invented to reduce the amount of the decontamination soil that must be disposed of. In the present study, dose estimation for workers and the public was conducted from the viewpoint of application of recycling material of decontamination soil for land reclamation by considering exposure pathways from the construction to the servicing of the land as a greenery-covered area. In the case of revegetation with trees, uptake of Cs into trees was considered and the exposure from trees, trimmed or thinned trees, and organic deposit made from litter fall were evaluated. From the results, the concentration levels of radiocesium, $$^{134}$$Cs and $$^{137}$$Cs, for which the annual effective exposure dose does not exceed 1 mSv/y was calculated. In addition, the thickness of the cover soil required to maintain the exposure dose lower than 10 $$mu$$Sv/y for the public during servicing was ascertained. Furthermore, disasters were considered; for instance, by considering that tsunamis, fires, and concentrated heavy rain can increase exposure doses based on changes in the conditions of the reclamation land, we confirmed that the additional exposure dose during disaster and rehabilitation is lower than 1 mSv/y. Based on these evaluation results, we determined the concentration levels amenable to recycling.

3247 (Records 1-20 displayed on this page)