Yamaguchi, Yoshihito; Hasegawa, Kunio; Li, Y.
Journal of Pressure Vessel Technology, 142(4), p.041507_1 - 041507_6, 2020/08
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.
Narukawa, Takafumi; Amaya, Masaki
Journal of Nuclear Science and Technology, 57(7), p.782 - 791, 2020/07
JAEA-Technology 2020-004, 14 Pages, 2020/06
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.
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.
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(1), p.34 - 36, 2020/06
no abstracts in English
Takahara, Shogo; Iijima, Masashi*; Watanabe, Masatoshi*
Health Physics, 118(6), p.664 - 677, 2020/06
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.
Hoshasen Seibutsu Kenkyu, 55(2), p.162 - 172, 2020/06
no abstracts in English
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.
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
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.
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, Cs and 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 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.
Yamaguchi, Yoshihito; Katsuyama, Jinya; Kaji, Yoshiyuki; Osaka, Masahiko; Li, Y.
Mechanical Engineering Journal (Internet), 7(3), p.19-00560_1 - 19-00560_12, 2020/06
Since the Fukushima Daiichi nuclear power plant accident, we have been developing a failure evaluation method that considers creep damage mechanisms using detailed three-dimensional finite element analysis model of lower head including penetration, stub tubes, and weld parts, etc., for the early completion of the decommissioning of the nuclear power plants in Fukushima Daiichi. For the finite element analysis, we have been obtaining material properties for which no data are provided in existing databases or in the literature. In particular, creep data corresponding to the high temperature region near the melting point of materials is important in evaluating creep deformation under severe accident conditions. In this study, we obtained the uniaxial tensile and creep properties for low-alloy steel, stainless steel, and Ni-based alloy. In particular, creep test data with long rupture times at high temperatures are expanded using a tensile test machine that can measure the elongation of test specimens in a noncontact measurement system. The parameters related to the failure evaluation were improved on the basis of the expanded creep database.
Maruyama, Yu; Kita, Toshinobu*; Kuramoto, Takahiro*
Nippon Genshiryoku Gakkai-Shi, 62(6), p.328 - 333, 2020/06
no abstracts in English
Tsujimura, Norio; Hoshi, Katsuya; Aoki, Katsunori; Yoshitomi, Hiroshi; Tanimura, Yoshihiko; Yokoyama, Sumi*
Radiation Measurements, 134, p.106305_1 - 106305_5, 2020/06
Taniguchi, Yoshinori; Udagawa, Yutaka; Amaya, Masaki
Annals of Nuclear Energy, 139, p.107188_1 - 107188_7, 2020/05
Udagawa, Yutaka; Mihara, Takeshi; Taniguchi, Yoshinori; Kakiuchi, Kazuo; Amaya, Masaki
Annals of Nuclear Energy, 139, p.107268_1 - 107268_9, 2020/05
Furuta, Hiroshige*; Tsujimura, Norio; Nishide, Akemi*; Kudo, Shinichi*; Saegusa, Shin*
Radiation Protection Dosimetry, 189(3), p.371 - 383, 2020/05
Hotta, Akitoshi*; Akiba, Miyuki*; Morita, Akinobu*; Konovalenko, A.*; Vilanueva, W.*; Bechta, S.*; Komlev, A.*; Thakre, S.*; Hoseyni, S. M.*; Skld, P.*; et al.
Journal of Nuclear Science and Technology, 57(4), p.353 - 369, 2020/04
Yamaguchi, Yoshihito; Katsuyama, Jinya; Li, Y.; Onizawa, Kunio
Journal of Pressure Vessel Technology, 142(2), p.021906_1 - 021906_11, 2020/04
Azuma, Kisaburo*; Li, Y.; Xu, S.*
Journal of Pressure Vessel Technology, 142(2), p.021207_1 - 021207_10, 2020/04