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Journal Articles

Fundamental study on scheduling of inspection process for fast reactor plants

Suzuki, Masaaki*; Ito, Mari*; Hashidate, Ryuta; Takahashi, Keita; Yada, Hiroki; Takaya, Shigeru

2020 9th International Congress on Advanced Applied Informatics (IIAI-AAI 2020), p.797 - 801, 2021/07

Journal Articles

Development of leak before break assessment guidelines for sodium cooled fast reactors in Japan

Yada, Hiroki; Wakai, Takashi; Miyagawa, Takayuki*; Machida, Hideo*

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 10 Pages, 2021/07

Journal Articles

Proposal of maintenance rationalization for next-generation fast reactors based on the analysis of the prolonged maintenance of the prototype fast-breeder reactor in Japan, "Monju", 1; Analysis of plant schedule of "Monju" in cold shutdown

Hashidate, Ryuta; Toyota, Kodai; Takahashi, Keita; Yada, Hiroki; Takaya, Shigeru

Hozengaku, 19(4), p.115 - 122, 2021/01

In order to improve both safety and economic efficiency of a nuclear power plant, it is necessary to realize rational maintenance based on characteristics of the plant. The prototype fast-breeder reactor in Japan, Monju, spent most of the year for the maintenance. Thus, it is important to identify causes of the prolonged maintenance of Monju and to investigate countermeasures for implementation of rational maintenance of next-generation fast reactors. In this study, the authors investigated the causes of the prolonged maintenance of Monju during reactor cold shutdown based on the plant schedule of Monju. In addition, we proposed the maintenance optimization idea for next-generation fast reactors to solve the revealed issues.

Journal Articles

Proposal of inspection rationalization method and application for sodium cooled fast reactor

Yada, Hiroki; Takaya, Shigeru; Enuma, Yasuhiro

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 7 Pages, 2020/08

Journal Articles

Development of LORL evaluation method and its application to a loop-type sodium-cooled fast reactor

Imaizumi, Yuya; Yamada, Fumiaki; Arikawa, Mitsuhiro*; Yada, Hiroki; Fukano, Yoshitaka

Mechanical Engineering Journal (Internet), 5(4), p.18-00083_1 - 18-00083_11, 2018/08

A calculation program was developed to evaluate and discuss the effectiveness of the countermeasures such as sodium pump-up and siphon-breaking against the loss-of-reactor-level (LORL) where the coolant circulation path is lost in loop-type sodium-cooled fast reactors. Due to the non-negligible possibility obtained by probabilistic risk assessment (PRA), sodium leakages in two points both occurred in primary heat transport system (PHTS) was assumed in this study. In addition, the crack size was discussed and evaluated realistically, instead of the value that was assumed in the conventional studies. Representative sequences and leakage positions were chosen, and the sodium level transient in reactor vessel (RV) was calculated. The calculations were also conducted where the larger crack size was set for the second leakage, in order to investigate additional requirements to maintain the RV sodium level. The evaluation results clarified that the coolant circulation loop can be maintained even after the second leakage in PHTS, taking into account the effects by the countermeasures.

Journal Articles

Effect of 3-D initial imperfections on the deformation behaviors of head plates subjected to convex side pressure

Yada, Hiroki; Ando, Masanori; Tsukimori, Kazuyuki; Ichimiya, Masakazu*; Anoda, Yoshinari*

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 9 Pages, 2018/07

Containment vessel (CV) of nuclear power plants is an important structure to prevent radioactive release, however, the safety margin of the CV against pressure are not numerically clarified. The head plate structure is included in CV boundary of fast reactor. In order to develop the evaluation method of the ultimate strength of the head plate structure at beyond the specified limit, pressure failure tests and finite element analysis (FEA) of the head plates subjected to convex side pressure were performed. In the test of the relative thin thickness head plate, non-axisymmetric deformations was observed in post buckling behavior and failure pressure was lower than other cases. To evaluate non-axisymmetric deformations in the test, FEA using 3-D solid model constructed by precise dimensions of the test specimen, moreover, FEA using simplified model with uniform or non-uniform thickness were performed. Through analyses, the feature of the post buckling behavior was discussed.

Journal Articles

Leak rate tests of penetrate cracked head plates and modeling of head plate thickness distribution for 3-D analyses

Tsukimori, Kazuyuki*; Yada, Hiroki; Ando, Masanori; Ichimiya, Masakazu*; Anoda, Yoshinari*

Proceedings of 12th International Conference on Asian Structure Integrity of Nuclear Components (ASINCO-12) (CD-ROM), p.105 - 121, 2018/04

In FBR plants the head plate constitutes a part of the boundary of the containment vessel (CV), therefore, it is an important issue if the function as the boundary is maintained or not in the severe accident. And also it is important to evaluate the leak rate from the penetrated crack of the head plate, in order to estimate the effect of released fission product out of CV. Authors conducted pressure endurance tests of head plate specimens subjected to external pressure, which covered post-buckling behaviors and until crack penetration. In this paper leak rate test results at several pressure levels are introduced and the tendency of leak rate behaviors with relation of the penetrate crack length and the pressure level are discussed. Also, the modeling of head plate thickness distribution for 3-D analyses based on the detailed 3-D measurement data of specimens is discussed, which possibly relates to the 3-D deformation patterns observed in the tests and the length of penetration cracks.

Journal Articles

Proposal on LBB evaluation conditions for sodium cooled fast reactor pipes and effects of pipe parameters

Yada, Hiroki; Takaya, Shigeru; Wakai, Takashi; Nakai, Satoru; Machida, Hideo*

Nihon Kikai Gakkai Rombunshu (Internet), 84(859), p.17-00389_1 - 17-00389_15, 2018/03

no abstracts in English

Journal Articles

Experimental study on the deformation and failure of the bellows structure beyond the designed internal pressure

Ando, Masanori; Yada, Hiroki; Tsukimori, Kazuyuki; Ichimiya, Masakazu*; Anoda, Yoshinari*

Journal of Pressure Vessel Technology, 139(6), p.061201_1 - 061201_12, 2017/08

 Times Cited Count:1 Percentile:10.91(Engineering, Mechanical)

In this study, in order to develop the evaluation method of the ultimate pressure of the bellows structure subject to the internal pressure beyond the specified, the failure test and finite element analysis (FEA) of the bellows structure were performed. The failure modes were demonstrated through the series of tests, and three kind of failure mode were observed. To simulate the buckling and deformation behavior during the test, the implicit and explicit analyses were performed.

Journal Articles

Experimental study on behaviours of two-ply bellows subjected to pressure and displacement loads

Tsukimori, Kazuyuki; Ando, Masanori; Yada, Hiroki; Ichimiya, Masakazu*; Anoda, Yoshinari*; Arakawa, Manabu*

Transactions of 24th International Conference on Structural Mechanics in Reactor Technology (SMiRT-24) (USB Flash Drive), 10 Pages, 2017/08

The analytical treatment of Multi-ply bellows behaviours is difficult compared with that of single-ply bellows, since the uncertainty of friction between plies exists. In this study verification was conducted based on experiments by comparing between two-ply and single-ply bellows test results. Following results were obtained. The spring rate of two-ply bellows is approximately twice of that of single-ply bellows, even if internal pressure is loaded. Typical buckling behaviour of bellows, in-plane squirm, was observed in both cases of two-ply and single-ply bellows. The deformation patterns were similar with each other, but the pressure levels of two-ply bellows were approximately twice of those of single-ply bellows. These means the friction force can be ignored practically. As the conclusion, two-ply bellows analyses can be replaced by the analyses of single-ply bellows model with half pressure load and the effort of numerical analysis can be reduced.

Journal Articles

Experimental demonstration of failure modes on bellows structures subject to internal pressure

Ando, Masanori; Yada, Hiroki; Tsukimori, Kazuyuki; Ichimiya, Masakazu*; Anoda, Yoshinari*

Proceedings of 2017 ASME Pressure Vessels and Piping Conference (PVP 2017) (CD-ROM), 11 Pages, 2017/07

In this study, in order to develop the evaluation method of the pressure toughness of bellows structure under the beyond design base event, the pressure failure tests and finite element analysis (FEA) of the bellows structure subjected to internal pressure were performed. In the test of five convolutions 0.5 mm-thickness bellows specimen with guard pipe, the maximum pressure was larger than those in the tests without guard pipe specimens and ductile failure was observed. On the other hand, in the test of five convolutions 0.5 mm-thickness bellows specimen without guard pipe, local failure was observed. In the test of the six convolutions 1.0 mm-thickness bellows specimen, ductile failure was observed in the both single and double ply bellows. The maximum pressure obtained in all tests were about 10 times larger than the estimated results of limiting design pressure based on in-plain instability by the EJMA standards.

Journal Articles

Failure mode of ED and AD type head plates subject to convex side pressure

Yada, Hiroki; Ando, Masanori; Tsukimori, Kazuyuki; Ichimiya, Masakazu*; Anoda, Yoshinari*

Proceedings of 2017 ASME Pressure Vessels and Piping Conference (PVP 2017) (CD-ROM), 8 Pages, 2017/07

The head plate that composes the boundary between primary and secondary coolant in intermediate heat exchanger of FBR has an important role when the progress of the BDBE is considered. In order to develop the evaluation method of the pressure toughness of the head plate under the BDBE, the pressure failure tests and finite element analysis of two types of head plate subjected to convex side pressure was performed in this study. It can be concluded that a failure mode of a head plate subjected convex side pressure is circumferential through-wall crack caused by straightening following the bending deformation near the rim.

Journal Articles

A Report on the meeting; 2016 ASME Pressure Vessels & Piping Conference (PVP2016)

Yada, Hiroki

Hozengaku, 15(3), P. 86, 2016/10

no abstracts in English

Journal Articles

Experimental study on ultimate strength of single and double type bellows under internal pressure

Ando, Masanori; Yada, Hiroki; Tsukimori, Kazuyuki; Ichimiya, Masakazu*; Anoda, Yoshinari*

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 8 Pages, 2016/07

To clarify the progress of the events under the beyond design basis events, it is necessary to evaluate the pressure toughness of containment vessel adequately. The containment vessel of fast reactor is composed of the various structures, and one of the thinnest boundary structures is bellows structure to absorb the thermal expansion of the coolant piping penetrating the containment vessel. In addition to the containment vessel boundary, evaluating the pressure toughness of reactor coolant and gas boundary is also important because of same reason of that in the containment vessel boundary. In the primary coolant and gas boundary, the cover gas bellows of the intermediate heat exchanger in fast reactor is one of the thinnest structures and has important role when the progress of the BDBE is considered. Therefore, in order to develop the evaluation method of the pressure toughness of bellows structure under the BDBE, the pressure failure tests and finite element analysis of the bellows structure subjected to internal pressure were performed in this study.

Journal Articles

Experimental study on ultimate strength of a ellipsoidal dished head plate under pressure on convex surface

Yada, Hiroki; Ando, Masanori; Tsukimori, Kazuyuki; Ichimiya, Masakazu*; Anoda, Yoshinari*

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 7 Pages, 2016/07

no abstracts in English

Journal Articles

Study on behaviours of multi-ply bellows subjected to pressure and displacement loads

Tsukimori, Kazuyuki; Ando, Masanori; Yada, Hiroki

Transactions of 23rd International Conference on Structural Mechanics in Reactor Technology (SMiRT-23) (USB Flash Drive), 10 Pages, 2015/08

Multi-ply bellows is widely used because its flexibility and pressure tightness. However, the analytical treatment of its behaviours is difficult compared with that of single-ply bellows, since the uncertainty of friction between plies exists. In this paper the strength evaluation equations of multi-ply bellows are examined and the friction effect between plies is investigated through simplified models and detailed FEM analyses of two-ply bellows for example including the effect of material plasticity and internal pressure. Mainly following results are obtained. (1) The behaviours of two-ply bellows without friction can be analysed approximately by using single-ply bellows model even in the elastic-plastic region. The effort of numerical analysis can be reduced if two-ply bellows analyses can be replaced by the analyses of single-ply bellows model. (2) The effect of friction is relatively small up to about 0.4 by friction coefficient. Therefore, the behaviours of two-ply bellows can be evaluated practically ignoring friction effect. (3) The strength of multi-ply bellows against pressure, i.e. buckling, can be evaluated conservatively by assuming no friction, even if considered the internal pressure with friction. Therefore, the evaluation method without friction is recommended for design.

Journal Articles

Development of constitutive models for fast reactor design

Tsukimori, Kazuyuki; Iwata, Koji*; Kawasaki, Nobuchika*; Okajima, Satoshi; Yada, Hiroki; Kasahara, Naoto*

Nuclear Engineering and Design, 269, p.23 - 32, 2014/04

 Times Cited Count:1 Percentile:10.7(Nuclear Science & Technology)

R&D to enable a practical fast breeder reactor plant is proceeding in Japan, which is called "FaCT" (Fast reactor Cycle Technology development). One of the key issues of R&D is to realize a reasonably compact reactor vessel by eliminating the wall protection equipment which is installed inside the vessel in order to reduce thermal loading in the conventional design. Most important concern is the amount of the inelastic strain of the vessel accumulated around the liquid sodium surface which moves upward and downward cyclically with start-up and shut-down. The aim of this study is to develop rational constitutive models that enable prediction of this kind of complex inelastic behaviors precisely and to prepare the design guide based on inelastic analysis. We developed a high accuracy plasticity model and a simplified plasticity model and valuated them by organized experiments.

Journal Articles

Research of using structural materials of decommissioning nuclear power plant for technical evaluation of ageing management for safe long term operating

Sakakibara, Yasuhide*; Yada, Hiroki

Nihon Hozen Gakkai Dai-10-Kai Gakujutsu Koenkai Yoshishu, p.477 - 481, 2013/07

Journal Articles

Cavitation inception and erosion in flowing system of water and liquid metal

Yada, Hiroki; Kanagawa, Akihiro*; Hattori, Shuji*

Nihon Kikai Gakkai Rombunshu, B, 78(788), p.811 - 820, 2012/04

no abstracts in English

76 (Records 1-20 displayed on this page)