Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Mihalache, O.; Yamamoto, Ikuo*
International Journal of Applied Electromagnetics and Mechanics, 78(1-3), p.141 - 146, 2025/07
Times Cited Count：0 Percentile：0.00(Engineering, Electrical & Electronic)Yamaguchi, Toshihiko; Mihalache, O.
Nuclear Engineering and Design, 401, p.112084_1 - 112084_14, 2023/01
Times Cited Count：6 Percentile：61.49(Nuclear Science & Technology)Yamaguchi, Toshihiko; Mihalache, O.
International Journal of Applied Electromagnetics and Mechanics, 64(1-4), p.895 - 903, 2020/09
Times Cited Count：0 Percentile：0.00(Engineering, Electrical & Electronic)Mihalache, O.; Yamaguchi, Toshihiko
International Journal of Applied Electromagnetics and Mechanics, 64(1-4), p.905 - 912, 2020/09
Times Cited Count：0 Percentile：0.00(Engineering, Electrical & Electronic)Yamaguchi, Toshihiko; Mihalache, O.
Hihakai Kensa, 68(11), p.527 - 534, 2019/11
no abstracts in English
Yamaguchi, Toshihiko; Mihalache, O.; Ueda, Masashi
International Journal of Applied Electromagnetics and Mechanics, 59(4), p.1469 - 1477, 2019/03
Times Cited Count：8 Percentile：35.32(Engineering, Electrical & Electronic)Mihalache, O.; Yamaguchi, Toshihiko; Shirahama, Takuma; Ueda, Masashi
International Journal of Applied Electromagnetics and Mechanics, 59(3), p.1161 - 1168, 2019/03
Times Cited Count：6 Percentile：35.32(Engineering, Electrical & Electronic)Yamaguchi, Toshihiko; Mihalache, O.
Journal of Nuclear Science and Technology, 54(11), p.1201 - 1214, 2017/11
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Mihalache, O.; Yamaguchi, Toshihiko; Shirahama, Takuma; Ueda, Masashi
E-Journal of Advanced Maintenance (Internet), 9(2), p.60 - 65, 2017/08
Mihalache, O.; Yamaguchi, Toshihiko; Shirahama, Takuma; Ueda, Masashi
Proceedings of 3rd International Conference on Maintenance Science and Technology (ICMST 2016) (Internet), 2 Pages, 2016/11
Mihalache, O.; Yamaguchi, Toshihiko; Shirahama, Takuma*; Ueda, Masashi
International Journal of Applied Electromagnetics and Mechanics, 52(1-2), p.659 - 666, 2016/09
Times Cited Count：3 Percentile：19.02(Engineering, Electrical & Electronic)Yamaguchi, Toshihiko; Mihalache, O.; Ueda, Masashi
Electromagnetic Nondestructive Evaluation (XVII), p.144 - 154, 2014/00
Times Cited Count：3 Percentile：83.57(Engineering, Electrical & Electronic)For a Fast Breeder Reactor (FBR) cooled by liquid sodium, the wall of steam generator tubes (SG) is the only barrier between sodium in the tubes vessel and water inside of tubes. By using eddy currents, the SG tube integrity is usually assured during the In-Service Inspection (ISI). During this procedure, the 500 degrees sodium is drained and then SG tubes cooled down slowly in 2 weeks to room temperature. After sodium draining, sodium adheres to SG tubes and other structures in the SG vessel in thin layers. Experimental data shows that sodium drops also appear in specific areas along tubes or tube support plates. The high electrical conductivity of sodium adhering to the outer SG tube surface influences the ECT signal according to sodium layer thickness or sodium deposits located on the outer SG tube surface. The sodium adhering properties depends on several factors among them being the surface roughness of tube material, sodium temperature and wetting time. The ECT effect of sodium adhering to the outer SG tube surface was measured using a small mock-up tank in which were introduced SG tubes similar with the ones in FBR (2.25Cr-1Mo alloy). Defects and support plates were added to tubes and ECT signal was measured before and after sodium draining. Variations in the sodium layer thickness and consequently its ECT effect were measured by filling and draining the tank three times in order to recreate each time new layers of sodium. The paper describes the experimental conditions for defects, SG support plates signal before and after draining of sodium. Additionally, sodium structures were visualized using a CCD camera, confirming the recorded ECT signals. The paper presents details about sodium layer measurements for several parts of the SG tubes by scratching and collecting the sodium on small areas 10x10 square mm. Numerical 3D simulations are performed using a 3D FEM code developed in our laboratory in order to validate the performance of the ECT sensors detection.
Mihalache, O.; Yamaguchi, Toshihiko; Ueda, Masashi
Electromagnetic Nondestructive Evaluation (XVII), p.109 - 119, 2014/00
Times Cited Count：3 Percentile：83.57(Engineering, Electrical & Electronic)Garcia Rodriguez, D.; Mihalache, O.; Ueda, Masashi
Proceedings of 16th International Symposium on Applied Electromagnetics and Mechanics (ISEM 2013), p.219 - 220, 2013/07
Mihalache, O.; Yamaguchi, Toshihiko; Ueda, Masashi
Abstracts of Electromagnetic Nondestructive Evaluation Series, p.42 - 43, 2012/07
Nishimura, Akihiko; Shobu, Takahisa; Oka, Kiyoshi; Yamaguchi, Toshihiko; Shimada, Yukihiro; Mihalache, O.; Tagawa, Akihiro; Yamashita, Takuya
Reza Kako Gakkai-Shi, 17(4), p.207 - 212, 2010/10
A prototype probe system with a hybrid optical fiber scope was designed for inspecting and re-pairing the micro cracks on heat exchanger tubes in fast breeder reactors (FBRs). It comprised a laser processing head combined with an eddy current testing unit. Ultrashort laser pulse ablation was used to remove work-hardened layers. And spot laser welding was used to repair the micro cracks. This system has both safe and economical options for the maintenance of FBRs because it extends the lifetime of the heat exchangers.
Mihalache, O.; Yamaguchi, Toshihiko; Ueda, Masashi; Miyahara, Shinya
International Journal of Applied Electromagnetics and Mechanics, 33(3-4), 6 Pages, 2010/00
Times Cited Count：12 Percentile：54.26(Engineering, Electrical & Electronic)In FBR, one of the techniques used in the ISI of magnetic steam generator (SG) tubes is the remote field eddy current technique (RF-ECT). The SG tubes, made of 2.25Cr-1Mo alloy, are very long, including several parts with helical, bent and straight shape. The longer parts of these tubes are fixed in a helical shape-structure using multiple support plates (SP) which are also ferromagnetic. The complicated shape of the SP and multiple connections of several tubes to the SP can be quantitatively analyzed only by a 3-dimensional analysis, in order to evaluate the influences in the ECT signal due to the close proximity of the SG tubes. Also, the tube curvature and additionally the presence of sodium on the outer tube surface induces supplementary effects. The paper presents 3D finite element simulations of the SG inspection using RF-ECT. It is evaluated the influences of the SG tubes curvature on the eddy current sensor signal.
Nishimura, Akihiko; Oka, Kiyoshi; Yamaguchi, Toshihiko; Akatsu, Tomohiro*; Seki, Takeshi*; Mihalache, O.; Shimada, Yukihiro; Tagawa, Akihiro; Yamashita, Takuya
Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.250 - 253, 2009/08
In order to maintain FBR heat exchanger tubes, a new probe system was designed. A coupling unit and operational software are key components in the second year. The coupling unit to combine a high energy laser beam and optical fiberscope images was developed. The operational software successfully controlled an eddy current testing device and a laser processing head.
Mihalache, O.; Ueda, Masashi; Yamaguchi, Toshihiko; Yamashita, Takuya
Proceedings of 15th International Conference on Nuclear Engineering (ICONE-15) (CD-ROM), 9 Pages, 2007/04
In the present paper we estimate the effect of sodium in the in-service inspection of non-magnetic steam generators tubes using eddy current technique and eddy current probes based on a differential double bobbin coil configuration. Experimental measurements of defects signals in steam generator tubes of fast breeder reactor are compared with simulations results of a two-dimensional axisymmetric finite element code to validate a reliable electromagnetic model of the system (eddy current coils, steam generator tube, defect) when there is no sodium on the outer steam generator tube surface. The electromagnetic code is used to evaluate the sodium band and sodium layer signals when a defect is located under steam generator support plate. Using a multi-frequency algorithm, its parameters are determined in the "no sodium condition" (there is no sodium on the outer steam generator tube surface), defects signal is enhanced during eddy currents inspection, even when the defects are located under support plate in the presence of sodium layers with thickness ranging from 10 to 300
m and sodium circumferential bands 5 mm wide and 2.5 mm high near support plate. The paper presents a full detailed analysis for detection of defects in various configurations, using eddy current technique, and tests the robustness of the multi-frequency approach to suppress support plate signal of non-magnetic SG tubes of fast breeder reactors.
Mihalache, O.; Yamaguchi, Toshihiko; Date, Koji*; Ueda, Masashi; Yamashita, Takuya
Proceedings of 12th Asia-Pacific Conference on Non-Destructive Testing 2006 (APCNDT 2006) (Internet), 9 Pages, 2006/11
Using numerical software optimization, new remote field eddy current systems based on small multiple vertical and horizontal coils were build in laboratory to investigate smaller outer tube defect detection in ferromagnetic steam generator tubes of nuclear power plants. Small defects located on the outer tube surface as pinholes axial and circumferential notches are better visualized using the C-scan experimental data, even when these defects are located near weld zones and the inspection is done from the inside of the tube. Comparing with the classical system, based on Bobbin coils, the new system shows an improved detection and a better coping with the electromagnetic signal noise in the data arising from unknowns in the: weld structure (from electromagnetic point of view), probe wobbling during inspection, variation in the inner tube surface.
