2D visualization and optimization of EMAT signal for small defect detection in thick plates

Yamaguchi, Toshihiko; Mihalache, O.

International Journal of Applied Electromagnetics and Mechanics, 64(1-4), p.895 - 903, 2020/09

https://doi.org/10.3233/JAE-209403

Development of a hybrid ECT sensor for fast reactor steam generator tube inspection

Yamaguchi, Toshihiko; Mihalache, O.

Hihakai Kensa, 68(11), p.527 - 534, 2019/11

no abstracts in English

Development of a hybrid ECT sensor for JSFR SG double-wall tubes

Yamaguchi, Toshihiko; Mihalache, O.

Journal of Nuclear Science and Technology, 54(11), p.1201 - 1214, 2017/11

https://doi.org/10.1080/00223131.2017.1359116

R&D of multi-frequency ECT algorithms for FBR SG tubes

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

Experimental measurements and simulations of ect signal for ferromagnetic SG tubes covered by a sodium layer

Yamaguchi, Toshihiko; Mihalache, O.; Ueda, Masashi

Electromagnetic Nondestructive Evaluation (XVII), p.144 - 154, 2014/00

https://doi.org/10.3233/978-1-61499-407-7-144

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.

Large scale 3D FEM electromagnetic simulations and validations for FBR steam generator tubes

Mihalache, O.; Yamaguchi, Toshihiko; Ueda, Masashi

Abstracts of Electromagnetic Nondestructive Evaluation Series, p.42 - 43, 2012/07

3D RFEC simulations for the in-service inspection of steam generator tubes in fast breeder reactors

Mihalache, O.; Yamaguchi, Toshihiko; Ueda, Masashi; Miyahara, Shinya

International Journal of Applied Electromagnetics and Mechanics, 33(3-4), 6 Pages, 2010/00

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.

Improvement of detection of small defects located near or far from welds of magnetic steam generator tubes using remote field eddy current

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.

3D finite element modeling for simulating remote field flaw detection in magnetic steam generator tubes

Mihalache, O.; Yamashita, Takuya; Ueda, Masashi;

THE 30TH ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE, 0 Pages, 2003/00

None

ADVANCED REMOTE FIELD COMPUTATIONAL ANALYSIS OF STEAM GENERATORS TUBES

Mihalache, O.

THE 8TH INTERNATIONAL WORKSHOP ON ELECTROMAGNETIC NONDESTRUCTIVE EVALUATION, 0 Pages, 2002/00

None