Progress in developments of an EMAT based on a Halbach magnet system for FBR vessel

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

International Journal of Applied Electromagnetics and Mechanics, 59(4), p.1469 - 1477, 2019/03

https://doi.org/10.3233/JAE-171226

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

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

E-Journal of Advanced Maintenance (Internet), 9(2), p.60 - 65, 2017/08

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.

EMAT simulations based on a two-dimensional FEM coupled electro-mechanical formulation

Garcia Rodriguez, D.; Mihalache, O.; Ueda, Masashi

Proceedings of 16th International Symposium on Applied Electromagnetics and Mechanics (ISEM 2013), p.219 - 220, 2013/07

Development of inspection and repair technology for the micro cracks on heat exchanger tubes

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.

Development of inspection and repairing technology for FBR heat exchanger tubes, 2; Preparation of operation software and performance check

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.

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

2D axisymmetric ECT simulation of the world federation's first eddy current benchmark problem

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

no journal, , 

This paper describes the numerical results of the first eddy current (ECT) benchmark problem proposed by the World Federation of Nondestructive Evaluation Centers in the year 2000. The ECT problem, consisting in predicting the signal from axisymmetric defects in an Inconel tube with ferromagnetic support plate, is solved using two simulations software: a 2 dimensional axisymmetric code (2D ECT) developed in-house and the commercial software FEMLAB, both codes being based on the Finite Element Method (FEM). The simulations compare the numerical results obtained with the two codes for several defect geometries and frequencies ranging from 1 to 200 kHz in the presence or absence of a ferromagnetic supportplate.

Detection of small EDM defects located under Monju support plate or near welds using multi-coils remote field eddy current

Mihalache, O.; Yamaguchi, Toshihiko; Ueda, Masashi; Yamashita, Takuya; Date, Koji*

no journal, , 

no abstracts in English