Regular Article

Eddy current testing system for bottom mounted instrumentation welds

¹ Power and Industrial Systems Research and Development Center, Toshiba Corporation, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523, Japan
² Power and Industrial Systems Research and Development Center, Toshiba Corporation, 1, Komukaitoshiba-cho, Saiwai-ku, Kawasaki 212-8581, Japan
³ Keihin Product Operations, Toshiba Corporation, 2-4, Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
⁴ Isogo Nuclear Engineering Center, Toshiba Corporation, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523, Japan

^* e-mail: noriyasu.kobayashi@toshiba.co.jp

Received: 19 June 2015
Received in final form: 18 August 2015
Accepted: 27 August 2015
Published online: 5 December 2015

Abstract

The capability of eddy current testing (ECT) for the bottom mounted instrumentation (BMI) weld area of reactor vessel in a pressurized water reactor was demonstrated by the developed ECT system and procedure. It is difficult to position and move the probe on the BMI weld area because the area has complexly curved surfaces. The space coordinates and the normal vectors at the scanning points were calculated as the scanning trajectory of probe based on the measured results of surface shape on the BMI mock-up. The multi-axis robot was used to move the probe on the mock-up. Each motion-axis position of the robot corresponding to each scanning point was calculated by the inverse kinematic algorithm. In the mock-up test, the probe was properly contacted with most of the weld surfaces. The artificial stress corrosion cracking of approximately 6 mm in length and the electrical-discharge machining slit of 0.5 mm in length, 1 mm in depth and 0.2 mm in width given on the weld surface were detected. From the probe output voltage, it was estimated that the average probe tilt angle on the surface under scanning was 2.6°.