Hitachi-GE Nuclear Energy, Ltd.

The eddy current testing (ECT) system has been established to inspect the surface of nickel based weld lines associating with for the structural integrity of nuclear reactor components.

Fig.1 shows a view of ECT system. Fig.2 shows the structure of flexible ECT array probe. This system is composed of flexible ECT array probe, data acquisition device and personal computer（PC）. The probe employing flexible technique performs stable scanning on three-dimensionally curved surfaces. The data acquisition device switches pairs of detector and exciting coils of probe in speedy succession, and then sends ECT signals of all detector coils to PC. The software installed in PC helps inspectors identify SCCs and measure their lengths.

Fig.3 shows applicable nickel based weld lines of ECT system in BWR reactor. ECT’s performance, testing procedure and range of application have already been certificated by Japanese third party NDE(non-destructive examination) certification organization. Verfication has also been performed by using remote access devices and mock-up test pieces simulating in-vessel components of BWR.

As mentioned above, The ECT inspection has been established for nickel based weld lines of BWR’s in-vessel components. This system is also applicable to nickel based weld lines of PWR’s in-vessel components.

This is the method of improving residual stresses all around by moving the region irradiated by laser beam on the outer surface in the circumference direction. In addition, temperature increase by high energy laser is so high that inside water cooling can be omitted especially for a small pipe or nozzle.

Fig. 1 A View of the ECT system

Fig. 2 The structure of flexible ECT array probe

Fig. 3 Applicable nickel based weld lines of ECT system in BWR reactor

Phase 2 :Industrial Confirmation Phase

-The performance of detection and length measurement, testing procedure and range of application have been certificated by Japan Power Engineering and Inspection Corporation in January, 2011. In this certification, ECT has been performed for test pieces including mock-up test pieces simulating shroud support H9 and H11, CRD(Control Rod Drive) stub tube and ICM(In-Core Monitor) housing, in which SCC(Stress Corrosion crack) s are given.

- Mock-up testing by using remote access devices has also been performed. In mock-up testing, the remote access devices were operated under water, and ECT was performed for mock-up test pieces of BWR bottom head, such as CRD stub tube, ICM housing and DP/SLC(Differential　Pressure　and　Standby　Liquid　Control) nozzle.