Verification of new thin ECT probe for reactor vessel head nozzle

The probe to be applied for the inner surface of the CRDM tubing having a narrow portion of the reactor vessel, however existing probe is not applicable to the minimum gap 1.5 mm of the CRDM tubing. It is necessary to study further thinning of the probe while maintaining sufficient detectability and flaw direction discrimination. Therefore, a new coil system using pancake coils was developed. As a result of a verification test, it was confirmed that an EDM flaw of 0.2 mm in length, 0.2 mm in width and 0.2 mm in depth could be detected and the flaw direction could be identified. (author)