The phased array UT technique has the feature that it is capable to detect in a flexible manner, such as its easy way of changing the ultrasonic direction and beam diameter, so its application was studied for the complicated shape of radius section inside the nozzles.

In case an inner radius section of nozzle is scanned from the external surface of a vessel, the plane of ultrasonic incident would be limited. Accordingly, the optimal incident location was investigated and the flaw detection method was also planned to conduct sector scanning by the array method using a piezo element type probe and to image its result.

The test result of this method applied to surge and spray nozzles of pressurise showed that the flaw (EDM) of 2. 5% thickness could be detected, and implanted fatigue crack of 2. 5% thickness at certain portions could be also detected.

Although EMAT can generate SH wave, which is suitable for detection of flaws in the austenitic welds, conventional EMAT has such disadvantages as shorter pulse length and poor time resolution. The phased array method enables pulse length to shorten and makes the scanning condition (incident angle) optimized by using the variable angular function.

The flaw detectability examination of this method applied to the dissimilar metal welds at R/V inlet and outlet nozzles, and spray and surge pipes showed that all the implanted flaws (EDM) of 10% thickness or more could be detected and that the implanted fatigue cracks and SCC of the same depth could be detected. In addition to this, the detectability of EMAT was found to be superior to that of longitudinal wave.