Yangjiang NPP uses phased array ultrasonics for seam weld detection

The Yangjiang Nuclear Power Plant (NPP) has become the first in the country to replace radiographic flaw detection technology with phased array ultrasonics technology for seam weld detection on conventional islands.

Radiographic flaw detection is a widely-used non-destructive detection method that uses X-rays and γ-rays to find internal flaws in seam welds. However, the use of radioactive sources hampers the detection process, as it requires long preparation time, a strict working window, and a large isolated area. The NPP must close the entire conventional island every time radiographic flaw detection is carried out, which means the process can only be carried out at night.

Phased array ultrasonics technology is superior to radiographic flaw detection due to its faster detection speed and greater flexibility. It can produce a real-time colored image that is easier to read. Its detection data can be stored just like the negative plate of radiographic flaw detection.

Meanwhile, the device is easy to use, eliminating problems such as accidental radiation exposure, and removing the hassle of separation boundaries.

In 2017, the Yangjiang NPP took the lead in the application of phased array ultrasonics technology in carbon steel seam weld detection, saving more than 220 hours in the detection of over 280 welded junctions. The NPP then moved toward applying the technology in stainless steel seam weld detection. With no precedent to draw from, the team managed to get hold of a whole set of industry-accepted standardized technology after nearly one year of research and testing.

To prove the reliability of the technology, a test was recently conducted on 45 stainless steel seam welds during a third outage on Unit 2 of the Yangjiang NPP. The results were consistent with those produced by radiographic flaw detection, marking the successful application of the technology.