Online and global structural health monitoring of high-temperature steam lines
Circumferential steam line welds in nuclear plant are currently inspected at the planned outages used for all categories of plant maintenance, using conventional ultrasonic testing. The steam lines are composed of chrome-molybdenum-vanadium (CNV) steel, which has a fine-grained structure so that defects with dimensions as small as the wavelength are readily detectable with MHzfrequency ultrasound. There are typically four steam lines per nuclear plant (reactor), containing some 500 welds. In practice, discrete (ie once only) measurements for weld defects are only made on around 20 per cent of the welds per planned outage, at intervals ranging from one-and-ahalf to four years, in order to limit the extra planned outage time required for inspection to two days. So total weld coverage is achieved only after around ten years (50 welds per year).
The project’s aim is the early detection of creep cracking, fatigue cracking and erosion thinning in superheated steam lines in nuclear plants, through the use of high-frequency long-range ultrasonic guided waves as a structural health monitoring system, permanently installed on line pipework.
The UltraSteamLine technology is applicable to both existing and future nuclear power plants.
This project was co-funded by the UK’s innovation agency, Innovate UK.