A Hybrid System for Measuring Solid and Liquid Contaminants in Steam Generators

This paper presents a hybrid device for real-time measurement and imaging of solid and liquid contaminants that may occur in steam generators. The device uses a dedicated near infrared device to determine the type of contaminants (i.e., water droplets and iron oxide particles) and a THz imaging system, which measures the amount of contaminants as well as its flow rate. The near infrared response (NIR) device can also determine the concentration of contaminants at sub-mg accuracy when its value is relatively low using spectrometry technique combined with principal component analysis (PCA). Three principal components (PC1, PC2, and PC3) were enough for this purpose. The PCA classification was performed using the least square support vector machine method. In case of relatively high concentration, the THz imaging system which uses block-based motion estimation algorithm can determine the velocity of individual contaminant particles to compute the global motion vector, the intensity and direction of which represents the overall flow rate and flow regime of the contaminants. The usage of image processing techniques together with an NIR spectrometry constitutes a new promising step in flow metering. This is demonstrated by the extensive experiments which have been conducted for different scenario where the NIR subsystem could determine the concentration of water droplets and solid contaminants with a maximum uncertainty of +/-1.45% and +/-1.16%, respectively. With the NIR subsystem, pixel-level accuracy of motion vector was achieved, whereas the concentration of solid contaminants showed consisted proportionality with the average pixel intensity.