Method for Measuring Feedwater Flow Rate Using Ultrasonic Technique in PWR Power Plant

Abstract

At present, differential pressure type flowmeters are widely used in feedwater systems of PWR plants. In these flowmeters, however, scales gradually deposit at the nozzle throat during the plant operation, causing the apparent flow rate to increase and consequently becoming a serious problem for efficient plant operations. Therefore, a new type of ultrasonic flowmeter (USFM) having good stability and free of the above phenomenon has been developed.
A method to compensate for the effect of dependency of sound velocity on water temperature and pressure corresponding to PWR feedwater conditions was contrived. The validity of the method was confirmed in an experiment for investigating the sound velocity dependency in practice. The performance of the USFM was also examined using a water loop in various flow conditions with satisfactory results. After the basic studies, finally, the USFM was tested in an actual PWR feedwater system for almost 3 yr. The USFM met all the required characteristics for PWR feedwater systems, those being linearity, accuracy and stability.