Moderator-Flow Measurements at Darlington and Bruce-B Nuclear Generating Stations

Abstract

Moderator flow measurements were performed on Units 2 and 4 of Darlington NGS and Unit 5 and 8 of Bruce B NGS during their respective maintenance outages in 1999. Heat exchanger outlet and calandria inlet flows were measured with each of the pumps running. Measurements were performed using the ultrasonic cross-correlation flow meter, and the results demonstrate that the total moderator flow with either of the main pumps running is substantially higher than the value assumed in the Safety Analysis confirming conservatism in present safe operating margins for moderator sub-cooling. The paper describes the ultrasonic cross-correlation flow meter, presents details of plant measurements and calibration work used to analyze measurement results, and provides rigorous evaluation of the measurement uncertainty.