Performance of a drag transducer under simulated PWR refill/reflood flow conditions

A strain gage-based drag transducer developed to measure two-phase flow in simulated PWR (pressurized-water reactor) test facilities is discussed. The drag sensor was designed to sample a large amount of the flow with minimum disturbance to the flow, to be sensitive over a 1000-to-1 range, to be accurate over a 200:1 turndown ratio, and to survive in a hostile steam/water environment. The drag transducer consists of a unique combination of an elongated proving ring, a temperature-compensated, full-bridge strain gage configuration, and a drag target that utilized part of the test vessel internals. The drag body measurement system produced high-quality data for a variety of test conditions, which has led to a better understanding of the phenomena occurring during the refill/reflood stages of a postulated PWR loss-of-coolant accident