Critical flow in small nozzles for saturated and subcooled water at high pressure. [PWR]

Critical flow rate measurements of 4 mm and 16 mm nozzles have been performed with saturated and subcooled water at high pressure. The steady state and transient critical flow tests were conducted by discharging the fluid from a pressurized vessel through a blowdown leg. The fluid stagnation conditions upstream of the nozzle were measured by a gamma densitometer, thermocouple, and pressure transducer. The pressure and temperature of the tests range from 4.5 MPa to 15.0 MPa and from 530 K to 560 K, respectively. The results show that the flow upstream of the nozzle is stratified. The discharge mass flux obtained by this experiment is in good agreement with General Electric (GE) critical flow test data and Henry-Fauske and Burnell critical flow model predictions using a multiplier of 1.0 +- 0.3