An ultrasonic imaging system that simultaneously measures the radius and rise velocity of large spherical discontinuities in liquids

A real time ultrasonic imaging system was developed that simultaneously measures the radius and the rise velocity of large spherical discontinuities in a liquid. This system has been designated the ultrasonic dynamic imaging system. It was developed as a possible technique for studying the dynamics of large vapor-filled bubbles in liquid sodium. The ultrasonic characterization of such bubbles is one part of a comprehensive investigative program at Oak Ridge National Laboratory that is known as the Fuel Aerosol Simulant Test (FAST). The purpose of the FAST program is to investigate the events following a simulated hypothetical core disruptive accident in a liquid metal fast breeder reactor.

The accuracy and the limitations of the system are evaluated using a variety of solid and air-filled spherical test targets in water. The diameters of the test spheres range from 3.26 cm to 24.1 cm. The magnitudes of the rise velocities range from approximately 40 cm/sec to approximately 1 m/sec. The uncertainty in the radii measurements within the interval from 3.26 cm to 9.10 cm is estimated to be within ± 7% at a confidence level of 95%. Theoretical calculations of the rise velocities are compared to the measurements performed with the UDI system. In addition, independent experimental measurements of the rise velocities are obtained with a laser-photocell system. Based upon those comparisons the uncertainty in the velocity measurements, at a confidence level of 95%, is estimated to be within ± 8%. That estimate is made with the tacit assumption that the size is precisely known. If both size and velocity are experimentally measured, the uncertainty in the determination of rise velocity is estimated to be within ± 15%.