Torsional Ultrasonic Technique for LWR (Light Water Reactor) Liquid Level Measurement.

摘要

In the late 1970's, a technique for determining the mean density of a fluid surrounding a waveguide of non-circular cross section was developed using slow torsional ultrasonic pulses. With the waveguide partially inserted in a liquid of known density, the fraction of the probe immersed in the liquid can be derived, and hence the level. The loss-of-cooling accident at TMI-2 in 1979 pointed out the need for a sensor to monitor continuously reactor vessel coolant level and density (i.e., void fractions). Devices utilizing torsional ultrasonic pulses can provide continuous readouts, in appropriate units, of level, average density (or void fraction), and temperature along the sensor in the reactor vessel, in each of a number of zones (limited to about 20 sections per probe in practice). Additional advantages of the torsional-wave level probe include ruggedness and long life resulting from the simplicity of the waveguide structure--only a strip of stainless steel contained in a stainless steel support tube is immersed in the reactor vessel. Thus the probe is expected to have a long life in high neutron and gamma fluxes as well as being adaptable to current reactor designs.