THE ON-LINE DETECTION OF ENTRAPPED AIR VOIDS IN LIQUID-FILLED SENSING LINES WILL BE INVESTIGATED.

THE ON-LINE DETECTION OF ENTRAPPED AIR VOIDS IN LIQUID-FILLED SENSING LINES WILL BE INVESTIGATED. IN NUCLEAR PLANTS THE SENSING LINES USED FOR MEASUREMENT OF FEEDWATER FLOWRATE AND REACTOR COOLANT LEVEL ARE OFTEN SEVERAL HUNDERED FEET IN LENGTH. THE PROBLEM ASSOCIATED WITH THE PRESENCE OF ENTRAPPED AIR CAN MANIFEST ITSELF AS EITHER A STATIC OR DYNAMIC OFFSET ERROR IN THE PROCESS PARAMETER MEASUREMENT. IN CERTAIN APPLICATIONS IN NUCLEAR POWER PLANTS, THIS CAN POSE A SAFETY CONCERN. IN THE ON-LINE, ACTIVE ACOUSTIC DETECTION TECHNIQUE TO BE STUDIED, AN INPUT SIGNAL IS SUPPLIED DIRECTLY TO THE LIQUID AT THE PROCESS END OF THE SENSING LINE. THIS INPUT SIGNAL WILL HAVE A KNOWN SPECTRAL CONTENT. A TRANSDUCER WILL ALSO BE PLACED AT THE OPPOSITE END OF THE SENSING LINE TO MONITOR THE SIGNAL. THE RELATIONSHIP BETWEEN THE SPECTRUM OF THE INPUT SIGNAL AND THE MONITORED SIGNAL IS A FUNCTION OF THE QUANITITY AND LOCATION OF AIR VOIDS IN THE LINE.