Method of ultrasonic measurement of the ratio of the volume of gas present in an enclosure containing a liquid-gas mixture to the total volume of the enclosure

摘要

The invention relates to a method of ultrasonic measurement of the ratio of the volume of gas present in an enclosure containing a diphase liquid-gas mixture to the volume of the enclosure, or void coefficient. Waves at different frequencies are propagated through the fluid filling the enclosure (1). The propagation times of the waves are measured and the difference between these propagation times is calculated. If the propagation times are identical, it is deduced that all the gas is in the form of a layer surmounting the liquid. The void coefficient is determined from the propagation velocities of the ultrasounds in the gas and the liquid and from the measured propagation time. If the propagation times are different, a part of the gas is in the form of bubbles in the liquid, the void coefficient due to the gas surmounting the liquid and the void coefficient due to the gas bubbles in the liquid are determined separately. The total void coefficient is determined by adding the two values obtained. The void coefficient due to the gas surmounting the liquid may be determined by virtue of the waves reflected by the gas-liquid interface. The void coefficient due to the gas bubbles is determined by virtue of the relationships existing between the velocity of the ultrasounds and the frequency of the waves, according to the pressure and the void coefficient. The invention is applicable to the measurement of the void coefficient in a pressurized water nuclear reactor after an accident.