Design and testing of a thermal liquid level sensor

During a reactor accident involving loss of coolant inventory, it is important to know the liquid level inside the reactor. Several techniques are available to accomplish this type of measurement, including pressure sensors, floats, and acoustic devices. Another technique involves the use of a directly or indirectly heated thermocouple to determine changes in the heat transfer coefficient on the outer surface of a level probe, such as would occur when a drop in liquid level exposes the probe to a gaseous environment. This paper presents the design and data from the testing of a thermal liquid level sensor, using an indirectly heated thermocouple. The probe has been specifically designed for use in the heavy-water-cooled and -moderated reactors at the Savannah River Plant (SRP)