The accumulation of gas voids in piping has been an issue that could adversely affect the operation of emergency cooling systems. In 2008, the United States Nuclear Regulatory Commission issued Generic Letter 2008-01 “Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems. Concerns of gas accumulating in these piping systems and potentially causing failure of the system created a need to monitor these systems periodically for gas entrapment. Typically, these locations are at high-points and may require scaffolding and manual access to check for gas voids. Furthermore, they often are checked at periodic intervals such as monthly or quarterly.
To eliminate the need for manual exams a wireless ultrasonic monitored system was demonstrated on a mockup at EPRI’s facility in Charlotte. A small section of pipe was set up and filled with water to assess the instrumentation. A small leak at a valve was used to slowly drip water out of the pipe and increase the amount of gas in the pipe. Data was collected over time and transmitted through a distributed antenna system (DAS) and transmitted to the cloud. The ultrasonic sensor was placed on the bottom side of the pipe, so a measurement of the water level was obtained from the velocity and time of flight and used to determine the amount of gas trapped at the top. The data was stored and monitored from a website that could be accessed by a laptop, desktop, tablet, or any browser enabled device.