Gas Void Monitoring and Control System (GVMCS) development for Gas Intrusion and Accumulation in Nuclear Power Plants

The NRC has issued a number of information notices and Generic Letters (GLs) on the subject. In 2008, the NRC issued GL 2008-01 to comprehensively address gas accumulation issues and to request each licensee evaluate its emergency core cooling, decay heat removal, and containment spray systems for licensing basis, design, testing, and corrective actions regarding pump response to suction voids. Licensees should evaluate and address deaeration, flashing, and other air entrainment mechanisms, as discussed in GL 2008-01. These include sources of gas, gas accumulation locations, determination of gas quantities, water hammer, cavitation, fluid induced vibration, and acceptable gas quantity with pump operation and control of gas. GVMCS aims at reducing the need for repeated containment entries for monitoring gas voids in high radiation, hard-to-reach locations by automatic venting.