Pressure spikes following pump start in a closed loop system at Millstone Unit 2, caused thermal relief valve lifting, and two remained partially open, draining 40 gpm (2.5 L/s). Entrapped air following maintenance activities caused these pressure spikes. Proposed solutions included changing pump impellers, removing all thermal relief valves, and vacuum filling the system. Altran proposed installing orifice plates as flow restrictors in the 8” (203 mm) lines from the surge tank. These flow restrictors reduced the collapse rate of the captive gas pockets and thus reduced the associated pressure spikes following pump start which was confirmed by tests performed in March, 2002.

This content is only available via PDF.
You do not currently have access to this content.