Evaluating 2 Mm Slot Wedgewire Screens for Reducing Entrainment at a High-Volume Cooling Water Intake

An array of 144, 72-in diameter wedgewire screens (WWS) with 2mm slot width was evaluated for potential to reduce entrainment at the Indian Point Energy Center, a 2000 MW nuclear facility located on the tidal Hudson River.  The evaluation had four components: review of existing WWS installations; flume studies of egg and larval entrainment through WWS at a range of slot widths, through-slot velocities, and sweeping velocities; computational fluid dynamic modeling of the flow around the WWS array; and a field test of a 2mm screen at the power plant site.  Existing WWS installations, even those with slot widths larger than 2mm, were seen to reduce entrainment of fish larvae through avoidance of the low-velocity intake flows.  Flume testing confirmed that larval avoidance is a key modality of WWS entrainment reduction, avoidance is strongly related to larval length, entrainment reductions are affected by sweeping velocity along the screen axis and through-slot velocity, and that screen length had no observable effect on larval avoidance.  Although the array of 144 screens, each withdrawing up to 44 m³/min, would reduce current velocity in the river, the velocity reductions would not substantively affect performance.