Patent Number: 051065738
Section: claims

1. A steam separator for a boiling water reactor comprising: a reactor pressure vessel having a reactor core disposed therein and containing water disposed at a level above said core with a vessel upper plenum extending upwardly from said water level for receiving steam generated by said core;  a chimney including an annular chimney wall having a proximal end disposed adjacent to said core and a distal end disposed below said water level for channeling upwardly therein steam voids and water flow from said core, said chimney wall being spaced radially inwardly from said vessel to define a downcomer therebetween for recirculating said water flow from said chimney over said chimney wall distal end and downwardly through said downcomer and back to said core; and  an annular partition wall spaced radially between said vessel and said chimney wall at said distal end to define the said chimney wall an annular collection chamber having an inlet for receiving a portion of said steam voids and water flow from said chimney, a steam outlet for discharging said steam voids as separated steam from said chamber to said upper plenum above said water level, and a flow outlet for discharging said water flow from said chamber into said downcomer.  a top portion having a plurality of circumferentially spaced collection pipes disposed in flow communication between said chamber and said upper plenum to define a plurality of said steam outlets, respectively;  a middle portion extending downwardly from said top potion; and  a bottom portion extending downwardly from said middle portion to said chimney wall, and having a plurality of circumferentially spaced apertures defining a plurality of said flow outlets, respectively, disposed in flow communication with said chamber and said downcomer.  a plurality of dampers, each disposed adjacent to a respective one of said chamber flow outlets, and positionable between closed and open positions for selectively controlling velocity of said water flow through said chamber; and  means for positioning said dampers between said open and closed positions. 2. A steam separator according to claim 1 wherein said partition wall includes: 3. A steam separator according to claim 2 further including a lip extending from said partition top portion and spaced upwardly from said chimney wall distal end to define therebetween said inlet. 4. A steam separator according to claim 3 wherein said collection pipes include first collection pipes having bottom ends disposed coextensively with said partition top portion for discharging from said chamber a first portion of said steam voids, and second collection pipes having bottom ends disposed generally coextensively with said chimney wall distal end for discharging from said chamber a second portion of said steam voids. 5. A steam separator according to claim 4 wherein said partition wall is sized and configured so that a terminal rise velocity of said steam voids in said chamber is greater than a velocity of said water flow downwardly in said chamber for allowing said steam voids to rise inside said chamber for discharge by said first and second collection pipes. 6. A steam separator according to claim 5 wherein said partition middle portion is spaced radially outwardly form said chimney wall so that a width of said downcomer at said partition middle portion is less than a width of said downcomer downstream of said partition. 7. A steam separator according to claim 5 wherein said first and second collection pipes discharge said steam voids from said collection chamber adjacent to said vessel in said upper plenum for reducing average leaving velocities of said steam discharged from said water level for reducing water carryover in said steam. 8. A steam separator according to claim 5 wherein said partition top portion extends horizontally from said middle portion radially inwardly toward said chimney, and said lip extends downwardly from said top portion toward said chimney distal end for channeling said steam voids first portion into said first collection pipes. 9. A steam separator according to claim 5 wherein said partition top portion extends radially inwardly and downwardly from said middle portion toward said chimney ending in said lip, and said first collection pipe bottom ends are disposed adjacent to said middle portion at said top portion, and said second collection pipe bottom ends are disposed adjacent to said chimney wall distal end. 10. A steam separator according to claim 5 wherein said partition top portion extends radially inwardly and upwardly from said middle portion toward said chimney, and said lip extends downwardly from said top portion toward said chimney wall distal end for channeling said steam voids first portion into said first collection pipes. 11. A steam separator according to claim 10 wherein both said first and second collection pipes are disposed adjacent to said chimney. 12. A steam separator according to claim 11 wherein said chimney further includes a plurality of flow partitions spaced radially inwardly from said chimney wall and having a height at least as high as a height of said chimney wall distal end. 13. A steam separator according to claim 4 further including: 14. A steam separator according to claim 13 wherein said chamber flow outlets are sized so that when said dampers are positioned to a fully open position a velocity of said water flow through said chamber exceeds a terminal rise velocity of said steam voids in said chamber.