Patent Number: 053217314
Section: claims

1. In a boiling water reactor of a type wherein housed within a reactor pressure vessel having an inlet for supplying feedwater and a steam outlet connected to a steam dome is a nuclear core disposed within a shroud having a shroud head within which is formed a core upper plenum for containing a two-phase mixture of steam-water discharged from the core, the shroud and the reactor pressure vessel defining an annulus extending from a downcomer region to a core lower plenum disposed beneath the reactor core and in fluid communication with the core upper plenum, the improvement which comprises a modular steam separator and integrated dryer comprising: a standpipe having a proximal end connected to the core upper plenum and having a distal end;  a steam separator having a proximal end connected to said standpipe distal end and having a distal end; and  a steam dryer having a steam inlet distribution channel in fluid communication with said steam separator distal end, a steam vent in fluid communication with the steam dome, and a water drain connected to said downcomer region, said standpipe, said steam separator, and said steam dryer being connected to one another to effect separation of the steam-water discharged from the core in two stages such that the steam supplied through said steam outlet to said steam dome passes through said steam separator and said steam dryer, respectively.  (a) passing said two-phase mixture into a modular steam separator and integrated dryer wherein;  a steam dryer having a steam inlet distribution channel in fluid communication with said steam separator, a steam vent in fluid communication with the steam dome, and a water drain connected to said downcomer region is connected to said steam separator;  (b) separating at least a portion of the water component from the two-phase mixture of step (a) in said steam separator;  (c) drying the two-phase mixture from step (b) in said steam dryer to separate additional water from the steam component; and  (d) effecting separation of the steam and water components discharged from the core into the upper plenum in two stages such that the steam supplied through the steam outlet to the steam dome passes through the steam separator and the steam dryer, respectively. 2. The modular steam separator and integrated dryer of claim 1 wherein said steam separator is of a centrifugal type. 3. The modular steam separator and integrated dryer of claim 1 wherein said steam dryer has internal vanes. 4. The modular steam separator and integrated dryer of claim 1 wherein said steam inlet distribution channel decreases in cross-sectional area from said steam separator distal end to said steam dryer. 5. The modular steam separator and integrated dryer of claim 1 wherein said steam vent increases in cross-sectional area away from said steam dryer. 6. The modular steam separator and integrated dryer of claim 1 further comprising a steam connection for fluid communication of the downcomer region with said steam separator. 7. The modular steam separator and integrated dryer of claim 1 wherein said water drain extends below the feedwater level of the RPV. 8. In a method for separating and drying steam from a two-phase mixture having a water and a steam component formed from the passage of feedwater in a heat transfer relationship with the core of a boiling water reactor wherein the core is housed within a reactor pressure vessel having a feedwater inlet and a steam outlet connected to a steam dome and is disposed within a shroud having a shroud head within which is formed a core upper plenum, the shroud and the reactor pressure vessel defining an annulus extending from a downcomer region to a core lower plenum disposed beneath the reactor core and in fluid communication with the core upper plenum, the improvement which comprises: 9. The method of claim 8 wherein said steam separator is of a centrifugal type. 10. The method of claim 8 wherein said steam dryer has internal vanes. 11. The method of claim 8 wherein said steam inlet distribution channel decreases in cross-sectional area from said steam separator to said steam dryer. 12. The method of claim 8 wherein said steam vent increases in cross-sectional area away from said steam dryer. 13. The method of claim 8 further comprising the step of passing the separated water from step (b) into the downcomer region. 14. The method of claim 8 further comprising the step of passing the separated water from step (c) into the downcomer region via said water drain. 15. The method of claim 8 further comprising the step of passing the steam component from step (c) into the steam dome via the steam vent. 16. The method of claim 8 wherein a steam connection is provided for fluid communication of the downcomer region with said steam separator. 17. The method of claim 8 wherein said water drain extends below the feedwater level of the reactor pressure vessel. 18. The modular steam separator and integrated dryer of claim 1 wherein said steam dryer has internal vanes and a steam connection affording communication between said downcomer region and said steam separator.