BWR natural steam separator

This patent describes a steam separator for a boiling water reactor. It comprises a reactor pressure vessel having a reactor core disposed therein and containing water disposed at a level above the core with a vessel upper plenum extending upwardly from the water level for receiving steam generated by the core; a chimney including an annular chimney wall having a proximal end disposed adjacent to the core and a distal end disposed below the water level for channeling upwardly therein steam voids and water flow from the core, the chimney wall being spaced radially inwardly from the vessel to define a downcomer therebetween for recirculating the water flow from the chimney over the chimney wall distal end and downwardly through the downcomer and back to the core; and an annular partition wall spaced radially between the vessel and the chimney wall at the distal end to define the the chimney wall an annular collection chamber having an inlet for receiving a portion of the steam voids and water flow from the chimney, a steam outlet for discharging the steam voids as separated steam from the chamber to the upper plenum above the water level, and a flow outlet for discharging the water flow from the chamber into the downcomer