Abstract: The steam/water separator includes a lower standpipe for receiving a two-phase mixture of water and steam at its lower end. Internal threads or elements spaced about the interior wall of the standpipe impart a swirl to the incoming mixture, producing a thin film along the walls. Standard pick-off rings or a porous wall may be employed to separate the liquid from the vapor. A central swirl is imparted to the flow in the region dominated by vapor. This combination of peripheral swirl followed by a central swirl for steam/water separation affords minimum pressure losses along the separator with reduced sensitivity to inlet and submergence conditions.