Forced and natural recirculation system for boiling water reactor.

摘要

A BWR coolant recirculation system includes a pump deck (30) disposed in a downcomer (28) and fixedly joined to a reactor pressure vessel (12) and reactor core shroud (26). A plurality of circumferentially spaced reactor internal pumps (RIPs) (32) are joined to the deck (30) and operable in a pumping mode for pumping downwardly a reactor coolant from the downcomer (28) and into a core inlet (42). In a pump inoperable mode, a portion of the coolant bypasses the RIPs (32) through bypass orifices (58,60) for allowing increased natural recirculation of the coolant from the downcomer and into the core inlet. In the pumping mode, backflow through the orifices (58,60) is preverented using conduits (62) surrounding the RIPs (32) and cooperating with them to form jet pumps.