Patent Number: 050826204
Section: claims

1. A recirculation system for a boiling water reactor having a cylindrical shroud surrounding a reactor core and spaced radially inwardly from a pressure vessel to define an annular downcomer for channeling downwardly a recirculation reactor coolant into an inlet of the core disposed at a lower plenum of the vessel comprising: an annular pump deck disposed in said downcomer and fixedly joined to said pressure vessel and said core shroud;  a plurality of circumferentially spaced impeller-driven reactor internal pumps (RIPs) disposed in said downcomer and joined to said pump deck for pumping a first portion of said coolant in said downcomer downwardly through said pump deck and into said lower plenum as RIP discharge flow to said core inlet; and  a plurality of circumferentially spaced fluid-driven jet pumps (JPs) disposed in said downcomer and joined to said pump deck for pumping a second portion of said coolant in said downcomer downwardly through said pump deck and into said lower plenum as JP discharge flow to said core inlet in parallel flow with said RIP discharge flow.  a nozzle for ejecting a JP driving fluid as a jet;  an inlet for receiving said JP driving fluid jet and said downcomer coolant second portion;  a mixer for mixing said jet and said coolant second portion;  a diffuser for diffusing said mixed jet and coolant second portion;  an outlet for discharging said mixed and diffused jet and coolant second portion through said pump deck and into said lower plenum as said JP discharge flow; and  means for supplying said JP driving fluid to said nozzle.  a feedwater driving pump for pressurizing said feedwater;  a flow control valve disposed in flow communication with said feedwater pump;  a feedwater sparger disposed inside said pressure vessel and in flow communication with said flow control valve; and  said flow control valve being disposed in flow communication with said JP nozzles in parallel flow with said feedwater sparger. 2. A recirculation system according to claim 1 wherein said RIPs and said JPs have diverse motive power sources for preventing simultaneous tripping thereof. 3. A recirculation system according to claim 2 wherein each of said RIPs has an RIP flow inertia, and each of said JPs has a JP flow inertia greater than said RIP flow inertia. 4. A recirculation system according to claim 3 wherein each of said JPs includes: 5. A recirculation system according to claim 4 wherein said JP nozzle and inlet are disposed above said reactor core. 6. A recirculation system according to claim 4 wherein said JP driving fluid is steam. 7. A recirculation system according to claim 6 wherein said steam supplying means are disposed in flow communication with a steam outlet nozzle of said boiling water reactor for receiving a portion of steam discharged from said boiling water reactor for flow to said JP nozzle as said JP driving fluid. 8. A recirculation system according to claim 7 wherein said steam supplying means include means for reheating said steam from said outlet nozzle for raising the temperature of said steam for flow to said JP nozzle. 9. A recirculation system according to claim 4 wherein said JP driving fluid is feedwater. 10. A recirculation system according to claim 9 wherein said feedwater supplying means include: 11. A recirculation system according to claim 10 wherein said feedwater driving pump is sized for effecting said JP flow inertia greater than said RIP flow inertia. 12. A recirculation system according to claim 10 wherein in a trip of said boiling water reactor, said JPs are effective for maintaining and increasing water level in said pressure vessel while said RIPs are effective for decreasing total flow of said reactor coolant into said core inlet for increasing steam void fraction in said core for decreasing reactivity of said core.