Patent Number: 
Section: claims

1. A system for measuring flow rate of fluid within a reactor vessel of a nuclear reactor module, the system comprising:a processing device configured to:measure a first time of flight of a first signal through the fluid from a first location outside the reactor vessel to a second location outside the reactor vessel, wherein the second location is different than the first location;measure a second time of flight of a second signal through the fluid from the second location to a third location that is different than the second location, wherein the third location is different than the first location; anddetermine the flow rate of the fluid within the reactor vessel based, at least in part, on both the first time of flight and the second time of flight. 2. The system of claim 1, wherein the first signal travels from the first location through the fluid along a substantially linear path before arriving at the second location. 3. The system of claim 2, wherein the second signal travels through the fluid along a substantially linear path from the second location before arriving at the third location. 4. The system of claim 2, the processing device further configured to:measure time of flights for additional signals through the fluid along a plurality of linear paths; anddetermine the flow rate based on an aggregation of the time of flights for the plurality of linear paths. 5. The system of claim 1, wherein determine the flow rate of the fluid within the reactor vessel based, at least in part, on both the first time of flight and the second time of flight comprises take an average of the first time of flight and the second time of flight. 6. The system of claim 1, wherein determine the flow rate of the fluid within the reactor vessel based, at least in part, on both the first time of flight and the second time of flight comprises take a weighted average of the first time of flight and the second time of flight. 7. The system of claim 1, the processing device further configured to compare the first time of flight with the second time of flight to identify irregularities in the flow rate of the fluid through the reactor vessel. 8. The system of claim 1, the processing device further configured to compare the first time of flight with the second time of flight to identify temperature changes in the fluid. 9. The system of claim 1, the processing device further configured to determine a temperature of the fluid based, at least in part, on the first time of flight and the second time of flight. 10. A system for measuring flow rate within a vessel, the system comprising:an emitter located at a first location outside the vessel, the emitter configured to transmit a signal through fluid contained within the vessel;a receiver located at a second location outside the vessel, wherein the second location is different than the first location, the receiver configured to receive the signal transmitted through the fluid by the emitter; anda processor configured to determine a flow rate of the fluid based, at least in part, on a time of flight of the signal from the first location to the second location;wherein the vessel comprises a reactor vessel of a nuclear reactor module. 11. The system of claim 10, including a relay device configured to propagate the signal transmitted from the first location to the second location. 12. The system of claim 11, wherein the relay device comprises an additional receiver and an additional emitter. 13. The system of claim 11, wherein the processor is configured to determine the flow rate of the fluid based, at least in part, on a first time of flight of the signal from the emitter to the relay device and a second time of flight from the relay device to the receiver. 14. A system for measuring flow rate within a vessel, the system comprising:an emitter located at a first location outside the vessel, the emitter configured to transmit a signal through fluid contained within the vessel;a receiver located at a second location outside the vessel, wherein the second location is different than the first location, the receiver configured to receive the signal transmitted through the fluid by the emitter;a relay device configured to propagate the signal transmitted from the first location to the second location; anda processor configured to determine a flow rate of the fluid based, at least in part, on a time of flight of the signal from the first location to the second locationwherein the processor is configured to determine the flow rate of the fluid based, at least in part, on a first time of flight of the signal from the emitter to the relay device and a second time of flight from the relay device to the receiver.