Patent Number: 
Section: claims

1. A generation system having a natural circulation reactor comprising:a reactor pressure vessel of the natural circulation reactor having a core with a chimney disposed above the core, the core and the chimney being disposed in the reactor pressure vessel;a feed water pipe connected to the reactor pressure vessel and configured to supply feed water which flows therein to the reactor pressure vessel;a feed water temperature detection apparatus disposed at the feed water pipe and configured to detect a temperature of the feed water in the feed water pipe;a power controller section which outputs a power adjustment demand signal so as to control reactor power in accordance with the detected temperature of the feed water in the feed water pipe which is detected by the feed water temperature detection apparatus; anda control rod driving section which controls the reactor power by inserting and withdrawing a control rod with respect to the core in accordance with the power adjustment demand signal from the power controller section. 2. The generation system to claim 1, wherein the feed water temperature detection apparatus has a pair of ultrasonic sensors disposed at a position outside of the reactor pressure vessel so as to enable detection of the temperature of the feed water in the feed water pipe in proximity thereto. 3. The generation system according to claim 1, wherein the feed water temperature detection apparatus has a plurality of pairs of ultrasonic sensors disposed at a position outside of the reactor pressure vessel so as to enable detection of the temperature of the feed water in the feed water pipe in proximity thereto. 4. The generation system according to claim 3, wherein the plurality of the pairs of the ultrasonic sensors enable detection of a temperature distribution of the feed water in the feed water pipe in proximity thereto. 5. The generation system according to claim 3, wherein the plurality of the pairs of the ultrasonic sensors are disposed on an outer peripheral portion of said feed water pipe so as to be parallel to each other. 6. The generation system according to claim 5, wherein the plurality of the pairs of the ultrasonic sensors are disposed so as to have a prescribed interval between them. 7. The generation system according to claim 3, wherein the plurality of the pairs of the ultrasonic sensors are disposed on an outer peripheral portion of the feed water pipe so as to cross each other. 8. The generation system of claim 1, wherein the plurality of the pairs of the ultrasonic sensors are disposed at a position outside of and in the vicinity of the reactor pressure vessel so as to enable detection of the temperature of the feed water in the feed water pipe in proximity thereto. 9. The generation system according to claim 1, wherein the feed water pipe is arranged externally of the reactor pressure vessel. 10. The generation system according to claim 9, wherein the feed water temperature detection apparatus is disposed with respect to the feed water pipe at a position externally of said reactor pressure vessel so as to enable detection of the temperature of the feed water in the feed water pipe in proximity thereto. 11. A generation system according to claim 1, wherein the feed water pipe is connected to a condenser so as to enable supply of the feed water which flows within the feed water pipe from the condenser to the reactor pressure vessel. 12. A generation system according to claim 1, wherein the feed water temperature detection apparatus is disposed at a position of the feed water pipe externally of the reactor pressure vessel and adjacent thereto so as to detect the temperature of the feed water in the feed water pipe immediately before the feed water flows into the reactor pressure vessel. 13. A generation system according to claim 1, wherein the feed water pipe is connected to the reactor pressure vessel so as to supply feed water to an interior of the reactor pressure vessel without extending within the reactor pressure vessel to an inlet of the core within the reactor pressure vessel. 14. A generation system according to claim 1, wherein the feed water pipe supplies feed water to an interior of the reactor pressure vessel so that the feed water is mixed with water within the reactor pressure vessel and the temperature of the feed water which flows in the feed water pipe to the reactor pressure vessel is different from a temperature of the feed water which is mixed with the water within the reactor pressure vessel at least at an inlet of the core.