Patent Number: 
Section: claims

1. A reactor instrumentation system for monitoring a state of a reactor, comprising:an instrumentation tube disposed in a reactor core;a gas flow pipe disposed in the instrumentation tube;a pump connected to the gas flow pipe and configured to supply gas containing oxygen into the gas flow pipe; anda nuclide analysis device connected to the gas flow pipe outside of the reactor core and configured to measure gamma rays emitted from one or more types of nuclides, including N-16, in the gas which has flowed out through the gas flow pipe in the instrumentation tube in the reactor core,wherein the gas flow pipe includes a plurality of pipes that extend different lengths in the same instrumentation tube in the reactor core, and the nuclide analysis device includes a plurality of nuclide analysis devices configured to respectively measure the gamma rays emitted from the plurality of pipes, andwherein a number of the gas flow pipes is equal to a number of neutron detectors in the reactor core and the gas flow pipes extend different lengths corresponding to the neutron detectors in the instrumentation tube. 2. The reactor instrumentation system according to claim 1, whereinthe nuclide analysis device is further configured to measure gamma rays emitted from O-19 in the gas flow pipe. 3. The reactor instrumentation system according to claim 1, further comprising:a monitoring device connected to the nuclide analysis device and configured to monitor reactor power on the basis of a measurement result transmitted from the nuclide analysis device. 4. The reactor instrumentation system according to claim 1, whereinsensitivity of the neutron detectors is calibrated on the basis of a measurement result from the nuclide analysis device. 5. The reactor instrumentation system according to claim 1, whereinan energy distribution of neutrons at an observation position is estimated on the basis of measurement results of the gamma rays emitted from O-19 and N-16 generated by irradiating the oxygen in the gas flow pipe with neutrons in the reactor core. 6. The reactor instrumentation system according to claim 1, whereinthe gas containing oxygen is carbon dioxide. 7. A reactor, comprising:a reactor pressure vessel; anda reactor core provided in the reactor pressure vessel,an instrumentation tube disposed in the reactor core;a gas flow pipe disposed in the instrumentation tube;a pump connected to the gas flow pipe and configured to supply gas containing oxygen into the gas flow pipe; anda nuclide analysis device connected to the gas flow pipe and configured to measure gamma rays emitted from one or more types of nuclides, including N-16, in the gas which has flowed out through the gas flow pipe in the instrumentation tube in the reactor core,wherein the gas flow pipe includes a plurality of pipes that extend different lengths in the same instrumentation tube in the reactor core, and the nuclide analysis device includes a plurality of nuclide analysis devices configured to respectively measure the gamma rays emitted from the plurality of pipes, andwherein a number of the gas flow pipes is equal to a number of neutron detectors in the reactor core and the gas flow pipes extend different lengths corresponding to the neutron detectors in the instrumentation tube.