Patent Number: 
Section: claims

1. A nuclear instrumentation system for surveilling reactor core parameters of the pressure vessel, including a source range channel, an intermediate range channel and a power range channel, wherein each channel includes one detector installed around the pressure vessel, wherein the detector of the power range channel includes at least one fission chamber and the detector of the intermediate range channel includes at least one fission chamber; wherein the detector of the power range channel and the detector of the intermediate range channel share at least one fission chamber. 2. The nuclear instrumentation system according to claim 1, wherein the detector of the power range channel includes four fission chambers connected sequentially, wherein, the four fission chambers are distributed with a same distance at both sides of a core plane at ½ height outside of the core along an axial direction of the pressure vessel, the detector of the intermediate range channel shares both two middle fission chambers of the detector of the power range channel; wherein two fission chambers are arranged at upside of the core plane while two fission chambers are arranged at downside of the core plane. 3. The nuclear instrumentation system according to claim 1, wherein the detector of the source range channel is installed in a core plane at ¼ height of the core along an axial direction of the pressure vessel. 4. The nuclear instrumentation system according to claim 1, wherein there are three source range channels, four intermediate range channels and four power range channels. 5. The nuclear instrumentation system according to claim 4, wherein the detectors of the four intermediate range channels and the detectors of the four power range channels are both installed in one first instrumentation guiding sleeve, the detectors of the three source range channels are installed in one second instrumentation guiding sleeve independently, the detectors of the three source range channels are installed with a same distance along a circumferential direction of the pressure vessel, the detectors of the four intermediate range channels and four power range channels are installed with a same distance along the circumferential direction of the pressure vessel, wherein the detectors of the three source range channels and the detectors of the four intermediate range channels and four power range channels are offset with each other. 6. The nuclear instrumentation system according to claim 5, wherein the detectors of the three source range channels are distributed at radial positions of 10°, 190°, 280° of the pressure vessel the detectors of the four intermediate range channels and four power range channels are distributed at radial positions of 45°, 135°, 225° and 315° of the pressure vessel. 7. The nuclear instrumentation system according to claim 5, wherein the first instrumentation guiding sleeve and the second instrumentation guiding sleeve are an instrumentation guiding sleeve with a bottom of opening structure is pre-embedded in a civil engineering structure of a reactor workshop, and the instrumentation guiding sleeve extends downward and obliquely along a wall to a position near a top of the pressure vessel, then extends vertically downward and exceeds a plane where a bottom of the pressure vessel locates. 8. The nuclear instrumentation system according to claim 5, wherein the nuclear instrumentation system further includes at least one lifting port in a connecting box of an operating platform of the reactor workshop, each lifting port is corresponding connected with one of the first instrumentation guiding sleeve and the second instrumentation guiding sleeve; wherein the first instrumentation guiding sleeve and the second instrumentation guiding sleeve are connected with the connecting box, and each detector in each channel is connected with an outer lifting device. 9. The nuclear instrumentation system according to claim 8, wherein each lifting port is installed with a cable connecting plate, a cable of the each detector in each channel is connected with a protection cabinet of the nuclear instrumentation system via the cable connecting plate. 10. The nuclear instrumentation system according to claim 8, wherein the outer lifting device is a polar crane of the reactor workshop. 11. The nuclear instrumentation system according to claim 5, wherein the nuclear instrumentation system further includes four protection cabinets, the detectors of the four intermediate range channels and four power range channels are connected with the four protection cabinets via coaxial cables, respectively, each of the detectors of the three source range channels is connected with one protection cabinet via a coaxial cable. 12. The nuclear instrumentation system according to claim 11, wherein the nuclear instrumentation system further includes one control cabinet connected with each protection cabinet. 13. The nuclear instrumentation system according to claim 11, wherein the nuclear instrumentation system further includes an interface system for connecting the four protection cabinet to following systems: a reactor protection system, a rod position indicating and rod control system, a main control room, and a core online surveillance system.