| 摘要 |
PURPOSE:To perform water level measurement of good accuracy by the simple constitution of simply providing a guide tube through a nuclear reactor pressure vessel by disposing a neutron detector and a gamma-ray detector movably in the guide tube provided along the vertical direction of the nuclear reactor vessel. CONSTITUTION:A guide tube 3 is provided along the vertical direction in a nuclear reactor pressure vessel 1 having a core 2. This guide tube 3 is so constituted that a detecting head 5 consisting of a gamma-ray detector and a neutron detector is moved vertically by a driving mechanism 7 by way of an MI cable 6 within said tube 3. If the head 5 is moved vertically by the mechanism 7, the signal output from the neutron detector decreases sharply at the time when the head 5 passes the water level, but the signal output from the gamma-ray detector hardly changes, and therefore this state is detected by the signal measuring circuit 13 and signal processing circuit 14 connected to the MIC cable 6, whereby the water level in the nuclear reactor pressure vessel is determined. |
