Abstract: A control rod drive mechanism according to the present invention includes a cylindrical guide tube having a latch hole, a hollow piston coupled to the control rod and freely moving up and down within the guide tube, a latch provided in the hollow piston so as to freely swing and freely engaging with and disengaging from the latch hole of the guide tube, and a spring locking the latch to the latch hole of the guide tube. Further, an elevating member having a latch guide which can come into contact with the latch is provided so as to freely move up and down within the guide tube. Further, the latch includes a guide surface coming into contact with the latch guide of the elevating member, and the latch guide includes a guide roller coming into contact with the guide surface of the latch.

Abstract: A control rod position detector including a permanent magnet that is attached on a control rod inserted in a reactor pressure vessel, where the permanent magnet is capable of moving together with the control rod, and a plurality of reed switch mechanisms that are arranged in the reactor pressure vessel at regular intervals in an insertion direction of the control rod. Each of the reed switch mechanisms is provided with a pair of reed switches that are placed so as to overlap with each other in the insertion direction of the control rod. The pair of reed switches are connected to a common wiring. The common wiring is connected to a detector that detects a position of the control rod based on signals from the reed switches.

Abstract: A control rod drive mechanism according to the present invention includes a cylindrical guide tube having a latch hole, a hollow piston coupled to the control rod and freely moving up and down within the guide tube, a latch provided in the hollow piston so as to freely swing and freely engaging with and disengaging from the latch hole of the guide tube, and a spring locking the latch to the latch hole of the guide tube. Further, an elevating member having a latch guide which can come into contact with the latch is provided so as to freely move up and down within the guide tube. Further, the latch includes a guide surface coming into contact with the latch guide of the elevating member, and the latch guide includes a guide roller coming into contact with the guide surface of the latch.

Abstract: The object of the present invention is to provide a control rod position detector that is capable of avoiding and preventing a situation which makes impossible a detection of a position of a control rod inserted in a reactor pressure vessel. A control rod position detector of the present invention includes: a permanent magnet 10 that is attached on a control rod 4 inserted in a reactor pressure vessel 1, the permanent magnet 10 being capable of moving together with the control rod 4; and a plurality of reed switch mechanisms 31 that are arranged in the reactor pressure vessel 1 at regular intervals in an insertion direction of the control rod 4, the reed switch mechanisms 31 being operated by a magnetic flux of the permanent magnet 10. Each of the reed switch mechanisms 31 is provided with a pair of reed switches 13 and 14 that are placed so as to overlap with each other in the insertion direction of the control rod 4. The pair of reed switches 13 and 14 are connected to a common wiring 11.