Position detecting device for a traversing incore probe

Purpose: To enable accurate detection for the position of a traversing incore probe that traverses in the incore instrumentation tube without worsening the performance of the reactor core. Constitution: An incore instrumentation guide tube is disposed with a radiation detector traversing therein. Magnetic detectors such as hole ICs or lead switches are attached to the upper and lower portion of the detector. While on the other hand, a magnetic member, for example, a permanent magnet is disposed to the spacer of a fuel assembly. Magnetic fluxes generated from the permanent magnet are detected by the magnetic detectors and the detection signals are formed into a DC voltage to determine the position for the traversing incore probe. The permanent magnet may be mounted to the incore instrumentation guide tube, channel box, cladding tube of fuel rods, etc. (Kawakami, Y.)