Apparatus for measuring for deflection of a movable member of control element drive mechanism

The present invention relates to a lower installation control rod driving device of a reactor. More particularly, the present invention relates to an apparatus for measuring the deflection of a movable member of a control rod driving device using LVDT. It accurately measures the deflection of a movable member in a control rod driving device by using LVDT principle and measures the accurate location of a control rod in a real reactor core. For this, the present invention includes a magnetic core which is arranged in a sealed guide pipe, interlinks with a movable member assembly and vertically moves; and a detection coil which includes a prime coil which is arranged in the outer surface of the guide pipe at which the magnetic core is located, and a secondary coil, detects the change of a voltage induced by the secondary coil according to the change of a magnetic field generated in the vertical movement of the magnetic core in the magnetic field formed around the first coil, and measures the deflection of the movable member assembly.