Detection device for control rod position

A contactless displacement sensor is secured at the top of a housing for control rod drives and has a sensor probe comprising a magnet restrictive wire extending downwardly. A control rod driving shaft is bored at the center thereof. A position detection rod is placed on the top of a control rod and extended upwardly through the control rod driving shaft so as to overlap with the sensor probe. A magnet is disposed at the upper end of a position detection rod. When the control rod driving shaft is moved vertically, the position detection rod is moved vertically together with the driving shaft in a state being placed on the control rod. Then, the position of the magnet on the upper end of the position detection rod is detected by the contactless displacement sensor to detect the position of the control rod. With such a constitution, the position of the control rod can be detected continuously over the entire stroke of the control rod. (I.N.)