Abstract: According to the invention, the drive of a nuclear reactor's control element comprises an electromotor having a stator and a rotor composed lengthwise of two parts whose total length is equal to that of the active part of the stator. One part of the rotor is a solid cylinder-shaped member. The other part of the rotor comprises at least three double-arm rocking levers, the pivot axes of which are parallel to the axis of a drive screw. One arm of each of said levers is a rotor pole. The other arm of each of said levers carries a roller, the axis of rotation of which is parallel to the axis of the drive screw. Said rollers make up a detachable roller nut which interacts with the drive screw under the action of an electromagnetic field.

Abstract: Disclosure is made of a position sensor comprising a plurality of inductance coils with open magnetic circuits. One of the coils has two pairs of poles. The position sensor further includes a shunting element designed for movement along the axis of the coils and connected to a moving body whose position is to be found. The shunting element has groups of holes arranged along its axis. In each group, the holes are arranged along the perimeter of the shunting element. The interpole distance of the coil with the two pairs of poles is specially selected with due regard for the diameter of the holes and the interhole spacing to ensure a high accuracy of the measurements.