Method for Expansion of Ball Screw Slit and Drive Mechanism with Ball Screw Expansion for Fine Movement of Nuclear Reactor Control Rods

摘要

It is an object of the present invention to provide a gap expanding method of a ball screw for preventing an increase in torque relative to an electric motor due to a protruding bulge caused by generation of a scar on the traveling side of the screw shaft of the ball screw, and to provide a control rod drive mechanism incorporating the gap expanded ball screw. In a ball screw disposed in a control rod drive mechanism, the ball screw has a screw shaft and a ball nut engaged with the screw shaft via travelling balls, and the balls are each configured to have a diameter smaller than that of the existing ball, thereby expanding a gap between a ball traveling side of the screw shaft and the ball and a gap between the ball and a ball traveling side of the ball nut.