Control rod drives for a nuclear reactor

Purpose: To enable rapid and sure insertion of control rods into the reactor core upon loss of gas pressures. Constitution: An acceleration cylinder is provided within a housing disposed on a reactor upper cover, and a piston slidably incorporated within the acceleration cylinder is secured to the lower end of a driving shaft connected by way of an electromagnet to a ball nut engaged to a reed screw. Both of inner and outer extention rods provided with a gripper mechanism for gripping a control rod are connected to the lower part of the piston. An acceleration spring for downwardly urging the piston is mounted in the acceleration cylinder. (Seki, T.)