Method of scrumming a control rod

Object: To permit a control rod to be reliably and quickly inserted into the reactor core by making use of water pressure in a method of scrumming a sealed type control rod drive means in a reactor for researches. Structure: At the time of normal operation, a control rod is held from the above by causing upward water pressure to act upon via a solenoid operated directional control valve. At the time of scrumming, water on the lower side of the water pressure plunger is caused to directly fall into a damp tank with the switching of the afore-said directional control valve, thereby obtaining high downward water pressure to achieve quick insertion of the control rod into the core. (Kamimura, M.)