JP2786773B

PURPOSE:To obtain a driving mechanism of a control rod which makes it possible to stop rotation of a drive shaft without fail by a rotation stop mechanism on the occasion of removing a motor from CRD at the time of periodic inspection and the like and has high reliability. CONSTITUTION:This driving mechanism 40 of a control rod transmits the rotation of a motor 10 to a piston elevation mechanism 42 through a shaft drive mechanism 41 so as to move a piston 19 up and down and thereby the control rod is inserted into and extracted from a reactor core. A rotation stop mechanism 44 equipped with a pawl body fixing the shaft drive mechanism 41 so that it can not rotate, when the motor 10 is removed, is provided, and this rotation stop mechanism 44 is provided with a forced operation mechanism 60 which makes the pawl body move back and forth toward the shaft drive mechanism 41 in linkage with fitting and removal of the motor 10.