Method of removing foreign substances from crdm and device for executing same

Abstract

A method of removing floating foreign substances that may interfere with a normal operation of an electromechanical mechanism of a control rod drive mechanism and a device for executing the same are provided. The method of removing the foreign substances from the control rod drive mechanism comprising a driving shaft including a plurality of teeth and disposed in a vertical direction in the control rod drive mechanism, a first part configured to hold or release a lower end portion of the driving shaft depending on whether a stationary gripper coil is activated, a second part configured to hold or release an intermediate portion of the driving shaft depending on whether a movable gripper coil is activated, and a third part configured to move the second part in the vertical direction depending on whether a lift coil is activated may include: activating at least one of the stationary gripper coil, the movable gripper coil, and the lift coil to drive the first part, the second part, or the third part in a state in which the driving shaft is not able to move; and removing the foreign substances from the first part, the second part, or the third part.

What is claimed is: 
     
         1 . A method of removing foreign substances from a control rod drive mechanism comprising a driving shaft including a plurality of teeth and disposed in a vertical direction in the control rod drive mechanism, a first part configured to hold or release a lower end portion of the driving shaft depending on whether a stationary gripper coil is activated, a second part configured to hold or release an intermediate portion of the driving shaft depending on whether a movable gripper coil is activated, and a third part configured to move the second part in the vertical direction depending on whether a lift coil is activated, the method comprising:
 activating at least one of the stationary gripper coil, the movable gripper coil, and the lift coil to drive the first part, the second part, or the third part in a state in which the driving shaft is not able to move;   removing the foreign substances from the first part, the second part, or the third part by driving any of the first part, the second part, or the third part, and allowing the first part to hold the lower end portion of the driving shaft in a state in which the stationary gripper coil is activated; and   activating the movable gripper coil so that the second part holds the intermediate portion of the driving shaft.   
     
     
         2 . The method of  claim 1 , further comprising:
 inactivating the movable gripper coil so that the second part releases the intermediate portion of the driving shaft.   
     
     
         3 . The method of  claim 1 , further comprising:
 repeating the activating and the inactivating the movable gripper coil.   
     
     
         4 . The method of  claim 1 , further comprising:
 inactivating the stationary gripper coil so that the first part releases the lower end portion of the driving shaft.   
     
     
         5 . The method of  claim 4 , further comprising:
 repeating the activating and the inactivating the stationary gripper coil.   
     
     
         6 . The method of  claim 1 , further comprising setting an operation prohibition condition with respect to the movable gripper coil, the operation prohibition condition being a state in which the lift coil is activated or the stationary gripper coil is inactivated. 
     
     
         7 . A method of removing foreign substances from a control rod drive mechanism comprising a driving shaft including a plurality of teeth and disposed in a vertical direction in the control rod drive mechanism, a first part configured to hold or release a lower end portion of the driving shaft depending on whether a stationary gripper coil is activated, a second part configured to hold or release an intermediate portion of the driving shaft depending on whether a movable gripper coil is activated, and a third part configured to move the second part in the vertical direction depending on whether a lift coil is activated, the method comprising:
 activating at least one of the stationary gripper coil, the movable gripper coil, and the lift coil to drive the first part, the second part, or the third part in a state in which the driving shaft is not able to move; and   removing the foreign substances from the first part, the second part, or the third part by driving any of the first part, the second part, or the third part, and allowing the second part to hold the intermediate portion of the driving shaft in a state in which the movable gripper coil is activated; and   activating the stationary gripper coil so that the first part holds the lower end portion of the driving shaft.   
     
     
         8 . The method of  claim 7 , further comprising setting an operation prohibition condition with respect to the stationary gripper coil, the operation prohibition condition being a state in which the lift coil is activated or the movable gripper coil is inactivated.