Overtravel

The Overtravel is the control rod position beyond the normal full-out notch position.

Reed switches are also provided at locations that are beyond the limits of normal rod movement. If the rod drive piston moves to the full-out overtravel position, an alarm is sounded in the Control Room. The overtravel alarm provides a means to verify that the drive-to-rod coupling is intact, because with the coupling in its normal condition, the drive cannot be physically withdrawn to the overtravel position. Coupling integrity can be checked by attempting to withdraw the drive to the overtravel position.