Control rod drive mechanism for a nuclear reactor

Claim 1

A CONTROL ROD DRIVE FOR A NYCLEAR REACTOR, SAID DRIVE COMPRISING A DRIVE SHAFT CARRIED FOR AXIAL MOVEMENT TOWARD AND AWAY FROM THE REACTIVE CORE OF THE REACTOR, END OF SAID DRIVE SHAFT ADJACENT TO THE REACTIVE CORE BEING ADAPTED FOR CONNECTION WITH A CONTROL ROD, A LEAD SCREW EXTENDING WITHIN SAID DRIVE SHAFT FROM THE OTHER END THEREOF, MEANS CONNECTING SAID LEAD SCREW AND SAID DRIVE SHAFT SO AS TO CAUSE RELATIVE MOVEMENT OF SAID DRIVE SHAFT AXIALLY OF SAID LEAD SCREW INCIDENT TO ROTATION OF SAID LEAD SCREW, A FLUID MOTOR DRIVINGLY CONNECTED TO SAID LEAD SCREW FOR ROTATIONAL DRIVING THEREOF, AN ELECTRIC MOTOR, A CLUTCH RELEASABLY CONNECTING SAID ELECTRIC MOTOR TO SAID LEAD SCREW SO AS TO FACILITATE POSITIONING OF SAID DRIVE SHAFT UNDER NORMAL CONDITIONS, SAID CLUTCH DISCONNECTING SAID ELECTRIC MOTOR FROM SAID LEAD SCREW INCIDENT TO ROTATION OF SAID LEAD SCREW BY SAID FLUID MOTOR THEREBY PERMITTING FREE MOVEMENT OF SAID LEAD SCREW RELATIVE TO SAID ELECTRIC MOTOR, MEANS FOR SUPPLYING PRESSUE FLUID TO SAID FLUID MOTOR IN RESPONSE TO DEVELOPMENT OF A SCRAM CONDITION IN THE REACTOR SO AS TO RAPIDLY ROTATE SAID LEAD SCREW THEREBY DISPLACING SAID DRIVE SHAFT TOWARD THE REACTIVE CORE OF THE REACTOR, AND MEANS INCLUDING A VALVE COMMUNICATING WITH SAID FLUID MOTOR AND OPERABLY CONNECTED TO SAID LEAD SCREW FOR THROTTLING THE FLOW OF PRESSURE FLUID THROUGH SAID FLUID MOTOR SO AS TO DECELERATE SAID LEAD SCREW AS THE DRIVE SHAFT APPROACHES THE LIMIT OF ITS TRAVEL TOWARD THE REACTIVE CORE OF THE REACTOR.