Patent Number: 
Section: claims

1. A transfer device for moving a control rod assembly between fuel assemblies employing an overhead crane, the control rod assembly having a plurality of spaced control rods which are supported from an overhead web frame, wherein the control rods are designed to be inserted within a plurality of spaced guide thimble tubes in the fuel assemblies, the transfer device comprising:an upper latch tube assembly having a longitudinal axis;an elongated inner member, slidably supported within the upper latch tube assembly and operable to telescope substantially coaxially with the longitudinal axis;a gripper assembly supported from a one axial end of the elongated inner member, having an actuation shaft reciprocally, slidably supported within the elongated inner member to move substantially along the longitudinal axis a selected distance to actuate a gripper at an axial first end of the gripper assembly opposite a second end of the gripper assembly adjacent the one end of the elongated inner member, another end of the elongated inner member including a bail adapted to attach to the overhead crane;an interlock assembly attached to the upper latch tube assembly selectively coupling said elongated inner member to the upper latch tube assembly at one or another of two elevations along the longitudinal axis, the one elevation being in a substantially extended position the another elevation being in a substantially retracted position;an elongated enclosure assembly extending along the longitudinal axis having a length at least substantially equal to the height of the control rod assembly, the enclosure assembly substantially rigidly connected to one end of the upper latch tube assembly and having another end configured to key on the top of the fuel assembly; anda plurality of alignment cards laterally disposed in a spaced tandem array along the length of the enclosure assembly, each of the alignment cards having openings that are aligned and sized to pass a control rod of the control rod assembly so that the control rods are withdrawn into the enclosure assembly in alignment with the guide thimble tubes of the fuel assembly, the alignment cards further including a central opening through which the gripper assembly can pass through and at least some of the alignment cards' central opening sized to pass at least a portion of the elongated inner member. 2. The transfer device of claim 1 wherein the alignment cards prevent rotation of the gripper assembly whether or not the gripper assembly is attached to the control rod assembly. 3. The transfer device of claim 2 wherein the gripper assembly includes a generally rectangular cross-section profile that fits in a corresponding central opening in at least some of the alignment cards. 4. The transfer device of claim wherein the gripper assembly includes at least one laterally extending fin that fits in a corresponding slot in at least some of the alignment cards. 5. The transfer device of claim 4 wherein the gripper assembly includes a plurality of laterally extending fins that are spaced around a circumference of the gripper assembly. 6. The transfer device of claim 5 wherein the laterally extending fins are equidistantly spaced around the circumference of the gripper assembly. 7. The transfer device of claim 4 wherein a distal lateral end of the fin is contoured to have an enlarged cross-section that fits in a corresponding opening in at least some of the alignment cards. 8. The transfer device of claim 7 wherein the contour is round. 9. The transfer device of claim 7 wherein the distal lateral end of the fin has a bullet nose in at least one end in a direction of travel of the gripper assembly. 10. The transfer device of claim 9 wherein the distal lateral end of the fin has a bullet nose in an end on either side of the direction of travel of the gripper assembly. 11. The transfer device of claim 1 wherein the gripper assembly is biased in a latched condition. 12. The transfer device of claim 1 wherein the enclosure assembly includes axially extending guide bars which guide the gripper assembly in between alignment cards and prevent rotation of the gripper assembly whether or not the gripper assembly is attached to the control rod assembly. 13. The transfer device of claim 1 wherein the elongated inner member includes an axially extending centering profile on an outer surface that slides within a centrally located bushing proximate an upper portion of the enclosure assembly. 14. The transfer device of claim 1 wherein the gripper assembly includes a weight compensating spring compressed around the actuation shaft. 15. The transfer device of claim 1 wherein the gripper is designed to increase an actuator locking force with increase in downward load. 16. The transfer device of claim 1 including means for preventing the interlock assembly from coupling the elongated inner member to the upper latch tube assembly at the elevation in the substantially extended position when the actuation shaft on the gripper assembly is in a position to actuate the gripper.