Removable and reusable locking pin for top nozzle assembly and

Abstract

A reconstitutable fuel assembly has a top nozzle which not only can be readily removed from and replaced back on the fuel assembly as a unitary subassembly, but also can be readily disassembled and reassembled itself in order to repair or replace some of its own components. The top nozzle uses a plurality of reusable locking pins releasably mounted in bores defined in the sidewall of the top nozzle lower adapter plate. The locking pins, in being mounted in the bores, extend across slots formed in the sidewall and, in so doing, close the open upper ends of slots so as to prevent upward movement of elements on the upper hold-down plate lugs out of the slots and thereby prevent disassembly of the upper hold-down plate from the lower adapter plate. In particular, the locking pins have radially flexible end tangs which are actuatable from a normally expanded position for preventing withdrawal of the locking pins from the sidewall bores to collapsed positions for allowing withdrawal and reinsertion of the locking pins from and into the bores. A knockout tool with a tapered end cavity is used to flex the tangs to their collapsed positions for withdrawal. The tool has a cross-sectional size smaller than that of the sidewall bore allowing it to be inserted into the bores during removal of the locking pins. The outer heads of the tangs are tapered or beveled which causes the tangs to flex radially inward to their collapsed position when the locking pins are being reinserted tang end first into the bores.