Reconstitutable fuel assembly having removable upper stops on guide

Abstract

The hold-down plate of the top nozzle of a fuel assembly is removably attached on the upper extension members of the fuel assembly guide thimbles by an improved structure associated with passageways through the hold-down plate which receive upper end portions of the guide thimble upper extension members. The improved attaching structure includes recesses on the upper end portions of the guide thimble extension members with the recesses terminating at upper terminal edges thereof, elements mounted in the upper hold-down plate and extending therefrom into the passageways of the plate and the recesses of the extension member upper end portions, and a plurality of stop members connectable on the upper end portions of the guide thimble extension members and having overhanging ledges respectively formed thereon which define upper limits of the respective recesses on the extension member upper end portions. The elements are positioned to slide upwardly along the corresponding recesses until making engagement with the ledges on the stop members when the stop members are connected on the corresponding extension member upper end portions for limiting upward movement of the upper hold-down plate along the guide thimble. Also, the elements are positioned to slide upwardly along and past the corresponding recesses when the stop members have been disconnected from the corresponding extension member upper end portions for allowing removal of the upper hold-down plate from the guide thimble.