Abstract: The adaptor plate of a top nozzle assembly is removably secured to selected thimble tubes in a nuclear fuel assembly by quick release couplings. The openings in the adaptor plate aligned with the selected thimble tubes are counterbored from above to form shoulders with diametrically opposed slots extending downward through the shoulders. The quick release couplings include a sleeve secured to the upper end of the thimble tube. A support plate fixed to the sleeve has a pair of upwardly extending bosses engaging the slots in the adaptor plate. A latch member with a pair of diametrically opposed outwardly projecting latch ears rotates on the sleeve between a first position in which the latch ears are aligned with the slots and are positioned over the bosses so that the adaptor plate may be lifted off, and a second position with the latch ears overlaying the shoulder to latch the adaptor plate to the thimble tube.