Patent Number: 046702130
Section: abstract

An improved top nozzle has an enclosure with a lower adapter plate and an upstanding sidewall surrounding and attached to the periphery thereof and an upper hold-down plate spaced above the adapter plate for abutmnet with a lower side of an upper core plate by a plurality of coil springs disposed between the lower and upper plates. The lower adapted plate and upper hold-down plate have respective openings and passageways defined therethrough in a pattern which matches that of the upper ends of the guide thimbles of the fuel assembly to which the improved top nozzle is attached. The upper ends of the guide thimbles extend upwardly through the adapter plate which is stationarily mounted on the guide thimbles. Tubular sleeves disposed between the lower and upper plates are surrounded by respective coil springs. The lower ends of the sleeves are releasably threaded to the upper ends of the guide thimbles, while the upper ends of the sleeves extend into the passageways of the upper hold-down plate. Bosses are disposed above the hold-down plate and connected thereto such that respective bores through the bosses are aligned with passageways of the hold-down plate. The bosses extend into holes in the upper core plate for aligning the fuel assembly with the upper core plate and for receiving the upper ends of the guide thimbles as the fuel assembly vertically moves upwardly relative to the upper core plate. A plurality of lugs on the periphery of the upper hold-down plate are coupled to the sidewall of the enclosure for accommodating vertical movement of the fuel assembly relative to the upper core plate.