Patent Number: 048204790
Section: claims

1. A guide pin assembly for aligning the upper hold down plate of the top nozzle of a fuel assembly with the upper core plate of a pressurized water nuclear reactor comprising: a guide pin having a generally circular cross-section including:  a guide pin having a generally circular cross-section including:  a top nozzle, a bottom nozzle, and a plurality of guide tubes extending between said top nozzle and said bottom nozzle, said top nozzle having an upper hold down plate with at least one second bore therethrough aligned with a first bore in the upper core plate of a said pressurized water nuclear reactor, said first and second bores being adapted to receive a guide pin to align said fuel assembly with said upper core plate so that said fuel assembly is disposed below, and spaced from, said upper core plate;  at least one guide pin having a generally circular cross-section, a nose, a threaded portion adjacent said nose, a shaft adjacent said threaded portion, and an end adjacent said shaft, said nose having engagement means thereon, said threaded portion having a threaded outer surface, said shaft having an upper section, a lower section, and a radial alignment section between said upper and lower sections, said radial alignment section of said shaft having a diameter that is approximately the diameter of said first bore in said upper core plate of a nuclear reactor, said lower section of said shaft having a diameter less than that of said radial alignment section, said end including a top having a diameter greater than that of the diameter of said first bore in said upper core plate, said guide pin being inserted within a said second bore in said top nozzle and a said first bore in said upper core plate so that said nose and at least a portion of said threaded portion of said guide pin protrude above said upper core plate;  a nut, including a top and a bottom, threaded on to said threaded portion of said threaded surface of said guide pin so that said bottom of said nut abuts the upper surface of said upper core plate; and  an annular locking cup secured about said nut and engaging said engagement means on said nose of said guide pin. 2. The guide pin assembly of claim 1 in which said engagement means on said nose is a plurality of elongated, annularly spaced slots. 3. The guide pin assembly of claim 2 in which said locking cup is adapted to be crimped about said nose of said guide pin. 4. The guide pin assembly of claim 1 in which said nut includes a first groove in the inner surface thereof and said locking cup includes an annular flange about the lower end thereof which is receivable within said first groove of said nut. 5. The guide pin assembly of claim 1 in which said locking cup is permanently securable to said nut. 6. A guide pin assembly for aligning the upper hold down plate of the top nozzle of a fuel assembly with the upper core plate of a pressurized water nuclear reactor comprising: 7. A fuel assembly for a pressurized water nuclear reactor comprising: 8. The nuclear reactor fuel assembly of claim 7 in which said fuel assembly includes two guide pins. 9. The nuclear reactor fuel assembly of claim 7 in which said engagement means on said nose is a plurality of elongated, annularly spaced slots. 10. The nuclear reactor fuel assembly of claim 9 in which said locking cup is crimped about said nose of said guide pin. 11. The nuclear reactor fuel assembly of claim 7 in which said nut includes a first groove in the inner surface thereof and said locking cup includes an annular flange about the lower end thereof which is received within said first groove of said nut. 12. The nuclear reactor fuel assembly of claim 7 in which said locking cup is permanently secured to said nut.