Combination of top nozzle and guide thimble for nuclear fuel assembly

摘要

A joint structure between a top nozzle and a guide thimble of a nuclear fuel assembly and, more particularly, a structure for joining an inner-extension tube, the top nozzle and the guide thimble. When an inner-extension tube head, which is provided as a means for facilitating removal of the top nozzle of the nuclear fuel assembly from the guide thimble, is removed from an inner-extension tube body to separate the top nozzle from the nuclear fuel assembly, the inner-extension tube body is prevented from undesirably rotating, so that the guide thimble and the inner-extension tube body can maintain the joined state.

主权项

1. A combination of a guide thimble and a top nozzle for a nuclear fuel assembly, the combination comprising:
a guide thimble, and a top nozzle coupled to the guide thimble, the top nozzle comprising:
a flow plate located above the guide thimble, with a coupling through hole formed through the flow plate;an outer guide post coupled at a lower end thereof to the coupling through hole of the flow plate;an inner-extension tube disposed in the outer guide post in such a way that a lower end of the inner-extension tube passes through the coupling through hole of the flow plate; andan inner-extension tube head coupled to an upper end of the inner-extension tube and to an upper end of the outer guide post, wherein: the inner-extension tube includes a rim disposed within the coupling through hole of the flow plate; the rim has a circumferential outer surface which includes a first region and a second region; a circumferential inner surface of the coupling through hole of the flow plate includes a first part disposed at a position corresponding to the first region of the rim of the inner-extension tube and a second part; and the first region and the first part, collectively, prevent the inner-extension tube from rotating when the inner-extension tube head is rotated.