Nuclear fuel assembly grid sleeve/guide thimble bulge orientation gage and inspection method

A gage for inspecting a nuclear fuel assembly to determine the orientation of a plurality of externally-projecting mated bulges connecting a hollow grid sleeve to a hollow guide thimble of the assembly, said gage comprising:

• (a) a radially-expandable tubular member insertable within the guide thimble and having externally-projecting embossments spaced circumferentially from one another about said tubular member, said embossments being the same in number as the bulges of the guide thimble and configured to fit therewithin;
• (b) an elongated expansion member rotatably mounting said tubular member and being axially movable within said tubular member when the latter is inserted within the guide thimble, said expansion member being movable relative to said tubular member between a first position in which said expansion member permits inward contraction of said tubular member and displacement of said embossments away from the interior of the guide thimble bulges for removing said embossments from registry therewith and a second position in which said expansion member produces radial expansion of said tubular member and displacement of said embossments toward the interior of the guide thimble bulges for placing said embossments in registry therewith;
• (c) means for rotating said tubular member relative to said expansion member so as to bring said embossments on said tubular member into alignment with the guide thimble bulges concurrently as said embossments on said tubular member are being displaced toward and into registry with the interior of the guide thimble bulges;
• and
• (d) an indicator mechanism responsive to rotation of said tubular member away from a reference position for providing an indication of the orientation of the guide thimble bulges relative to a reference point upon displacement of said embossments into registry with the guide thimble bulges;
• (e) said tubular member having a plurality of elongated resiliently-yieldable fingers defined by a plurality of longitudinally extending and circumferentially spaced apart slots defined in said tubular member and opening at a forward edge thereof, each of said embossments being formed on a forward end portion of one of said fingers;
• (f) said indicator mechanism including an upright member at an inner end portion being attached to said tubular member at a rearward end portion so as to undergo pivotal movement as said tubular member is rotated, and an elongated pointer element pivotally mounted to an outer end portion of said upright member so as to adapt said pointer element to pivot relative to said upright member in responsive to rotation of said tubular member away from the reference position in bringing said embossments into registry with the guide thimble bulges, the extent of pivoting of said pointer element away from a reference location providing said indication of the orientation of the guide thimble bulges relative to the reference point.

A method of inspecting a fuel assembly to determined the orientation of a plurality of externally-projecting mated bulges connecting a grid sleeve to a guide thimble of the assembly, said method comprising the steps of:

• (a) inserting a radially-expandable tubular member within the guide thimble, the tubular member having externally-projecting embossments thereon spaced circumferentially from one another about the tubular member, the embossments being the same in number as the bulges of the guide thimble and configured to fit therewithin;
• (b) axially moving an elongated expansion member, which extends through and rotatably mounts the tubular member, relative to the tubular member from a first position in which the expansion member permits inward contraction of the tubular member and displacement of embossments thereon away from the interior of the guide thimble bulges for removing the embossments from registry therewith and a second position in which the expansion member produces radial expansion of the tubular member and displacement of the embossments thereon toward the interior of the guide thimble bulges for placing the embossments in registry therewith;
• (c) rotating the tubular member relative to the expansion member so as to bring the embossments on the tubular member into alignment with the guide thimble bulges as the embossments on the tubular member are being displaced toward and into registry with the interior of the bulges;
• and
• (d) responsive to rotation of the tubular member away from a reference position, providing an indication of the orientation of the guide thimble bulges relative to a reference point upon displacement of the embossments into registry therewith.