Abstract: A locking mechanism for securing an upper tie plate to the tie rods of a nuclear fuel bundle. The mechanism includes an upper tie plate assembly and locking sleeves fixed to the ends of the tie rods. The tie plate is part of the upper tie plate assembly and is secured to the fuel bundle by securing the entire upper tie plate assembly to the locking sleeves fixed to the tie rods. The assembly includes, in addition to the tie plate, locking nuts for engaging the locking sleeves, retaining sleeves to operably connect the locking nuts to the assembly, a spring biased reaction plate to restrain the locking nuts in the locked position and a means to facilitate the removal of the entire assembly as a unit from the fuel bundle.

Abstract: A system for capturing a grid spacer in a nuclear fuel bundle which comprises a split sleeve fixed to a capture rod. The sleeve is used in conjunction with a grid spacer having openings formed by intersecting walls which include protrusions and coacting springs extending from the walls. The sleeve includes pairs of longitudinally spaced bosses and a standoff boss extending radially outward from the surface of the rod. The pairs of bosses are positioned astride the protrusions from the walls to prevent longitudinal movement of the grid spacer. The split serves as a guide slot to orient the capture rod so that it may pass through the grid spacer openings unencumbered by the protrusions from the grid space walls. The standoff boss is in surface contact with a wall of the grid spacer.

Abstract: A bimetallic grid spacer comprising a grid structure of zircaloy formed by intersecting striplike members which define fuel element openings for receiving fuel elements and spring strips made of Inconel positioned within the grid structure for cooperating with the fuel elements to maintain them in their desired position. A plurality of these spring strips extend longitudinally between sides of the grid structure, being locked in position by the grid retaining strips. The fuel rods, which are disposed in the fuel openings formed in the grid structure, are positioned by means of the springs associated with the spring strips and a plurality of dimples which extend from the zircaloy grid structure into the openings. In one embodiment the strips are disposed in a plurality of arrays with those spring strip arrays situated in opposing diagonal quadrants of the grid structure extending in the same direction and adjacent spring strip arrays in each half of the spacer extending in relatively perpendicular directions.

Abstract: In a nuclear power reactor fuel bundle having tie rods fastened to a lower tie plate and passing through openings in the upper tie plate, the assembled bundle is secured by locking lugs fixed to rotatable locking sleeves which engage the upper tie plate. Pressure exerted by helical springs mounted around each of the tie rods urge retaining lugs fixed to a retaining sleeve associated with respective tie rods into a position with respect to the locking sleeve to prevent accidental disengagement of the upper plate from the locking lugs. The bundle may be disassembled by depressing the retaining sleeves and rotating the locking lugs to the disengaged position, and then removing the upper tie plate.

Abstract: A spacer capture system for nuclear fuel assemblies of the type in which fuel rods are disposed in parallel array between supporting end plates. At intervals along the fuel rods spacer grids are provided which properly position the fuel rods, reducing vibration and obtaining proper spacing to assure uniform heat removal from the fuel rods during operation. The spacers hold the fuel rods by spring pressure against protrusions formed from the side walls of the grids. The spacers are held in the proper position against vibration and the force of water passing adjacent the tubes by lugs provided on special fuel containing spacer capture rods which engage the protrusions on each spacer and thereby preventing its longitudinal movement relative to the fuel rods. The lugs are so mounted as to permit freeing of the spacer capture rods by a 45.degree. rotation of the spacer capture rods and conversely, the spacers may be locked in position by a 45.degree. rotation of the spacer capture rods from the unlocked position.

Abstract: In a nuclear power reactor fuel bundle having tie rods fastened to a lower tie plate and passing through openings in the upper tie plate, the assembled bundle is secured by rotatable locking sleeves which engage slots provided in the upper tie plate. Pressure exerted by helical springs mounted around each of the fuel rods urge the upper tie plate against the locking sleeves. The bundle may be disassembled after depressing the upper tie plate and rotating the locking sleeves to the unlocked position.