Abstract: A spacer retaining element, which may be a fuel rod or water-containing rod, is provided with axially-spaced lugs, each adapted to be received in a slot in a fuel element spacer of a nuclear fuel assembly. When assembled, the lugs maintain proper axial spacing between the individual spacers and the lug-slot arrangement prevents the rod from rotating. Moreover, because the slot in the spacer can receive the lug from only one direction, the arrangement prevents the spacer from being inserted into the assembly upside down.

Abstract: An improved means is provided to control coolant leakage between the flow channel and the lower tie plate of a nuclear fuel assembly. The means includes an opening in the lower tie plate and a movable element adjacent thereto. The coolant pressure within the tie plate biases the movable means toward the inner surface of the surrounding flow channel to compensate for any movement of the flow channel away from the lower tie plate to thereby control the leakage of coolant flow from the fuel assemblies to the spaces among the fuel assemblies of the core.

Abstract: Means are provided to minimize crud buildup at the interface between the tie plate and end plug in a nuclear fuel bundle. The means may comprise serrations in the end plug and/or serrations in the surface of the tie plate which serrations provide a flow of coolant through the end plug receptacles. A bleed hole extending into the interior of the tie plate may be provided to provide coolant circulation through any blind holes that may be in a tie plate.