Patent Number: 042657083
Section: claims

1. In a nuclear reactor fuel assembly having a control rod guide tube including a guide post at its upper end, the guide post having a uniform inner diameter, the tube and post adapted to receive a reciprocating control rod from above and a coolant flow from below, wherein the improvement comprises the guide post having an upper portion with a flow restriction having a smaller diameter than the remainder of the tube, and wall means defining a plurality of flow relief channels spaced around the circumference of the post, the channels extending in a generally radial direction from inside the tube below the flow restriction to openings on the surface of the guide post. 2. The fuel assembly of claim 1, wherein the guide post includes a head portion having a larger outside diameter than the remainder of the guide poast, and wherein the flow restriction is within the head portion and the relief channel openings are on the outer surface of the head portion. 3. The assembly of claim 1 or 2, wherein the wall means are obliquely upwardly oriented relative to the longitudinal axis of the guide tube. 4. The assembly of claim 3, wherein the wall means define at least four discrete flow channels.