Abstract: The oscillatory forces acting on an eccentric rod within a diffuser are reduced by an annular bypass collar around the rod immediately upstream of the diffuser region. The collar includes a sleeve portion that completely surrounds the rod and a bypass channel outside the sleeve which carries most of the fluid into the diffuser region on a path parallel to but spaced from the rod. The collar is most effective when a multiplicity of discrete bypass channels are provided.

Abstract: An apparatus for providing a high, positive locking force at the bottom of a nuclear fuel assembly to resist upward coolant flow forces. A latch on the fuel assembly alignment post is cammed to engage the fuel alignment pin in the core support stand and is linked to an actuating rod extending through the lower end of the fuel assembly center guide tube. The upward flow of coolant against the link and actuating rod causes the link to approach the horizontal, thereby exerting a high locking force between the latch and the fuel alignment pin. In the preferred embodiment spring means interact between the lower end fitting and the actuating rod to maintain an upward bias on the rod.

Abstract: An improved nuclear reactor fuel assembly of a type having a control rod guide tube through which a control rod may be reciprocated from above and through which a coolant flow is maintained from below wherein the improvement comprises the guide tube having a flow restriction at its upper end and having a plurality of flow bypass channels spaced around the tube circumference below the restriction for directing coolant flow generally radially outward from the guide tube.