Abstract: A control rod having a spring device on its lower end for eliminating oscillatory contact of the rod against its adjacent guide tube wall. The base of the device is connected to the lower tip of the rod. A plurality of elongated extensions are cantilevered downward from the base. Each extension has a shoulder for contacting the guide tube, and the plurality of shoulders as a group has a transverse dimension that is preset to be larger than the inner diameter of the guide tube such that an interference fit is obtained when the control rod is inserted in the tube. The elongated extensions form an open-ended, substantially hollow member through which most of the liquid coolant flows, and the spaces between adjacent extensions allow the flow to bypass the shoulders without experiencing a significant pressure drop.

Abstract: A retainer to provide supplemental holddown force for a control component assembly latched into a fuel assembly of a nuclear reactor. Upon failure of latching mechanism the retainer precludes the ejection of the control component assembly from the fuel assembly by the upward coolant flow drage force. The spring loaded retainer is mounted at the top of the control component assembly and engages both the control component assembly and the core grid plate to form a structural blocking of the grid plate hole thereby precluding the ejection of the control component assembly therethrough.