A nuclear reactor includes a pressure vessel, and a control rod assembly (CRA) including at least one movable control rod, a control rod drive mechanism (CRDM) for controlling movement of the at least one control rod, and a coupling operatively connecting the at least one control rod and the CRDM. The coupling includes a connecting rod engaged with the CRDM and a terminal element connected with a lower end of the connecting rod and further connected with the at least one control rod. In some embodiments the terminal element includes a first portion comprising a first material having a first density and a second portion comprising a second material having a second density that is greater than the first density. In some embodiments the terminal element has a largest dimension parallel with the connecting rod that is greater than or equal to a largest dimension transverse to the connecting rod.