A control rod drive mechanism (CRDM) configured to latch onto the lifting rod of a control rod assembly and including separate latch engagement and latch holding mechanisms. A CRDM configured to latch onto the lifting rod of a control rod assembly and including a four-bar linkage closing the latch, wherein the four-bar linkage biases the latch closed under force of gravity.
 This application was conceived in the course of work supported by the Department of Energy Cooperative Agreement No. DE-NE0000583. The Department of Energy may have certain rights in this application.