A Simple, Compact Rod Drive Using a Stepping Motor

A rod drive using a stepping motor has been developed for the Argonne Advanced Research Reactor critical experiment. The control rod is suspended from a roller chain which meshes with a sprocket driven by the motor. Rod position is indicated by counting the number of steps. Scram is produced by interrupting the power to the motor windings, thus removing the motor's holding torque. This design offers significant reductions in size and cost compared to existing types.