Redundant Actuators without Direct Communication for Reactor Control Rod Positioning

In the design of nuclear reactor systems, reliability is always a top consideration. Their main control method is the movement of “control rods” which inhibit the rate of reaction. Various gravity-based fail-safe methods are available during the failure of an actuator, but even safe failures limit reactor capability. This is especially important for mobile platforms like submarines and aircraft carriers where it may be months before maintenance can be performed. By introducing a redundant system and adding features like hot-swapping, overall system reliability is improved. This paper proposes a design for supporting reactor control rods utilizing three independently powered and controlled linear motors. By utilizing a three motor design, the system becomes resilient to two points of motors failing off, or a single point of failure should a motor fail on or become corrupted in some way. In addition, there is no central computer, failure detection logic, or direct communication between these motors, which makes the system simpler and avoids single points of failure. Each motor acts independently and if one has a failure, the other two will overpower it.