TCR CENTRAL SHUTDOWN ROD FINE MOTION CONTROL

The Transformational Challenge Reactor (TCR) is a helium-cooled 3 MWt test reactor with a design that leverages advances in materials and manufacturing, computing, and artificial intelligence. Gravity, pneumatics, or springs are typically used to quickly release the central shutdown rod—which contains the neutron absorber—into the reactor core, thus stopping the nuclear reaction. The rod’s motor/actuator typically resides outside the reactor, and the motion is transmitted through a penetration into the pressure vessel. Some control rod designs incorporate magnetic latches with a coil outside the pressure boundary to ensure precise position control. The proposed design comprises a magnetic coupling to position the shutdown rod, with no penetration into the pressure vessel for the entire drive length of TCR shutdown rod. Electromagnets are used in nonpower nuclear reactors for shutdown rod control, but they reside inside the reactor pressure vessel. This paper describes the use of an electromagnet outside the pressure vessel to position and release the shutdown rod. A prototype was developed at Oak Ridge National Laboratory to demonstrate the concept, and the ferritic core and material design was optimized to maximize the electromagnet’s lift force. An elevated temperature test was also conducted to ensure that the system will perform effectively inside an operating reactor.