  This paper develops a Nearly Autonomous Management and Control (NAMAC) system
for advanced reactors. The development process of NAMAC is characterized by a
three layer-layer architecture: knowledge base, the Digital Twin (DT)
developmental layer, and the NAMAC operational layer. The DT is described as a
knowledge acquisition system from the knowledge base for intended uses in the
NAMAC system. A set of DTs with different functions is developed with
acceptable performance and assembled according to the NAMAC operational
workflow to furnish recommendations to operators. To demonstrate the capability
of the NAMAC system, a case study is designed, where a baseline NAMAC is
implemented for operating a simulator of the Experimental Breeder Reactor II
during a single loss of flow accident. When NAMAC is operated in the training
domain, it can provide reasonable recommendations that prevent the peak fuel
centerline temperature from exceeding a safety criterion.
