Taxonomies of levels of automation for small modular reactors based on operational conditions

Many fields, including the nuclear energy industry, commonly use a taxonomy of levels of automation (LOAs) as a reference for function allocation, a process conducted to determine whether functions are assigned to humans or automation. An emerging issue is that existing LOA taxonomies have limitations when applied to small modular reactors (SMRs), as SMRs tend to adopt higher levels of automation and expanded passive safety systems than large nuclear power plants. This paper proposes detailed LOA taxonomies that reflect the operational characteristics of SMRs under different operational conditions—normal, abnormal, and emergency conditions—with specific consideration of operator support systems as a major automation domain. For normal operations, the LOA taxonomies are divided into system automation and operation automation based on whether control systems are utilized. For abnormal operations, in which operators’ cognitive functions are emphasized, the taxonomy is classified based on data acquisition, diagnosis, and abnormal operating procedure implementation, with various roles of automation as an operator support system. For emergency conditions, the taxonomy integrates the concepts of passive safety systems and automation. The proposed LOA taxonomies provide a foundation for defining human–automation roles in greater detail from the early stage of SMR design, as well as support designers in considering different types and levels of operator support systems.