Functional analysis, diversity and defense-in-depth principle applied for instrumentation and control architecture in accordance with U.S.NRC / Análise funcional, diversidade e princípio da defesa em profundidade aplicado à arquitectura de instrumentação e controlo em conformidade com o U.S.NRC

According to IAEA (2020), a large number of nuclear power plants (NPP) is completing 30 to 40 years of operation, and many of them can extend the lifetime for variable periods of operation. Besides that, new applications and methods of NPP design are in direction of adopting small modular reactors (SMR) to optimize the NPP projects in relation to cost and safety (Black et al., 2021). Other way is to apply NPP in naval plants, providing efficient manners to generate energy (Freire, 2018). All these ways can make nuclear energy a viable alternative, and consequently to contribute with low carbon power demands, and stabilize the global energy matrix helping to meet climate goals in the next decades (IAEA, 2020). One of the sensing points in NPP project nowadays is the introduction of advanced digital I&C technologies (Santos, 2021). In digital I&C design based on nuclear normative basis, it is imperative to be adherent with the safety and human factors engineering (HFE) requirements. This paper proposes the formalization of a plant-level Functional Analysis (FA) methodology with Diversity and Defense-in-Depth (D3) principles, considering the U.S.NRC normative basis.