scope:

I&C systems important to safety may be designed using conventional hard-wired equipment, computer-based equipment or by using a combination of both types of equipment. This International Standard provides requirements and recommendations1 for the overall architecture of I&C systems, which may contain either or both technologies. The scope of this standard is: a) to give requirements related to the avoidance of CCF of I&C systems that perform category A functions; b) to additionally require the implementation of independent I&C systems to overcome CCF, while the likelihood of CCF is reduced by strictly applying the overall safety principles of IEC SC 45A (notably IEC 61226, IEC 61513, IEC 60880 and IEC 60709); c) to give an overview of the complete scope of requirements relevant to CCF, but not to overlap with fields already addressed in other standards. These are referenced. This standard emphasises the need for the complete and precise specification of the safety functions, based on the analysis of design basis accidents and consideration of the main plant safety goals. This specification is the pre-requisite for generating a comprehensive set of detailed requirements for the design of I&C systems to overcome