IEC 60709:2018 is applicable to nuclear power plant instrumentation and control (I&C) and electrical systems and equipment, whose functions are required to be independent due to their contribution to:

• a redundant or diverse safety group;
• different defence in depth levels;
• different safety classes and also with non-classified (NC) systems.

This standard is also applicable to temporary installations which are part of those I&C and *electrical systems important to safety (for example, auxiliary equipment for commissioning tests and experiments or mobile power supply systems).

This new edition includes the following significant technical changes with respect to the previous edition:

• include requirements referring to the separation principle in electrical systems important to safety;
• define separation criteria for I&C and electrical systems in a generic way;
• align with the new revisions of IAEA documents and broaden the scope to include other aspects of separation.