scope:

Scope and object

This standard is applicable to highly reliable software required for computers to be used in the safety systems of nuclear power plants for safety functions - Class 1 functions according to IEC hblication 643: Application of Digital Computers to Nuclear Reactor Instrumentation and Control. This includes the safety actuation systems, the safety system support features and the protection systems.

For the utilization of computer systems for non-safety functions the principles of IEC Publication 639: Nuclear Reactors - Use of the Protection System for Non-safety Purposes, are applicable.

This standard provides requirements for each stage of software generation, including design, development, qualification and operation as well as the documentation for each stage of the software generation for the purpose of achieving highly reliable software.

The principles applied in developing these requirements include:

- best available practice;

 - top-down design methods;

 - modularity;

 - verification of each phase;

- clear documentation;

- auditable documents;

- validation testing.

Additional guidance and information on how to comply with the requirements of the main part of this standard is given in Appendices A to F. References to those appendices are given in brackets.

If practices differing from those of the appendices are used, they shall be documented and auditable according to the requirements of the main part of this standard.