Software requirements for high integrity systems-the CEGB guidelines for the use of programmable electronic systems for reactor protection

A description is given of the CEGB's guidelines for the use of programmable electronic systems for reactor protection. System and hardware requirements are briefly described, with a fuller discussion of the requirements and restrictions for the use of software within protection systems. The maximum figures which are allowed to be ascribed to software in the reliability calculation for a system containing the software are discussed. The author concludes that the PES guidelines limit the use of software within a reactor protection system and only allow very conservative claims to be made for its correctness and reliability. For a system to be classified as 'highly reliable' it has to incorporate diversity and redundancy of design and implementation.<
>