Qualifying software for class 1E equipment

As the number of nuclear applications using computers and programmable controllers increases, more and more designers face the challenge of specifying embedded controllers and qualifying software according to NRC (Nuclear Regulatory Commission) guidelines. The authors describe the experience gained at Spectrum Technologies and Northern States Power during the development of a computer-based safeguard load sequencer for the Prairie Island Nuclear Generating Plant. Emphasis is placed on the methodology of software development and the requirements imposed by the NUREG 4640 handbook and the relevant IEEE and ANSI standards. Experience at Spectrum Technologies has taught that there are no ´magic cookbook´ steps to follow during software development. Rigid approaches result in a poor quality product. Once the unique characteristics of software development are recognized, standards and procedures can be used to minimize the negative effects of these characteristics.<>