Safety critical software design approaches developed for Canadian nuclear power plants / Verfahren zur Entwicklung von Software für Sicherheitssysteme in kanadischen Kernkraftwerken.

Abstract

The principles of the development of software for the instrumentation and control of nuclear power plants in Canada are outlined. Recently two methodologies were developed that comply with a high safety critical standard : the Rational Design Process, which can be characterized as a methodology based on state machines where the required behaviour of the software is defined using mathematical functions written in a notation which has a well defined syntax and semantics, and the Integrated Approach, which uses a graphical functional notation to specify the functional software requirements. The first implementations based on the two methodologies are discussed. Results from all phases of testing show a remarkably low number of errors, demonstrating that the new methodologies have indeed led to a higher demonstrable level of software reliability.