Traditional software substantiation methods for computer-based systems important to safety (CBSIS) often rely on retrospective, late-stage testing. In the UK nuclear sector, this back-end activity can add significant project risk, expense, and time which challenges the economic viability of modern reactor designs like SMRs.

 

Holtec Britain have worked with Ennuvo to outline a new approach to software assurance. The research draws on international standards, nuclear sector practice and lessons from other high-hazard industries to identify where software assurance can be undertaken more efficiently whilst continuing to demonstrate risks have been reduced to as low as reasonably practicable.  We have worked with the University of York, 61508 Association and industry experts to produce the research and thank them for their input.

 

At the centre of the research is the VARIA framework, which stands for V-model, Architecture, Requirements, Independence and Assurance. VARIA is designed to help develop a more proactive, evidence-led approach to software assurance.  The report argues that software assurance should be built around robust requirements, strong system and software architecture, independent scrutiny throughout the lifecycle, and a risk-based selection of assurance techniques and measures. It also questions whether some late-stage activities, such as statistical testing and final-code static analysis, always provide proportionate safety benefit when compared with assurance evidence gathered earlier and continuously through development.

 

The research concludes that a more lifecycle-focused approach could reduce unnecessary duplication, make better use of previous regulatory scrutiny and vendor evidence, and support the safe and efficient deployment of modern nuclear technologies.  The outcomes of this research paper were presented to the ONR at one of their innovation cafe’s and we look forward to future engagements and further interaction to discuss the approach to software assurance the research paper proposes.