Proceedings of the

The 33rd European Safety and Reliability Conference (ESREL 2023)
3 – 8 September 2023, Southampton, UK

Safety Argumentation for a Nuclear Reactor Protection System – an Assessor's View

Xueli Gao1,a, Peter Karpati1,b, Bjørn Axel Gran2 and Alan Wassyng3

1Safety and Risk Department, Institute for Energy Technology, Norway.

2Digital System, Institute for Energy Technology, Norway.

3McMaster Centre for Software Certification, McMaster University, Canada.


Structured safety argumentation has several advantages over safety demonstrations provided through a free text form. However, there are few publicly available examples of broadly accepted safety assurance cases with sufficient detail to demonstrate best practice. Furthermore, they usually reflect the system developers' viewpoint. This paper presents simplified extracts of a safety assurance case from a case study that uses an assessor's viewpoint to structure the argument. The case study is based on relevant sections of US Nuclear Regulatory Commission regulation. The argument is partial and focuses on the conceptual design level of the "trip" safety function allocated to the Reactor Protection System of a nuclear power plant. Reflections and general observations from the discussion with an expert assessor aim to support readers with practical considerations for similar safety assurance cases.

Keywords: Safety demonstration, Structured safety argumentation, Safety assurance case.

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