Application of human reliability analysis in the deterministic safety analysis for nuclear power plants

Licensing of nuclear power plants relies on safety analyses showing compliance of the design and operation with safety requirements. The safety analyses comprise of both deterministic analyses, where the compliance with deterministic rules shall be shown, and probabilistic analyses where the compliance with risk criteria shall be shown. Human reliability analysis (HRA) is a vital part of probabilistic safety assessment (PSA). There are a variety of methods and analysis principles that can be applied in the PSA context. On the other hand, there has been very little discussion and guidance on how human interactions should be assessed in the context of deterministic safety analyses (DSA). Since human interactions can be relevant contributors for many accident scenarios, there is clearly a need to develop rules on the treatment of human interactions in DSA. This paper discusses the consideration of human interactions in DSA, such as linking human interactions into DSA scenario categorisation, principles for crediting and not crediting human interactions and implications to the safety demonstration. The aim with the proposed approach is to improve the formalism in the treatment of human interactions context of DSA. Hypothetical but realistic assessment cases are presented as examples on how the principles can be applied.