Risk-informed graded quality assurance

The grading of quality assurance (QA) controls at nuclear power plant aims at assuring an acceptable safety level but also at allocating QA resources cost-effectively. Historically, QA requirements stem from the safety classification of the systems, structures and components based on deterministic safety criteria. Risk-informed approaches applying the probabilistic safety assessment (PSA) are considered as one solution to rationalise and potentially relax the QA system. In this paper, risk-based conditions are formulated for the assignment of QA grades. The risk-based formulation is a reference model to explore possibilities, requirements and obstacles of this application of PSA. (orig.)