(GRS-821) AnTeS-PRIO Reliability and Safety Assessment of the Prioritization Between Safety and Operational I&C Systems in Nuclear Power Plants

Förderkennzeichen 4722R01215

The increasing complexity of digital Instrumentation and Control (I&C) systems in nuclear power plants necessitates advanced methodologies for assessing their reliability and safety. This report presents the development, validation, and application of a comprehensive analytical framework for evaluating I&C architectures, with a particular focus on the prioritization between safety I&C (SIC) and operational I&C (OIC) systems. The study was conducted using the Analysis and Test System (AnTeS), a modular platform developed by GRS that combines real and simulated I&C systems with a comprehensive set of tools and methods for system analysis. Within the scope of this project, AnTeS was significantly extended to include additional operational I&C systems, prioritization and actuation control modules, and enhanced field system components, thereby expanding its capabilities for the detailed investigation of complex I&C architectures.

The inclusion of real and simulated OIC systems as well as prioritization and actuation control (PAC) modules in AnTeS enabled detailed reliability assessments under realistic conditions, particularly for architectures where multiple I&C systems interact. These real systems supported direct fault injection and response testing, ensuring that actual hardware behavior could be observed and analyzed. The corresponding simulation models, implemented in a high-fidelity simulation environment, allowed for extensive failure mode analyses, probabilistic safety assessments, and Monte Carlo simulations. This ensured a comprehensive evaluation of both the I&C systems and the prioritization mechanisms responsible for resolving command conflicts between SIC and OIC. The integration of these new real and simulated systems into AnTeS significantly expanded its analytical capabilities, enabling a more detailed examination of complex I&C architectures.

The simulation and analysis methodology used during the project was validated by comparing real-system behavior with simulation results, ensuring that the models accurately reflect real I&C system performance. The validation process demonstrated a high degree of consistency between different analytical approaches. Using the validated framework, a series of model systems with varying configurations of SIC, OIC, and PAC modules were analyzed to assess the impact of redundancy, functional diversity, and general diversity on system reliability. The results, summarized in this report, illustrate the influence of these design parameters on overall system availability and failure risk.

From a regulatory perspective, the findings are highly relevant for technical support organizations such as GRS and nuclear safety authorities. The ability to model, validate, and analyze complex I&C architectures is essential for licensing new reactors, evaluating modifications to existing plants, and ensuring compliance with international safety standards. The insights gained in this study contribute to risk-informed decision-making, e.g., by identifying the predominant failure modes, in particular common cause failures, through the systematic analysis of redundant and diverse I&C architectures. The analyses also provide a robust foundation for supporting regulatory reviews and technical safety analyses, and contribute to training and knowledge transfer by enabling GRS to strengthen its expertise in the field of I&C assessment through validated methodologies.

In conclusion, this study demonstrates that the applied methodology provides a systematic, reliable, and transparent approach for evaluating digital I&C architectures, particularly in the context of SIC-OIC prioritization. The successful development and testing of real and simulated SIC, OIC, and PAC systems significantly enhance the ability of GRS to perform detailed assessments of modern nuclear I&C architectures. The results establish a solid foundation for future research and regulatory developments, ensuring that nuclear power plants maintain the highest levels of safety and reliability in their I&C architectures.