b"Quantitative reliabilityModeling cyber-physical systems optimizes safety and reliability analysis for unattendeddesigns for fission battery nuclear microreactors.operation of fission batteries F ission batteries are designed for autonomous operation and a plug and play approach for the life of the reactor. These features along with tamper-proof designs and self-detect and self-protect systems against cyber and physical threats distinguish fission batteries from existing plants and many advanced reactors. However, reliability analyses for these cyber-physical systems are challenging due to the complexity of modern cyber-physical systems, which incorporate distributed and networked software, hardware, and physical components that operate and interact PROJECT NUMBER:in parallel. 21A1053-019FPTraditional probabilistic risk assessment tools struggle to model and assess time TOTAL APPROVED AMOUNT:or looping scenarios for these highly integrated cyber-physical system designs. $905,000 over 3 years To address these challenges, this project utilized the dynamic probabilistic PRINCIPAL INVESTIGATOR:risk assessment tool Event Modeling Risk Assessment using Linked Diagrams Steven Prescott (EMRALD) and linked it with the dual-graph error propagation methodology. This approach was expected to overcome some of the limitations of traditional and CO-INVESTIGATORS: dynamic probabilistic risk assessment. The project's main objectives were to model Thomas Ulrich, INL cyberattacks to evaluate mitigation options, demonstrate time-based scenarios Troy Unruh, INL for autonomous reactor safety, and develop methods to compare operator vs. Mihai Diaconeasa, North Carolinaautonomous control systems. State UniversityKey findings and results from the project include the development of two distinct COLLABORATOR: analytical methods for evaluating time dependent failure rates in complex systems. North Carolina State University These methods were implemented in EMRALD, providing a more realistic and accurate dynamic probabilistic risk assessment of complex systems. The team also successfully integrated dual-graph error propagation methodology with EMRALD to create a comprehensive framework for dynamic modeling of cyber-physical fission battery designs. This combined approach overcame some of the tools limitations when used independently and enabled detailed dynamic analysis to produce time-specific results for traditional probabilistic risk assessment models of fission batteries. These outcomes have implications for the design and operation of fission batteries and contribute to the broader field of nuclear reactor design and operation.48"