There has been growing interest in passive safety systems since the Fukushima accident. Passive systems rely on physical principles, such as gravity and natural circulation, to cool nuclear reactors, while active systems in large commercial light-water reactors (LWRs) require complex emergency components driven by electricity. The development of small modular reactors (SMRs) is rapidly progressing worldwide to support decarbonization, supply reliable power for data-intensive industries, and serve as a clean heat source for hydrogen production, with passive safety becoming a fundamental design criterion.

Inherent safety features reinforce the resilience of advanced reactors. For example, TRISO fuel in high-temperature gas-cooled reactors (HTGRs) confines fission products with multiple coating layers; molten salt reactors (MSRs) operate at low pressure with high thermal capacity, which inherently limits rapid temperature and pressure increases; and sodium fast reactors (SFRs) possess negative reactivity coefficients that inherently stabilize reactor power.

This Research Topic explores passive and inherent safety in advanced reactors, with the goals of advancing the understanding of these systems, showcasing credible and quantifiable safety improvements, establishing robust acceptance criteria, and providing validated, transferable methodologies for the reliable safety assessment and licensing of next-generation reactors.

This collection will highlight innovative design concepts that enhance or simplify safety systems; report on recent results from integral tests, scaled experiments, and separate-effect studies that provide crucial validation data; and feature high-fidelity simulations—ranging from system codes and CFD to reduced-order and AI-assisted models—with benchmark-quality datasets.

Advances in passive safety systems, such as gravity-driven cooling, natural circulation, passive decay-heat removal, and in-vessel retention, which minimize reliance on active components and external power are of particular interest. Also of interest are studies of inherent safety features, including TRISO fuel performance in HTGRs, large thermal inertia of molten salt in MSRs, and negative reactivity feedback in SFRs.

We welcome contributions across design, experiment, simulation, and regulatory perspectives. Manuscripts must offer new insights into passive and/or inherent safety in advanced reactors. Topics within the scope of this collection include:
• Design and assessment of passive safety systems
• Inherent safety features in advanced reactors
• Integral- and Separate-effect tests for validation of passive and inherent safety systems
• High-fidelity simulations with V&V/UQ
• Comparative safety analysis of SMRs and Gen-IV reactors relative to large LWRs
• Digital and AI-enabled safety diagnostics and monitoring in advanced reactors
• Development of safety metrics, acceptance criteria, and licensing frameworks for passive and inherent safety.

Are you interested in contributing a manuscript to this Research Topic?

Passive and Inherent Safety Assessment in Advanced Reactors