Severe accidents in nuclear reactors, though low-probability events, pose significant risks to human safety, the environment, and public trust in nuclear energy. With the global transition toward low-carbon energy systems, advanced nuclear reactors (e.g., Generation IV reactors, small modular reactors, microreactors) and the continued operation of existing fleets demand rigorous, state-of-the-art severe accident analyses to ensure robust safety margins, optimize mitigation strategies, and support licensing and regulatory compliance.

Experimental investigations and numerical simulations are the dual pillars of severe accident research. Experimental studies provide critical data for validating physical models, quantifying key phenomena (e.g., core degradation, fission product transport, containment thermal-hydraulics), and scaling laws for reactor-scale applications. Numerical simulations enable the prediction of accident progression, evaluation of complex multi-physics coupling effects, and assessment of mitigation system performance—often in scenarios where experiments are impractical or cost-prohibitive.

Despite decades of progress, severe accident analyses still face challenges such as incomplete understanding of transient multi-physics phenomena, uncertainties in material properties under extreme conditions, and the need for high-fidelity modeling of complex systems.

This Research Topic aims to consolidate cutting-edge research at the intersection of experiment and simulation, bridging knowledge gaps and advancing the state-of-the-art in severe accident analysis for both existing and advanced nuclear reactors. We invite contributions that highlight innovative experimental methodologies, novel numerical techniques, and interdisciplinary insights to strengthen the safety and resilience of nuclear energy systems.

We welcome articles covering (but not limited to) the following themes:
• Experimental investigations of severe accident phenomena (e.g., core melting, fuel-coolant interactions, hydrogen generation and combustion, fission product release/retention)
• Development and validation of numerical models for severe accident analyses (e.g., multi-physics coupling of thermal-hydraulics, neutronics, materials science, and aerosol dynamics)
• High-fidelity simulations (e.g., CFD, DEM, DNS) of key severe accident processes and their integration with system analysis codes
• Design, operation, and data interpretation of severe accident test facilities (e.g., integral effect tests, separate effect tests)
• Scaling analysis and extrapolation of experimental data to reactor-scale conditions
• Uncertainty quantification and sensitivity analysis in severe accident numerical simulations
• Severe accident mitigation strategies (passive/active systems, containment design, accident management procedures) and their performance evaluation
• Fission product transport, deposition, and release mechanisms during severe accidents
• Severe accident analyses for advanced reactor technologies (e.g., sodium-cooled fast reactors, lead-cooled fast reactors, molten salt reactors, high-temperature gas-cooled reactors)
• Lessons learned from historical severe accidents and their implications for current and future reactor safety.

Impact

Frontiers in Nuclear Engineering

Nuclear Safety