A Unified 3D Framework for Zone models and Computational Fluid Dynamics models for Fire Risk Assessment in Small Modular Reactors.
18th International Seminar on Fire Safety in Nuclear Installations
20–22 May 2025 · Montrouge, France
The 18th International Seminar on Fire Safety in Nuclear Installations was held as a post-conference seminar for SMiRT 27 and a pre-conference seminar for SMiRT 28, organized by edvance in Montrouge, France. Over two days it brought together 60 participants from 12 countries across Europe, Asia, and North America for detailed technical discussion of topics relevant to the analysis and assurance of fire safety in nuclear power plants and other nuclear installations.
The proceedings are published by GRS (Gesellschaft für Anlagen- und Reaktorsicherheit) as GRS-806 (2026), edited by M. Röwekamp and H.-P. Berg.
A Unified 3D Framework for Zone Models and Computational Fluid Dynamics Models for Fire Risk Assessment in Small Modular Reactors
Ramprasad Sampath¹, Steven Prescott², Curtis Smith³
- Centroid Lab, Torrance, CA, USA
- Idaho National Laboratory, Idaho Falls, ID, USA
- Massachusetts Institute of Technology, Cambridge, MA, USA
Abstract. Internal fires pose a significant risk in nuclear power plants (NPPs), making fire probabilistic risk assessment (PRA/PSA) essential for informed decision-making by operators and regulators. Originally developed under the Light Water Reactor Sustainability (LWRS) Program, the Fire Risk Investigation in 3D (FRI3D) software has evolved to support fire risk assessment and design for Small Modular Reactors (SMRs).
Advanced fire modeling in nuclear plants relies on tools such as zone models (CFAST) and computational fluid dynamics (CFD) models like Fire Dynamics Simulator (FDS), often coupled with codes for cable failure analysis based on Nuclear Regulatory Commission reports (NUREG-2178, NUREG-6931). However, transitioning between models, updating scenarios, and incorporating regulatory changes — such as revised Heat Release Rates and incorporating guidelines like High Energy Arcing Faults (HEAF) — can be resource-intensive, requiring substantial effort and cost across multiple platforms.
This paper presents the underlying FRI3D framework, which integrates plant model databases, Computer-Aided Design (CAD) models, and Building Information Models (BIM) into a unified 3D environment. By seamlessly incorporating fire modeling tools, the outlined framework enables rapid, accurate visualizations of fire scenarios based on simulation results, while allowing users to choose between zone models and CFD-based approaches. A case study of a Small Modular Reactor room illustrates its capabilities. Additionally, this paper highlights key insights that enhance fire modeling for SMRs, aiding design decisions and Probabilistic Risk Assessment (PRA/PSA) while serving as a digital twin for fire risk and hazard analysis.
Keywords: PSA, RiskSpectrum, Fire PRA, Fire PSA
Read the paper. It appears in the GRS-806 proceedings — open the PDF at the paper (p. 232), download the full proceedings (PDF, ~15 MB), or see the GRS-806 publication record.