Methods and Tools
METHODS & TOOLS
Methods and Tools for External Hazard Assessment
The Hazards catalog describes what can threaten a plant; this section describes how those threats are evaluated — from initial screening through probabilistic quantification and programmatic integration.
This page catalogs selected analytical methods, software tools, and field processes used across external hazard assessments at nuclear power plants. This is not an exhaustive set of methods and tools. Individual method/tool/process pages provide detailed descriptions, workflow diagrams, and key references; links are provided where such pages are available.
Methods and Tools: from Screening to Integration
A typical external hazard assessment moves through several functional stages. The methods and tools cataloged here map onto those stages, and most assessments will use a combination of them.
| Functional Stage | What Happens | Representative Methods / Tools |
|---|---|---|
| Screening & Prioritization | Identify which external hazards are credible for a given site and warrant detailed analysis using qualitative and quantitative screening criteria | EPRI screening guidance (3002005287) |
| Walkdowns & Field Verification | Physically inspect the plant to identify vulnerable structures, systems, and components (SSCs), confirm as‑built configurations, and verify conditions assumed in the analysis | Hazard‑specific field inspections and surveys (for example, high winds vulnerable‑SSC walkdowns and missile surveys per 3002008092) |
| Deterministic Approaches | Evaluate whether hazard effects are bounded by design‑basis protections or can be resolved without full probabilistic analysis | Design‑basis evaluation; TMRE; ASCE 7‑22 wind‑load provisions |
| Probabilistic Risk Assessment | Quantify hazard frequency, SSC fragility, and plant response to estimate risk metrics (core damage frequency (CDF), large early release frequency (LERF)) | External events PRA (HWPRA, XFPRA, SPRA) Typically comprised of event‑tree and/or fault‑tree models |
| Fragility Analysis | Develop conditional failure probabilities for SSCs as a function of hazard intensity | Empirical fragility functions; impact testing correlations |
| Software & Calculation Tools | Compute hazard‑specific parameters — missile strike probability, flood annual exceedance probability, geomagnetically induced current (GIC) levels, and so forth | TMSC, TMRE, TORMIS, PFHA models, JPM |
| Program Integration | Fold hazard results into plant risk models, licensing decisions, and operational programs | climate vulnerability assessment (CVA) |
Pages in This Section
- Assessment Process
- Analytical Methods
- Deterministic Approaches
- Probabilistic Risk Assessment
- Beyond Design Basis
- Climate Vulnerability Assessment (CVA)
- Tools and Platforms
EPRI technical point of contact: Chris Rochon (CRochon@epri.com)
Date last reviewed: 2026-05-20