Taxonomy
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Canonical External Hazard Taxonomy
Purpose
This page defines the authoritative canonical hazard taxonomy for external hazards applicable to nuclear power plants. It establishes a single, stable set of canonical hazard identifiers (IDs), their scope boundaries, and their relationships.
These canonical IDs are used consistently across:
- the External Hazards wiki
- the document index and RAG database
- future member‑facing LLM/chat tools
The taxonomy normalizes terminology used across EPRI, the NRC, ASME/ANS, and international guidance. It does not replace regulatory language and does not remove technical or site‑specific nuance.
Core principles
The following principles govern how this taxonomy is used:
- Canonical hazard IDs are immutable.
- Once published, an ID must never be renamed, edited, or deleted.
- Changes in understanding are handled through descriptions, hierarchy updates, aliases, or deprecation (see below).
- Canonical IDs are labels, not filters.
- They improve grouping, traceability, and explainability.
- They must never be used to gate retrieval or render content inaccessible.
- Free text remains authoritative content.
- Canonical IDs complement semantic search and embeddings; they do not replace them.
How to use this taxonomy
- Each hazard overview wiki page must reference exactly one canonical hazard ID.
- Sub‑mechanisms or refinements reference both the child and parent IDs.
- Documents and index records may map to one or more canonical hazard IDs.
- Mapping improves consistency and long‑term usability.
- Lack of a mapping does not make content invisible or invalid.
- Initiating events (for example, LOOP, LUHS) are not hazards and are excluded.
Governance and change control
This taxonomy is designed to evolve without breaking downstream systems.
Allowed changes
The following may change at any time:
- Preferred hazard names
- Descriptions and scope notes
- Parent–child relationships
- Aliases and explanatory notes
Prohibited changes
- Canonical hazard IDs must never be renamed, reused, or removed.
Deprecation policy
When a hazard definition changes materially:
- The existing ID is marked deprecated.
- One or more replacement IDs are identified.
- Existing documents and index records remain valid and unchanged.
This approach preserves historical consistency while allowing the taxonomy to evolve.
Relationship to other structures
- Canonical hazard IDs define what external phenomenon is being referenced.
- Canonical concepts (defined elsewhere) describe how reasoning is performed.
- Terminology and prose remain flexible and human‑readable.
Together, these elements form a stable semantic backbone that supports long‑term knowledge retention, analysis, and AI‑assisted use.
Top-Level Classes
| Canonical ID | Preferred Name | Scope |
|---|---|---|
| EH-HYD | Hydrological Hazards | Water-related natural hazards including flooding, precipitation, and coastal events |
| EH-ATM | Atmospheric Hazards | Wind, storm, and weather-related hazards including tornados, hurricanes, and extreme temperatures |
| EH-GEO | Geological Hazards | Earth-related natural hazards including seismic, volcanic, and ground instability events |
| EH-BIO | Biological & Environmental Hazards | Hazards from biological organisms, drought, wildfire, and ecological phenomena |
| EH-ANT | Anthropogenic Hazards | Human-caused external hazards including industrial accidents, transportation, and nearby facility events |
| EH-ELE | Electrical & Electromagnetic Hazards | Hazards affecting electrical systems including lightning, electromagnetic interference, and grid disturbances |
| EH-CMB | Combined & Correlated Hazards | Multi-hazard scenarios and hazard combinations |
| EH-EVL | Hazard Evaluation & PRA Methods | Methodologies for identifying, screening, and assessing external hazards |
Hydrological Hazards
| Canonical ID | Preferred Name | Parent |
|---|---|---|
| EH-HYD-RIV | Riverine Flooding | EH-HYD |
| EH-HYD-PLV | Pluvial Flooding (Local Intense Precipitation) | EH-HYD |
| EH-HYD-CST | Coastal Flooding & Storm Surge | EH-HYD |
| EH-HYD-TSU | Tsunami | EH-HYD |
| EH-HYD-SEI | Seiche | EH-HYD |
| EH-HYD-DAM | Dam & Levee Failure | EH-HYD |
| EH-HYD-ICE | Ice-Induced Flooding (Ice Jam / Frazil Ice) | EH-HYD |
| EH-HYD-SLR | Sea Level Rise | EH-HYD |
| EH-HYD-GW | Groundwater Ingress | EH-HYD |
| EH-HYD-WDR | Wind-Driven Rain Intrusion | EH-HYD |
Atmospheric Hazards
| Canonical ID | Preferred Name | Parent |
|---|---|---|
| EH-ATM-TOR | Tornado | EH-ATM |
| EH-ATM-HUR | Hurricane / Tropical Cyclone | EH-ATM |
| EH-ATM-STW | Straight-Line / High Wind | EH-ATM |
| EH-ATM-DRT | Derecho / Thunderstorm Wind | EH-ATM |
| EH-ATM-HAL | Hail | EH-ATM |
| EH-ATM-SNW | Extreme Snow / Ice Storm | EH-ATM |
| EH-ATM-EHT | Extreme Heat | EH-ATM |
| EH-ATM-ECL | Extreme Cold / Freeze | EH-ATM |
| EH-ATM-MSL | Wind-Borne Missiles (Tornado / Hurricane Debris) | EH-ATM |
| EH-ATM-SND | Sandstorm / Dust Storm | EH-ATM |
Geological Hazards
| Canonical ID | Preferred Name | Parent |
|---|---|---|
| EH-GEO-SEI | Seismic (Vibratory Ground Motion) | EH-GEO |
| EH-GEO-FLT | Surface Faulting & Tectonic Deformation | EH-GEO |
| EH-GEO-VOL | Volcanic Activity (Ash, Lava, Lahar) | EH-GEO |
| EH-GEO-LND | Landslide / Slope Instability | EH-GEO |
| EH-GEO-SUB | Subsidence / Sinkhole / Karst Collapse | EH-GEO |
| EH-GEO-LIQ | Soil Liquefaction | EH-GEO |
| EH-GEO-ERO | Erosion & Sedimentation | EH-GEO |
Biological & Environmental Hazards
| Canonical ID | Preferred Name | Parent |
|---|---|---|
| EH-BIO-DRT | Drought / Low Water | EH-BIO |
| EH-BIO-WFR | Wildfire / Forest Fire | EH-BIO |
| EH-BIO-FOL | Biological Fouling (Mussels, Jellyfish, Algae) | EH-BIO |
| EH-BIO-VEG | Vegetation Encroachment | EH-BIO |
| EH-BIO-INF | Infestation (Insects, Rodents) | EH-BIO |
| EH-BIO-CLM | Climate Change Effects (Long-Term Trends) | EH-BIO |
Anthropogenic Hazards
| Canonical ID | Preferred Name | Parent |
|---|---|---|
| EH-ANT-IND | Nearby Industrial Facility Accident | EH-ANT |
| EH-ANT-TRN | Transportation Accident (Rail, Road, Pipeline) | EH-ANT |
| EH-ANT-AIR | Aircraft Impact | EH-ANT |
| EH-ANT-TMI | Turbine Missile (Internally Generated External Hazard) | EH-ANT |
| EH-ANT-EXP | External Explosion / Blast Wave | EH-ANT |
| EH-ANT-TOX | Toxic Gas / Chemical Release | EH-ANT |
| EH-ANT-FIR | External Fire (Non-Wildfire, for example, Fuel Storage) | EH-ANT |
| EH-ANT-SAB | Sabotage / Security Threat | EH-ANT |
Electrical & Electromagnetic Hazards
| Canonical ID | Preferred Name | Parent |
|---|---|---|
| EH-ELE-LTN | Lightning Strike | EH-ELE |
| EH-ELE-GRD | Grid Disturbance / Loss of Offsite Power (LOOP) | EH-ELE |
| EH-ELE-EMP | Electromagnetic Pulse (EMP) / Geomagnetic Disturbance | EH-ELE |
| EH-ELE-EMI | Electromagnetic Interference (EMI) | EH-ELE |
| Canonical ID | Preferred Name | Parent |
|---|---|---|
| EH-CMB-SEF | Seismic + Flooding (Seismically-Induced Flooding) | EH-CMB |
| EH-CMB-HWF | High Wind + Flooding (Hurricane Multi-Hazard) | EH-CMB |
| EH-CMB-SLP | Seismic + LOOP | EH-CMB |
| EH-CMB-WLP | Wind + LOOP | EH-CMB |
| EH-CMB-CAS | Cascading / Sequential Hazard Events | EH-CMB |
| EH-CMB-COR | Correlated Hazard Groups | EH-CMB |
Hazard Evaluation & PRA Methods
| Canonical ID | Preferred Name | Parent |
|---|---|---|
| EH-EVL-SCR | Hazard Screening & Identification | EH-EVL |
| EH-EVL-PRA | External Events PRA (Probabilistic Risk Assessment) | EH-EVL |
| EH-EVL-FRG | Fragility Analysis | EH-EVL |
| EH-EVL-MAR | Margins Assessment | EH-EVL |
| EH-EVL-SMA | Seismic Margins Assessment (SMA) | EH-EVL |
| EH-EVL-WDN | Walkdown & Inspection Procedures | EH-EVL |
| EH-EVL-OPX | Operating Experience (OpE) Review | EH-EVL |
| EH-EVL-CLR | Climate Resilience Assessment | EH-EVL |
EPRI technical point of contact: Chris Rochon (CRochon@epri.com)
Date last reviewed: 2026-03-23