PRA with CAFTA

FRI3D integrates with CAFTA (Computer-Aided Fault Tree Analysis), a widely used software for performing Probabilistic Risk Analysis (PRA) in the nuclear power industry.

CAFTA is a Probabilistic Risk Analysis (PRA) toolkit developed and maintained by the
Electric Power Research Institute (EPRI).

Most nuclear plants in the United States use Computer-Aided Fault Tree Analysis (CAFTA) software for performing Fire Risk Analysis.
Alongside CAFTA is FRANX (Fault tree/Risk Assessment Network eXchange), a logical database that identifies the basic events which initiate a fire and their mappings to plant equipment and systems.

FRANX and Plant Data Integration#

FRANX is a Microsoft Access–based database used to help generate fire scenarios by linking plant and component information to specific failure events modeled in the PRA.
It associates initiating events and failure modes with corresponding components, cables, and targets to support event-driven analysis.

FRANX allows specific initiators to damage defined targets so that the program can:

Identify failure modes and affected components.
Determine which targets (systems, cables, or rooms) to include or exclude from each scenario.
Facilitate the generation of scenario case data for downstream quantification.

CAFTA, in turn, uses this information to develop and quantify fault trees that model the credited systems, components, and human actions used to mitigate initiating events that could lead to plant trips or accidents.
It quantifies these fault trees to determine measurable results such as:

Likelihood of accidents
Drivers of overall plant risk

While FRANX can also perform quantification, it is typically used for fire or flood analyses.
CAFTA handles all types of initiators, including internal events, seismic, and external hazards.

Plant Data Model System (PDMS)#

Each plant maintains a Plant Data Model System (PDMS) — a database that tracks relevant components, equipment, cables, cable raceways, and other plant data.

PDMS is used to gather:

Component and cable links
Location and zone information
Associated drawings and documentation

Although most plants use a similar structure, each PDMS can vary significantly in:

Level of detail
Table contents and relationships
Reference methods and identifiers

FRI3D integrates with the plant’s PDMS via component identifiers and spatial location data, allowing simulated fire scenarios to map directly to plant equipment and cable systems.

Importing Custom Plant Databases#

In addition to standard PDMS and FRANX data sources, FRI3D includes a custom import module that allows users to import data from non-standard or plant-specific databases.
This module provides flexible configuration options to map external database fields to FRI3D’s internal component and cable models.

Supported sources include:

SQLite, or Access databases
CSV, Excel, or JSON formatted plant inventories
Proprietary data models exported from engineering or maintenance systems

The import module can be customized to handle specific plant data structures, including:

Custom field mapping (e.g., component IDs, zone names, cable tray references)
Schema validation against FRI3D’s internal structure
Incremental updates for recurring data synchronization

Once imported, these databases are treated identically to native PDMS sources, allowing complete integration with FRI3D’s fire simulation and PRA export workflows.

FRI3D ↔ CAFTA Integration Overview#

FRI3D interfaces with CAFTA by consolidating simulation outputs with FRANX input data.
The integration enables FRI3D to automatically:

Identify components and cables affected by fire.
Translate physical damage into Basic Event failures.
Populate or update FRANX tables .
Export consolidated data for direct import into CAFTA for quantification.

This process connects 3D fire dynamics from FRI3D to the CAFTA fault tree logic used in PRA modeling.

General FRI3D ↔ CAFTA Process#

Fire Scenario Creation
- Fire scenarios are created in FRI3D or imported from existing PRA definitions.
Fire Simulation Execution
- FRI3D runs detailed 3D fire simulations and determines affected zones, cables, and components.
Scenario Consolidation
- Results from all scenarios are merged with the plant’s FRANX or PDMS data.
- Each damaged component is mapped to its corresponding Basic Event within the CAFTA model.
FRANX File Generation
- FRI3D generates or modifies a FRANX data file (Access database or XML) that includes:
  - Scenario identifiers
  - Affected components and cables
  - Updated failure probabilities
  - Ignition frequency, severity, and non-suppression factors
Import into CAFTA
- The updated FRANX file is imported into CAFTA, where fire scenarios are linked to system fault trees.
Quantification
- CAFTA performs quantification using the updated failure data to compute CDF and LERF changes from baseline.

Model Preparation in CAFTA#

Before importing FRI3D results, ensure the following are set up in CAFTA:

Baseline PRA Model
- The CAFTA model should include defined event trees, fault trees, and basic events for the plant systems.
FRANX Interface Enablement
- Confirm the CAFTA model supports FRANX database exchange or XML import/export.
Component and Cable Tagging
- Ensure each component and cable in CAFTA (via FRANX) has identifiers that match those used in FRI3D’s exported mapping.

FRI3D / CAFTA Export Workflow#

The following steps outline the export workflow from FRI3D to CAFTA and are automated within FRI3D.

Export FRANX Base Model
- The base FRANX file (Access ) is exported from CAFTA to a working directory.
Merge FRI3D Simulation Data
- FRI3D imports the base FRANX model and merges simulation-derived failures with existing plant and component data.
Generate Updated FRANX File
- FRI3D outputs a modified FRANX file with updated event states, fire frequencies, and metadata for each scenario.
Import Updated File into CAFTA
- Use CAFTA’s FRANX Import utility to load the updated data.

Finally in CAFTA the user can

Run Quantification
- Quantify each fire scenario or case group to compute the change in plant risk due to fire.

Example Integration Flow#

flowchart LR
A[FRI3D Fire Simulation] --> B[Identify Damaged Components & Cables]
B --> C[Map to FRANX Basic Events]
C --> D[Generate Updated FRANX Database]
D --> E[Import into CAFTA]
E --> F[Quantify Fire PRA Model]
F --> G[Compute ΔCDF and Fire Risk Metrics]

FRI3D / CAFTA Preferences#

FRI3D provides a CAFTA Export Configuration Panel that allows users to specify:

Path to the CAFTA project
Path to the FRANX database or XML file
Fire scenario identifiers and metadata

Summary#

CAFTA and FRANX are widely used EPRI tools for probabilistic fire risk assessment.
FRI3D integrates directly with these tools to generate, consolidate, and export fire simulation results for PRA quantification.
The integration automatically updates FRANX models with component failures, ignition frequencies, severity factors, and suppression data.
Custom plant databases can also be imported using FRI3D’s flexible import module, enabling compatibility with diverse data systems.
Once imported, CAFTA quantifies the updated model to determine the increase in plant risk due to fire events.
This combined workflow provides a robust link between 3D physical simulation and probabilistic safety analysis.

References#

CAFTA User Manual (EPRI) — Computer-Aided Fault Tree Analysis System
https://www.epri.com
FRANX User Guide (EPRI) — Fault Tree / Risk Assessment Network eXchange Specification
Defines data schema and interoperability for CAFTA integration.
NUREG/CR-6850 — Fire PRA Methodology for Nuclear Power Facilities, U.S. NRC / EPRI
Basis for fire risk quantification and scenario modeling.
FRI3D Fire PRA Export Guide — Internal Technical Note, Centroid LAB, 2025
Details FRI3D-to-FRANX data mapping, export schema, and validation steps.

⚠️ Disclaimer:
The CAFTA export functionality in FRI3D automates fire scenario generation and FRANX updates.
Due to model-specific configurations, all exported files should be validated in CAFTA before formal quantification or reporting.