Risk Spectrum PSA Output

Fire Modeling using FRI3D and Risk Spectrum

There are multiple ways to incorporate fire scenarios into a PSA/PRA model, such as adding them directly into fault trees and generating fire event trees sequences or modify initiating events in the existing event tree. Scenarios can be incorporated directly into existing internal event analysis.

A fire model consists of a set of “Full room burnup” scenarios or all the fire sources as scenarios for each compartment/area in a facility. A fire scenario is an initiating event with the frequency of the combined fields fire initiating event frequency, severity factor, non-suppression probability.

This is used to quantify event tree sequences where all the basic events associated with components that failed in the fire which are set to a 1.0. After adding all the fire scenarios, the fire scenarios are quantified and the difference in the CDF from vs the normal initiating event CDF gives the increased risk due to fire.

General FRI3D <=> RiskSpectrum PSA Process

1. Fire scenario in FRI3D is created by user or imported from RiskSpectrum.
2. FRI3D runs the scenario and stablished the scope of cable trays affected by the fire -> Components failed, cable damaged, Basic Events failed and triggered HRA flags.
3. User analyses the results from FRI3D and determines which Event Tree should be quantified. In addition, the user defines the ignition frequency of the case, severity factos, non-suppression probability, etc.
4. FRI3D integrates the analysis and exports to RiskSpectrum in which further analysis can continue.

In view of the above steps the following detailed steps are outlined to run a fire PRA/PSA in RiskSpectrum via FRI3D.

Model Preparation

A few pre-requisites are needed before fire modeling can be performed. To simplify calculations, Risk Spectrum allows you to create an analysis case group. A new group needs to be created to put all the individual analysis cases under, so they can all be solved at the same time . A fire basic event also needs to be added with the frequency of 1.0. This event will be substituted for all the failed basic events for a scenario, likely causing an increased probability for the cut sets using those events when the fire scenario is quantified.

Integration with RiskSpectrum model.

To create or add scenarios from FRI3D to the RiskSpectrum model the following steps are performed:

1. Use the Risk Spectrum Macro commands to export the base project that the user has specified links to the FRI3D model to a temporary work location using the excel output feature in Risk Spectrum.
2. Add the fire exchange event to substitute for the basic events that fail due to fire.
3. Create a fire analysis case group so that all the fire scenarios can easily be calculated.
4. For each FRI3D fire scenario the user wants to calculate do the following:
   1. Create a house event for the scenario.
   2. Link the house event and the fire exchange event for each basic event in the scenario.
   3. Copy the analysis case this fire scenario is based upon as a new fire analysis case.
   4. Add the fire analysis case to the fire analysis case group
   5. Create a boundary condition to include this fire scenario
5. Save the modified Excel sheets
6. Run the Risk Spectrum Macro commands to import the modified PRA Excel sheets
7. Open RiskSpectrum to solve and execute the fire analysis case group

FRI3D/Risk Spectrum Preferences

Appropriate modifications to the FRI3D interface was made to accommodate Risk Spectrum output, these included specification of the Risk Spectrum master PSA file, the user credentials , analysis case and the initiating event.

RiskSpectrum Fire PSA Model

In Risk Spectrum PSA, all the fire related events corresponding to FRI3D are created with a prefix FI. The house events are created for each fire scenario run. For example: FI_FSOURCE_1_CFAST and FI_SGR-A_FULLROOM are created which are exchanged with the corresponding basic events. could be examples of a fire scenario with a fire at one section of a room and a full room burnout.

The house events from the scenario are exchanged with these basic events via Exchange Events in RiskSpectrum.

What's next?