Fire Risk Quantification (Task 14)

Task Overview

Background

The task description provides recommendations for quantification and presentation of fire risk results.

Purpose

This section describes the procedure for performing fire risk quantification. This procedure provides the user a general method for quantifying the final Fire PRA Model to generate the final fire risk results.

Scope

This procedure addresses the following major steps for each of the major fire risk quantification tasks:

• Step 1–Quantify Final Fire CDF Model
• Step 2–Quantify Final Fire LERF Model
• Step 3–Conduct Uncertainty Analysis

In this task, the final Fire PRA model is quantified to obtain the final fire risk results. The final CDF and LERF models are quantified for each fire scenario.

Note that per Task 7, Quantitative Screening, it is expected that a number of fire compartments or fire scenarios will be screened out from the formal fire quantification results (i.e., not added into the calculated total plant fire-related CDF and LERF). It is expected that as a minimum, total plant CDF and LERF estimates will be provided by summing all the CDFs and LERFs for the unscreened fire compartments/scenarios. The significant contributors to the plant CDF and LERF should also be provided. In addition, it is also expected that the nature (e.g., type of sequences) of the screened out compartments/scenarios are at least identified and as a check of the cumulative screening criteria discussed in Task 7, it is recommended that the screened CDFs and LERFs also be summed separately to provide a perspective on the total residual risk from the screened compartments/scenarios. It should be emphasized that these screened portions of the results represent various levels of analysis (for instance, some may only involve fire scoping modeling; others may involve both detailed fire modeling and some detailed circuit analysis, etc.). Thus any ranking of these screened scenarios is not particularly appropriate and these screened summations of CDF/LERF are upper bounds of the residual risk and that in actuality, the residual risk is probably much less than these sums would indicate.