Quantitative Screening (Task 7)
Contents
Task Overview
Background
A Fire PRA allows the screening of fire compartments and scenarios based on their contribution to fire risk. This approach considers the cumulative risk associated with the screened compartments (i.e., the ones not retained for detailed analysis) to ensure that a true estimate of fire risk profile (as opposed to vulnerability) is obtained.
Purpose
This section describes the procedure for performing the following quantitative screening tasks:
- Task 7A–Quantitative Screening I
- Task 7B–Quantitative Screening II
- Task 7C–Quantitative Screening III (Optional)
- Task 7D–Quantitative Screening IV (Optional)
This procedure provides the user an approach to quantify the Fire PRA Model using the procedure provided in Task 5, and to screen out fire compartments based on quantitative criteria. This procedure develops the bases for the quantitative screening criteria and provides specific methods for implementing the screening process.
Scope
This procedure addresses the following steps for each of the major quantitative screening tasks.
- Step 1–Quantify CDF Model
- Step 2–Quantify LERF Model
- Step 3–Quantitative Screening
In Tasks 7A and 7B, the Fire PRA Model is quantified at the fire compartment level. In Tasks 7C and 7D, the Fire PRA Model is quantified at the fire scenario level. Although not recommended, the quantitative screening can be implemented for screening fire scenarios. Therefore, Tasks 7C and 7D are considered optional tasks in this procedure. The basis for the quantitative screening criteria is developed and an approach for implementing the screening process is provided. To address future use of the Fire PRA Model for risk-informed applications, quantitative screening criteria also consider the impact of equipment unavailability.
Related Element(s) of ASME/ANS PRA Standard, ASME-RA-Sb-2013
Quantitative Screening (QNS)
Related EPRI 1011989 NUREG/CR-6850 Appendices
Appendix D, Appendix for Chapter 7, Technical Bases
