ML18213A097
| ML18213A097 | |
| Person / Time | |
|---|---|
| Issue date: | 07/31/2018 |
| From: | Tammie Rivera NRC/RES/DRA/FRB, Electric Power Research Institute |
| To: | |
| Shared Package | |
| ML18213A072 | List: |
| References | |
| Download: ML18213A097 (15) | |
Text
Module III - Fire Analysis Task 11c - Multi-Compartment Fire Analysis Joint EPRI/NRC-RES Fire PRA Workshop August 6-10, 2018 A Collaboration of the Electric Power Research Institute (EPRI) & U.S. NRC Office of Nuclear Regulatory Research (RES)
Multi-Compartment Fires Objective Fire scenarios involving multiple, interconnected or adjacent fire compartments are analyzed in this part of Task 11.
Fire propagation Smoke propagation A rare event in U.S. NPP fire experience Screening process 2
Multi-Compartment Fires Overall Approach Multi-compartment analysis is focused on screening of potential scenarios before any detailed analysis is attempted.
- Single compartment analysis to be conducted before this step
- Reduce number of multi-compartment combinations
- Same analytical approach as in Detailed Fire Modeling Corresponding PRA Standard SRs: FSS-G1 through FSS-G6 3
Multi-Compartment Fires Definitions The following two terms are specifically defined for this part of the analysis:
- Exposing Compartment: The compartment where fire ignition occurs
- Exposed Compartments: The compartments to which fire from the exposing compartment propagates 4
Multi-Compartment Fires Analysis Steps The following steps define one possible approach for multi-compartment fire risk analysis:
- Step 1.c: Exposing and Exposed Compartments Matrix
- Step 2.c: First Screening-Qualitative
- Step 3.c: Second Screening-Low Fire Load Exposing Compartments
- Step 4.c: Third Screening-Frequency of Occurrence
- Step 5.c: Fourth Screening-CDF Based
- Step 6.c: Detailed Analysis
- Step 7.c: Document the Analysis 5
Multi-Compartment Fires Step 1.c: Exposing and Exposed Compartments Matrix Develop a matrix to identify all potential multi-compartment fire scenarios that start with an exposing compartment and propagate into a set of exposed compartments.
- Well defined pathways
- Means of propagation (i.e., hot gas, smoke, etc.)
- Special characteristics to be noted (e.g., self closing doors, fire dampers and vents near the ceiling)
- More than one exposed compartment
- Supported by a walk-down 6
Multi-Compartment Fires Step 1.c: Exposing and Exposed Matrix (contd)
The following rules are suggested to identify multi-compartment scenarios:
- Postulate only one barrier failure (e.g., door left open)
Unless there is a clear reason to assume common cause failure of multiple barriers
- Assume minimal smoke damage
- Hot gas can travel to all physically possible exposed compartments For a large number of compartments open into each other, detailed analysis may be warranted 7
Multi-Compartment Fires Step 1.c: Exposing and Exposed Matrix (contd)
Example:
Exposing Compartment Exposed Compartment
- # # Path Comments ID Name ID Name 1 9 SWG Access Room 1.1 10 Swtich Gear Room A 1.1.1 Door The door is 3-hr rated and normally closed 1.1.2 Opening Ventilation opening between rooms with fusible link activated fire dampers.
1.2 11 Swtich Gear Room B 1.2.1 Door The door is 3-hr rated and normally closed 1.2.2 Opening Ventilation opening between rooms with fusible link activated fire dampers.
1.3 -- Stairway 1.3.1 Door The door is 3-hr rated and normally closed 2 4A RHR Room 2.1 4B AFW Pump Room 2.1.1 Door The door is 3-hr rated and normally closed 2.1.2 HVAC Duct There are two HVAC ducts with opening in both compartments providing intake and discharge 2.2 -- Stairway 2.2.1 Door The door is 3-hr rated and normally closed 3 4B AFW Pump Room 3.1 4A RHR Room 3.1.1 Door The door is 3-hr rated and normally closed 3.1.2 HVAC Duct There are two HVAC ducts with opening in both compartments providing intake and discharge 8
Multi-Compartment Fires Step 2.c: First Screening - Qualitative The first screening of the scenarios can be based on the contents of the exposed compartments.
The following criteria may be used:
- The exposed compartment(s) do not contain any Fire PRA components or cables, or
- The fire PRA components and cables of the exposed compartment(s) are identical to or less than those in the exposing compartment.
Corresponding PRA Standard SRs: FSS-G2 and FSS-G3 9
Multi-Compartment Fires Step 3.c: Second Screening-Low Fire Load Exposing compartments that do not include combustible loading sufficient for generating a hot gas layer in any of the exposed compartments can be screened out.
- Conservative HRR values Ignition sources with highest 98% HRR Add HRR of intervening combustibles
- Determine damaging HRR values Hand calculations Hot gas layer damage in exposed compartment
- Compare HRRs Corresponding PRA Standard SRs: FSS-G2 and FSS-G3 10
Multi-Compartment Fires Step 4.c: Third Screening-Occurrence Frequency Scenario likelihood is established from the following three parameters:
- Ignition frequency
- Combined severity factor and non-suppression probability HRR comparison (preceding step) can give the severity factor May assume PNS = 1.0
- Barrier failure probability Corresponding PRA Standard SRs: FSS-G2 through FSS-G5 11
Multi-Compartment Fires Step 4.c: Third Screening / Barrier Failure Generally, data on barrier failure probability is sparse, and what is available is subject to many limitations.
- Initial attempt may be based on a screening value May use Pr(barrier failure) = 0.1 for screening
- For scenarios that do not screen out, may use the following:
For water curtain, use detection and suppression approach Verify that there are no plant-specific barrier failure problems Use the following generic barrier failure probabilities
- Type 1 - fire, security, and water tight doors - 7.4E-03
- Type 2 - fire and ventilation dampers - 2.7E-03
- Type 3 - penetration seals, fire walls - 1.2E-03 12
Multi-Compartment Fires Step 5.c: Fourth Screening-CDF Based Those scenarios that survive the preceding screening steps may be screened based on their CDF.
- Assume all PRA components and cables of exposing and exposed compartments are failed
- Estimate CCDP
- Use scenario frequency of preceding step Corresponding PRA Standard SR: FSS-G6 13
Multi-Compartment Fires Step 6.c: Detailed Analysis Those scenarios that do not screen out in the preceding steps may be analyzed using the same methods as for single compartments.
- Same set of steps as in single compartment analysis
- Include target sets from exposed compartment(s)
Corresponding PRA Standard SR: FSS-G1 14
Multi-Compartment Fires Concluding Remarks Multi-compartment fire analysis should be performed to ensure completeness of the Fire PRA.
- Compartment partitioning process (Task 1) has a direct impact on this task
- Develop a matrix of exposing and exposed compartments to ensure completeness
- Screening analysis is necessary to limit the level of effort
- Barrier failure probabilities should be treated conservatively
- May have to revisit some of the partitioning definitions 15