ML24256A034
| ML24256A034 | |
| Person / Time | |
|---|---|
| Issue date: | 09/12/2024 |
| From: | Michelle Kichline NRC/NRR/DRA/APOB |
| To: | |
| References | |
| Download: ML24256A034 (12) | |
Text
Revision of IMC 0609 Appendix F, Fire Protection Significance Determination Process Michelle Kichline Senior Reliability and Risk Analyst Office of Nuclear Reactor Regulation / Division of Risk Assessment
Purpose of Revision
- Revise the IMC to ensure that the fire protection guidance used in the IMC is consistent with current methods and guidance.
- Specifically, this revision incorporates updated fire protection guidance from the following NUREGs:
- NUREG/CR-6850, Vol 2, EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities, Volume 2: Detailed Methodology
- NUREG-2178 Vol. 2, Fire Modeling Guidance for Electrical Cabinets, Electric motors, Indoor Dry Transformers, and the Main Control Board
- NUREG-2232, "Heat Release Rate and Fire Characteristics of Fuels Representative of Typical Transient Fire Events in Nuclear Power Plants,"
- NUREG-2233, Methodology for Modeling Transient Fires in Nuclear Power Plant Fire Probabilistic Risk Assessment
- NUREG-2262, High Energy Arcing Fault Frequency and Consequence Modeling
Documents Revised
- IMC 0609 Appendix F, Fire Protection Significance Determination Process (ML24150A359 or package ML24241A154)
- Attachment 1, Fire Protection Significance Determination Process Worksheets (ML24145A028)
- Attachment 2, Degradation Rating Guidance (ML24145A029)
- Attachment 3, Guidance for Identifying Credible Fire Scenarios (ML24145A030)
- Attachment 4, Guidance for Determining Fire Ignition Frequency (ML24145A031)
- Attachment 5, Characterizing Fire Ignition Sources (ML24145A032)
- Attachment 6, Guidance for Identification of Targets and Their Ignition and Damage Criteria (ML24145A033)
- Attachment 7, Guidance for Non-Suppression Probability Analysis (ML24150A357)
- Attachment 8, Tables and Plots Supporting the Phase 2 Risk Quantification (ML24150A358)
- IMC 0308 Attachment 3, Appendix F, Technical Basis for the Fire Protection Significance Determination Process (ML24150A361)
Major Changes
- Adopted heat soak method and adjusted solid flame model in the zone of influence (ZOI), time to damage, and severity factor (SF) calculations (NUREG-6850 Vol 2 and NUREG-2232).
- In general, this change results in smaller ZOIs and SFs and a longer time to damage than the previously used point source model.
- The heat soak method was not used for the hot gas layer calculations.
- Incorporated new guidance for high energy arching fault (HEAF) ZOIs, heat release rates (HRRs), non-suppression probability, counting rules, and fire ignition frequencies (FIFs) (NUREG-2262).
Major Changes - Continued
- Updated ignition source categories for pumps, motors, dry transformers, and electrical enclosures (NUREG-2178 Vol 2).
- Dry transformers have their own category and are no longer motors.
- Pumps are now motors and defined by motor size.
- Incorporated new HRRs for dry transformers and class A, B, and C electric motors (NUREG-2178 Vol 2).
- Revised HRRs and categories of transient fires (NUREG-2233).
- Transients are either generic or in a transient combustible control location (TCCL).
- Updated FIF and non-suppression probability curve for main control board fires (NUREG-2178 Vol 2).
Questions
Backup Slides
Ignition Source and HRR Changes HRRs for Fixed Ignition Sources Ignition Source 2018 Revision HRR (kW) 2024 Revision HRR (kW)
Class A Motors (>5-30 hp) 69 15 Class B Motors (>30-100 hp) 37 Class C Motors (>100 hp) 100 Pumps 211 Use motor size Class A Dry Transformers (>45-75 kVA)
Use motors 69 30 Class B Dry Transformers (>75-750 kVA) 70 Class C Dry Transformers (>750 kVA) 130 Group 1 Switchgear and Load Center (TP, Closed) 170 170 Group 2 MCCs and Battery Chargers (TP, Closed) 130 130 Group 3 Power Inverters (TP,Closed) 200 200 Group 4a Large Enclosures [>50 ft3] (TP, Closed) 400 400 Group 4a Large Enclosures [>50 ft3] (TP, Open) 1000 1000 Group 4b Medium Enclosures [>12 ft3] (TP, Closed) 200 200 Group 4b Medium Enclosures [>12 ft3] (TP, Open) 325 325 Group 4c Small Enclosures [12 ft3] (All) 45 45
Transient HRR Changes HRRs for Transient Ignition Sources Ignition Source 2018 Revision HRR (kW) 2024 Revision HRR (kW)
Loose/Generic Transient 317 278 Contained/TCCL Transient 317 143
Fire Ignition Frequencies for HEAFs HEAF Type Counting Unit Zone-Wide FIF Load Centers (1000 V)
HEAF fault zone 3 5.3E-04**
Zone 1 Switchgear (>1000 V)
HEAF fault zone 1 1.7E-03**
Zone 2 Switchgear (>1000 V)
HEAF fault zone 2 2.8E-04**
Non-segregated Bus Ducts zones BDUAT & BDSAT 2.6E-03**
zones BD1, BD2 & LVBD 9.0E-04**
Iso-Phase Bus Ducts per bus duct end 5.0E-04
- To determine the per unit fire frequency the analyst should make an estimate of the affected fraction zone-wide and use this to apportion.
Zone of Influence for HEAFs Table A3.1 - Screening ZOIs for Load Center HEAFs Circuit Breaker Location and Target Fragility Back and Front Side (ft.)
Top (ft.)
End location, upper elevation: 15 MJ/m² (TP)
None 2.5 2
End location, upper elevation: 30 MJ/m² (TS)
None 1.5 1
End location, lower elevation: 15 MJ/m² (TP)
None 2.5 None End location, lower elevation: 30 MJ/m² (TS)
None 1.5 None Interior, upper elevation: 15 MJ/m² (TP)
Interior, upper elevation: 30 MJ/m² (TS)
Interior, lower elevation: 15 MJ/m² (TP)
None None None Interior, lower elevation: 30 MJ/m² (TS)
None None None Screening ZOIs for HEAFs Radial ZOI Switchgear 4.5 ft for TP (15 MJ/m2) Target 3.5 ft for TS (30 MJ/m2) Target Iso-Phase Bus Bar 5 ft
Non-Segregated Bus Duct HEAF ZOIs Table A3.2 - Screening ZOIs for Non-segregated Bus HEAFs (in ft.)
Bus Duct HEAF Fault Zone Steel Encl.
15 MJ/m² (TP) Target Steel Encl.
30 MJ/m² (TS) Target Aluminum Encl.
15 MJ/m² (TP) Target Aluminum Encl.
30 MJ/m² (TS) Target BDUAT 2.5 1.5 3.0 2.0 BDSAT 3.0 2.0 3.5 2.0 BD1-UAT*
4.5 3.0 5.0 3.0 BD1-SAT**
3.0 2.0 3.5 2.0 BD2 1.0 0.5 1.5 1.0 BDLV 1.0 0.5 1.5 1.0
- Normally powered by UAT
- Normally powered by SAT