ML18039A624

Fpra FAQ 17-0013 High Energy Arcing Fault (Heaf) Non-Suppression Probability (NSP) - Draft

ML18039A624
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Issue date:	01/18/2018
From:	Office of Nuclear Reactor Regulation
To:	Humphrey M, Meade B, Schairer M
Wu A
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ML18039A549	List: ML18039A624 ML18039A653 ML18039A661 ML18039A856 NUREG-2180, Data Collection in Support of Integrating Operating Experience Into NUREG-2180
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FAQ 17-0013
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FAQ Number 17-0013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Plant: Various Date:March 21January 18 , 20172018 Contact: Beth Meade Mark Schairer Mark Humphrey Phone:(508) 532-7139 (508) 532-7317 (508) 532-7269 Email:bah@epm-inc.com mvs@epm-inc.com msh@epm-inc.com Distribution: (NEI Internal Use)

FPRA TF BWROG PWROG Purpose of FAQ:

This FAQ provides an update to the non-suppression probability (NSP) for high energy arcing fault (HEAF) fires based on a review of additional fire event data.

Relevant NRC document(s):

NUREG/CR-6850 NUREG/CR-6850 Supplement 1 (FAQ 08-0050) NUREG 2169 Details: NRC document needing interpretation (include document number and title, section, paragraph, and line numbers as applicable):

See list of relevant NRC documents Circumstances requiring interpretation or new guidance:

The non-suppression probability for high energy arcing fault (HEAF) fires provided in NUREG/CR-6850 Supplement 1 (FAQ 08-0050) and NUREG 2169 are considered overly conservative based on durations that extended past the control point in the fire event. As a result, the risk associated with HEAFs in critical fire areas may be artificially high.

Detail contentious points if licensee and NRC have not reached consensus on the facts and circumstances:

FAQ Number 17-0013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Although recent guidance has sought to provide a better estimate of non-suppression probability, in the case of HEAF fire events, the probability of non-suppression is believed to be overly conservative.

Potentially relevant existing FAQ numbers:

FAQ 08-0050, "Manual Non-Suppression Probability" Response Section:

Proposed resolution of FAQ and the basis for the proposal:

1. Introduction The total duration for high energy arcing fault (HEAF) fires utilized in NUREG/CR-6850 Supplement 1 (FAQ 08-0050) to develop the lambda mean value for HEAFs is 276 minutes. Three events were used to develop this total, resulting in an average of 90 minutes per fire. In some casescases, the long suppression duration has had significant impact on the total risk of a fire area. NUREG-2169 expanded the number of reviewed events to eight (8) with a total duration of 602 minutes. The resulting change to the lambda mean was nominal, increasing from the 0.011 established in NUREG/CR-6850 Supplement 1, to 0.013. A further review to verify the suppression rate has been performed, to ensure the analyses of HEAF fires are not providing overly conservative results

, and that the results are providing appropriate risk insights for the scenarios.

The fire event times for the majority of the HEAF events in NUREG-2169 are one hour (60 minutes) or longer, with several exceeding two hours (120 minutes) in duration. The probability of non-suppression is based on the average time to suppression within a specific fire bin. The times reported and utilized in NUREG-2169 are considered excessive considering that many HEAF sources are located in accessible areas provided with automatic detection and the failures due to the HEAF often initiate a signal to the control room early in the event. Therefore , fire brigade response is expected to occur quickly after the initial HEAF. In addition, complete fire suppression is not required for an assessment of non-suppression probability

. as aArresting the fire spread and development propagation eliminates additional target damage and effectively suppresses controls the fire, but and may not necessarily correspond with a fire being extinguished.

This FAQ review expanded upon the data in NUREG-2169 by obtaining reviewing Licensee Event Reports (LERs) and related documentation (where available) for several of the extended duration fires in order to assess whether the fire was in fact under control earlier in the scenario than the event duration implies. During review of the LERs, it became apparent that there are several contributors that extend the reported fire duration beyond the time required to suppress and contain control the fire spread. First, it appears that there is a lag between when the fire is under control in the field and when it is reported to the control room as extinguished. It also FAQ Number 17-0013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP) appears that there is a potentially significant lag between when the fire is under control and when the fire is declared extinguished due to the need to de-energize the high energy equipment. Both factors result in over-estimation of the fire duration in some event reports and affected fire events included in NUREG/CR-6850 Supplement 1 and NUREG-2169. For purposes of Fire PRAs, the time to control is a more appropriate time, since this is when the fire is no longer considered a challenging event. The fire events reviewed are described below. The fire event number provided represents the number assigned in the EPRI Fire Events Database (Ref. 3)

. while the acronym represents an identification number based on plant and/or country of origin and date.

2. Revised Fire Event Times 2.1. Fire Event #947 (OC 19890103): This fire event was reported as having a 59 minute duration in NUREG-2169 and NUREG/CR-6850 Supplement 1 and a 46 minute duration in NUREG/CR-6850 (Ref. 2, 3, and 5). A review of the LER indicates that the fire event started at 1916 and the fire was "reported to be out" at 2015 (Ref. 11). However, further details indicate that the first attempt to extinguish the fire was at 1933 hours0.0224 days <br />0.537 hours <br />0.0032 weeks <br />7.355065e-4 months <br /> utilizing CO2 and dry chemical extinguishers, which were unsuccessful due to reflash (Ref. 11). Plant personnel determined that water fog was required to extinguish the fire without continued risk of reflash. At 2002 hours0.0232 days <br />0.556 hours <br />0.00331 weeks <br />7.61761e-4 months <br /> the bus was de-energized, for personnel safety, and water was applied (Ref. 11). Given this timeline, it is likely that the fire was under control between 1933 and 2002 hours0.0232 days <br />0.556 hours <br />0.00331 weeks <br />7.61761e-4 months <br />; however

, the fire was definitively under control at 2002 establishing a 46- minute event duration for the purposes of calculating PNS NSP (Ref. 11). This fire is an example of cautious firefighting resulting in a delay to fire suppression due to a fire in high energy equipment.

2.2. Fire Event #74 (WF 19950610): This fire event was reported as having a 136 minute duration in the FEDB and NUREG-2169 (as Fire Event #74); a 57 minute duration in NUREG/CR-6850 (reported as event number 2175); and a 76 minute duration in NUREG/CR-6850 Supplement 1 (as 2175) (Ref. 2, 3, 4 and 5). A review of the LER indicates that the event initiated at 0858, which varies only slightly from the FEDB which reports the event initiating at 0857 (Ref. 2 and 10). The fire brigade responded and attempted to extinguish the fire at 0935 via Halon, CO2, and dry chemical extinguishers (Ref. 10). The fire was reported extinguished at 1022, after the local fire department applied water to the insulation above the bus at 1018 (Ref. 10). Since the fire was under control at 1018, the appropriate fire duration for the PNSNSP calculation is 80 minutes. The extended fire duration time reported in the FEDB and NUREG-2169 coincides with the official declaration that the fire was extinguished (Ref. 10).

2.3. Fire Event #100 (DC 20000515): This fire event was reported as having a 78 minute duration in NUREG-2169 and the FEDB (Ref. 2 and 4). The event was not included in NUREG/CR-6850 or NUREG/CR-6850 Supplement 1 (Ref. 3 and 5). The event was reported to begin at 0025 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> on May 15, 2000. The fire was declared out at 0143 hours0.00166 days <br />0.0397 hours <br />2.364418e-4 weeks <br />5.44115e-5 months <br />, providing the 78 minute duration. However, additional details provided in the Preliminary Notification of Event or Unusual Occurrence (Ref. 7) as reported by the Region IV staff, FAQ Number 17-0013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP) indicates that the fire was extinguished "using carbon dioxide, by 1 a.m." Although PNO is not the official documentation of the fire event, such as the LER, the additional information agrees with the LER (Ref. 6) which states:

When the fire brigade entered the room, they quickly extinguished the fire with a CO2 extinguisher, before offsite assistance arrived. After clearing smoke from the room, the fire was declared out at 0143 PDT.

This suggests that a significant time lag may have occurred between extinguishing what is referred to as the "small fire" and the official declaration. A 35 minute fire duration is considered reasonable based on the available data and is a refinement on the original, conservative duration provided in the FEDB and utilized in NUREG-2169.

2.4. Fire Event #106 (SG 20010203): This fire event was reported as having a 154 minute duration in NUREG-2169 and a 156 minute duration in the FEDB (Ref. 2 and 4). The event is also cited as 141 minutes in NUREG/CR-6850 Supplement 1, which is a revision from the NUREG/CR-6850 duration of 136 minutes (Ref. 3 and 5). There is no explanation provided in NUREG-2169 or NUREG/CR-6850 Supplement 1 for the discrepancy between the documents. The LER for this event details that the event began around 1514 1513 (1514 was reported in the FEDB and is used here) and that fire responders reported the fire extinguished at 1544; it was later determined that the fire was not extinguished at that time, but flames were no longer visible (Ref. 8). The delay is attributed to extinguishing due to high energy and resistance to using water; however

, the fire was under control and limited to the cubicle at the time of the report (Ref. 8). Therefore, an event duration of 31 minutes is appropriate for use in the PNSNSP curve, as this reflects the time required for the fire to be suppressed and controlled.

2.5. Fire Event #127 (VY 20040618): This fire event was reported as having a 71 minute duration in NUREG 2169 and the FEDB (Ref. 2 and 4). The event was not included in NUREG/CR-6850 or NUREG/CR-6850 Supplement 1 (Ref. 3 and 5). The FEDB reports that the fire was under control by 0717; however

, the FEDB utilizes the time to extinguishment of 0751 to calculate the fire duration (Ref.

3). The LER for this event establishes that the event occurred at 0640 and that the fire brigade declared the fire under control at 0717, resulting in a 37 minute duration (Ref. 9). Therefore, an event duration of 37 minutes is appropriate for use in the NSP curve, as this reflects the time required for the fire to be controlled. The FEDB also reports that the fire was under control by 0717 but that the fire was not extinguished until 0751; use of the time to extinguishment resulted in the 71 minute duration (Ref. 3).

3. Additional Fire Events This FAQ review also identified two fire events that were originally binned as electrical fires for the calculations of non-suppression probability in NUREG-2169 but which are bin 16.1 and 16.2 HEAF fires for fire ignition frequency (Ref. 2). The fire events in this category are #922 and #792 with a fire duration of 5 minutes and 3 minutes respectively. The LER for fire event FAQ Number 17-0013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

1. 922 was reviewed and it was determined that several of the characteristic challenges that have been shown to inhibit fire suppression in HEAF events, specifically the need to de-energize the high energy equipment and suppress secondary fires, were present in this scenario (Ref. 12). The fire originated in a bus bar connecting the Main Auxiliary Transformers from 6160 volt busses due to a phase to ground (Ref. 12). In order to suppress the fire, the Main Auxiliary Transformer was de-energized and plant personnel manually suppressed a secondary fire caused by slag emitted from the bus (Ref. 12). Based on the characteristics of this fire, although it occurred outside of an electrical panel, the fire is considered to represent the same challenges as a typical HEAF scenario and inclusion in the HEAF non-suppression probability calculations is considered appropriate.

Fire event #792 occurred in the "A" isolated-phase bus duct due to damaged ground straps and a deteriorated gasket (Ref. 13). Although the fire does not represent similar combustibles to that of a typical electrical cabinet, the challenges related to the fire are similar to that of a typical HEAF; specifically

, that the bus ducts were required to be de-energized prior to suppression (Ref. 13). Therefore, inclusion of this fire event in the calculations for the HEAF non-suppression probability of a HEAF fire is considered more appropriate than inclusion in the electrical fire bin.

In addition, the most recent revision to the EPRI FEDB includes an additional published event that was not available for review at the time of NUREG-2169. Fire Event #162 occurred on August 5, 2009 and is reported to have a 46 minute fire duration (Ref. 4). The event was detected at 0751 hours0.00869 days <br />0.209 hours <br />0.00124 weeks <br />2.857555e-4 months <br /> when the conductor in one of the supply busses catastrophically failed, melting all three phases of the conductor (Ref. 14). The fire was declared out at 0811 hours0.00939 days <br />0.225 hours <br />0.00134 weeks <br />3.085855e-4 months <br /> (Ref. 14).

These three fire events, as well as the refined event durations above have been included in the updated calculations of HEAF non-suppression probability.

The re-binning of Fire Events #792 and #922 as HEAF fires versus electrical fires for the non-suppression probability necessarily results in a revision to the electrical fire non-suppression probability. The changes are reflected in the proposed revisions to NUREG-2169 included as part of this FAQ.

4. Comparison with International Events The scope of the previous non-suppression probability analyses has been limited to events occurring in the United States. However, the Organisation for Economic Co-operation and Development (OECD) has recently released Fire Project Topical Report No. 1 "Analysis of High Energy Arching Fault (HEF) Fire Events" (Ref. 1). This report identified 48 HEAF events that had been reported to the OECD from Canada, Czech Republic, Finland, France, Germany, Japan, Korea, Spain, Sweden and the United States. The database includes 11 events in the United States, although this included non bin 16 HEAFs (e.g., cable HEAFs and HEAFs occurring in the Yard transformers). The OECD report included 18 bin 16 HEAF events occurring outside of the United States. The average duration for these fires was 31.3 minutes; FAQ Number 17-0013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP) while the average time for the US only events reviewed as part of this FAQ is 35 minutes. The average time for all events, both US and international, is 32.7 minutes. The use of an average time of 35 minutes for US HEAF events is

, therefore

, considered conservative and in agreement with the trend of HEAF fire event durations internationally.

5. Summary/Conclusion Based on the documentation review and considering the expanded data set, the mean suppression rates proposed in NUREG/CR-6850 Supplement 1 and NUREG 2169 are overly conservative. It is proposed that the mean suppression rate should be increased by approximately a factor of two (from 0.011/0.013 to 0.029) to reflect the revised average fire duration for HEAFs originating in high energy equipment in the US.

A chi squared distribution was applied, consistent with NUREG-2169, to calculate the percentiles based on the number of events and total durations presented in table 5-1.

Attachment 1 and Attachment 2 to this FAQ are provided to summarize the fire event data review and the resulting average durations and non-suppression probability that would result from expanding the data set. The unique identifier in Attachment 2 represents an identification number based on plant and/or country of origin and date.

If appropriate, provide proposed rewording of guidance for inclusion in the next Revision:

The following are proposed revisions to NUREG 2169:

FAQ Number 17-0013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Table 5-1 Probability distribution for rate of fires suppressed per unit time, (Originally, Table P-2 from NUREG/CR-6850)

Suppression Curve Number of Events in Curve Total Duration (minutes) Rate of Fire Suppressed () Mean 5th Percent 50th Percent 95th Percent T/G fires 30 1167 0.0260.019 0.025 0.034 Control room 12 37 0.3240.187 0.315 0.492 PWR containment (AP) 3 40 0.0750.020 0.067 0.157 Containment (LPSD) 31 299 0.1040.075 0.103 0.136 Outdoor transformers 24 928 0.0260.018 0.026 0.035 Flammable gas 8 234 0.0340.017 0.033 0.056 Oil fires 50 562 0.0890.069 0.088 0.111 Cable fires 4 29 0.1380.047 0.127 0.267 Electrical fires 175 1807 0.0970.085 0.097 0.109 Welding fires 52 484 0.1070.084 0.107 0.133 Transient fires 43 386 0.1110.085 0.111 0.141 HEAFs 11 385 0.029 0.016 0.029 0.044 All fires 443 6358 0.070 0.064 0.070 0.075 FAQ Number 17-00020013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Table 5-2 Updated numerical results for suppression curves (Originally, Table 14-1 from NUREG/CR-6850, Supplement 1)

Time (min) T/G fires HEAFs Outdoor Transformers Flammable Gas Oil fires Electrical fires Transient fires PWR containment (AP) Containment (LPSD) Welding Control Room Cable Fires All Fires 0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 5 0.879 0.867 0.879 0.843 0.641 0.616 0.572 0.687 0.595 0.584 0.198 0.502 0.705 10 0.773 0.751 0.772 0.710 0.411 0.380 0.328 0.472 0.355 0.341 0.039 0.252 0.497 15 0.680 0.651 0.678 0.599 0.263 0.234 0.188 0.325 0.211 0.200 0.008 0.126 0.350 20 0.598 0.565 0.596 0.505 0.169 0.144 0.108 0.223 0.126 0.117 0.002 0.063 0.247 25 0.526 0.490 0.524 0.425 0.108 0.089 0.062 0.153 0.075 0.068

• 0.032 0.174 30 0.462 0.424 0.460 0.359 0.069 0.055 0.035 0.105 0.045 0.040

• 0.016 0.123 35 0.407 0.368 0.404 0.302 0.044 0.034 0.020 0.072 0.027 0.023

• 0.008 0.087 40 0.358 0.319 0.355 0.255 0.028 0.021 0.012 0.050 0.016 0.014

• 0.004 0.061 45 0.314 0.276 0.312 0.215 0.018 0.013 0.007 0.034 0.009 0.008

• 0.002 0.043 50 0.277 0.240 0.274 0.181 0.012 0.008 0.004 0.024 0.006 0.005

• 0.001 0.030 55 0.243 0.208 0.241 0.153 0.007 0.005 0.003 0.016 0.003 0.003 *

• 0.021 60 0.214 0.180 0.212 0.129 0.005 0.003 0.002 0.011 0.002 0.002 *

• 0.015 65 0.188 0.156 0.186 0.108 0.003 0.002

• 0.008 0.001 0.001 *

• 0.011 70 0.165 0.135 0.164 0.091 0.002 0.001

• 0.005 * * *

• 0.007 75 0.145 0.117 0.144 0.077 0.001 0.001

• 0.004 * * *

• 0.005 80 0.128 0.102 0.126 0.065 * *

• 0.002 * * *

• 0.004 85 0.112 0.088 0.111 0.055 * *

• 0.002 * * *

• 0.003 90 0.099 0.076 0.098 0.046 * *

• 0.001 * * *

• 0.002 95 0.087 0.066 0.086 0.039 * * * * * * *

• 0.001 100 0.076 0.057 0.075 0.033 * * * * * * *

• 0.001 5-5 FAQ Number 17-00020013 FAQ Revision 0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Figure 5-2 Non-suppression curve plots: probability vs. time to suppression Formatted: Top: 0.01" FAQ Number 17-00020013 FAQ Revision 0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

References

1. NEA/CSNI/R(2013)6, Nuclear Energy Agency OECD Fire Project - Topical Report No. 1, "Analysis of High Energy Arcing Fault (HEAF) Fire Events," June 25, 2013

2. NUREG 2169, "Nuclear Power Plant Fire Ignition Frequency and Non-Suppression Probability Estimation Using the Updated Fire Events Database," December 2014

3. NUREG/CR-6850 Supplement 1, "Fire Probabilistic Risk Assessment Methods Enhancements," September 2010

4. EPRI 1025284, "The Updated Fire Events Database: Description of Content and Fire Event Classification Guidance," July 2013

5. NUREG/CR-6850, "Fire PRA Methodology for Nuclear Power Facilities," September 2005 6. PG&E Letter DCL-00-115, Licensee Event Report 1-2000-004-01, "Unit 1 Unusual Event Due to a 12kV Bus Fault," August 30 2000

7. Preliminary Notification of Event or Unusual Occurrence, PNO-IV-00-011, "Unusual Event Because of a Fire Lasting Greater than 15 Minutes," May 15, 2000

8. Southern California Edison Docket No. 50-362, Licensee Event Report 2001-001, "Fire and RPS/ESF Actuations Caused by the Failure of a Non-Safety Related 4.16kV Circuit Breaker" April 2, 2001

9. Entergy Licensee Event Report 2004-003-01, "Vermont Yankee Nuclear Power Station License No. DPR-28 (Docket No. 50-271) Reportable Occurrence No. LER 2004-003-01," June 14, 2005

10. Waterford Licensee Event Report 95-002-01, Accession # 9801160136, "Reactor Trip and Non-Safety Related Switchgear Fire," January 13, 1998

11. Oconee Nuclear Station Unit 1 Licensee Event Report, "Fire in ITA Switchgear Due to Unknown Cause," February 2, 1989

12. Kewaunee Nuclear Power Plant Licensee Event Report 87-009-00, "Electrical Bus Bar Failure Causes Undervoltage on RXCP Buses and Reactor Trip," August 10, 1987

13. EPRI 1003111, "Fire Events Database and Generic Ignition Frequency Model for U.S. Nuclear Power Plants," November 2001

14. US Nuclear Regulatory Commission Region IV Report 05000397/2009010, "Columbia Generating Station - NRC Special Inspection Report," November 23, 2009

FAQ Number 17-00020013 FAQ Revision 0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Attachment 1: Data Summary Table

FAQ Number 17-00020013 FAQ Revision 0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

BIN 16 HEAF Analysis # Events Total Duration AVG time/event Mean Suppression Rate (/min) NUREG/CR-6850 3 239 79.67 0.013 NUREG/CR-6850 Supplement 1 3 276 92.00 0.011 NUREG 2169 8 602 75.25 0.013 International and US Fire Events 29 948 32.69 0.031 International Events Only 18 563 31.28 0.032 FAQ 17-0002 0013 Proposed Values - US Events Only 11 385 35.00 0.029

FAQ Number 17-00020013 FAQ Revision 0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Attachment 2: Fire Event Data Summary

FAQ Number 17-00020013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Unique Identifier BIN *Reference FEDB # Include/Exclude Reason for Include/ Exclude Outlier (Y/N)/ Basis Country Plant Date Event Title Component Voltage Level Location Fuel Damage Limited to Initial Component Extinguished by (all means involved) Time Data Duration [h:min] GER 20040823 12 1 None Exclude - BIN 12 Cable HEAF Yes - No suppression time available Germany GER009 20040823 Failure in the auxiliary power supply with consequential reactor scram high voltage cable 10 kV outside the plant, Not switchyard, other cable roomcable insulation materials No self- extinguished Unknown 0:00 USA 20100328 12 1 None Exclude - BIN 12 Cable HEAF N/A USA USA027 20100328 Plant trip due to electrical fault cable run (self-ignited): power cables 4 kV turbine building cable insulation material No on-site plant fire brigade; people available in the fire area Unknown 0:15 GER 19790811 16.b 1 None Exclude No suppression time is available N/A Germany GER027 19790811 High energy electric arc at circuit breaker and isolator circuit breaker (sub- distribution board) Unknown auxiliary building, room for ventilation cable insulation materials Yes self- extinguished Unknown Unknown USA 19840802 16.a 1, 2 434 Exclude Event time undetermined N/A USA Unknown 19840802 Electrical cabinets with HEAF Electrical cabinet Unknown Unknown UnknownUnknown Unknown Unknown Unknown JPN 19850831 16.b 1 None Include Bin 16 N/A Japan JPN044 19850831 Fire at the cabinet containing 6.9 kV bus for start-up high or medium voltage electrical cabinet 6.9 kV turbine building, switchgear roomcable insulation materials Yes fixed extinguishing system, manually actuated; external fire brigade participated Unknown 2:14 GER 19860530 16.a 1 None Include Bin 16 N/A Germany GER011 19860530 Damage of the 380 V busbar CR (auxiliary power supply of train 4) by a fire bus bar 380 V electrical building, cable spreading room cable insulation materials; other insulations No on-site plant fire brigade Unknown 0:25 KW 19870710 16.1 2, 4 922 Include Bin 16 N/A USA Kewaunee 19870710 Bus-duct Bus duct Unknown Unknown UnknownUnknown Unknown Unknown 0:03 GER 19870909 16.b 1 None Include Bin 16 N/A Germany GER022 19870909 Short circuit in the exciter system of an emergency diesel generator unithigh or medium voltage electrical cabinet (emergency diesel) Unknown electrical building, switchgear roomcable insulation materials Yes on-site plant fire brigade Unknown 0:09 GER 19880419 16.b 1 None Include Bin 16 N/A Germany GER024 19880419 Short circuit in the 220 kV/380 kV switchgear with consequential loss of offsite power high voltage switchgear220 kV switchyard hardly inflammable liquid Yes on-site plant fire brigade Unknown 0:46 USA 19880715 16.2 2, 4 792 Include Bin 16 N/A USA Unknown 19880715 Iso-phase bus ducts Iso-phase bus ducts Unknown Unknown UnknownUnknown Unknown Unknown 0:05 OC 19890103 16.b 2, 4 947 Include Bin 16 N/A USA Oconee 19890103 During power escalation after startup following a trip a Fire occurred in the Unit 1 6900 V switchgear 6.9 KV Switchgear 6.9kV Switchgear RoomUnknownUnknown fire brigade (water, CO2, dry chemical) 1916-2002 0:46 GER 19890517 16.a 1 None Include Bin 16 N/A Germany GER025 19890517 Electric arc at a feeder control panel in the 380 V switchgear switchgear (380 V switchgear, injection area) 380 V electrical building, switchgear roomcable insulation materials Yes people available in the fire area Unknown 0:12 FAQ Number 17-00020013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Unique Identifier BIN *Reference FEDB # Include/Exclude Reason for Include/ Exclude Outlier (Y/N)/ Basis Country Plant Date Event Title Component Voltage Level Location Fuel Damage Limited to Initial Component Extinguished by (all means involved) Time Data Duration [h:min] GER 19890908 16.b 1 None Include Bin 16 N/A Germany GER001 19890908 Short circuit in the auxiliary electrical system high voltage switchgear (10 kV injection cell); circuit breaker 10 kV electrical building, switchgear roomcable insulation materials; plastics / polymeric materials No (multiple components) on-site plant fire brigade Unknown 0:26 USA 19900713 16.b 2, 4 18 Include Bin 16 N/A USA Unknown 19900713 HEAF for medium voltage electrical cabinet (>1000V) Electrical cabinet >1kV Unknown UnknownUnknown Unknown Unknown 0:10 FRA 19901030 16.b 1 None Include Bin 16 N/A France FRA042 19901030 Loss of a 6.6 kV emergency switchboard. high or medium voltage electrical cabinet 6.6 kV electrical building, switchgear roomcable insulation materials Yes shift personnel Unknown 0:07 FIN 19910412 16.b 1 None Include Bin 16 N/A Finland FIN001 19910412 Fire at 6.6 kV switchgear electrical cabinet, high or medium voltage (current transformer inside cabinet) 6.6 kV electrical building, switchgear roomcable insulation materials, other insulationsNo (multiple components) on-site plant fire brigade Unknown 0:37 USA 19911014 16.b 2, 4 20284 Include Bin 16 N/A USA Unknown 19911014 HEAF - other electrical or electronic equip Unknown Unknown Unknown in-situ Yes Unknown Unknown 0:02 WF 19950610 16.b 2, 3, 4 74 Include Bin 16 N/A USA Waterford 19950610 Fault on lightning arrestor in the switchyard, reactor trip, and then fire in a 4.16kV Non-safety related bus. Damage limited "mainly" to breaker and adjoining cabinet fault in 230kV/34.5kV transformer, fire in 4.16kV Switchgear 230kV/34.5k V transformer (4.16kV) TG Building UnknownNo brigade (halon, CO2 and dry chem extinguishers), fire department (water) 0858-1018 1:20 GER 19960208 16.b 1 None Include Bin 16 N/A Germany GER017 19960208 Disconnection of a main bus due to a short circuit in a switching module electrical cabinet (busbar, breaker subassembly) 500 V auxiliary building, switchgear roomcable insulation materials Yes on-site plant fire brigade Unknown 0:17 JPN 19960907 16.1 1 None Include Bin 16 N/A Japan JPN029 19960907 Fire of the bus-duct in the power supply room for the emergency diesel generator bus duct 460 V reactor building, EDG switchgear room cable insulation materials No shift personnel; external fire brigade participated Unknown 0:42 DC 20000515 16.1 1, 2, 4 100 Include Bin 16 N/A USA Diablo Canyon 20000515 Unit 1 unusual event due to a 12 kV bus fault and fire 12kV bus, busbar/ bus duct 12kV 12kV Switchgear room, auxiliary building other solid material; plastics, solid material; plastics/ polymeric materials No fire brigade extinguished the small fire with C02 0025-0100 0:35 FRA 20010119 16.b 1 None Include Bin 16 N/A France FRA008 20010119 Incipient fire on ultimate emergency diesel generator high or medium voltage electrical cabinet 6.6 kV diesel generator building, electrical / process room other insulations, plastics / polymeric materials No (multiple components) self- extinguished Unknown 0:05 FAQ Number 17-00020013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Unique Identifier BIN *Reference FEDB # Include/Exclude Reason for Include/ Exclude Outlier (Y/N)/ Basis Country Plant Date Event Title Component Voltage Level Location Fuel Damage Limited to Initial Component Extinguished by (all means involved) Time Data Duration [h:min] SG 20010203 16.b 1, 4 437 Exclude Duplicate This event occurs on the same day and at the same time as FEDB event 106. FEDB event 437 was not included in NUREG 2169. USA SONGS 20010203 Fire and RPS/ESF actuations caused by the failure of a Non-safety related 4.16 kV circuit breaker 4.16kV bus 3A07 4.16kV turbine switchgear room cable insulation, solid materials No second breaker in same bus failed & arced due to smoke fire brigade 1514-1544 0:31 SG 20010203 16.b 2, 3, 4 106 Include Bin 16 There are two entries in the FEDB for the same day and time (106 and 437). .NUREG 2169 cites only event 106 SG SONGS 20010203 The event was caused when breaker x faulted which caused arcing, localized overheating and started a fire within the breaker cubicle. HEAF medium voltage electrical cabinet (>1kV) 4kV Auxiliary buildingcircuit breaker No on-site plant fire brigade, external fire brigade participated 1514-1544 0:31 Pr Isl 20010803 16.b 2, 4 112 Include Bin 16 N/A USA Prairie Island 20010803 During startup, operators transferring power, closed breaker and breaker failed initiating a fire in bus cubicle. It was a "c-phase to ground arcing event, which quickly involved all phases. The arcing led to actuation of the protective relaying, which resulted in a turbine/reactor trip" 4 kV Bus 4 kV Bus 12 fire brigade Unknown 1:30 FRA 20010918 16.b 1 None Include Bin 16 N/A France FRA022 20010918 Loss of 400 kV power supply following a fire in the 6.6 kV AC Normal distribution system cubicle high or medium voltage electrical cabinet 6.6 kV electrical building, switchgear roomhardly inflammable liquid, plastics / polymeric materials No (multiple components) shift personnel; external fire brigade participated Unknown 1:11 GER 20020811 16.b 1 None Include Bin 16 N/A Germany GER017 20020811 Fire in the 500 V switchgear of one train of the independent emergency system switchgear 500 V independent emergency building, switchgear roomcable insulation materials No on-site plant fire brigade Unknown 1:25 GER 20021030 16.b 1 None Include Bin 16 N/A Germany GER009 20021030 HEAF with consequential fire occurred by exchange of a 0.4 kV switchgear subassembly switchgear 400 V electrical building, room for electrical control equipment cable insulation materials No self- extinguished Unknown < 00:03 VY 20040618 16.2 1, 2, 4 127 Include Bin 16 N/A USA Vermont Yankee 20040618 Iso-phase bus duct two- phase electrical fault and fire with secondary fires 22kV iso-phase bus 22kV turbine building and yard (main xfmr) flammable liquid, hydrogen; other solid material No auto suppression, fire brigade extinguished using hose stream and nearby hydrant 0640-0717 0:37 FAQ Number 17-00020013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Unique Identifier BIN *Reference FEDB # Include/Exclude Reason for Include/ Exclude Outlier (Y/N)/ Basis Country Plant Date Event Title Component Voltage Level Location Fuel Damage Limited to Initial Component Extinguished by (all means involved) Time Data Duration [h:min] CAN 20051015 16.a 1 None Include Bin 16 N/A Canada CAN004 20051015 Electrical arc resulting in injury low voltage electrical cabinet 600 V electrical building, switchgear roomcable insulation materials Yes on-site plant fire brigade Unknown < 00:05 GER 20080314 16.b 1 None Include Bin 16 N/A Germany GER003 20080314 Fire in a circuit breaker and switch-of f of the emergency busbar FB high voltage circuit breaker 660 V electrical building, switchgear roomplastics / polymeric materials Yes on-site plant fire brigade Unknown 0:34 USA 20080727 16.1 2, 4 10584 Exclude No suppression time is available Indeterminate Supp Time USA Unknown 20080727 HEAF for segmented bus duct HEAF for segmented bus duct Unknown Unknown UnknownUnknown Unknown Unknown Unknown CO 20090805 16.b 2, 4 162 Include Bin 16 event duration Not well established USA Columbia 20090805 Cable tray HEAF? Non-safety related 6.9kV feed bus 7KV Turbine BuildingInsulationconfined to floor of originself-extinguished 0750-0811 0:46 CZE 20100217 16.a 1 None Include Bin 16 N/A Czech Republic CZE003 20100217 Fire at 0.4 kV switchgear switchgear 0.4 kV electrical building, switchgear roomcable insulation materials Yes on-site plant fire brigade Unknown 0:05 JPN 20110311 16.b 1 None Consider Excluding Seismic event initiates the HEAF and may explain the significant duration time compared to other events Yes - duration is significantly greater than all other reported events Japan JPN022 20110311 Seismic induced arcing fault in Non-emergency metal clad (M/C) switchgear cabinet high or medium voltage electrical cabinet 6.9 kV turbine building, switchgear roomcable insulation materials No on-site fire brigade Unknown 7:58 USA 20050825 21 2, 4 135 Exclude A condensate pump is the initiating component N/A USA Unknown 20050825 Electrical Failure (overheating, spark, HEAF) Contained to the object of origin electric motor driven pumps 7KV Turbine Buildingin-situ Yes fire brigade 1125-1317 SWD 20060915 21 1 None Exclude Pump N/A Sweden SWD007 20060915 Fire in a 6 kV electrical cabinet in room D2.21, cabinet feed power to the pump 725 P1. A breaker in the cabinet is burningelectrically driven pump6 kV turbine building, process room other solid material No on-site plant fire brigade Unknown 1:05 USA 20061212 21 1, 4 1 Exclude The circ water pump is the initiating component, N/A USA USA066 20061212 Automatic reactor trip due to circulating water pump surge capacitor failure electrically driven pump12 kV intake building, process room capacitor, insulation material Yes on-site plant fire brigade 0025-0100 0:34 USA 20070925 21 4 10472 Exclude The fault originated in a circ water pump N/A USA Unknown 20070925 HEAF - other electrical or electronic equip Unknown Unknown Unknown in-situ Yes Unknown Unknown Unknown SWD 20061114 23 1 None Exclude A transformer is the originating component N/A Sweden SWD010 20061114 Fire in transformer supplying the 6 kV on-site electrical systems train A and C from the generator 20 kV busbar c medium or low voltage transformer - oil filled 6 kV / 20 kVoutside plant buildings hardly inflammable liquid No on-site plant fire brigade; external fire brigade participated Unknown 2:40:00 FAQ Number 17-00020013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Unique Identifier BIN *Reference FEDB # Include/Exclude Reason for Include/ Exclude Outlier (Y/N)/ Basis Country Plant Date Event Title Component Voltage Level Location Fuel Damage Limited to Initial Component Extinguished by (all means involved) Time Data Duration [h:min] GER 20070628 23 1 None Exclude The main transformer is the initiating component N/A Germany GER014 20070628 Reactor trip caused by a temporary loss of station service supply due to a short circuit with a subsequent fire in a generator transformer high voltage transformer (main transformer) 400 kV other building / area, other type o f room flammable liquid, paper, woodYes fixed extinguishing system, automatically actuated; on-site plant fire brigade; external fire brigade participated Unknown 6:58 SPN 19880622 27 1 None Exclude The main transformer is the initiating component N/A Spain SPN001 19880622 Trip of main transformer, followed by fire in phase "S" due to manufacturing defect. Subsequently, turbine trip and, with permissive P- 7, reactor trip high voltage transformer (main transformer) 20 kV /400 kV outside plant buildings (Not switchyard) hardly inflammable liquid Yes fixed extinguishing system, actuated; on- site plant fire brigade; shift personnel Unknown 0:58 SPN 19880820 27 1 None Exclude The main transformer is the initiating component N/A Spain SPN001 19880820 Trip of main transformer, followed by fire in phase "S" due to manufacturing defect. Subsequently, turbine trip and, with permissive P- 7, reactor trip high voltage transformer (main transformer) 20 kV / 400kV outside plant buildings (Not switchyard) hardly inflammable liquid Yes fixed extinguishing system, actuated; on- site plant fire brigade; shift personnel Unknown 0:15 SPN 19881202 27 1 None Exclude The main transformer is the initiating component N/A Spain SPN001 19881202 Main transformer tripped, followed by fire in phase "R" high voltage transformer (main transformer) 20 kV /400 kV outside plant buildings (Not switchyard) hardly inflammable liquid Yes fixed extinguishing system, actuated; on- site plant fire brigade; shift personnel Unknown Unknown CZE 19940203 27 1 None exclude A transformer is the originating component N/A Czech Republic CZE003 19940203 Fire of the station service load transformer 3BT02 caused by a defect on the power part of the branch lines switch followed by an explosion medium and low voltage transformer - oil filled 15.75 kV/ 6 kV outside the plant, Not switchyard, voltage transformers near to main transformer flammable liquid No on-site plant fire brigade Unknown 0:16 USA 20000524 27 2, 4 50701 Exclude Binned as "Transformer Yard" in NUREG 2169 N/A USA Unknown 20000524 HEAF - other electrical or electronic equipment XFMR Unknown Yard in-situ Yes automatic suppression Unknown Unknown KOR 20010130 27 1 None Exclude The main transformer is the initiating component N/A Korea KOR010 20010130 High energy arcing fault on phase 'B' of the main transformer which led to the reactor trip high voltage transformer (main transformer) 22/345kV outside plant buildings insulation material Yes self- extinguished Unknown 0:00 KOR 20020422 27 1 None Exclude The main transformer is the initiating component N/A Korea KOR001 20020422 Fire on the main transformer leading to a generator trip high voltage transformer(main transformer) > 50 kV outside flammable liquid Yes fixed extinguishing system, automatically actuated, Unknown 0:13 FAQ Number 17-00020013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Unique Identifier BIN *Reference FEDB # Include/Exclude Reason for Include/ Exclude Outlier (Y/N)/ Basis Country Plant Date Event Title Component Voltage Level Location Fuel Damage Limited to Initial Component Extinguished by (all means involved) Time Data Duration [h:min] FRA 20040929 27 1 None Exclude The main transformer is the initiating component N/A France FRA035 20040929 Electric fault on the main transformer leading to a reactor trip high voltage transformer (main transformer) > 50 kV other building cable insulation materials Yes shift personnel Unknown 0:20 USA 20080816 27 4 127 Exclude The main transformer is the initiating component N/A USA Unknown 20080816 Transformer oil - HEAF confined to object of origin Main bank transformer13kV or greater Main Transformer or Switch Yard XFMR oilYes Unknown 2357-0202 2:05 USA 20090201 27 4 157 Exclude The main transformer is the initiating component N/A USA Unknown 20090201 Transformer oil - HEAF confined to object of origin Main transformer 13kV or greater Main Transformer or Switch Yard XFMR oilYes Unknown 2156-2227 0:31 FRA 20100725 27 1 N/A Exclude The main transformer is the initiating component N/A France FRA012 20100725 Automatic shutdown of the reactor following an explosion and a consequential fire on the main power transformer high voltage transformer (main transformer) 225 kV switchyard (transformer room / bunker) hardly inflammable liquid, cable No fixed extinguishing system, automatically actuated; on- site plant fire brigade; external fire brigade participated Unknown 2:45 USA 20021003 28 1, 2, 4 116 Exclude A transformer is the originating component N/A USA USA095 20021003 Failure of start-up transformer ST 20 high voltage transformer> 50 kV transformer yardhardly inflammable liquid Yes fixed extinguishing system 1513-1738 < 00:10 USA 20051029 28 1, 2, 4 137 Exclude A yard transformer is the originating component N/A USA USA064 20051029 Reactor trip due to main transformer fault and fire high voltage transformer> 50 kV outside the plant building (Not switchyard), main transformer hardly inflammable liquid Yes fixed extinguishing system; on-site plant fire brigade Unknown 0:28 USA 20070406 28 1, 2, 4 148 Exclude A yard transformer is the originating component N/A USA USA043 20070406 Automatic reactor trip due to a turbine generator trip caused by a fault on the 31 main transformer phase B high voltage bushing high voltage transformer34.5 kV transformer yardhardly inflammable liquid Yes on-site plant fire brigade Unknown 0:12 USA 19991009 29 1, 2, 4 7 Exclude A yard transformer is the originating component N/A USA USA039 19991009 Under voltage actuation due to a loss of reserve station service transformer busbar 4.16 kV outside turbine building cable connector / insulation materials Yes on-site plant fire brigade Unknown 0:09 FRA 20030830 29 1 None Exclude A transformer is the originating component N/A France FRA024 20030830 Explosion of an oil-filled current transformer leading to a fire in the 400 kV platform high voltage transformer (current transformer) 6.6 kV / 400 kV switchyard hardly inflammable liquid No fixed extinguishing system, manually actuated; shift personnel; external fire brigade participated Unknown 0:48 CAN 20050415 29 1 None Exclude A transformer is the originating component N/A Canada CAN002 20050415 Unit 6 forced outage due to M.O.T. failurehigh voltage transformer500 kV switchyard, switchgear roomflammable liquid (transformer insulating oil) Yes fixed extinguishing system, automatically actuated Unknown < 00:08 FAQ Number 17-00020013 FAQ Revision0 (Draft BC) FAQ Title High Energy Arcing Fault (HEAF) Non-Suppression Probability (NSP)

Unique Identifier BIN *Reference FEDB # Include/Exclude Reason for Include/ Exclude Outlier (Y/N)/ Basis Country Plant Date Event Title Component Voltage Level Location Fuel Damage Limited to Initial Component Extinguished by (all means involved) Time Data Duration [h:min] FIN 20060927 29 1 None Exclude A transformer is the originating component N/A Finland FIN002 20060927 Voltage transformer fire due to human error during maintenance outage medium or low voltage transformer - oil filled 15.1 kV outside the plant (Not switch yard), voltage transformers near to main transformer hardly inflammable liquid,; other insulationsNo (multiple components) on-site plant fire brigade (one fire); self- extinguished (another fire) Unknown 0:05 JPN 20070716 29 1 None Exclude A transformer is the originating component N/A Japan JPN047 20070716 House transformer fire induced by the Niigata- Chuetsu-Oki earthquake medium or low voltage transformer - oil filled 19 kV /6.9 kV outside flammable liquid Yes fixed extinguishing system, manually actuated; external fire brigade participated Unknown 1:55 SWD 20021030 33 1 None Exclude The rectifier is part of the exciter for the turbine. N/A Sweden SWD007 20021030 Auto fire alarm about an arc event in a rectifier. The failure led to stop of one turbine. rectifier 600 V turbine building, process room other solid material; plastics / polymeric materials No (multiple components) on-site plant fire brigade; external fire brigade participated Unknown 2:31 USA 20011026 9999 4 10624 Exclude Fire originated in the primary power distribution pole that feeds the HEEC transformer. N/A USA Unknown 20011026 HEAF - other electrical or electronic equip Unknown Unknown Unknown in-situ No Unknown Unknown Unknown USA 20080917 9999 4 50566 Exclude basket contacts power line causing explosion N/A USA Unknown 20080917 HEAF - other electrical or electronic equip Unknown 13kV or greater Unknown in-situ Yes self-extinguished 0930-unknown <0:05 SWD 20110510 9999 1 None Exclude Vacuum Cleaner N/A Sweden SWD008 20110510 Fire in the reactor containment: Arc in an electrical part in the portable vacuum cleaner vacuum cleaner Unknown containment plastics / polymeric materials No self - extinguished Unknown Unknown USA 20020612 SB4 1, 2, 4 113 Exclude "Special bin, Not FPRA applicable" per NUREG 2169 Yes, special Bin USA USA059 20020612 Switchyard fire in 34.5 kV circuit breaker high voltage breaker 34.5 kV switchyard flammable liquid Yes on-site plant fire brigade Unknown Unknown *Reference 1: NEA/CSNI/R(2013)6, Nuclear Energy Agency OECD Fire Project - Topical Report No. 1, "Analysis of High Energy Arcing Fault (HEAF) Fire Events," June 25, 2013 *Reference 2: NUREG 2169, "Nuclear Power Plant Fire Ignition Frequency and Non-Suppression Probability Estimation Using the Updated Fire Events Database," December 2014 *Reference 3: NUREG/CR-6850 Supplement 1, "Fire Probabilistic Risk Assessment Methods Enhancements," September 2010 *Reference 4: EPRI 1025284, The Updated Fire Events Database: Description of Content and Fire Event Classification Guidance," July 2013