Nuclear Power Plant Fire 

Ignition Frequency and 

Non-Suppression Probability 

Estimation Using the Updated 

Fire Events Database 

United States Fire Event

Experience Through 2009

U.S. Nuclear Regulatory Commission Electric Power Research Institute

Office of Nuclear Regulatory Research 3412 Hillview Avenue

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NUREG-2169 EPRI 3002002936
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Nuclear Power Plant Fire 

Ignition Frequency and 

Non-Suppression Probability 

Estimation Using the Updated 

Fire Events Database

United States Fire Event 

Experience Through 2009

NUREG-2169 EPRI 3002002936

January 2015 

U.S. Nuclear Regulatory Commission Electric Power Research Institute (EPRI)

Office of Nuclear Regulatory Research (RES) 3420 Hillview Avenue

Washington, D.C. 20555-0001 Palo Alto, CA 94304-1338

U.S. NRC-RES Project Manager EPRI Project Manager

N. Melly A. Lindeman
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iii

ABSTRACT

This report documents the development of updated fire ignition frequencies (FIFs) and nonsuppression probability (NSP) estimates as potential improvements for nuclear power plant fire 

(NPP) fire probabilistic risk assessment (FPRA) applications. This research follows prior Electric 

Power Research Institute (EPRI) research aimed at providing an updated methodology to 

estimate FIFs and collect more recent fire event data. 

Fire ignition frequencies and non-suppression probabilities were previously developed in the 

NUREG/CR-6850/EPRI 1011989 and revised in Supplement 1 to NUREG/CR-6850/EPRI 

1019259. In this report, the FIF estimation benefits from an enhanced methodology and 

incorporates updated data from EPRI’s updated Fire Events Database (FEDB). The report also 

updates low-power and shutdown (LPSD) FIFs from those published in NUREG/CR-7114. NSP 

estimates are calculated using the existing methodology and have been updated with new fire 

event experience. 

The fire ignition frequencies and non-suppression probabilities published in NUREG/CR-6850 

and Supplement 1 incorporate fire event experience through the year 2000. The research 

presented in this report incorporates U.S. NPP fire event experience through the year 2009. The 

fire event data are split and analyzed into three distinct periods—1968–1989, 1990–1999, and 

2000–2009. The 1968–1989 data are used to develop a diffuse empirical prior to account for 

operating experience in that period as a starting point for the Bayesian update. Sparse bins (<2.5 

fire events) use a 20-year update period, whereas medium and dense bins use only data from 

2000–2009.

Approximately 400 of the events from 1990–2009 are of significance for FPRA applications. 

Included in the estimation of manual NSPs are 442 fire events from 1981 to 2009. The insights 

conclude that the data from 2000–2009 are the most complete and accurate for characterizing 

and estimating FIFs for FPRAs.

v

CONTENTS

ABSTRACT...............................................................................................................................iii

CONTENTS................................................................................................................................v

LIST OF FIGURES ...................................................................................................................vii

LIST OF TABLES......................................................................................................................ix

EXECUTIVE SUMMARY ...........................................................................................................xi

CITATIONS .............................................................................................................................xiii

ACKNOWLEDGMENTS...........................................................................................................xv

LIST OF ACRONYMS ............................................................................................................xvii

1 INTRODUCTION ..................................................................................................................1-1

2 BACKGROUND....................................................................................................................2-1

3 FIRE EVENT HISTORICAL DATA ANALYSIS AND QUALITATIVE EXAMINATION..........3-1

3.1 Overview of Fire Event Data..........................................................................................3-1

3.2 Qualitative Examination of Fire Event Data: Sources and Completeness ......................3-7

3.3 Analysis of Fire Event Data for Trends in Time and Power Mode Considerations........3-11

3.3.1 Statistical Methodology for Comparing Classes ...................................................3-12

3.3.2 Comparison of Time Periods................................................................................3-12

3.3.3 Analysis of Plant Modes.......................................................................................3-14

4 BIN FIRE IGNITION FREQUENCY ESTIMATION................................................................4-1

4.1 Bin FIF Estimation Methodology....................................................................................4-1

4.2 Estimation of Bin FIFs ...................................................................................................4-8

5 NON-SUPPRESSION PROBABILITY ..................................................................................5-1

5.1 NSP Methodology..........................................................................................................5-1

5.2 NSP Estimation Update.................................................................................................5-4

5.3 NSP Sensitivity and Supplemental Considerations ........................................................5-6
vi

6 OBSERVATIONS AND CONCLUSIONS..............................................................................6-1

6.1 Fire Event Data .............................................................................................................6-1

6.2 Fire Ignition Frequency..................................................................................................6-2

6.3 Fire Non-Suppression Probabilities ...............................................................................6-2

6.4 Future Research............................................................................................................6-3

7 REFERENCES .....................................................................................................................7-1

APPENDIX A DATA FROM THE FEDB .................................................................................A-1
vii

LIST OF FIGURES

Figure 3-1 Comparison of reporting types for different periods (Overall counts, all 

modes) ................................................................................................................3-8

Figure 3-2 Trends in fire event data ......................................................................................3-9

Figure 3-3 Comparison of fire event counts per reactor year for three periods......................3-9

Figure 3-4 Comparison of fire ignition occurrence rates by causal factor ............................3-10

Figure 3-5 Comparison of fire ignition occurrence rates by causal factors...........................3-11

Figure 4-1 Conceptual diagram of an HB model (Adapted from Ref [10].).............................4-1

Figure 4-2 Comparison of bin fire ignition frequencies using recent FEDB updated data 

(new FEDB) to values provided in NUREG/CR-6850, Supplement 1 .................4-15

Figure 5-1 Conceptual relationship between the fire detection time, suppression time, 

and fire brigade response time.............................................................................5-1

Figure 5-2 Non-suppression curve plots: probability vs. time to suppression ........................5-6

ix

LIST OF TABLES

Table 3-1 FPRA bin summary descriptions and applicability................................................3-1

Table 3-2 Fire event data sources for three periods.............................................................3-6

Table 3-3 Fire occurrence rates for each period ................................................................3-13

Table 3-4 Fire occurrence rates for sparse and non-sparse bins for each period...............3-13

Table 3-5 Comparison of p-values for various time periods ...............................................3-13

Table 3-6 PRA fire count data and associated total reactor years and unavailability..........3-15

Table 3-7 Comparisons of all modes, at power, and shutdown occurrence rates...............3-15

Table 3-8 Fire frequencies for FPIE and LPSD bins...........................................................3-16

Table 4-1 Parameters of the prior distributions used to perform the FIF updates .................4-4

Table 4-2 FPIE fire ignition bin identification and PRA counts for three periods ...................4-4

Table 4-3 LPSD-only bins and counts..................................................................................4-7

Table 4-4 Fire ignition frequency distributions for FPIE PRA applications ............................4-9

Table 4-5 Fire ignition frequency distributions for LPSD PRA applications.........................4-13

Table 4-6 FPIE bin fire frequency comparisons to previous estimates ...............................4-16

Table 5-1 Probability distribution for rate of fires suppressed per unit time, λ

(Originally, Table P-2 from NUREG/CR-6850) .....................................................5-4

Table 5-2 Updated numerical results for suppression curves (Originally, Table 14-1 

from NUREG/CR-6850, Supplement 1)................................................................5-5

Table 5-3 Comparisons of the mean NSP rate parameter, λ , from NUREG/CR-6850, 

Supplement 1, and updated suppression rates (λ)...............................................5-7

Table A-1 Fire event data for 2000–2009 ...........................................................................A-1

Table A-2 Fire event data for 1990–1999 ..........................................................................A-35

Table A-3 Fire event data for 1968–1989 ..........................................................................A-62

xi

EXECUTIVE SUMMARY

In 2002, the Electric Power Research Institute (EPRI) and the Nuclear Regulatory Commission 

(NRC) Office of Nuclear Regulatory Research (RES), embarked on a program to develop a 

methodology to perform internal fire probabilistic risk assessments (PRAs). The technical report, 

EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities, Volume 2: Detailed 

Methodology [1], also referred to as NUREG/CR-6850/EPRI 1011989, was published in 2005. 

This report was divided into specific tasks comprised of methods, data and technical bases to 

evaluate risk from fire initiation to plant-response modeling as well as fire modeling and 

suppression.

Background

Task 6 of NUREG/CR-6850, fire ignition frequencies, divides potential plant fire sources into 

bins that represent location, causal and mechanistic factors deemed important to depict the 

likelihood of fire scenarios at different NPPs. The generic bin definitions, plant operating mode 

applicability, and associated frequencies used in FPRA were originally developed and provided 

in NUREG/CR-6850/EPRI 1011989. An interim revision of those fire frequencies to emphasize 

the more recent but still 10-year-old data was developed by EPRI and incorporated into 

Supplement 1 (1019259). 

In July 2013, EPRI published The Updated Fire Events Database: Description of Content and 

Fire Event Classification Guidance (1025284), a comprehensive, consolidated source of fire 

incident data for nuclear power plants operating in the United States. EPRI obtained fire event 

data from 2000–2009 through an extensive plant-by-plant data collection effort in which more 

than 300,000 plant records of potential interest were collected and 12,000 potential fire events 

were identified. Data from 1990–1999 (from the original EPRI Fire Events Database [FEDB])

were updated in quality to the extent such information was available. Fire event data from the 

period 1968–1989 were retained from the original data set reported in NUREG/CR-6850/EPRI 

1011989. 

Objectives

This report provides updated fire ignition frequency estimates using the most current FEDB data 

while applying methodology enhancements. It also provides updated fire non-suppression 

probability estimates, also using the most current FEDB data with the existing non-suppression 

probability methodology.
xii

Approach

The effort to revise the fire ignition frequencies and non-suppression probability methodology

estimates spanned multiple years. An effort was made to obtain more detailed and recent fire 

event experience for the most current decade (2000–2009), and there was an emphasis on 

confirming records from 1990–1999. Published in 2013, The Updated Fire Events Database 

(1025284) provides the most complete, relevant U.S. nuclear power plant operating experience. 

Eighty four U.S. nuclear power plant completed the full data collection protocol. In addition to 

the updated database, EPRI reviewed the calculation methods for estimating fire ignition 

frequencies. The concluded research, titled An Improved Methodological Approach for 

Estimating Fire Ignition Frequencies (1022994), was published in 2011. The report serves as 

an improved methodology to derive fire ignition frequency distributions for use in FPRAs. As a 

benefit of the updated methodology, the 2000–2009 data heavily influence the results for the 

non-sparse bins, account for between-plant variability of fire ignition frequencies, and can handle 

sparse fire event data sets. EPRI 1022994 provides the technical approach for calculating fire 

ignition frequencies for the present report. The only deviation from the EPRI 1022994 

methodology was to use a more diffuse prior with hyperprior parameter σmed=3 for the mediumdensity and high-density bins with 2.5 or more PRA fire counts in the 2000–2009 period.

The non-suppression probability methodology estimates are calculated using the existing 

methodology as amended in FAQ 08-0050 in NUREG/CR-6850, Supplement 1 (1019259). 

Therefore, fire brigade response time is already included in the distribution for suppression time. 

Fire events with sufficient timing information are binned into one of twelve groups. A new curve 

was developed for low-power and shutdown suppression events in containment. 

Results

The results confirm that the fire event data from 2000–2009 are the most complete and accurate. 

A review of the fire events shows smaller occurrence rates for fires during the 1990–1999 period, 

possibly due to underreporting, although this could not be confirmed. The rate of fires during 

shutdown has increased due to lower plant availability and fewer hours spent in shutdown. The 

sum of fire ignition frequencies has increased 36% relative to that previously estimated in 

Supplement 1 to NUREG/CR-6850 (1019259), with eight bins having notable increases and four 

having notable decreases. The remainder of the bins experienced less significant changes.

Keywords

Fire ignition frequency (FIF) 

Fire probabilistic risk assessment (FPRA)

Non-suppression probability (NSP) 

Fire events
This publication is a corporate document that should be cited in the literature in the following 

manner:

Nuclear Power Plant Fire Ignition Frequency and Non-Suppression Probability Estimation 

Using the Updated Fire Events Database: United States Fire Event Experience Through 2009. 

EPRI, Palo Alto, CA, and U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory 

Research (RES), Washington, D.C.: 2014. 3002002936/NUREG-2169.

xiii

CITATIONS

This report was prepared by:

Electric Power Research Institute (EPRI) U.S. Nuclear Regulatory Commission (NRC)

3420 Hillview Avenue Office of Nuclear Regulatory Research

Palo Alto, CA 94304 Washington, DC 20555

Principal Investigator: Principal Investigator:

A. Lindeman N. Melly

Under contract to EPRI:

ERIN Engineering and Research, Inc. 

7272 Wisconsin Ave, Suite 345

Bethesda, MD 20814

Principal Investigator: 

P. Baranowsky

EPRI and the NRC acknowledge C. Atwood of Statwood Associates and J. Facemire and 

K. Hardjoko of ERIN Engineering and Research for their contributions to this report.

This report describes research sponsored by EPRI and the NRC.

xv

ACKNOWLEDGMENTS

The authors thank those who have provided time and effort to support the ultimate calculation 

of fire ignition frequencies and non-suppression probability estimates. This includes individuals 

who took their time to review and code the fire events in The Updated Fire Events Database: 

Description of Content and Fire Event Classification Guidance (EPRI 1025284) and those who 

have reviewed An Improved Methodological Approach for Estimating Fire Ignition Frequencies

(EPRI 1022994). EPRI and the NRC also acknowledge Shawn St. Germain of Idaho National 

Laboratory for providing additional details of plant operating history at the time of fire events.

xvii

LIST OF ACRONYMS

aa PRA counts for AA bins (all plants all power modes)

AA All plants all modes

AA-RY Total reactor years for all plants (at power plus shutdown) 

AL All plants LPSD

ap PRA counts for AP bins (all plants at power)

AP All plants at power

apinAP ap events in AP bins

AP-RY At power reactor years for all plants for the period

BL BWR plants LPSD

BP BWR plants at power

BWR Boiling water reactor

CD Cold shutdown

CFR Code of Federal Regulations

CH Challenging

DEP Diffuse empirical priors

EF Error factor

EN Emergency Notifications

EPIX Equipment Performance Information Exchange

EPRI Electric Power Research Institute

FAQ Frequently Asked Questions

FEDB Fire Events Database

FIDs Fire Event IDs

FIF Fire ignition frequencies

FPIE Full-power initiating event

HB Hierarchical Bayesian

HBDEP Hierarchical Bayesian with Diffuse Empirical Prior

HEAF High energy arcing fault

HS Hot shutdown

INPO Institute of Nuclear Power Operations

LER Licensee Event Report

LN Lognormal distribution

LPSD Low power-shutdown 
xviii

MCMC Markov Chain Monte Carlo

MG Motor generator

MOU Memorandum of understanding

NC Not challenging

NEI Nuclear Energy Institute

NEIL Nuclear Electric Insurers Limited

NFPA National Fire Protection Association

NPE Nuclear Power Experience

NPP Nuclear power plant

NPRDS Nuclear Plant Reliability Data System

NRC Nuclear Regulatory Commission

NSP Non-suppression probability

PC Potentially challenging

PL PWR plants LPSD

Pns Probability of non-suppression

PO Power operations

PP PWR plants at power

PRA Probabilistic risk assessment

PWR Pressurized water reactor

RES NRC Office of Nuclear Regulatory Research

RF Refueling

RPS Reactor protection system

RY Reactor year

sd PRA counts for SD bins (all plants at shutdown conditions)

SD Shutdown

sdinSD sd events in SD bins

SD-RY Shutdown reactor years for all plants for the period

T/G Turbine generator

Tdet Detection time

Tfb Time for detection until fire brigade begins to apply suppressant agents

Tsupp Suppression time

U Undetermined

U(NC-PC) Undetermined – at least potentially challenging, with insufficient 

information available to make a definitive challenging fire

U(PC-CH) Undetermined – potentially a fire, with insufficient information available to 

make a definitive potentially challenging fire

US United States
1-1

1

INTRODUCTION

This report describes the analysis of recently updated fire event data to estimate fire ignition 

frequencies (FIFs) and non-suppression probabilities (NSPs) as potential improvements for NPP 

fire probabilistic risk assessment (FPRA) applications. These original analyses were previously 

developed in NUREG/CR-6850 [1] and revised in Supplement 1 [2] to that report. The new fire 

event data extend the Electric Power Research Institute’s (EPRI’s) Fire Events Database (FEDB) 

[3] through 2009—by 10 years from prior studies—and are considered a significant enhancement 

to the original analyses. The fire ignition frequency estimates provided in Supplement 1 [2] were 

limited to full-power initiating event (FPIE) FPRA applications. In this report, the FIF estimation 

has been expanded in scope to include low-power and shutdown (LPSD) FPRA applications 

according to NUREG/CR-7114 [4].

In summary, this report provides updated FIF estimates using the most current FEDB data and 

applying methodology enhancements. Means and uncertainties are provided in the form of point 

estimates and probability distributions. The report also provides updated fire NSP estimates,

likewise using the most current FEDB data with the existing NSP methodology.

This report provides the details of the approach, bases, data, and methods used for recalculation 

of FIFs and NSP estimates. Section 2 provides relevant historical perspective on the development 

of FIF and NSP estimates. Section 3 examines fire event data quality, completeness, trends, and 

power mode implications relevant to the data’s use in FIF estimates (such issues are much less 

relevant for NSPs, as will be covered in the relevant section). Those data, along with the existing 

historical data, have been analyzed for consistency and applicability for estimating updated FIFs 

and NSPs. Data quality and quantitative factors have also been assessed to ensure proper use of 

data that were collected, coded, and classified from multiple, somewhat different data sources 

with varying information, quality, and completeness. Section 4 provides a discussion of the 

methodology and results for FIF for both full-power initiating events and low-power-shutdown 

FPRA applications. The previously developed methodology for estimating the updated FIFs for 

FPRAs was adjusted to account for data anomalies. Then, the fire event data were applied to 

assess FIFs using the revised method. The updated frequencies have been compared with fire 

frequencies currently used in FPRAs with initial insights into the differences indicated. Section 5 

provides a discussion of the methodology and results for NSP estimates, including comparisons 

with previous estimates. Appendix A provides the data used in the analyses.

2-1

2

BACKGROUND

Between 2006 and 2009, several early applications of the report EPRI/NRC-RES Fire PRA 

Methodology for Nuclear Power Facilities (EPRI 1011989, NUREG/CR-6850 [1]) resulted in 

seemingly conservative fire-induced risk estimates. These early results necessitated timely 

development of clarification and enhancements to the report to support the plants transitioning to 

the risk-informed and performance-based fire protection rule 10CFR50.48(c). This led to an 

increased focus on the National Fire Protection Association (NFPA) 805 frequently asked 

questions (FAQs) related to FPRA methods and applications. Meetings in 2008 and early 2009 

regarding these FAQs indicated that there were still important technical considerations that 

needed to be resolved in order to generate timely resolution to support plants transitioning to 

NFPA 805.

In order to document the responses and final resolution of NFPA 805 FAQs related to the fire 

PRA methodology, specifically those in EPRI 1011989, NUREG/CR-6850, a supplement to this 

document was jointly prepared by EPRI and RES [2]. The FAQ resolutions were considered 

interim and could be expected to undergo further enhancement as supporting data and 

methodology evolved and became available. In particular, the fire ignition frequencies were 

updated in the EPRI report Fire PRA Methods Enhancements: Additions, Clarifications, and 

Refinements to EPRI 1011989 [5] and included in the resolution to FAQ 08-0048 (published in 

Chapter 10 of Reference 2), with interim application guidance pending future acquisition of more 

current fire event data and reanalysis of those data. Resolution of FAQ 08-0050, manual nonsuppression probability, was also provided using the original fire event data used to develop 

NUREG/CR-6850. 

Subsequently, EPRI and the Nuclear Energy Institute (NEI) embarked on a project to update the 

fire event data, reanalyze the fire ignition frequencies, and evaluate apparent trends. An update to 

the fire non-suppression analyses was later added to the project scope. In parallel, enhanced fire 

frequency analysis methods were developed and tested by EPRI to better account for betweenplant variability when the newer data became available for analysis [6, 7]. 

The development of the FEDB was led by EPRI in cooperation with the NRC Office of Nuclear 

Regulatory Research (RES) in accordance with the EPRI-NRC Memorandum of Understanding.

As an integral part of the process, the NRC performed audits of the data to ensure accuracy, 

completeness, and a strong degree of agreement between EPRI and the NRC on fire severity 

classification and coding. The FEDB, excluding references to the actual plants, was completed 

and released in July 2013. 

The fire events database that supported the development of NUREG/CR-6850 was primarily 

based on the fire incident data reported in the Nuclear Electric Insurers Limited (NEIL) fire

incident database, Licensee Event Reports (LERs), Emergency Notifications (ENs), the 

Equipment Performance Information Exchange (EPIX), and other available sources. The 
Background

2-2

documentation and traceability of many data entries and event classifications were not rigorously 

provided. The updated FEDB uses data collected from a voluntary, but encouraged initiative to 

provide updated operating experience and enhanced incident detail. The data was collected 

directly from the plants with explicit traceability to source documents for classification and audit 

of the data records. Fire event data from the 2000–2009 period were obtained from an extensive 

plant-by-plant data collection effort in which more than 300,000 plant records of potential 

interest were collected and 12,000 potential fire events were identified. Existing events from the 

prior release of the FEDB from the years 1990–1999 have been upgraded in quality to the extent 

such information is available. This resulted in the addition of a few fire events and the removal 

of several others that had uncertain fire severity in the 1990–1999 period. Approximately 400 of 

the fire events from 1990–2009 are of significance for FPRA applications. Fire event data from 

the period 1968–1989 were retained from the original data set reported in NUREG/CR-6850. 

These data were determined to be too outdated to update for completeness and quality in a 

meaningful way. The fire event data collection protocol and review by individual plants had been 

completed for 84 plants1 when the updated FEDB was documented and published in the EPRI 

report The Updated Fire Events Database: Description of Content and Fire Event Classification 

Guidance [3].

 

1 Twenty nuclear power plants did not complete the full fire event report quality reviews to ensure condition reports’

quality and consistency for the severity level binning process. Fire events from these plants were excluded from this 

analysis, and the reactor year calculations were reduced to 84 years for the period 2000–2009. 
3-1

3

FIRE EVENT HISTORICAL DATA ANALYSIS AND 

QUALITATIVE EXAMINATION

3.1 Overview of Fire Event Data

The fire ignition sources used in FPRAs are divided into groups called bins that represent 

location, causal, and mechanistic factors deemed important to depict frequencies of initiating fire 

scenarios at different plants. The generic bin definitions, plant operating mode applicability, and 

associated frequencies used in FPRAs were originally developed and provided in NUREG/CR6850 [1]. An interim revision of those fire frequencies to emphasize the more recent 10-year-data 

was developed by EPRI and incorporated in Supplement 1 to NUREG/CR-6850 [2]. Some 

clarification of fire bin definitions and associated fire event data was also provided in that 

supplement. The Supplement 1 fire bin definitions have been used in this work for FPIE FIF

estimates. More recently, the NRC has defined fire ignition frequency bins for LPSD fire 

probabilistic risk analyses in NUREG/CR-7114 [4]. These bin definitions have been used for 

LPSD FIF estimates provided in this report. A simplified summary of the FPIE and LPSD fire 

ignition frequency bins is provided in Table 3-1. The FPRA and operating mode applicability 

can be traced directly back to guidance provided in NUREG/CR-6850 [1] and NUREG/CR-7114 

[4]. To be consistent with plant practices, separate frequency values have been developed for 

certain bins where explicit differences are to be expected during LPSD operation.

Table 3-1

FPRA bin summary descriptions and applicability

Bin Location Ignition Source FPRA and 

Operating Mode 

Applicability

Source

FPIE LPSD

1 Battery room Batteries All All NUREG/CR-6850 and NUREG/CR-7114

2 Containment 

(PWR)

Reactor coolant 

pump

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

3 Containment 

(PWR)

Transients and 

hotwork (at power)

At 

power

N/A NUREG/CR-6850

3P Containment 

(PWR)

Transients and 

hotwork (LPSD)

N/A LPSD NUREG/CR-7114

3B Containment 

(BWR)

Transients and 

hotwork (LPSD)

N/A LPSD NUREG/CR-7114

4 Control room Main control board All All NUREG/CR-6850 and NUREG/CR-7114
Fire Event Historical Data Analysis and Qualitative Examination

3-2

Table 3-1 (continued)

FPRA bin summary descriptions and applicability

Bin Location Ignition Source FPRA and 

Operating Mode 

Applicability

Source

FPIE LPSD

5 Control/Aux/ 

Reactor Building

Cable fires caused 

by welding and 

cutting

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

6 Control/Aux/ 

Reactor Building

Transient fires 

caused by welding 

and cutting

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

7 Control/Aux/ 

Reactor Building

Transients At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

8 Diesel generator 

room

Diesel generators All All NUREG/CR-6850 and NUREG/CR-7114

9 Plant-Wide 

Components

Air compressors All All NUREG/CR-6850 and NUREG/CR-7114

10 Plant-Wide 

Components

Battery chargers All All NUREG/CR-6850 and NUREG/CR-7114

11 Plant-Wide 

Components

Cable fires caused 

by welding and 

cutting

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

12 Plant-Wide 

Components

Cable run (selfignited cable fires)All All NUREG/CR-6850 and NUREG/CR-7114

13 Plant-Wide 

Components

Dryers All All NUREG/CR-6850 and NUREG/CR-7114

14 Plant-Wide 

Components

Electric motors All All NUREG/CR-6850 and NUREG/CR-7114

15 Plant-Wide 

Components

Electrical cabinets 

(non high-energy 

arcing fault 

[HEAF])

All All NUREG/CR-6850 and NUREG/CR-7114

16.a Plant-Wide 

Components

HEAF low-voltage 

electrical cabinet 

(480–1000 V)

All All FAQ 06-0017

16.b Plant-Wide 

Components

HEAF mediumvoltage electrical 

cabinet (>1000 V)

All All FAQ 06-0017

16.1 Plant-Wide 

Components

HEAF segmented 

bus duct

All All FAQ 07-0035
Fire Event Historical Data Analysis and Qualitative Examination

3-3

Table 3-1 (continued)

FPRA bin summary descriptions and applicability

Bin Location Ignition Source FPRA and 

Operating Mode 

Applicability

Source

FPIE LPSD

16.2 Plant-Wide 

Components

HEAF iso-phase 

bus duct

All All FAQ 07-0035

17 Plant-Wide

Components

Hydrogen tanks All All NUREG/CR-6850 and NUREG/CR-7114

18 Plant-Wide 

Components

Junction boxes All All NUREG/CR-6850 and NUREG/CR-7114

19 Plant-Wide 

Components

Misc. hydrogen 

fires

All All NUREG/CR-6850 and NUREG/CR-7114

20 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

21 Plant-Wide 

Components

Pumps All All NUREG/CR-6850 and NUREG/CR-7114

22 Plant-Wide 

Components

Reactor protection 

system (RPS) 

motor generator 

(MG) sets

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

23 Plant-Wide 

Components

Transformers All All NUREG/CR-6850 and NUREG/CR-7114

24 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

25 Plant-Wide 

Components

Transients At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

26 Plant-Wide 

Components

Ventilation 

subsystems

All All NUREG/CR-6850 and NUREG/CR-7114

27 Transformer 

yard

Transformer –

Catastrophic

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

28 Transformer 

yard

Transformer –

Non Catastrophic

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

29 Transformer 

yard

Yard transformers 

(others)

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

30 Turbine building Boiler All All NUREG/CR-6850 and NUREG/CR-7114

31 Turbine building Cable fires caused 

by welding and 

cutting

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114
Fire Event Historical Data Analysis and Qualitative Examination

3-4

Table 3-1 (continued)

FPRA bin summary descriptions and applicability

Bin Location Ignition Source FPRA and 

Operating Mode 

Applicability

Source

FPIE LPSD

32 Turbine building Main feedwater 

pumps

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

33 Turbine building Turbine generator 

(T/G) excitor

At 

power

N/A NUREG/CR-6850 and NUREG/CR-7114

34 Turbine building T/G hydrogen At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

35 Turbine building T/G oil At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

36 Turbine building Transient fires 

caused by welding 

and cutting

At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

37 Turbine building Transients At 

power

LPSD NUREG/CR-6850 and NUREG/CR-7114

Nuclear power plant fire events that are countable as PRA fires include classifications of 

challenging (CH), potentially challenging (PC), and undetermined (U). Note that additional 

distinctions for fire event severity classifications are used in the updated FEDB [3]. These are 

designated as U(NC-PC), which is identical to U in this report, and U(PC-CH), which is identical 

to PC in this report. In this report, fire events classified as U were counted as half a fire in a 

manner similar to the counting scheme used in NUREG/CR-6850. Fire events classified as nonchallenging (NC) were not used or counted in any analyses. A summary of the fire severity 

classifications is provided in the following bullets. For additional details concerning event 

classification, refer to The Updated Fire Events Database: Description of Content and Fire 

Event Classification Guidance (EPRI 1025284) [3]. 
Fire Event Historical Data Analysis and Qualitative Examination

3-5

The events contained in the FEDB have been classified into one of the following fire severity 

groups:

• Challenging. CH fires are those that had an observable and substantive effect on the 

environment outside the initiating source, regardless of the exact location of the fire, what 

was potentially under threat, or what was actually damaged by the fire. The size of the fire is 

not the only determining characteristic, but rather the ability of the fire to adversely affect 

components beyond the initial fire source. These include fires in the growth, fully developed, 

and decay stages. Data fields considered here include those associated with the observed fire 

characteristics, the means of suppression applied, ignition of secondary combustibles, and the 

fire-induced environmental conditions. It should be emphasized that damage to additional 

components beyond the initiating source does not have to occur to meet this condition (for 

example, an explosion and resulting fire at a main transformer that is limited to the main 

transformer would be classified as challenging). 

• Potentially challenging. PC fires are those events that were not judged to be CH events, but 

under foreseeable alternative circumstances could have reached a CH state. That is, PC fires 

could have led to fire growth, fire spread, equipment damage, or cable damage beyond the 

fire ignition source had the circumstances of the fire event been different. Foreseeable 

alternative circumstances could include failure of any successful defense-in-depth fire 

protection measure, delays in successful intervention actions, and occurrence of a similar fire 

involving an alternative fire ignition source. The data fields considered in the PC 

determination are the same as those considered in the CH fire category, but for the PC case, 

the fire did not develop into a challenging fire. For example, a fire occurring in an unvented 

electrical cabinet might be contained within the cabinet and have relatively low severity; 

however, if it had occurred in a vented cabinet, the potential for a more severe fire that could 

damage nearby cabinets would exist. Therefore, the unvented cabinet fire is likely to be PC. 

• Undetermined. U fires are potential fire events where there is insufficient information to 

determine if the event should be classified as CH, PC or non-challenging (NC). The updated 

FEDB further classifies undetermined events into U(PC-NC) and U(PC-CH). 

• Non-challenging. NC-classified fires did not cause or would not have caused adjacent 

objects or components to become damaged or to ignite, regardless of location and for 

essentially any amount of time. These fires could be detected automatically by an incipient 

fire detection system and could be related to component failures involving ignition of the 

component followed by self-extinguishment without any required intervention. Fires that 

remained in a smoldering state with no apparent potential for open flaming might also be 

classified as NC. Another typical example of NC would include component overheating 

incidents with light or moderate smoking but without any flaming. The NC classification is 

also applied to fires of a type or in a location that would not be considered relevant to an 

FPRA (such as an automobile fire in an on-site parking lot or an off-site grass fire). Fires 

that occurred during plant construction would also be classified as NC.
Fire Event Historical Data Analysis and Qualitative Examination

3-6

Due to its evolution over many years, the quality and content of the FEDB vary for different 

periods. The version of the FEDB used to support the development of NUREG/CR-6850 

captured fire event data for the period 1968–2000. The update of the FEDB focused on adding 

fire event data from 2000 to 2009. A limited update to the fire event data for the period 1990–

1999 was also included to enhance the completeness and quality of that earlier data where 

practical. The updated FEDB, EPRI 1025284 [3], included details and data for the latter two 

periods of interest—1990–1999 and 2000–2009. It reports the details only for fire events from 

the 84 plants that completed the full data collection protocol and plant review. The earlier data 

from 1968–1989 were not updated or published in EPRI 1025284. Fire events from this period 

remain a separate, proprietary, archived data element of the FEDB. Therefore, the FEDB can be 

considered to have three distinct data sets with somewhat different data sources, content, quality, 

and completeness. These three distinct periods are 1968–1989, 1990–1999, and 2000–2009. 

Fire event data sources for all three time periods are summarized in Table 3-2. Although the 

data sources are similar, there are also some significant differences. For instance, in 1984, the 

reporting requirements for LER according to 10CFR50.73 were substantially changed to move 

away from component-level to significant event–level reporting. Moreover, the emphasis on 

and access to fire event data from many sources changed significantly. These included NEIL, 

the Nuclear Plant Reliability System (NPRDS), and, most important, plant-based records. The 

latter are the most complete and the principal source for the newer data in the FEDB for the 

period 2000–2009.

Table 3-2

Fire event data sources for three periods

1968–1989 1990–1999 2000–2009

Data Sources

• LERs (component-level 

reporting rules)

• Additional data available: 

ENs, NEIL, NPRDS, plant 

reports 

• LERs (significant event and 

system-level reporting rules)

• Additional data available: ENs, 

NEIL, NPRDS, plant reports 

• Systematic collection of plantsupplied reports and data 

records

• Supplemented with details 

from LERs and ENs

PRA Fire Event Counts and Reactor Years (all operating modes)

413 in 1282 reactor years 163.5 in 1081 reactor years 217 in 850 reactor years

At-Power PRA Fire Event Counts and Reactor Years

273 in 899 reactor years 102 in 848 reactor years 138.5 in 771 reactor years

LPSD PRA Fire Event Counts and Reactor Years

140 in 383 reactor years 61.5 in 233 reactor years 78.5 in 79 years

It should be noted that the updated FEDB data collection for 2000–2009 included all plants that 

supplied fire event data to EPRI. However, with one exception, the only data from 2000–2009 

used in this report are from the 84 plants that completed the full data collection protocol and 

plant review. This was to ensure that the fire event data used in the analyses were complete and 

that plants did a quality review of the data compiled before they were used. The fire event counts 
Fire Event Historical Data Analysis and Qualitative Examination

3-7

and associated reactor years cited in Table 3-2 are for the 84 plants that completed the full data 

collection protocol and plant quality assurance review. The one exception involved mediumvoltage electrical cabinet HEAF events (bin 16.b) and bus duct events (bins 16.1 and 16.2). 

With respect to the bus duct events, the potential for missing fire event data for these bins was 

not considered applicable because all such fire events were provided in FAQ 07-0035 in 

NUREG/CR-6850, Supplement 1 [2]. Similarly, HEAF events in medium-voltage electrical 

equipment are likely to be reported to the NRC, thus minimizing the chance for missed events. 

Therefore, for these bins, 1040 reactor years were used to represent all operating plant years in 

the period.

The FEDB data from the period 1968–1989 were classified for fire ignition bin categories in 

NUREG/CR-6850 with a few bin adjustments from Supplement 1. Because additional data and 

details were obtained for the FEDB fire event data from the 1990–1990 period, these data were 

re-reviewed for binning classification along with the newer data from 2000–2009. The review 

was performed by the NRC and EPRI in a consensus-based manner. As a result, the fire event 

details were checked for numerous events, and some fire data details captured in the FEDB were 

revised. Several fire severity reclassifications were identified. A second, similar review was 

conducted to ensure the correctness of fire suppression time details provided in the data from 

1990 through 2009. Erroneous fire suppression times based on the FEDB default suppression 

time algorithm values and suppression-related coding details were corrected for several events. 

For instance, in some cases, fire event timelines were estimated by plant personnel and reported 

as the time the plant exited an emergency declaration. These estimations led to suppression times 

that far exceeded the reported time to fire suppression or fire control. The results of these 

reviews produced the data set that was used in the analyses for FIF and NSP updates provided in 

this report. The revised FEDB data sets for the periods 1990–1999 and 2000–2009 are provided 

in Appendix A for key data elements used in the analyses. The data set for 1968–1989 from the 

original FEDB that was used in this report is also provided in Appendix A. Events with revisions 

to fire ignition source, location, severity determination, and suppression timing from the updated 

FEDB [3] are noted. A few events were determined to be composed of two separate fires. These 

were identified, split, and classified for FIF and NSP use, as appropriate. Fire event 

identifications (FIDs) are provided as reference to the more complete fire event data that are 

available in the updated FEDB report [3] for 1990–2009 data and NUREG/CR-6850 for 1968–

1989 data.

3.2 Qualitative Examination of Fire Event Data: Sources and Completeness

The fire event data from the 1968–2009 period were examined to better understand the 

implications of data quality and completeness in the selection and adaptation of the individual 

bin fire frequency estimation methodology. The first step was to develop a historical perspective 

of the occurrence rate of fires from all countable sources contained in the complete and updated 

FEDB over the full period of interest (1968–2009) for which data were available. 

The following examination and depictions of the FEDB data trends were derived using “all 

operating modes” data. The applicability of the fire events that occur at power or shutdown 

conditions in deriving bin FIFs is provided in NUREG/CR-6850 [1] and Supplement 1 [2].
Fire Event Historical Data Analysis and Qualitative Examination

3-8

Figure 3-1 is an illustration of the contributions to the fire counts from the different data sources 

for the three time periods. It shows the comparison of fire events reported in the various data 

sources. There is some reporting overlap, especially for the more severe fires that have been 

reported in more than one source. Nonetheless, this gives a good indication of the relative 

magnitude of the data source reports for the three periods.

Figure 3-1

Comparison of reporting types for different periods (Overall counts, all modes)

Figure 3-2 shows the historical perspective of the annual PRA fire event occurrence rate (counts 

per year) over the period 1968–2009. The FEDB data are depicted as original and updated to 

facilitate visualizing and analyzing differences in the fire event data sets that were collected, 

coded, and classified over time using different data sources with varying information quality 

and completeness. There is an obvious discontinuity in the 1990s data. For comparison and 

insight as to the implications and significance of the apparent deviation in the overall fire counts 

and associated frequency in the 1990s, fire counts for some of the more significant fires are also 

shown. These include the challenging fires from the FEDB and fires that the NRC classified as 

“severe” fires, including any fire event reported through 10CFRCFR50.72(a)(1)(i) or any fire 

reported through other 50.72 or 50.73 reports that, if plant personnel had not taken action, would 

have likely required reporting through 10CFR50.72(a)(1)(i) [8]. A review of the challenging fires 

between 1990 and 2009 does not show a discernable difference in the fire occurrence rate. One 

possible conclusion is that there was underreporting of the more common but less severe 

potentially challenging fire events in the 1990–1999 period, which could have provided the 

frequency decrease in Reference 2.

0.00E+00

5.00E-02

1.00E-01

1.50E-01

2.00E-01

2.50E-01

3.00E-01

1968-1989 1990-1999 2000-2009

Count/Reactor Year

Reporting Peroid

EPRI

Reports

NPE

Station

Fire Report

Plant Condition

 Report

NPRDS

NEIL

EN

LER

Other

(multiple sources)
Fire Event Historical Data Analysis and Qualitative Examination

3-9

Figure 3-2

Trends in fire event data

Figure 3-3 provides a similar pattern in a simple bar chart comparison for the three periods and 

their different data sources. Further review suggests that the data collected in the 1990s may not 

have had the same level of completeness as the data from the 1968–1989 and 2000–2009 

periods. As a result, additional investigation into the factors driving the differences in the three 

data periods was made.

Figure 3-3

Comparison of fire event counts per reactor year for three periods

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

NRC severe

fire

Ch Ch&PC

+0.5U

Count/Reactor year

Fire Severity Category

Original FEDB: 1968-1989

Original FEDB: 1990-1999

Updated FEDB 1990-1999

Updated FEDB 2000-2009
Fire Event Historical Data Analysis and Qualitative Examination

3-10

Figures 3-4 and 3-5 show the main fire ignition components and causal factors with significant 

fire frequency differences from the 1990–1990 period. Most follow the trend of lower 

frequencies in the 1990–1999 period than in the earlier and later periods. Other fire ignition 

components and causal factors did not exhibit this behavior in a significant way, in many cases 

because of their smaller data counts. Lower rates shown in the 1990–1999 period suggest the 

possibility of missing data.

Figure 3-4

Comparison of fire ignition occurrence rates by causal factor

0.0E+00

1.0E-02

2.0E-02

3.0E-02

4.0E-02

5.0E-02

6.0E-02

7.0E-02

8.0E-02

9.0E-02

Electric

Motors

Electrical

Cabinets

Diesel

Generators

Other Pumps

Count/Reactor year

Fire Components

2000-2009 PC+0.5U

2000-2009 CH

1990-1999 PC+0.5U

1990-1999 CH
Fire Event Historical Data Analysis and Qualitative Examination

3-11

Figure 3-5

Comparison of fire ignition occurrence rates by causal factors

Given the multitude and nature of the fire data sources, including federal regulatory requirements 

for reporting LERs and ENs, and the trends for severe fires shown in Figure 3-1, the most severe 

fires are assumed to be fully reported by one or more of the reporting types for all time periods. 

These fires correlate to the NRC severity classifications as well as the CH fires. The fire event 

data collection protocol used to update the fire event data for the 2000–2009 period is also 

assumed to be very complete for the 84 plants that fully participated in the FEDB update. As a 

result, further examination of the data suggests that the less severe fires are a prominent factor in 

the apparent deviation in fire frequencies associated with the 1990s fire event data. In addition, 

the extensive effort by the NRC and its contractors to collect fire event data in the 1970s and 

1980s to support development of NUREG/CR-6850 suggests that the data from 1968–1989 may 

be fairly complete.

3.3 Analysis of Fire Event Data for Trends in Time and Power Mode 

Considerations

Additional analyses of the FEDB were performed to determine if there were statistically valid 

inferences of the trends previously observed and power mode observations.
Fire Event Historical Data Analysis and Qualitative Examination

3-12

3.3.1 Statistical Methodology for Comparing Classes

To perform the analyses, the fire frequencies were divided into the following classes:

• Three periods—1968–1989, 1990–1999, and 2000–2009

• Selected pairs of these periods, in particular, 1968–1989 vs. 2000–2009, 1990–1999 vs. 

2000–2009, and 1968–1989 vs. 1990–2009

• The two plant modes—at-power and LPSD

To test the hypothesis that the fire frequency is the same in the two or three classes under 

consideration, the Pearson chi-squared test was used. This is a standard test, valid for large 

samples. For small samples, page 6-23 of Reference 9 quotes a rule of thumb that the expected 

number of fires in each class should be at least one, or two if the classes are not approximately 

equally probable. Thus, the test is appropriate for the present work, except for bin-specific 

comparisons with small data (fire counts), as previously indicated. 

There is another well-known test that is valid even for small samples—Fisher’s exact test. 

However, it can be used only with integer (not fractional) counts, and only when comparing two 

classes, not three. Therefore, it was not considered for the present work.

Bin subgroups were also defined based on the PRA counts of fires for the bins identified in 

Table 3-1, in the 2000–2009 period, and in a manner consistent with the fire ignition frequency 

methodology described in the EPRI report An Improved Methodological Approach for 

Estimating Fire Ignition Frequencies (1022994) [7] and summarized in Section 4.1 of the 

present report. The sparse-density bin group was defined as all bins with fewer than 2.5 FPRA 

event counts in the most current period of data (2000–2009). The non-sparse bin group consisted

of all other bins that are noted as high-density (>6.5 fire event counts) or medium-density 

(≥2.5 to 6.5 fire event counts).

3.3.2 Comparison of Time Periods

Figure 3-2 shows graphically that the fire frequency seems to vary from period to period. The 

present section shows the corresponding comparison using statistical tests and p-values.

First, the three periods were considered, with the fires that would be appropriate in an FPIE 

FPRA—the all-modes bins and the at-power portion of at-power/LPSD bins. These differ from 

all counts of fires and reactor years occurring at power, as shown in Table 3-2, or at shutdown as 

a result of bin definitions for counting fires. The counts for the 40 FPIE bins were combined to 

derive total FPIE fire occurrence rates for an average plant using FPIE applicable data. All of the 

FPIE applicable fires in the bins were counted, and the average of the FPIE applicable reactor 

years for the bins was used, so that the quotient estimated the average FPIE fire frequency per 

year at a plant. The results are shown in Table 3-3.
Fire Event Historical Data Analysis and Qualitative Examination

3-13

Table 3-3

Fire occurrence rates for each period

1968–1989 1990–1999 2000–2009

FPIE countable fires 338.12 128.75 155.5

FPIE average reactor years 1050 930 798

Average FPIE fire frequency 0.322 0.138 0.195

LPSD countable fires 74.49 34.75 51.5

LPSD average reactor years 383 233 78.8

Average LPSD fire frequency 0.194 0.149 0.654

The four tests mentioned in the first and second items of the preceding list were performed. 

In every case, the p-value was small—typically, extremely small—indicating very strong 

evidence against the hypothesis of equal frequencies. That is, the three periods have clearly 

different frequencies, whether considered as a group of three or as pairs.

The results were more complicated when separate analyses were made for sparse bins and nonsparse bins. Recall that sparse bins are defined as those with <2.5 fires in the 2000–2009 period. 

Table 3-4 shows the results of the comparison of sparse and non-sparse bin frequency for each 

period.

Table 3-4

Fire occurrence rates for sparse and non-sparse bins for each period

1968–1989 1990–1999 2000–2009

Average FPIE fire frequency, non-sparse bins 0.238 0.110 0.179

Average FPIE fire frequency, sparse bins 0.078 0.026 0.013

The sparse bins show a steadily decreasing frequency. Table 3-4 does not show whether the trend 

is statistically significant; this is considered next. Table 3-5 displays the p-values that were 

obtained when comparing various pairs of periods. P-values less than 0.05 are indicative of 

statistically significant differences [9].

Table 3-5

Comparison of p-values for various time periods

All Periods 1990s vs. 2000s 1968–1989 vs. 

2000s

1968–1989 vs. 

1990–2009

Non-sparse bins 5E-11 1.2E-4 5.6E-3 N/A

Sparse bins 4E-12 8E-2 N/A 9E-13

Consider first the sparse bins. The p-values in Table 3-5 show that pooling sparse data from the 

1990s and 2000s might be considered reasonable. For most sparse bins, it raises the estimated 

frequency slightly, compared to using only the fire events from the 2000s. However, the added 

benefit of having twice as many years of data is very desirable.
Fire Event Historical Data Analysis and Qualitative Examination

3-14

One reason that the sparse bins show a downward trend from the 1990s to 2000s may lie in the 

definition of sparse. Sparse bins are defined as having <2.5 fires in the 2000s. This puts a ceiling 

on the frequency in the 2000s period but not in the 1990s and makes it more likely for the trend 

to be downward than upward. Fire counts in the 1990s for the sparse bins are almost always 

larger than counts in the 2000s. Thus, the asymmetrical definition of sparse builds a small 

conservatism into the FIF methodology described in Section 4 when data from the 1990s are 

combined with sparse bin data from the 2000s to perform the FIF analyses. In addition, the prior 

distribution biases the results upward because it is based on 1968–1989; however, this bias is 

small because the prior is so diffuse.

For non-sparse bins, the 1990s and 2000s may not be pooled—the very small p-value shows that 

the two frequencies are different. The prior in this case is generated from the 1968–1989 data, 

which biases the results upward somewhat. However, the effect is very small because the prior 

distribution is made to be very diffuse—more diffuse than was planned in the methodology 

report [7] because when the report was issued, the abrupt changes and discontinuities in fire 

occurrence rates for the periods were not anticipated.

3.3.3 Analysis of Plant Modes

Before the comparisons of classes can be described, it must be mentioned that the database 

includes fires that occurred during two plant modes: when the plant is at power and when the 

plant is at LPSD conditions. 

As cited in Table 3-1 and based on engineering considerations provided in NUREG/CR-6850, 

the estimation of fire frequency for some bins is assumed to be essentially the same during both 

at-power and LPSD plant modes. These bins are designated by the phrase all modes. Most of 

these bins use combined data from all plants to estimate fire frequencies, but a few are restricted 

to PWRs or BWRs. A simple estimate of the fire frequency for such bins is (number of 

fires)/(number of reactor years).

The other bins are considered to have different frequencies during power and LPSD conditions. 

These bins are designated by the phrase at power/LPSD. Again, most use combined data from 

both PWRs and BWRs to estimate fire frequencies. Simple estimates of these two fire 

frequencies are (number of fires at power)/(number of reactor years at power) and (number of 

fires during LPSD)/(number of reactor years during LPSD).

The total PRA fire event counts for the reactor power mode groups are provided in Table 3-6 

along with the unavailability for the nuclear plant fleet during the three periods of interest. These

fire counts are not the same as FPIE bin fire counts cited in Table 3-3 because they include all 

PRA countable fires, irrespective of bin definitions for fire counting during specified power 

conditions for FPIE or LPSD fire probabilistic risk assessments. Therefore, it is the total fire 

counts used for both FPIE and LPSD applications, without double-counting.
Fire Event Historical Data Analysis and Qualitative Examination

3-15

Table 3-6

PRA fire count data and associated total reactor years and unavailability

Time Periods (years)

PRA counts for: 1968–1990 1990–1999 2000–2009

All fire events, all modes (aa) 413 163.5 217

At-power fire events (ap) 273 102 138.5

At-shutdown fire events (sd) 140 61.5 78.5

Total reactor years in period 1282 1081 850

Unavailability for period 0.3 0.21 0.09

Unavailability is the number of reactor years when the reactor was not at power divided by the 

total reactor years (plant capacity factor) considered in the period of interest. Most notable is the 

substantial decline in unavailability, whereas the shutdown fire count is more consistent. These 

considerations are further developed in Table 3-7.

Table 3-7

Comparisons of all modes, at power, and shutdown occurrence rates

Occurrence Rate Category Occurrence Rate per Period

1968–1989 1990–1999 2000–2009

All events in all bins

aa/(AA-RY) 0.322 0.151 0.255

ap/(AP-RY) 0.303 0.120 0.180

sd/(SD-RY) 0.366 0.264 0.996

Events in AA bins

aainAA/(AA-RY) 0.163 0.073 0.129

apinAA/(AP-RY) 0.160 0.061 0.120

sdinAA/(SD-RY) 0.170 0.115 0.216

Events in AP and SD bins

(apinAP+sdinSD)/(AA-RY) 0.159 0.079 0.126

apinAP/(AP-RY) 0.144 0.059 0.060

sdinSD/(SD-RY) 0.195 0.149 0.780

All ap and sd events per calendar year

ap/(AA-RY) 0.213 0.094 0.163

sd/(AA-RY) 0.109 0.057 0.092
Fire Event Historical Data Analysis and Qualitative Examination

3-16

Table 3-7 (continued)

Comparisons of all modes, at power, and shutdown occurrence rates

Occurrence Rate Category Occurrence Rate per Period

1968–1989 1990–1999 2000–2009

Events in AA and SD bins per calendar year

apinAP/(AA-RY) 0.101 0.046 0.054

sdinSD/(AA-RY) 0.058 0.032 0.072

Nomenclature Description

AA all plants, all power modes

AP all plants, power modes only

SD all plants, shutdown conditions only

Aa PRA counts for AA bins (all plants all power modes)

Ap PRA counts for AP bins (all plants at power)

Sd PRA counts for SD bins (all plants at shutdown conditions)

apinAP ap events in AP bins

sdinSD sd events in SD bins

AA-RY total reactor years for all plants (at power plus shutdown) for the period

AP-RY at power reactor years for all plants for the period

SD-RY shutdown reactor years for all plants for the period

Next, the data used to generate Table 3-6 were examined for FPIE bins to determine the 

statistical significance of the differences in fire frequencies for power condition. In each of the 

three periods (1968–1989, 1990–1999, and 2000–2009), the at-power and shutdown reactor 

years and fires were counted separately. Then, the hypothesis that the frequency at power and the 

frequency during LPSD conditions were equal for each of the periods was tested. The counts and 

p-values obtained when all of the bins were pooled by power condition are shown in Table 3-8.

Table 3-8

Fire frequencies for FPIE and LPSD bins

1968–1989 1990–1999 2000–2009

At-power reactor years 899 848 771

At-power fires 273 102 138.5

At-power fire frequency 0.303 0.120 0.180

SD reactor years 383 233 78.8

SD fires 140 61.5 78.5

SD fire frequency 0.366 0.265 0.996

p-value comparing frequencies 0.97 2E-4 4E-20

The results in Table 3-8 show a remarkable change over time. In the early years, the at-power 

and shutdown fire frequencies were nearly the same. It is not clear what happened in the 1990s 

due to the issue of fire data completeness described in Section 3. However, in the 2000s, the 
Fire Event Historical Data Analysis and Qualitative Examination

3-17

shutdown fire frequency rose greatly, not because the number of fires increased greatly, but 

because the time in shutdown went down sharply, consistent with the average plant 

unavailability factor shown in Table 3-6. When the data were examined on a bin-by-bin basis, 

only the bins designated as at-power/LPSD had statistically significant differences in the atpower and shutdown fire frequencies. This confirms that at least for some bins, it is necessary 

to have separate estimates for at-power and LPSD frequencies. On the other hand, none of the 

all-modes bins had statistically significant fire frequency differences depending on power 

condition; as a group, though, the power condition appears to have some effect on fire frequency, 

with a p-value of about 0.01. This suggests that the separation of data by power condition for 

those bins might be considered but cannot be determined for the individual bins. 

Now consider only the bins that are categorized as “all modes.” In the 2000s, their estimated fire 

frequencies for at-power and LPSD were 0.120 and 0.216, respectively. Although not the same, 

the two estimated frequencies are not enormously different. The p-value for testing equality of 

the frequencies is 0.018, which is less than 0.05 but not less by orders of magnitude. For the 

individual bins, no bin has a bin-specific p-value smaller than 0.079. The conclusion is that there 

is some difference in the frequency at power and the frequency at LPSD, but it is not statistically 

significant for any one bin. Splitting such a bin into two and estimating two separate frequencies 

would result in larger uncertainty, especially for the LPSD frequency. It is arguably best for each 

of these bins to estimate a single fire frequency that is used for both plant modes. This is what is 

done in this report.

A more complete set of comparisons for at-power and shutdown fire occurrence rates over the 

three periods is shown in Table 3-7. All fire events in all bins were included in the tabulations 

with power mode and bin specifications as noted in Table 3-7.

Some potentially important observations of the reactor operating mode data partitioning are as 

follows:

• All plant and operating mode data (aa/(AA-RY)) and all plant at-power data (ap/(AP-RY)) 

followed the pattern exhibited in prior figures. 

• This held for the all-power-bins data when looking at the at-power contribution only 

(apinAP/(AP-RY)). On the other hand, the at-power bins with at-power-only data showed a 

slight decrease in rates across the three periods.

• The all-plant shutdown data (sd/(SD-RY)) showed a marked increase in the rates for 2000–

2009. The rates for 2000–2009 were much higher than the 1968–1989 rates.

• This held for the all modes (sdinAA/(SD-RY)) and shutdown (sdinSD/(SD-RY)) bins when 

looking at shutdown data only.

Some additional observations were made to look at the fire event data on a total reactor year 

basis (that is, combining at-power and shutdown reactors years, or calendar reactor years). When 

this was done, both the at-power (ap/(AA-RY)) and shutdown (sd/(AA-RY)) events in total 

followed the earlier trend in occurrence rates. However, when looking at the at-power 

(apinAP/(AA-RY)), the occurrence rates were consistent from the 1990s to the 2000s and about 

half of the 1968–1989 rate. On the other hand, the same look at the shutdown (sdinSD/(AA-RY)) 

showed a slightly higher occurrence rate for the 2000s than the 1968–1989 period and double the 

1990s rate.

4-1

4

BIN FIRE IGNITION FREQUENCY ESTIMATION

4.1 Bin FIF Estimation Methodology

The approach to update FPIE fire ignition frequencies for individual bins is described in the 

EPRI report An Improved Methodological Approach for Estimating Fire Ignition Frequencies

(1022994) [7]. This approach was designed to account for between-plant variability, which was 

found to be present in the fire ignition data set as a whole and for fire ignition bin combinations 

with denser data sets. It used a two-stage hierarchical Bayesian (HB) update process with 

noninformative and minimally informed diffuse empirical priors. The OpenBUGS software [10] 

was used to perform the calculations. The HB methodology is depicted conceptually in Figure 

4-1. It is a procedure in which the uncertainty in the prior distributions is represented by diffuse 

“hyperprior” distributions for the parameters of the population-variability distribution. In the 

methodology described in An Improved Methodological Approach for Estimating Fire Ignition 

Frequencies [7], fire event data from the period 1968–1989 were used to develop diffuse 

empirical priors to account for the operating experience in that period as a starting point for the 

Bayesian update.

Figure 4-1

Conceptual diagram of an HB model (Adapted from Ref [10].)

The standard approach for accounting for between-plant variability is the HB. In it, the assumed 

fire frequency, λ, varies from plant to plant, following an underlying distribution. In the 

methodology described by EPRI [7], the log-normal distribution was used: 

( ) 



 



 = − − 2

2 ln

2

1

exp 2

1 ( ) l μ

σ p σ

l

y

f

Then, λ was estimated as a Bayesian parameter with very diffuse hyperprior distributions for the 

median (μ = ln [median]) and σ. Appropriate past industry data were used to update the 

distribution. In this methodology, the distribution for the hyperprior median was also described 

as lognormal distribution, LN(medmed, σmed). The distribution for σ was described by a uniform 

distribution, uniform(0,B), with B set at 6, a very broad distribution that is sufficient to cover the 
Bin Fire Ignition Frequency Estimation

4-2

posterior distribution of σ, which typically lies between 0 and 2. Thus, the basic model was 

termed Hierarchical Bayes with Diffuse Empirical Priors (HBDEP). Calculations to derive the 

distribution for f (λ) are carried out by Markov Chain Monte Carlo sampling using OpenBUGS. 

Additional details are provided in Appendix B of An Improved Methodological Approach for 

Estimating Fire Ignition Frequencies (EPRI 1022994) [7]. 

The selection of the priors and update period proposed in EPRI 1022994 assumed that the data 

from the 1990s showed a valid decrease in the fire frequency trends from the 1970s and 1980s 

to the 1990s. It was assumed that the data from the 1990s would be reasonably similar to or 

consistent with the newer data from the 2000s being collected at that time. That would allow 

using all of the data from the 1990s and 2000s in the HB update. 

As covered in Section 3, the examination of the newer data collected for the period 2000–2009 

indicates that this assumption is probably not correct in general and in particular for higherdensity bins as a group and some individually. Moreover, the differences appear to be due to 

missing data. The sparse-density bins did not have statistically significant differences between 

the data for the 1990s and 2000s as a group. Examining the counts for those bins individually, 

but not statistically, also indicated good consistency and, in some cases, higher counts in the 

1990s. As a result, the methodologies recommended in EPRI 1022994, which included both an 

HB model and update period, were re-evaluated for each bin density type. In general, the 

intention was to make minimal modifications to the recommended methodology or one of the

alternatives cited in EPRI 1022994, where the data from the 1990s have highly questionable 

applicability. 

Two primary HB models were proposed in EPRI 1022994, depending largely on the bin data 

density that was required to get a convergent solution using the OpenBUGS HB methodology. 

High-density bins were defined as those with more than 6.5 FPRA event counts, medium as those 

with 2.5–6.5 event counts, and sparse as fewer than 2.5 FPRA event counts. The data density 

metric applies to the most current data (2000–2009). For consistency and because the results did 

not vary significantly for alternative methods, the same HBDEP methodology with σmed = 1.3 

and a 10-year update period (termed HBDEP-1.3, +10) was recommended for high- and 

medium-density bins. A similar methodology but with a 20-year update period and a more 

diffuse prior (σmed = 3) was recommended for the sparse bins. This model, termed HBDEP-3, 

+20, allowed the sparse data to be the principal factor driving the results, not the prior.

For sparse-density bins that have fire event count consistency or a decrease from 1990 to 2009, 

the HBDEP-3, +20-year update methodology was still considered applicable (as originally 

recommended in EPRI 1022994). This methodology model was considered still appropriate 

because the fire event occurrence rate from the 1990s was equal to or greater than that from the 

2000s for almost all sparse bins. Thus, the asymmetrical definition of sparse described in Section 

3.3 builds a small conservatism into the methodology when the data from the 1990s are 

combined with sparse bin data from the 2000s to perform the HB update analyses. In addition, 

the prior distribution pulls the results upward because it is based on the higher occurrence rate 

data from 1968–1989. However, the effect is small because the prior is so diffuse. The exception 

was for bins 16.b, 16.1, and 16.2, for which the data were considered complete, as covered in 

Section 3.1 of this report.
Bin Fire Ignition Frequency Estimation

4-3

For the high- and medium-density bin types, the 10 years of data from the 2000s were considered 

sufficient to make a good Bayes updated estimate using a diffuse prior based on the 1968–1989 

period and a 10-year update period using the most current data. This is based on the results of the 

many sensitivity studies described in EPRI 1022994 [7]. The HBDEP-3, +10-year update 

method was selected as a replacement for the HBDEP-1.3, +10-year method that was originally 

proposed for high- and medium-density bins. This model replaces σmed = 1.3 with σmed = 3 and 

uses 10 years of update data. The HBDEP-3 prior with 10 years of current data used in the 

update was found to give robust results that are strongly driven by the more current data. 

The following is a summary of the HB models that were used:

• Bins with PRA fire event counts <2.5: HBDEP-3, +20-year update. This is the methodology 

that was proposed for sparse bins in EPRI 1022994. The period 1968–1989 is used to 

develop a prior median based on Jeffreys noninformative prior and a very diffuse prior 

distribution with σmed=3. The update period is the 20 years from 1990 to 2009. No sparse 

bins had data anomalies in the 1990s that would cause potential underestimation of the 

updated FIFs (posterior distributions). 

• Bins with PRA fire event counts ≥2.5: HBDEP-3, +10-year update. This is a modification 

of HBDEP-1.3 prior that was proposed for the medium- and higher-density bins in EPRI 

1022994. The prior is the same as that used for the sparse bins with σmed=3, creating a more 

diffuse prior that adds more weight to the update years. The 1968–1989 fire event data were 

used to develop a prior median based on Jeffreys noninformative prior, also the same as the 

sparse bin method. However, for the update, only fire event data from 2000–2009 were used 

to avoid fire count anomalies in the 1990–1999 period that would cause potential 

underestimation of the updated FIFs (posterior distributions).

The FPIE methodology was adapted for use in the estimation of the bin fire ignition frequencies 

for LPSD FPRA applications. Because the AA bins already use fire event data from all power 

modes and they do not change for LPSD applications, only LPSD bins designated SD only need 

to be analyzed. Therefore, the medmed prior’s parameters for SD-only bins were derived using 

shutdown fire event data only for the bins designated as SD only by NUREG/CR-7114 [4]. The 

prior parameter σmed was set equal to 3 as with the FPIE priors, and the update periods were used 

in the same manner as in the FPIE analyses. The mathematical formulation and derivation of 

prior parameters and posterior update results are the same as for the FPIE analyses.

Table 4-1 provides the mathematical parameters of the prior distributions used to perform 

the FIF updates. Additional details of the HB methodology models are provided in EPRI 

1022994 [7].
Bin Fire Ignition Frequency Estimation

4-4

Table 4-1

Parameters of the prior distributions used to perform the FIF updates

Method 

Designation

Variability 

Distribution

Hyperprior Specification Prior Data 

Period

Update 

Period

HBDEP-3, 

+20-year 

update

LN(median,σ) median~LN(medianmed, σmed) 

where medianmed=Jeffreys med 

and σmed=3

σ~uni(0,6) 1968–1989 20 years 

(1990–

2009)

HBDEP-3, 

+10-year 

update

LN(median,σ) median~LN(medianmed, σmed) 

where medianmed=Jeffreys med 

and σmed=3

σ~uni(0,6) 1968–1989 10 years 

(2000–

2009)

Because the data from the 1990s were assumed to be missing fire event reports that would be 

comparable to those of the 2000s, special care was used in selecting and adapting methods that 

did or did not use the data from the 1990s.

Table 4-2 provides a summary of the FPIE bin-by-bin data, with FPRA counts provided for 

the three periods. The data from 1968–1989 are essentially the same as those used in 

NUREG/CR-6850 and EPRI 1016735. The data from 1990–1999 were updated during the 

update of the FEDB, as discussed in EPRI 1025284, and the data from 2000–2009 are newer 

data from that report, unless otherwise indicated herein. Half-counts were used for events of 

undetermined fire severity, as previously indicated in Section 3. In a few instances, the plant 

operating condition could not be accurately determined from the older data. For these instances, 

the at-power and shutdown counts were adjusted by weighting them according to the fraction of 

time that the plant was at power or shutdown, as was done in NUREG/CR-6850. The LPSD data 

summary is provided in Table 4-3. Counting criteria and ignition source definitions can be found 

in Chapter 6 of NUREG/CR-6850 [1] or in Supplement 1 to NUREG/CR-6850 [2].

Table 4-2

FPIE fire ignition bin identification and PRA counts for three periods

Bin Location Ignition Source Power 

Modes

FPRA Counts

1968–1989 1990–1999 2000–2009

1 Battery room Batteries AA 1 0 0

2 Containment 

(PWR)

Reactor coolant 

pump

PP 5.5 1 0

3 Containment 

(PWR)

Transients and 

hotwork (at power)

PP 2.11 0 0

4 Control room Main control board AA 3.5 2.5 4

5 Control/Aux/ 

Reactor Building

Cable fires caused by 

welding and cutting

AP 0 1 0

6 Control/Aux/ 

Reactor Building

Transient fires 

caused by welding 

and cutting

AP 9.5 1 3
Bin Fire Ignition Frequency Estimation

4-5

7 Diesel generator 

room

Transients AP 2.21 2.75 2

Table 4-2 (continued)

FPIE fire ignition bin identification and PRA counts for three periods

Bin Location Ignition Source Power 

Modes

FPRA Counts

1968–1989 1990–1999 2000–2009

8 Plant-Wide 

Components

Diesel generators AA 42 2.5 6.5

9 Plant-Wide 

Components

Air compressors AA 0.5 2 4

10 Plant-Wide 

Components

Battery chargers AA 3 2 0

11 Plant-Wide 

Components

Cable fires caused by 

welding and cutting

AP 2 0 0

12 Plant-Wide 

Components

Cable run (selfignited cable fires)AA 9.5 1 0

13 Plant-Wide 

Components

Dryers AA 5.5 1 3

14 Plant-Wide 

Components

Electric motors AA 6.5 4 4.5

15 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

AA 64.5 29.5 25.5

16.a Plant-Wide 

Components

HEAF for low-voltage 

electrical cabinets 

(480–1000 V)

AA 0.5 0 0

16.b Plant-Wide 

Components

HEAF for mediumvoltage electrical 

cabinets (>1000 V)

AA 1 2.5 2

16.1 Plant-Wide 

Components

HEAF for segmented 

bus ducts

AA 5 0 2

16.2 Plant-Wide 

Components

HEAF for iso-phase 

bus ducts

AA 2 0 1

17 Plant-Wide 

Components

Hydrogen tanks AA 3 1 4

18 Plant-Wide 

Components

Junction boxes AA 2 1 3

19 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

AA 4.5 0 4

20 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

BP 22.5 2.5 0
Bin Fire Ignition Frequency Estimation

4-6

21 Plant-Wide 

Components

Pumps AA 32.5 14 23

Table 4-2 (continued)

FPIE fire ignition bin identification and PRA counts for three periods

Bin Location Ignition Source Power 

Modes

FPRA Counts

1968–1989 1990–1999 2000–2009

22 Plant-Wide 

Components

RPS MG sets AP 3 3 0.5

23 Plant-Wide 

Components

Transformers AA 13 7.5 8

24 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

AP 5.975 2 3.5

25 Plant-Wide 

Components

Transients AP 3.93 3.5 6.5

26 Plant-Wide 

Components

Ventilation 

subsystems

AA 8.5 7 14

27 Transformer yard Transformer –

Catastrophic

AP 6 2 5

28 Transformer yard Transformer – Non 

Catastrophic

AP 13.5 7.5 5

29 Transformer yard Yard transformers 

(others)

AP 0 4.5 3

30 Turbine building Boiler AA 1 1 1

31 Turbine building Cable fires caused by 

welding and cutting

AP 1.5 0 0

32 Turbine building Main feedwater 

pumps

AP 11.5 5 2

33 Turbine building T/G excitor AP 5 1 0

34 Turbine building T/G hydrogen AP 7 4.5 3

35 Turbine building T/G oil AP 12.5 2.5 4

36 Turbine building Transient fires 

caused by welding 

and cutting

AP 8.74 4 3.5

37 Turbine building Transients AP 6.655 2.5 5

Applicable Power Modes

AA= all plants, all power modes; AP=all plants at power; BP=BWR plants at power; PP=PWR plants at power
Bin Fire Ignition Frequency Estimation

4-7

Table 4-3

LPSD-only bins and counts

Bin Location Ignition Source Power 

Modes

FPRA Counts

1968–1989 1990–1999 2000–2009

2 Containment 

(PWR)

Reactor coolant pump PL 3 1 1

3B Containment 

(BWR)

Transients and hotwork BL 12 5.5 2

3P Containment 

(PWR)

Transients and hotwork PL 12.5 4 21.5

5 Control/Aux/ 

Reactor Building

Cable fires caused by 

welding and cutting

AL 0 0 0

6 Control/Aux/ 

Reactor Building

Transient fires caused 

by welding and cutting

AL 7 6.5 2

7 Control/Aux/ 

Reactor Building

Transients AL 1.79 2.75 4

11 Plant-Wide 

Components

Cable fires caused by 

welding and cutting

AL 1 0.5 0

20 Plant-Wide 

Components

Off-gas/H2 recombiner 

(BWR)

BL 2 0 0

22 Plant-Wide 

Components

RPS MG Sets AL 4 0 0

24 Plant-Wide 

Components

Transient fires caused 

by welding and cutting

AL 7.025 1 3.5

25 Plant-Wide 

Components

Transients AL 1.57 1.5 1.5

27 Transformer yard Transformer –

Catastrophic

AL 3 1 0

28 Transformer yard Transformer – Non 

Catastrophic

AL 1 2 1

29 Transformer yard Yard transformers 

(others)

AL 1 1 0

31 Turbine building Cable fires caused by 

welding and cutting

AL 0 0 0

32 Turbine building Main feedwater pumps AL 1 0 0

34 Turbine building T/G hydrogen AL 1 0 0

35 Turbine building T/G oil AL 1 1 1

36 Turbine building Transient fires caused 

by welding and cutting

AL 11.76 5 14

37 Turbine building Transients AL 2.845 2 10

Applicable Power Modes

AA=all plants, all power modes; AP= all plants at power; BP= BWR plants at power; PP=PWR plants at power
Bin Fire Ignition Frequency Estimation

4-8

Bins designated as AA are applicable for both full-power initiating event and LPSD FPRA 

applications. Bins that are designated as AP, BP, or PP applicability have counterpart LPSD bins 

that are designated AL, BL, or PL, respectively. Bins with fewer than 2.5 FPRA counts in the 

2000–2009 period are the sparse bins that have been updated with data from the 1990s and 

2000s. Note that almost all sparse bins have FPRA counts in the 1990s that are greater than or 

equal to the FPRA counts in the 2000s. The exceptions are bins 16.b, 16.1, and 16.2, which do 

not have completeness-of-data concerns for the 1990s. They are considered to have all applicable 

HEAF fire events identified through the 2000s at all plants by virtue of the reporting and FAQ 

07-0035 discussion provided in Section 3. 

4.2 Estimation of Bin FIFs

The FIF distributions for at-power conditions and LPSD conditions are displayed in Table 4-4 

and Table 4-5, respectively. Tables 4-4 and 4-5 provide the bin identifier along with PRA type 

applicability. Then, the OpenBUGS derived mean, median, and 5th and 95th percentiles. Since 

the OpenBUGS results are in the form of numerical simulation data, parameters for a log-normal 

distribution that are exact fits to the mean and error factor of the numerical results have also been 

provided (mu, sigma, EF). This fit produces small differences with the median and 95th 

percentile values of the lognormal distribution compared to the OpenBUGS numerical results, 

but less than 15% in most cases. In the two cases with the largest deviation (25–30%), the 

medians of the fitted distribution overestimated the numerical results. The largest underestimate 

of the 95th percentile is less than 10%. The log-normal distribution was used because it was of 

the form of the underlying distribution used for the HB model and had better fit characteristics 

than others tested (such as gamma). The FEDB data used in the analyses are identified in 

Appendix A.
Bin Fire Igni

Table 4-4

Fire ignition frequency distributions for FPIE PRA applications

Bin Location Ignition Source Power 

Modes

PRA Type Mean Median 5th 

percent

95th 

percent

1 Battery room Batteries AA FPIE/LPSD 1.96E-04 2.97E-05 1.97E-07 7.70E-04 

2 Containment 

(PWR)

Reactor coolant 

pump

PP FPIE 1.37E-03 4.02E-04 1.68E-06 3.99E-03 

3 Containment 

(PWR)

Transients and 

hotwork (at 

power)

PP FPIE 4.21E-04 7.97E-05 4.63E-07 1.59E-03 

4 Control room Main control 

board

AA FPIE/LPSD 4.91E-03 5.69E-04 8.50E-07 1.85E-02 

5 Control/auxiliary/

reactor building

Cable fires 

caused by welding 

and cutting

AP FPIE 7.83E-04 9.75E-05 7.98E-08 2.24E-03 

6 Control/auxiliary/

reactor building

Transient fires 

caused by welding 

and cutting

AP FPIE 4.44E-03 5.75E-04 8.78E-07 1.51E-02 

7 Diesel generator 

room

Transients AP FPIE 3.33E-03 1.64E-03 1.94E-05 9.62E-03 

8 Plant-Wide

Components

Diesel generators AA FPIE/LPSD 7.81E-03 5.93E-03 4.87E-04 2.01E-02 

9 Plant-Wide 

Components

Air compressors AA FPIE/LPSD 4.69E-03 2.31E-03 1.50E-05 1.45E-02 

10 Plant-Wide 

Components

Battery chargers AA FPIE/LPSD 1.12E-03 4.06E-04 2.83E-06 3.52E-03 

4-9
Bin Fire Ignition Frequency Estimation

Table 4-4 (continued)

Fire ignition frequency distributions for FPIE PRA applications

Bin Location Ignition Source Power 

Modes

PRA Type Mean Median 5th 

percent

95th 

percent

11 Plant-Wide 

Components

Cable fires 

caused by welding 

and cutting

AP FPIE 2.77E-04 4.70E-05 4.13E-07 9.45E-04 

12 Plant-Wide 

Components

Cable run (selfignited cable fires)AA FPIE/LPSD 7.02E-04 3.31E-04 1.29E-05 2.21E-03 

13 Plant-Wide

Components

Dryers AA FPIE/LPSD 3.66E-03 1.79E-03 1.89E-05 1.13E-02 

14 Plant-Wide 

Components

Electric motors AA FPIE 5.43E-03 3.36E-03 1.15E-04 1.57E-02 

15 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

AA FPIE 3.00E-02 2.31E-02 3.72E-03 8.00E-2 

16.a Plant-Wide 

Components

HEAF for lowvoltage electrical 

cabinets (480–

1000 V)

AA FPIE/LPSD 1.52E-04 1.99E-05 1.28E-07 5.89E-04 

16.b Plant-Wide 

Components

HEAF for 

medium-voltage

electrical cabinets 

(>1000 V)

AA FPIE/LPSD 2.13E-03 1.35E-03 5.36E-05 5.93E-03 

16.1 Plant-Wide 

Components

HEAF for 

segmented bus 

ducts

AA FPIE/LPSD 1.10E-03 4.70E-04 1.97E-06 3.11E-03 

16.2 Plant-Wide 

Components

HEAF for isophase bus ductsAA FPIE/LPSD 5.91E-04 1.86E-04 1.60E-06 1.93E-03 

4-10
Bin Fire Igni

Table 4-4 (continued)

Fire ignition frequency distributions for FPIE PRA applications

Bin Location Ignition Source Power 

Modes

PRA Type Mean Median 5th 

percent

95th 

percent

17 Plant-Wide 

Components

Hydrogen tanks AA FPIE/LPSD 4.93E-03 6.95E-04 1.37E-06 1.85E-02 

18 Plant-Wide 

Components

Junction boxes AA FPIE/LPSD 3.61E-03 1.62E-03 8.77E-06 1.13E-02 

19 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

AA FPIE/LPSD 4.82E-03 2.57E-03 3.89E-05 1.46E-02 

20 Plant-Wide 

Components

Off-gas/H2

recombiner 

(BWR)

BP BP 5.81E-03 3.57E-03 1.60E-04 1.72E-02 

21 Plant-Wide 

Components

Pumps AA FPIE/LPSD 2.72E-02 2.49E-02 8.85E-03 5.13E-02 

22 Plant-Wide 

Components

RPS MG sets AP FPIE 2.31E-03 5.09E-04 1.96E-06 7.92E-03 

23 Plant-Wide 

Components

Transformers AA FPIE/LPSD 9.56E-3 5.29E-03 1.55E-04 3.05E-02 

24 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

AP FPIE 4.79E-03 3.07E-03 1.61E-04 1.36E-02 

25 Plant-Wide 

Components

Transients AP FPIE 8.54E-03 6.62E-03 9.35E-04 2.07E-02 

26 Plant-Wide 

Components

Ventilation 

subsystems

AA FPIE/LPSD 1.64E-02 1.16E-02 1.06E-03 4.68E-02 

27 Transformer yard Transformer –

Catastrophic

AP FPIE 6.61E-03 4.18E-03 1.35E-04 1.96E-02 

4-11
Bin Fire Ignition Frequency Estimation

Table 4-4 (continued)

Fire ignition frequency distributions for FPIE PRA applications

Bin Location Ignition Source Power 

Modes

PRA Type Mean Median 5th 

percent

95th 

percent

28 Transformer yard Transformer –

Non Catastrophic

AP FPIE 6.53E-03 4.40E-03 1.94E-04 1.85E-02 

29 Transformer yard Yard transformers 

(others)

AP FPIE 3.69E-03 1.07E-03 1.86E-06 1.24E-02 

30 Turbine building Boiler AP FPIE/LPSD 1.09E-03 4.12E-04 2.89E-06 3.37E-03 

31 Turbine building Cable fires 

caused by welding 

and cutting

AA FPIE 3.47E-04 6.96E-05 6.02E-07 1.16E-03 

32 Turbine building Main feedwater 

pumps

AP FPIE 4.38E-03 2.54E-03 8.98E-05 1.35E-02 

33 Turbine building T/G excitor AP FPIE 8.36E-04 2.52E-04 1.31E-06 2.74E-03 

34 Turbine building T/G hydrogen AP FPIE 4.12E-03 1.84E-03 9.14E-06 1.29E-02 

35 Turbine building T/G oil AP FPIE 5.49E-03 3.05E-03 6.33E-05 1.66E-02 

36 Turbine building Transient fires 

caused by welding 

and cutting

AP FPIE 4.67E-03 2.71E-03 7.30E-05 1.38E-02 

37 Turbine building Transients AP FPIE 6.71E-03 4.51E-03 1.31E-04 1.83E-02 

4-12
Bin Fire Igni

Table 4-5

Fire ignition frequency distributions for LPSD PRA applications

Bin Location Ignition Source Power 

Modes

PRA 

Type

Mean Median 5th 

percent

95th 

percent

2 Containment 

(PWR)

Reactor coolant pump PL LPSD 1.17E-02 3.65E-03 9.97E-06 3.87E-02 

3B Containment 

(BWR)

Transients and hotwork BL LPSD 6.69E-02 4.82E-02 2.77E-03 1.91E-01 

3P Containment 

(PWR)

Transients and hotwork PL LPSD 3.76E-01 3.30E-01 8.75E-02 8.13E-01 

5 Control/Aux/ 

Reactor Building

Cable fires caused by 

welding and cutting

AL LPSD 8.94E-04 7.97E-05 6.61E-07 2.91E-03 

6 Control/Aux/ 

Reactor Building

Transient fires caused by 

welding and cutting

AL LPSD 2.68E-02 1.93E-02 1.80E-03 7.19E-02 

7 Control/Aux/ 

Reactor Building

Transients AL LPSD 5.62E-02 1.59E-02 2.63E-05 1.91E-01 

11 Plant-Wide 

Components

Cable fires caused by 

welding and cutting

AL LPSD 2.07E-03 5.08E-04 4.36E-06 6.63E-03 

20 Plant-Wide 

Components

Off-gas/H2 recombiner 

(BWR)

AL LPSD 3.82E-03 6.24E-04 3.48E-06 1.33E-02 

22 Plant-Wide 

Components

RPS MG sets BL LPSD 1.10E-03 1.66E-04 1.32E-06 3.76E-03 

24 Plant-Wide 

Components

Transient fires caused by 

welding and cutting

AL LPSD 4.48E-02 3.12E-02 1.65E-03 1.25E-01 

25 Plant-Wide 

Components

Transients AL LPSD 9.40E-03 5.38E-03 1.13E-04 2.76E-02 

27 Transformer yard Transformer – Catastrophic AL LPSD 4.82E-03 1.11E-03 9.43E-06 1.46E-02 

4-13
Bin Fire Ignition Frequency Estimation

Table 4-5 (continued)

Fire ignition frequency distributions for LPSD PRA applications

Bin Location Ignition Source Power 

Modes

PRA 

Type

Mean Median 5th 

percent

95th 

percent

28 Transformer yard Transformer – Non 

Catastrophic

AL LPSD 9.43E-03 4.10E-03 1.42E-05 2.86E-02 

29 Transformer yard Yard transformers (others) AL LPSD 3.55E-03 1.04E-03 4.86E-06 1.17E-02 

31 Turbine building Cable fires caused by 

welding and cutting

AL LPSD 9.09E-04 8.21E-05 6.08E-07 3.01E-03 

32 Turbine building Main feedwater pumps AL LPSD 1.12E-03 1.37E-04 1.16E-06 4.03E-03 

34 Turbine building T/G hydrogen AL LPSD 1.12E-03 1.37E-04 1.16E-06 4.03E-03 

35 Turbine building T/G oil AL LPSD 6.89E-03 2.31E-03 8.84E-06 2.27E-02 

36 Turbine building Transient fires caused by 

welding and cutting

AL LPSD 1.92E-01 1.30E-01 1.10E-02 5.66E-01 

37 Turbine building Transients AL LPSD 1.28E-01 1.04E-01 1.75E-02 2.97E-01 

4-14
Bin Fire Ignition Frequency Estimation

4-15

The results of the FPIE fire bin frequency estimates in comparison to the NUREG/CR-6850 

Supplement 1 [2] recommended FIFs are shown in Figure 4-2. In aggregate, the updated fire 

frequency results are higher than the NUREG/CR-6850 Supplement 1 results by 36%. This is 

primarily due to the difference in how the data from the 1990s were used in each analysis. 

Specifically, the update performed in this report did not apply data from the 1990s that had 

strong evidence of an incompleteness bias based on analyses and discussions presented in 

Section 3.

Figure 4-2

Comparison of bin fire ignition frequencies using recent FEDB updated data (new FEDB) 

to values provided in NUREG/CR-6850, Supplement 1 [5]

Table 4-6 provides a numerical tabulation and comparison between this update and the previous 

FIF estimates from NUREG/CR-6850, Supplement 1. There are some substantial differences; 

however, they are not larger than the estimated uncertainties. Typically, there are fewer FPRA 

event counts in the 1990s than the 2000s, but there are fewer applicable reactor years in the 

2000s. This combination is a primary contributor to the difference in the mean of the two

estimates. The uncertainty is much larger for the current updated estimate, which is primarily 

due to the methodology used in the update.

0.0E+00

5.0E-03

1.0E-02

1.5E-02

2.0E-02

2.5E-02

3.0E-02

3.5E-02

123456789

101112131415

 16.a

 16.b

16.116.2

171819202122232425262728293031323334353637

Mean (updated FEDB, HBDEP-3)

Mean (NUREG/CR-6850, Supplement 1)
Bin Fire Ignition Frequency Estimation

4-16

Table 4-6

FPIE bin fire frequency comparisons to previous estimates

Bin Location Ignition Source Power 

Modes

Fire Ignition Frequency

Updated 

FEDB

NUREG/

CR-6850, 

Supplement 1

1 Battery room Batteries AA 1.96E-04 3.26E-04

2 Containment (PWR) Reactor coolant pump PP 1.37E-03 2.35E-03

3 Containment (PWR) Transients and hotwork 

(at power)

PP 4.21E-04 2.34E-03

4 Control Room Main control board AA 4.91E-03 8.24E-04

5 Control/Auxiliary/ Reactor 

Building

Cable fires caused by 

welding and cutting

AP 7.83E-04 1.25E-03

6 Control/Auxiliary/ Reactor 

Building

Transient fires caused by 

welding and cutting

AP 4.44E-03 2.46E-03

7 Control/Auxiliary Reactor 

Building

Transients AP 3.33E-03 4.81E-03

8 Diesel Generator Room Diesel generators AA 7.81E-03 5.04E-03

9 Plant-Wide Components Air compressors AA 4.69E-03 4.65E-03

10 Plant-Wide Components Battery chargers AA 1.12E-03 1.18E-03

11 Plant-Wide Components Cable fires caused by 

welding and cutting

AP 2.77E-04 9.43E-04

12 Plant-Wide Components Cable run (self-ignited cable 

fires)

AA 7.02E-04 1.32E-03

13 Plant-Wide Components Dryers AA 3.66E-03 4.20E-04

14 Plant-Wide Components Electric motors AA 5.43E-03 3.41E-03

15 Plant-Wide Components Electrical cabinets 

(non-HEAF)

AA 3.00E-02 2.36E-02

16.a Plant-Wide Components HEAF for low-voltage 

electrical cabinet 

(480-1000 V)

AA 1.52E-04 4.80E-04

16.b Plant-Wide Components HEAF for medium-voltage 

electrical cabinet (>1000 V)

AA 2.13E-03 1.40E-03

16.1 Plant-Wide Components HEAF for segmented bus 

duct

AA 1.10E-03 1.27E-03

16.2 Plant-Wide Components HEAF for iso-phase bus duct AA 5.91E-04 8.24E-04

17 Plant-Wide Components Hydrogen tanks AA 4.93E-03 1.18E-03

18 Plant-Wide Components Junction boxes AA 3.61E-03 1.11E-03

19 Plant-Wide Components Miscellaneous hydrogen fires AA 4.82E-03 1.24E-03

20 Plant-Wide Components Off-gas/H2 recombiner 

(BWR)

BP 5.81E-03 8.83E-03
Bin Fire Ignition Frequency Estimation

4-17

Table 4-6 (continued)

FPIE bin fire frequency comparisons to previous estimates

Bin Location Ignition Source Power 

Modes

Fire Ignition Frequency

Updated 

FEDB

NUREG/

CR-6850, 

Supplement 1

21 Plant-Wide Components Pumps AA 2.72E-02 1.42E-02

22 Plant-Wide Components RPS MG sets AP 2.31E-03 9.33E-04

23 Plant-Wide Components Transformers AA 9.56E-03 8.02E-03

24 Plant-Wide Components Transient fires caused by 

welding and cutting

AP 4.79E-03 3.65E-03

25 Plant-Wide Components Transients AP 8.54E-03 8.28E-03

26 Plant-Wide Components Ventilation subsystems AA 1.64E-02 6.12E-03

27 Transformer yard Transformer – Catastrophic AP 6.61E-03 1.62E-03

28 Transformer yard Transformer – Non 

Catastrophic

AP 6.53E-03 8.38E-03

29 Transformer yard Yard transformers (others) AP 3.69E-03 1.89E-03

30 Turbine building Boiler AA 1.09E-03 9.78E-04

31 Turbine building Cable fires caused by 

welding and cutting

AP 3.47E-04 4.50E-04

32 Turbine building Main feedwater pumps AP 4.38E-03 5.44E-03

33 Turbine building T/G excitor AP 8.36E-04 2.10E-03

34 Turbine building T/G hydrogen AP 4.12E-03 3.23E-03

35 Turbine building T/G oil AP 5.49E-03 3.89E-03

36 Turbine building Transient fires caused by 

welding and cutting

AP 4.67E-03 7.55E-03

37 Turbine building Transients AP 6.71E-03 3.41E-03

FPIE Frequency Totals 2.06E-01 1.51E-01

Results Comparison Categories

> 100% increase from EPRI 1016735

50–100% increase from EPRI 1016735

25% to <50% increase from EPRI 1016735

-50% or more reduction from EPRI 1016735

25% to <50% reduction from EPRI 1016735

Power Modes: AA=all plants, all modes; AP=all plants at power; BP=BWR plants at power; PP=PWR plants at 

power
Bin Fire Ignition Frequency Estimation

4-18

There are eight bins with FIF increases greater than a factor of two, the largest being dryers 

(bin 13) with a factor of about nine. One of the more important bins involves main control 

board (bin 4) fires. It has an increase of about a factor of six. Hydrogen fires (bin 17 and bin 34) 

also showed significant increases. One particularly notable result is bin 15, which has been a 

risk-significant contributor in many FPRAs. It is the largest contributor to the total FIF. It has a 

similar FPRA event count in the 1990s and 2000s, but there are fewer applicable reactor years in 

the 2000s, as noted previously. Again, the difference in the two estimates is well bounded by the 

uncertainty.

Notable decreases in FIFs were obtained for transients and hotwork inside PWR containments 

at power (bin 3), with none reported in the last 20 years of data; plantwide cable fires caused by 

welding and cutting (bin 11); low-voltage (480–1000V) HEAF (bin 16.a); and T/G-related (bin 

33) fires. It is also notable that the self-ignited cable run fire bin had a decrease by nearly a factor 

of two—only one such fire event was included in the last 20 years of the data. The differences in 

the rest of the fire ignition bins are smaller. Nonetheless, the differences observed between the 

NUREG/CR-6850 Supplement 1 FIFs and the current updated values are of limited significance 

with regard to trending due to the fire event data completeness issues for the data from the 1990s, 

as discussed in Section 3.

A review of the split fractions by FIF bin was completed as part of the recalculation process. The 

split fractions were reviewed against those reported in NUREG/CR-6850 [1]. All but one split 

fraction was deemed to be representative of the NUREG/CR-6850 reported values. One 

discrepancy was noted—pumps (bin 21) had a split fraction of 0.54 electrical and 0.46 oil 

in Reference 1. Combining the legacy NUREG/CR-6850 experience with the updated FEDB 

experience, the new Bayesian estimate is 0.69 electrical and 0.31 oil. Although the new split 

fraction has a smaller percentage of oil fires, the split fraction provided in NUREG/CR-6850 is 

bounding as more risk would be going toward the more challenging oil fires.
5-1

5

NON-SUPPRESSION PROBABILITY

5.1 NSP Methodology

The following description of the fire NSP methodology is a condensed and minimally edited 

description of the NSP methodology derived from NUREG/CR-6850 Supplement 1 [2], 

FAQ 08-0050.

Figure 5-1 shows the conceptual relationship between the fire start time, fire detection time, and 

fire suppression time. The detection time (Tdet) is the time interval from the start of the fire up to 

the time when the fire is initially detected. The suppression time (Tsupp) is the time interval from

when the fire is detected until it is suppressed. The time from fire detection until the fire brigade 

begins to apply suppressant agents (Tfb) is also noted. 

As discussed in NUREG/CR-6850, EPRI 1011989, the probability of non-suppression by time t, 

Pns(t), is given by

Pns(t) = Pr(Tsupp ≥ t)

Note that in accordance with the revised methodology described in NUREG/CR-6850 

Supplement 1, the fire brigade response time is already included in the distribution for Tsupp. 

This definition of time available to suppress the fire differs from NUREG/CR-6850 in that it 

does not require an adjustment for Tfb (the fire brigade response time).

Figure 5-1

Conceptual relationship between the fire detection time, suppression time, and fire 

brigade response time
Non-Suppression Probability

5-2

FAQ 08-0050 resolution provided clarification and revised guidance for the estimation of Pns(t). 

It re-estimated the industry average response for the fire suppression time and associated fire 

NSP, and it provided a new model to account for plant-specific fire brigade response 

adjustments. This update addresses only the reassessment of the non-suppression curves used for 

industry average fire suppression response (NSP curves) for the 11 fire suppression groups and 

the overall fire non-suppression curve. In addition, a new fire suppression group was added for 

fires that occur inside containment during LPSD plant conditions. The following suppression 

probability categories have been developed:

• Transients. All transient events not specified as belonging to any of the following categories 

were used. 

• Welding. Welding events are usually labeled “transient fires caused by welding and cutting” 

or “cable fires caused by welding and cutting.” This curve should be used for calculating the 

probability of prompt suppression.

• Electrical. This data set contains events involving electrical cabinets, electric motors, indoor 

transformers, and junction boxes, among other electrical equipment. Electrical events in the 

control room, transformer yard, and T/G excitor bins were excluded. Note that events 

including overheated electrical equipment, such as bearings due to lack of lubricating oil, 

were included in this set. Events labeled as high-energy arcing faults were not included in 

this curve.

• Cable. This category refers to cables in raceways. Extension cord–related fires were included 

in the transient data set. Events describing wiring or cable fires inside cabinets or other 

electrical equipment were included in the electrical data set. Records with insufficient details, 

simply reporting a “cable/wiring” fire, were included in this cable data set.

• Oil. The oil data set includes all the events in which a lubricating substance was ignited.

• Flammable gas. This data set includes only events involving hydrogen fires. Fires and 

explosions in off-gas/H2 recombiners are also included.

• Transformer yard. This data set includes events labeled as transformer yard. As previously 

mentioned, events suppressed by fixed fire suppression system only were excluded. Events in 

which the fire brigade decided to let the fire burn out were also excluded from the set.

• Containment PWR. A separate curve is developed for the PWR containment at power. It is 

considered that fire brigade access to the building in the event of a fire is relatively different 

from other locations in the plant. Events in this data set include all the ignition source bins in 

the containment (PWR) location for at power conditions.

• Containment (LPSD). This is a new containment suppression curve category that applies to 

LPSD only conditions. It would be applicable when the containment is open to maintenance 

and operations staff when the reactor is not at power. It primarily includes hotwork of all 

types but can include electrical or other in-containment fires. It applies to both PWRs and 

BWRs.

• Control room. Events in this bin are the ones labeled Control Room/Electrical Cabinets or 

other fires occurring within the control room location. 
Non-Suppression Probability

5-3

• Turbine-generator. Events in this set include the ones labeled as T/G oil, T/G hydrogen, 

and T/G excitor. Some of the T/G hydrogen events were excluded from the data set because 

they were suppressed with an automatic system.

• HEAFs. These includes events labeled as high-energy arcing faults.

• All events. This data set includes all events that were not considered as “prompt 

suppression” cases. The purpose of this data set is to generate a generic suppression time 

probability curve that may be used for those cases where the analyst cannot find a proper 

match from the preceding list of categories.

The probability that the fire brigade or other first responders failing to suppress the fire 

[Pr(Tsupp ≥ t)] is estimated with suppression probability curves developed using the suppression 

time data reported in the FEDB. The data used for this analysis are provided in Appendix A. 

They include the same data used in NUREG/CR-6850 Supplement 1 updated with a few 

corrections and additional data from the 1990–2009 period. Fire events before 1/1/1981 were 

excluded from the manual NSP curves. This is the date when Appendix R of 10 CFR Part 50 

was issued. The curves were developed using events where manual suppression was involved 

and suppression time information was available. Suppression time was defined as the time the 

fire was extinguished or the time the fire was reported to have been brought under control by the 

fire brigade on scene. Events including self-extinguished fires, supervised burnouts, and fires 

extinguished with automatic fire suppression systems were excluded from the curves. If the time 

from detection to suppression was not known but the duration of the fire event from start to 

suppression was known, the reported fire duration was used instead.

The mathematical model to derive Pr(Tsupp ≥ t) is described in NUREG/CR-6850 as follows:

The data for analysis consists of reported fire durations in commercial U.S. NPPs. These 

times are treated as being generated by an underlying probabilistic model. The final 

output of interest is the suppression curve, which gives the probability that a fire lasts 

longer than a specified time. If T is the random variable describing when the fire is 

suppressed, and λ(t) is the rate at which the fire is suppressed (possibly time-dependent), 

this probability of non-suppression is given by: 

t

Pr(T>t)= exp(−∫ λ (s)ds)

0

In this equation, λ(t) is a function of the parameters of the probabilistic model chosen 

for T. The simplest model for T is the exponential distribution, whose probability density 

function is:

f (t) = λe −λt 

In this model, λ is estimated directly and is not a function of time, giving

Pr(T > t ) = e −λt 

The non-suppression probability is calculated using the above equation, usually selecting 

t as the time to target damage.

The same mathematical model has been used in this report unless otherwise noted.
Non-Suppression Probability

5-4

5.2 NSP Estimation Update

The update of the NSP curves for Pr(Tsupp ≥ t) for the 12 fire suppression categories plus the 

overall industry average curves are represented by the summary data, and non-suppression curve 

parameters are provided in Table 5-1. The numerical values of the non-suppression curve 

probabilities are provided in Table 5-2. A cutoff or 0.001 in NSP has been used, consistent with 

the guidance of NUREG/CR-6850, Supplement 1. The uncertainty in the NSPs is given by the 

uncertainty in the mean of the non-suppression parameter estimates for λ, also in a manner 

consistent with NUREG/CR-6850, Supplement 1. The results for NSP curves are also shown 

graphically in Figure 5-2.

Table 5-1

Probability distribution for rate of fires suppressed per unit time, λ (Originally, Table P-2 

from NUREG/CR-6850)

Suppression Curve Number 

of Events 

in Curve

Total 

Duration

(minutes)

Rate of Fire Suppressed (λ)

Mean 5th 

Percent

50th 

Percent

95th 

Percent

T/G fires 30 1167 0.026 0.019 0.025 0.034

Control room 12 37 0.324 0.187 0.315 0.492

PWR containment (AP) 3 40 0.075 0.020 0.067 0.157

Containment (LPSD) 31 299 0.104 0.075 0.103 0.136

Outdoor transformers 24 928 0.026 0.018 0.026 0.035

Flammable gas 8 234 0.034 0.017 0.033 0.056

Oil fires 50 562 0.089 0.069 0.088 0.111

Cable fires 4 29 0.138 0.047 0.127 0.267

Electrical fires 177 1815 0.098 0.086 0.097 0.110

Welding fires 52 484 0.107 0.084 0.107 0.133

Transient fires 43 386 0.111 0.085 0.111 0.141

HEAFs 8 602 0.013 0.007 0.013 0.022

All fires 442 6583 0.067 0.062 0.067 0.072
No

Table 5-2

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

(min)

Time T/G 

fires

HEAFs Outdoor 

transformers

Flammable 

gas

Oil 

fires

Electrical 

fires

Transient 

fires

PWR 

containment

(AP)

Containment

(LPSD)

Weld

0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 

5 0.879 0.936 0.879 0.843 0.641 0.614 0.572 0.687 0.595 0.58

10 0.773 0.876 0.772 0.710 0.411 0.377 0.328 0.472 0.355 0.34

15 0.680 0.819 0.678 0.599 0.263 0.232 0.188 0.325 0.211 0.20

20 0.598 0.767 0.596 0.505 0.169 0.142 0.108 0.223 0.126 0.11

25 0.526 0.717 0.524 0.425 0.108 0.087 0.062 0.153 0.075 0.06

30 0.462 0.671 0.460 0.359 0.069 0.054 0.035 0.105 0.045 0.04

35 0.407 0.628 0.404 0.302 0.044 0.033 0.020 0.072 0.027 0.02

40 0.358 0.588 0.355 0.255 0.028 0.020 0.012 0.050 0.016 0.01

45 0.314 0.550 0.312 0.215 0.018 0.012 0.007 0.034 0.009 0.00

50 0.277 0.515 0.274 0.181 0.012 0.008 0.004 0.024 0.006 0.00

55 0.243 0.481 0.241 0.153 0.007 0.005 0.003 0.016 0.003 0.00

60 0.214 0.451 0.212 0.129 0.005 0.003 0.002 0.011 0.002 0.00

65 0.188 0.422 0.186 0.108 0.003 0.002 * 0.008 0.001 0.00

70 0.165 0.394 0.164 0.091 0.002 0.001 * 0.005 * * 

75 0.145 0.369 0.144 0.077 0.001 * * 0.004 * * 

80 0.128 0.345 0.126 0.065 * * * 0.002 * * 

85 0.112 0.323 0.111 0.055 * * * 0.002 * * 

90 0.099 0.302 0.098 0.046 * * * 0.001 * * 

95 0.087 0.283 0.086 0.039 * * * * * * 

100 0.076 0.265 0.075 0.033 * * * * * * 
Non-Suppression Probability

5-6

Figure 5-2

Non-suppression curve plots: probability vs. time to suppression

Note that the data for the PWR containment suppression curve group include only three fire 

suppression events. There were no fire events identified for this fire suppression curve after 1994 

in NUREG/CR-6850, Supplement 1, and no new fire events with suppression time data were 

included in the 2000s FEDB data. Another small fire suppression data group involved cable fires. 

This group has only four recorded manual fire suppression events, all of which occurred before 

1990.

The fire suppression curves were developed from 442 FPRA applicable events for which 

suppression time information was available. There were 108 PRA countable fire events from the 

1990s and 2000s data that had insufficient details to estimate a fire suppression time. Fire events 

with undetermined suppression times from the pre-1990 timeframe were also excluded from the 

NUREG/CR-6850, Supplement 1 suppression data and were not reviewed to ascertain their 

count in this project. There were 22 self-extinguished fires and three supervised burnouts in the 

PRA countable fire suppression events for the 1990s and 2000s data that were not used to derive 

fire NSPs, consistent with the practice used in NUREG/CR-6850, Supplement 1.

5.3 NSP Sensitivity and Supplemental Considerations

For comparison, the mean of the NSP rate parameter, λ, from NUREG/CR-6850, Supplement 1, 

and this update are provided in Table 5-3. Although the overall NSP curve is very similar and 

most individual curves are similar given the limited data for many of the curves, there is one 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Probability of Nonsuppression

Time in Minutes

Control Room

Cable

Welding

Transients

Containment LPSD

Electrical

Oil

Containment AP

All

Flammable Gas

Transformer Yard

Turbine Generator

HEAF
Non-Suppression Probability

5-7

notable difference—a marked increase in the mean suppression time (smaller suppression rate) 

for the welding curve. An examination of the longer-duration welding fires did not indicate a 

consistent reason for this increase.

Table 5-3

Comparisons of the mean NSP rate parameter, λ , from NUREG/CR-6850, Supplement 1, 

and updated suppression rates (λ)

NUREG/CR-6850, 

Supplement 1

Updated FEDB Analysis

Suppression 

Curve

Number 

Supplement 1 

Events/ 

Updated 

Events

Total 

Suppression 

Time

(minutes)

Mean 

Suppression 

Rate [/min]

Updated 

Total 

Suppression 

Time

(minutes)

Updated Mean 

Suppression 

Rate [/min]

T/G fires 21/30 846 0.025 1167 0.026

Control room 6/12 18 0.33 37 0.324

PWR 

containment (AP)

3/3 40 0.075 40 0.075

Containment 

(LPSD)

N/A/31 N/A N/A 299 0.104

Outdoor 

transformers

14/24 390 0.036 928 0.026

Flammable gas 5/8 197 0.025 234 0.034

Oil fires 36/50 474 0.076 562 0.089

Cable fires 5/4 31 0.161 29 0.138

Electrical fires 113/177 1113 0.102 1815 .098

Welding fires 18/52 106 0.188 484 0.107

Transient fires 22/42 174 0.126 386 0.111

HEAFs 3/8 276 0.011 602 0.013

All fires 246/442 3655 0.067 6583 0.067

For both the electrical and all-fire suppression curve categories, two other NSP curve distribution 

functions were examined—log-normal and two-parameter Weibull. The log-normal had a better 

overall fit to the data, producing somewhat lower NSP values in the 5-minute to about 30-minute 

time frame, but it had a much more substantial NSP tail. During a review of the NSP data, 

questions were raised regarding the correctness of using some of the very long-duration fire 

suppression times in the development of the NSP curves. The use of an exponential probability 

distribution ameliorates this issue somewhat. However, it also produces sometimes notably 

higher NSP values in the 5- to 30-minute time frame.

6-1

6

OBSERVATIONS AND CONCLUSIONS

Several key observations and results are described in this section.

6.1 Fire Event Data

Fire event data collected for the 2000–2009 period are believed to be the most complete and 

accurate data for characterizing fire events and estimating fire ignition frequencies for U.S. 

FPRAs. The data from this period were collected in a uniform manner and underwent extensive 

review for fire severity classification, ignition frequency binning, and suppression analysis. 

Fire event data exhibit a discontinuity for the period 1990–1999 that is statistically significant. 

That anomaly may actually start a year or two earlier, but the detailed level of determination has 

not been attempted. The discontinuity appears to be related to the nature of the fire event data 

sources and completeness of the collection of the potentially challenging fires in the 1990s. 

The 1990s has a smaller occurrence rate for reported fire events than either the earlier or later 

time periods, and this difference is statistically significant. This supports but does not confirm 

the more qualitative observation cited previously that the completeness of the fire data for the 

1990s is highly questionable and that the data might be missing some fire events important to the 

determination of FIF.

The overall fire occurrence frequency for full-power PRA bins combined has declined since the 

1970s and 1980s by about 39%. This difference in the fire occurrence rate between the 1968–

1989 and 2000–2009 periods is statistically significant. No attempt was made to correlate this 

decrease in frequency to improvements in fire protection regulations or plant practices.

Bins with fewer than 2.5 fires in the 2000s had a lower overall fire occurrence rate in the 2000s 

than the 1990s. Although the statistical significance could not be established for individual bins 

due to the small data population of each bin, in just about every case, the fire counts in the 2000s 

were less than the 1990s for sparse bins only. The exceptions involved medium-voltage electrical 

cabinet HEAF and bus duct HEAF bins with known fire event counts from all plants in both the 

1990s and 2000s.

The rate of fires during shutdown increased significantly (by nearly 300%) in 2000–2009 in 

comparison to earlier periods, when these rates are expressed as fires per shutdown reactor year. 

The number of such fires was roughly consistent with the earlier data, but the time spent in 

shutdown was shorter in the most recent period, leading to higher calculated fire frequencies per 

shutdown reactor year.
Observations and Conclusions

6-2

6.2 Fire Ignition Frequency

The methodology used to estimate the updated FIFs for the individual FPRA bins is essentially 

the same as that developed in the EPRI report An Improved Methodological Approach for 

Estimating Fire Ignition Frequencies (1022994) [7]. The only change was to use a more diffuse 

prior with hyperprior parameter σmed=3 for the medium-density and high-density bins with 2.5 or 

more PRA fire counts in the 2000–2009 period. This prior weights the data from the update 

period more than the original proposal using σmed=1.3 and produces a slightly larger error factor 

(uncertainty). However, it is now consistent with the hyperprior specification for the sparse bins 

with fewer than 2.5 PRA fire counts. The revised methodology provides very similar fire 

frequency estimates to the original proposal. See EPRI 102294 [7] for insights from sensitivities 

performed for variations prior models.

The updated fire ignition frequencies for full-power PRA applications had an overall increase 

from the revised fire frequencies in NUREG/CR-6850, Supplement 1, of 36%. However, the 

results varied considerably for individual bins, including the following:

• Notable increases in eight bins, ranging from a factor of two to nine (largest increase for 

dryers)

• Notable decreases in four bins, ranging from a factor of two to four decrease

• Variations of less significance for the remaining bins

The data used to estimate fire frequencies consisted of fire events with significant variation in the 

magnitude and consequence of fires, including many relatively low-severity fire events that did 

not grow vigorously but still were deemed to be potentially challenging in the context of FPRA. 

6.3 Fire Non-Suppression Probabilities

Fire non-suppression methodology from NUREG/CR-6850, Supplement 1, was used to derive 

updated fire suppression curves using the data from that report supplement with newer and 

updated fire event data from the FEDB. The plant-specific correction factor for fire brigade 

response time was not addressed in this report because it is not dependent on updating the fire 

suppression time data.

One new fire suppression curve category was created to address the suppression of fire events 

inside containment during plant shutdown periods for both PWRs and BWRs, designated 

containment (LPSD). The data for this bin were primarily associated with hotwork fires and 

transients that would be expected to occur only during shutdown conditions.

Several fire suppression curves are derived with very small data sets. These include the PWR 

containment fire suppression curve group, which has only three recorded fire events, all of which 

occurred before 1995. Another is the cable fire suppression curve group, which has only four 

recorded manual fire suppression events that all occurred before 1990.
Observations and Conclusions

6-3

6.4 Future Research

To maintain a sustainable and consistent process of gathering future fire event data, the Institute 

of Nuclear Power Operations (INPO), is collecting events in their INPO Consolidated Event 

System (ICES). It is envisioned that this process will help streamline the effort required to 

produce fire frequencies on a more frequent basis to support risk-informed, performance based 

fire protection programs. 

The new EPRI updated FEDB, containing reference event reports, captures more details and 

fire attributes than prior releases of the database. Future research can benefit from this expanded 

information by evaluating data from the FEDB against existing assumptions and methods. The 

current effort was focused on updating the current fire frequency bins with an enhanced 

methodology and updated fire event data. No changes (for example, further subdivisions) 

were considered for binning of fire events. Future evolution of frequency and NSP estimation 

can benefit from insights from recent fire events and changes in methodology and binning. 

A preliminary review of the electrical cabinet fires over the past 20 years of experience has 

demonstrated that it would be feasible to break bin 15 into smaller subcategories. This bin has 

the highest PRA count out of all bins and is often a current driver for plant risk. Future revisions 

should evaluate subdividing bin 15 to better characterize plant risk and reflect fire event trends 

more accurately in the future.

The frequencies in this report, like the original frequencies, are plant-based. This can cause 

redistribution of frequencies if components are added or removed. Moving toward a componentbased approach eliminates the need for counting and redistribution when plant equipment 

changes occur. The first steps in moving to component-based fire frequencies include a 

feasibility and methodology exploration as well as understanding the variability of fixed ignition 

source counts from plant to plant. 

The review of fire suppression events suggests that many fire events are rapidly suppressed by 

personnel other than the fire brigade. Differentiating the suppression curves into two curves 

based on extinguishing roles—that is, plant personnel versus fire brigade—may provide further 

enhancement to the non-suppression methodology. Research to improve the methodology based 

on separating fire severity classifications (potentially challenging versus challenging fire events) 

is also being investigated.

7-1

7

REFERENCES

1. EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities. EPRI, Palo Alto, CA, 

and U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research (RES), 

Rockville, MD: 2005. EPRI 1011989 and NUREG/CR-6850.

2. Fire Probabilistic Risk Assessment Methods Enhancements: Supplement 1 to NUREG/CR6850 and EPRI 1011989. EPRI, Palo Alto, CA, and NRC, Washington, D.C.: December 

2009. 1019259.

3. The Updated Fire Events Database: Description of Content and Fire Event Classification 

Guidance. EPRI, Palo Alto, CA: 2013. 1025284. 

4. Methodology for Low Power/Shutdown Fire PRA. U.S. Nuclear Regulatory Commission, 

Office of Nuclear Regulatory Research (RES), Rockville, MD: December 2011. 

NUREG/CR-7114.

5. Fire PRA Methods Enhancements: Additions, Clarifications, and Refinements to EPRI 

1011989. EPRI, Palo Alto, CA: 2008. 1016735.

6. Baranowsky et al., Applying Hierarchical Bayes Methods to Fire Ignition Frequency 

Estimation, ANS PSA 2011 International Topical Meeting on Probabilistic Safety 

Assessment and Analysis, Wilmington, NC: March 2011.

7. An Improved Methodological Approach for Estimating Fire Ignition Frequencies. EPRI, Palo 

Alto, CA: 2011. 1022994.

8. Development of Metric Monitoring Methodologies. Nuclear Regulatory Commission, Office 

of Nuclear Regulatory Research (RES), Rockville, MD: March 2012. ML112700482.

9. Rates of fires event at U.S. Nuclear Power Plants 1987–2011. U.S. Nuclear Regulatory 

Commission. Available from http://nrcoe.inel.gov/resultsdb/publicdocs/Fire/fire-eventssummary-2011.pdf.

10. C. Atwood et al., Handbook of Parameter Estimation for Probabilistic Risk Assessment. U.S. 

Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, Rockville, MD: 

September 2003. NUREG/CR-6823.

11. OpenBUGS website, http://www.openbugs.info/w/FrontPage.

Appendix A

DATA FROM THE FEDB

Data 

A-1

Table A-1

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

on Tim

8 5/7/2000 Transformer 

Yard

Yard transformers 

(others)

PO PC 29 Excluded 30 

100 5/15/2000 Plant-Wide 

Components

HEAF segmented 

bus duct

PO CH 16.1 HEAF 78 

101 9/3/2000 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 29

106 2/3/2001 Plant-Wide 

Components

HEAF mediumvoltage electrical 

cabinet (>1000 V)

PO CH 16.b HEAF 154

109 4/24/2001 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 2

111 8/2/2001 Transformer 

Yard

Transformer –

Catastrophic

PO CH 27 Excluded 22 

112 8/3/2001 Plant-Wide 

Components

HEAF mediumvoltage electrical 

cabinet (>1000 V)

PO PC 16.b HEAF 90 

113 6/12/2002 Transformer 

Yard

Yard transformers 

(others)

PO CH SB4 Excluded 46 

114 8/21/2002 Plant-Wide 

Components

Pumps PO CH 21 Excluded NA 
Appendix A

Data From the FEDB

A-2

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

Tim

115 8/22/2002 Turbine 

Building

T/G hydrogen PO CH 34 Turbine 

Generator

18 

116 10/3/2002 Transformer 

Yard

Transformer –

Non Catastrophic 

PO CH 28 Excluded N/A 

117 10/9/2002 Plant-Wide 

Components

Pumps PO U 21 Electrical 23

118 1/15/2003 Transformer 

Yard

Transformer –

Catastrophic

PO CH 27 Excluded 35 

120 4/7/2003 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 33

121 4/26/2003 Plant-Wide 

Components

Pumps PO U 21 Electrical 37

122 4/29/2003 Turbine 

Building

T/G oil PO CH 35 Turbine

Generator

15 

125 1/6/2004 Control/Aux/

Reactor 

Building

Transients PO CH 7 Transients 22

126 5/21/2004 Transformer 

Yard

Yard transformers 

(others) 

PO PC 29 Transformer 

Yard

33
Data 

A-3

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppres

on Time

127 6/18/2004 Plant-Wide 

Components

HEAF iso-phase 

duct

PO CH 16.2 HEAF 71 

128 8/31/2004 Plant-Wide 

Components

Pumps PO PC 21 Oil 8

129 11/6/2004 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding 17

130 12/14/2004 Turbine 

Building

T/G oil PO PC 35 Turbine 

Generator

9

131 1/14/2005 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 23

132 3/4/2005 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF NC NC Excluded 64 

133 5/4/2005 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containmen

t

20

134 6/27/2005 Transformer 

Yard

Transformer –

Catastrophic

PO CH 27 Transformer 

Yard

27 

135 8/25/2005 Plant-Wide 

Components

Pumps PO PC 21 Electrical 13 
Appendix A

Data From the FEDB

A-4

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severi

ty

Bin 

Designation

NSP 

Category

Suppres

sion 

Time

136 10/25/2005 Turbine 

Building

T/G oil HS PC 35 Turbine 

Generator

13

137 10/29/2005 Transformer 

Yard

Transformer –

Non Catastrophic 

PO CH 28 Transform

er Yard

28 

139 2/24/2006 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO PC SB4 NA 153 

141 5/1/2006 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO PC SB4 NA 11 

143 8/15/2006 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO PC SB4 NA 36 

144 10/30/2006 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 4

146 2/27/2007 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 23

148 4/6/2007 Transformer 

Yard

Transformer –

Catastrophic

PO CH 28 Transform

er Yard

12 
Data 

A-5

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severi

ty

Bin DesignationNSP 

Category

Suppr

essio

n 

Time

150 4/25/2007 Plant-Wide 

Components

Hydrogen tanks PO CH 17 Flammable 

Gas

28

152 10/23/2007 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Excluded NA Se

in

154 9/20/2008 Turbine 

Building

T/G hydrogen PO CH 34 Turbine 

Generator

23

157 2/1/2009 Transformer 

Yard

Transformer –

Catastrophic

PO CH 27 Transform

er Yard

31 Ex

su

160 2/7/2009 Turbine 

Building

T/G hydrogen PO CH 34 Turbine 

Generator

18

161 4/22/2009 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 5 S

169 11/13/2003 Plant-Wide

Components

Pumps PO PC 21 Electrical 2

172 12/7/2003 Turbine 

Building

Main feedwater 

pumps

PO CH 32 Oil 20

175 11/22/2009 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

CD CH 15 Electrical 45

176 12/12/2009 Control/Aux/

Reactor 

Building 

Transients fires 

caused by welding 

and cutting

PO PC 6 Welding 23
Appendix A

Data From the FEDB

A-6

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

Ti

266 11/9/2006 Turbine 

Building

Transients PO PC 37 Transients 10

267 6/1/2000 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

PO U 24 Welding NA 

269 12/12/2000 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

PO PC 24 Welding 2

270 11/18/2005 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 8

275 10/14/2003 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 2

288 10/10/2006 Plant-Wide 

Components

Pumps RF NC NA N/A 3 

303 3/1/2000 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

CD PC 15 Electrical 2

308 10/14/2005 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding 2

320 10/24/2000 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 2
Data 

A-7

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ssion 

Time

333 5/11/2007 Diesel 

Generator 

Room 

Diesel generators PO PC 8 Oil 2

335 8/3/2007 Diesel 

Generator 

Room 

Diesel generators PO NA NA N/A 6 

346 3/1/2002 Plant-Wide 

Components

Electric motors RF PC 14 Electrical 2

350 7/11/2002 Turbine 

Building

Transients RF PC 37 Excluded N/A 

356 4/19/2006 Plant-Wide 

Components

Ventilation 

subsystems

CD PC 26 Electrical 8

375 10/16/2009 Plant-Wide 

Components

Pumps CD NC NC Excluded 2 

381 3/6/2005 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 13

411 3/8/2001 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Excluded N/A 

420 6/24/2001 Plant-Wide 

Components

Pumps PO U 21 Electrical N/A 

422 3/7/2003 Plant-Wide 

Components

Transients PO PC 25 Transients N/A 
Appendix A

Data From the FEDB

A-8

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

on Ti

423 6/23/2003 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical N/A 

424 3/10/2005 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO PC SB4 N/A N/A 

498 12/19/2000 Plant-Wide 

Components

Pumps PO U 21 Electrical N/A 

504 10/9/2002 Turbine 

Building

Transients RF U 37 Transients N/A 

515 10/5/2005 Control/Aux/

Reactor 

Building

Transients RF PC 7 Transients N/A 

516 10/25/2005 Plant-Wide 

Components

Transformers PO PC 23 Electrical N/A 

517 3/23/2006 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 15

520 6/6/2006 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 8

588 11/30/2006 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO CH 15 Excluded N/A 
Data 

A-9

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

on Ti

591 7/19/2006 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical 2

592 6/11/2009 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

RF U 24 Welding N/A 

595 2/13/2000 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

CD U 24 Welding N/A 

598 10/12/2000 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

CD U 24 Welding 2

602 9/29/2006 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding N/A 

603 11/14/2007 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical 10

606 10/31/2006 Plant-Wide 

Components

Ventilation 

subsystems

RF PC 26 Electrical 2

607 11/13/2008 Plant-Wide 

Components

Ventilation 

subsystems

CD U 26 Electrical 17

10286 5/10/2004 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding 2
Appendix A

Data From the FEDB

A-10

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

sion 

Tim

10287 5/19/2004 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF U 36 Welding 2

10291.1 9/18/2004 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting 

PO PC 6 Welding 9 

10291.2 9/18/2004 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting 

PO PC 6 Welding 11 

10313 4/3/2009 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF U 36 Welding 2

10331 3/24/2009 Diesel 

Generator 

Room 

Diesel generators PO PC 8 Oil 10

10334 3/30/2000 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF U 3P Electrical 2

10338 9/13/2001 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical N/A 

10386 3/1/2003 Plant-Wide 

Components

Crane PO U SB2 N/A 2 

10389 9/8/2003 Control 

Room

Main control board PO PC 4 Control Room 2 
Data 

A-11

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

sion 

Time

10394 2/22/2005 Control 

Room

Main control board PO PC 4 Excluded N/A 

10397 10/12/2005 Plant-Wide 

Components

Electric motors PO PC 14 Electrical 2

10407 6/3/2007 Control 

Room

Main control board PO PC 4 Control Room 2

10430 12/21/2000 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical 8

10482 10/22/2006 Plant-Wide 

Components

Pumps PO U 21 Electrical 2

10489 4/6/2008 Diesel 

Generator 

Room 

Diesel generators PO CH SB5 Oil 5 

10492 9/30/2008 Turbine 

Building

Transients RF PC 37 Transient N/A 

10493 10/23/2008 Plant-Wide 

Components 

Cable run (selfignited cable fires) 

PO U (NCPC)SB4 NA Indete

nate

10508 3/28/2001 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO U SB4 N/A N/A 
Appendix A

Data From the FEDB

A-12

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

on Ti

10514 8/26/2001 Diesel 

Generator 

Room 

Diesel generators PO PC 8 Oil 2

10515 9/30/2001 Diesel 

Generator 

Room 

Diesel generators RF PC SB5 Oil 10 

10516 11/20/2001 Containment 

(PWR) 

Transient and 

hotwork (LPSD)

RF PC 3P Containment 10

10522 11/2/2003 Diesel 

Generator 

Room 

Diesel generators PO PC SB5 Oil 2 

10524 1/7/2004 Diesel 

Generator 

Room 

Diesel generators PO PC SB5 Oil 2 

10555 5/5/2004 Turbine 

Building

Transients RF U 37 Transients N/A 

10558 1/19/2005 Plant-Wide 

Components

Air compressors RF PC 9 Oil 12

10565 8/15/2005 Exclude Exclude RF PC SB4 NA Indete

ate

10576 7/26/2006 Plant-Wide 

Components

Misc. hydrogen 

fires

PO PC 19 Flammable 

Gas

2
Data 

A-13

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

10579 4/4/2008 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF U 36 Welding 2

10582 12/9/2005 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF U 3B Containment N/A 

10584 7/27/2008 Plant-Wide 

Components 

HEAF for 

segmented bus 

duct 

PO U 

(NC-PC)

16.1 HEAF Indete

nate

10585 4/24/2003 Plant-Wide 

Components

Electric motors RF U 14 Electrical N/A 

10599 3/25/2006 Diesel 

Generator 

Room 

Diesel generators PO PC SB4 Excluded 2 

10604 5/14/2001 Turbine 

Building

T/G oil PO PC 35 Turbine 

Generator

14

10605 1/31/2006 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical 1

10611 8/20/2009 Plant-Wide 

Components

Pumps PO PC 21 Electrical 10

10614 2/25/2004 Plant-Wide 

Components

Lighting, ballast, 

or electric outlet

PO U SB1 N/A N/A 
Appendix A

Data From the FEDB

A-14

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppres

ion Tim

10615 10/15/2005 Containment 

(PWR) 

Reactor coolant 

pump 

RF NC NA N/A N/A 

10617 2/14/2003 Plant-Wide 

Components

Pumps PO U 21 Electrical N/A 

10618 2/15/2000 Plant-Wide 

Components

Dryers PO PC 13 Transients 33 

10626 12/11/2002 Plant-Wide 

Components

Pumps PO PC 21 Electrical 27 

10628 12/30/2005 Plant-Wide 

Components

Transients PO U 25 Transients N/A 

10630 6/6/2007 Plant-Wide 

Components

Air compressors PO PC 9 Electrical 2 

10664 10/2/2000 Diesel 

Generator 

Room 

Diesel generators PO U 8 Excluded N/A 

10665 11/3/2000 Diesel 

Generator 

Room 

Diesel generators PO U SB5 Oil 2 

10684 4/6/2005 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO PC 36 Excluded N/A 
Data 

A-15

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Supp

ssio

Time

10699 4/24/2008 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO PC SB4 N/A N/A 

10708 9/22/2004 Diesel 

Generator 

Room 

Diesel generators PO U SB5 Oil 2 

10713 3/25/2007 Diesel 

Generator 

Room 

Diesel generators PO U SB5 Oil 2 

10715 2/5/2009 Turbine 

Building 

Boiler RF PC 30 Electrical 2

10720 4/8/2006 Diesel 

Generator 

Room 

Diesel generators PO U SB5 Oil 2 

10723 10/4/2007 Diesel 

Generator 

Room 

Diesel generators PO PC SB5 Oil 2 

10729 4/3/2009 Turbine 

Building

Transients fires 

caused by welding 

and cutting

CD U 36 Welding 2

20378 2/25/2000 Plant-Wide 

Components

Pumps PO PC 21 Electrical 12
Appendix A

Data From the FEDB

A-16

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Supp

on T

20380 8/16/2000 Plant-Wide 

Components

Pumps PO PC 21 Electrical 21

20381 10/17/2000 Control/Aux/

Reactor 

Building 

Transient fires 

caused by welding 

and cutting 

RF U 6 Welding 2

20382 10/23/2000 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF PC 15 Electrical 2

20383 11/5/2000 Plant-Wide 

Components

Lighting, ballast, 

or electric outlet

RF U SB1 N/A 10 

20385 12/27/2000 Plant-Wide 

Components

Pumps PO PC 21 Electrical 2

30266 1/20/2009 Plant-Wide 

Components

Ventilation 

subsystems

PO NA See FID 

50728

Electrical 5 

30270 3/16/2003 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding 5

30271 9/11/2003 Turbine 

Building

Main feedwater 

pumps 

PO PC 32 Oil N/A 

30276 7/24/2006 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Control room 2 

30277 12/3/2007 Turbine 

Building

Transients PO PC 37 Transients 2 
Data 

A-17

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30281 6/5/2008 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF PC 15 Control room N/A 

30292 6/17/2001 Exclude Exclude PO PC SB4 NA 2 

30296 11/22/2002 Plant-Wide 

Components

Lighting, ballast, 

or electric outlet

RF PC SB1 N/A 10 

30302 1/26/2007 Plant-Wide 

Components

Electric motors PO PC 14 Electrical 2

30312 3/29/2003 Plant-Wide 

Components

Pumps HS PC 21 Electrical 2 

30314 12/19/2001 Control/Aux/

Reactor 

Building 

Transients PO PC 7 Transients 10

30317 4/18/2005 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 2

30322 10/28/2006 Turbine 

Building

Transients RF PC 37 Transients 2

30324 1/11/2007 Plant-Wide 

Components

Transformers PO PC 23 Electrical 2

30327 3/6/2009 Plant-Wide 

Components

Pumps PO PC 21 Electrical 10

30330 4/30/2000 Turbine 

Building

Transients RF PC 37 Transients 2 
Appendix A

Data From the FEDB

A-18

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30333 7/31/2003 Plant-Wide 

Components

Transients PO PC 25 Transients N/A 

30338 3/30/2006 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical 3

30340 11/10/2000 Plant-Wide 

Components

Air compressors PO PC 9 Electrical 2

30341 1/2/2001 Plant-Wide 

Components

Under-capacity 

component

PO PC SB3 N/A 10 

30342 2/11/2002 Plant-Wide 

Components

Crane PO U SB2 N/A N/A 

30344 1/23/2003 Plant-Wide 

Components

Air compressors PO PC 9 Electrical 8

30350 7/26/2004 Turbine 

Building

Transients PO PC 37 Transients 7

30354 2/8/2005 Plant-Wide 

Components

Transients PO U (NCPC)SB4 Exclude 19 

30355 2/17/2005 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U (NCPC)SB4 NA Indete

nate

30357 6/20/2007 Control/Aux/

Reactor 

Building 

Transient fires 

caused by welding 

and cutting 

CD U 6 Welding 8
Data 

A-19

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30358 8/2/2007 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC SB4 NA 2 

30361 4/11/2001 Turbine 

Building

Transients RF PC 37 Transients N/A 

30362 12/16/2001 Plant-Wide 

Components

Pumps RF PC 21 Electrical 45

30363 5/5/2003 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 2

30370 10/31/2005 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 2

30374 11/30/2005 Control/Aux/

Reactor 

Building 

Transients RF PC 7 Transients N/A 

30380 12/17/2007 Turbine 

Building

Transients RF U 37 Transients N/A 

30392 3/20/2000 Containment 

(BWR) 

Transients and 

hotwork (LPSD)

RF U 3B Containment 9

30393 3/24/2000 Containment 

(BWR) 

Transients and 

hotwork (LPSD)

RF U 3B Containment N/A 

30394 2/2/2003 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical N/A 
Appendix A

Data From the FEDB

A-20

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30395 3/21/2004 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding N/A 

30404 4/21/2009 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

PO U 24 Excluded N/A 

30407 4/30/2002 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 5

30408 3/19/2001 Turbine 

Building

Transients PO PC 37 Transients N/A 

30409 8/21/2000 Transformer 

Yard

Yard transformers 

(others) 

PO PC 29 Excluded N/A 

30410 10/25/2000 Plant-Wide 

Components

Pumps PO PC 21 Electrical 5

30412 4/25/2002 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 1

30418 2/19/2002 Plant-Wide 

Components

Transients RF U 25 Excluded N/A 

30421 3/5/2002 Turbine 

Building

Transients RF U 37 Excluded N/A 

30422 11/27/2001 Plant-Wide 

Components

Pumps PO PC 21 Electrical 5
Data 

A-21

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30424 4/11/2001 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment N/A 

30425 10/7/2002 Plant-Wide 

Components

Ventilation 

subsystems

PO NA NA N/A 3 

30429 5/6/2004 Containment 

(PWR)

Reactor coolant 

pump

RF PC 2 Containment 

(PWR, LPSD) 

or Oil

5

30434 8/12/2007 Diesel 

Generator 

Room 

Diesel generators PO PC 8 Oil 11

30437 10/6/2000 Containment 

(PWR)

Transients and 

hotwork (LPSD)

CD PC 3P Containment 10

30439 3/21/2008 Plant-Wide 

Components

Pumps PO U 21 Oil N/A 

30440 10/26/2005 Diesel 

Generator 

Room

Diesel generators PO U SB4 N/A N/A 

30446 4/1/2003 Plant-Wide 

Components

Transformers PO PC 23 Electrical N/A 

30447 7/11/2004 Transformer 

Yard

Transformer –

Non Catastrophic

PO PC 28 Transformer 

Yard

N/A 
Appendix A

Data From the FEDB

A-22

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP

Category

Suppr

ion Ti

30453 1/30/2009 Plant-Wide 

Components

Pumps PO PC 21 Oil N/A 

30456 3/7/2001 Plant-Wide 

Components

Crane PO PC SB2 N/A N/A 

30457 10/24/2006 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF U 36 Welding 13

30459 3/9/2003 Plant-Wide 

Components

Transients PO PC 25 Transients N/A 

30460 3/18/2003 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO PC SB4 N/A N/A 

30465 9/24/2008 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding N/A 

30469 11/11/2007 Plant-Wide 

Components

Transformers PO PC 23 Electrical 13

30471 4/4/2008 Diesel 

Generator 

Room 

Diesel generators PO PC 8 Oil 2
Data 

A-23

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30478 9/9/2005 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 5

30493 7/24/2008 Transformer 

Yard

Transformer –

Catastrophic

PO CH 28 Transformer 

yard

162

30507 7/26/2005 Diesel 

Generator 

Room 

Diesel generators PO PC 8 Oil 2

30508 3/26/2009 Turbine 

Building

Transients RF PC 37 Transients 10

30512 2/15/2006 Turbine 

Building

Transients RF PC 37 Transients 2

30513 5/27/2008 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 2 

30516 6/25/2005 Transformer 

Yard 

Switch yard 

breaker

PO U (PCCH)SB4 NA 13 

30517 7/29/2005 Exclude Exclude PO NC NA NA 13

30522 9/12/2000 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical N/A 

30524 12/14/2000 Plant-Wide 

Components

Pumps PO U 21 Electrical N/A 

30525 3/7/2001 Plant-Wide 

Components

Transients PO U (NCPC)SB4 NA Indete

nate
Appendix A

Data From the FEDB

A-24

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30541 7/6/2005 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical 12

30556 4/4/2008 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

RF U 24 Welding N/A 

30558 10/20/2008 Plant-Wide 

Components

Ventilation 

subsystems

PO NC NC N/A N/A 

30566 9/11/2000 Plant-Wide 

Components

Transients PO PC 25 Transients N/A 

30578 2/27/2003 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical N/A 

30586 1/11/2006 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO NC NC N/A N/A 

30587 3/4/2009 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U SB1 N/A N/A 

30593 2/7/2008 Plant-Wide 

Components

Transformers PO PC 23 Electrical 6

30597 2/5/2009 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

PO PC 19 Flammable 

Gas

5 

30598 11/20/2009 Turbine 

Building

Turbine generator 

oil

PO PC 35 Turbine 

Generator

N/A 
Data 

A-25

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30604 5/28/2005 Plant-Wide 

Components

Transients PO PC 25 Transients N/A 

30693 2/3/2004 Diesel 

Generator 

Room 

Diesel generators PO N/A N/A N/A N/A 

30712 4/24/2002 Exclude Exclude PO NC NA NA Indete

nate

30717 12/10/2002 Plant-Wide 

Components

Transients PO U 25 Transients 2

30718 4/15/2003 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO U SB4 N/A N/A 

30719 6/11/2003 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO PC SB4 N/A N/A 

30722 10/19/2003 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO U SB4 N/A N/A 

30725 4/12/2000 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical N/A 
Appendix A

Data From the FEDB

A-26

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30727 10/30/2000 Plant-Wide 

Components

Transients PO NA NA N/A N/A 

30730 3/5/2001 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF U 3P Containment N/A 

30731 3/19/2001 Containment 

(PWR)

Transients and 

hotwork (LPSD)

CD PC 3P Containment N/A 

30732 12/3/2001 Plant-Wide 

Components

Ventilation 

subsystems

RF NC NC N/A N/A 

30733 6/27/2002 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO PC SB4 N/A N/A 

30734 8/26/2002 Plant-Wide 

Components

Junction boxes PO PC 18 Electrical 10

30736 3/13/2003 Plant-Wide 

Components

Unknown PO U SB4 N/A N/A 

30740 2/6/2004 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

PO PC 24 Welding 8

30750 5/9/2005 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

CD PC 19 Flammable 

Gas

N/A 

30752 4/3/2007 Turbine 

Building

Transients PO PC 37 Transients 9
Data 

A-27

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ion Ti

30756 11/23/2008 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

RF U 24 Welding N/A 

30757 8/24/2009 Plant-Wide 

Components

Transients PO U 25 Transients N/A 

40733 3/14/2001 Plant-Wide 

Components

Hydrogen tanks PO PC 17 Flammable 

Gas

N/A 

40735 4/4/2001 Plant-Wide 

Components

Hydrogen tanks PO PC 17 Flammable 

Gas

N/A 

40749 6/13/2008 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO CH 36 Excluded 9 

50358 6/1/2000 Plant-Wide 

Components 

Transient fires 

caused by welding 

and cutting 

PO CH SB4 NA 50 

50361 4/11/2001 Containment 

(PWR) 

Transients and 

hotwork (LPSD)

CD PC 3P Containment 2

50378 7/27/2005 Plant-Wide 

Components

Transformers PO PC 23 Electrical 10

50409 10/5/2006 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF U 3P Containment N/A 

50411 7/9/2005 Plant-Wide 

Components

Ventilation 

subsystems

PO U 26 Electrical N/A 
Appendix A

Data From the FEDB

A-28

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

sion 

Time

50425 3/16/2000 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 2

50426 5/2/2000 Plant-Wide 

Components

Pumps PO PC 21 Electrical 13

50442 11/8/2004 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

PO PC 19 Excluded N/A 

50447 9/14/2005 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 14 Electrical 2 

50448 10/11/2005 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO PC 36 Welding N/A 

50449 2/21/2006 Containment 

(PWR)

Transients and

hotwork (LPSD)

RF U 3P Containment 2

50452 8/18/2006 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

PO U 24 Welding 4

50457 7/28/2007 Transformer 

Yard 

Switch yard 

breaker

PO CH SB4 NA 102 

50467 2/4/2006 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical N/A 

50473 6/26/2000 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 3
Data 

A-29

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

sion 

Time

50477 3/18/2000 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding 2

50479 3/22/2000 Plant-Wide 

Components

Dryers RF PC 13 Transients 19

50482 3/8/2006 Plant-Wide 

Components 

Pumps UN PC 21 Electrical Indete

nate

50494 2/5/2009 Plant-Wide 

Components

Transients PO CH SB4 Exclude 16 

50504 5/20/2002 Plant-Wide 

Components

Transients RF PC 25 Electrical 2

50515 11/30/2001 Containment 

(PWR)

Transients and 

hotwork (LPSD)

CD U 3P Containment N/A 

50518 11/18/2001 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF U 3P Containment N/A 

50522 9/8/2003 Plant-Wide 

Components

Pumps PO U 21 Electrical N/A 

50530 10/21/2008 Transformer 

Yard

Transformer: non 

catastrophic 

RF PC 28 Transformer 

Yard

4 

50543 3/27/2001 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF PC 3P Containment 8

50553 5/2/2003 Control 

Room

Main control board RF PC 4 Control Room 2 
Appendix A

Data From the FEDB

A-30

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

sion 

Time

50556 2/25/2005 Plant-Wide 

Components

RPS MG sets PO U 22 Excluded N/A 

50563 11/16/2005 Plant-Wide 

Components

Hydrogen tanks PO PC 17 Flammable 

gas

N/A 

50570 6/21/2004 Plant-Wide 

Components

Pumps PO NC NA N/A 8 

50650 9/26/2003 Plant-Wide 

Components

Pumps UN U (NCPC)21 Electrical 2

50655 12/4/2007 Plant-Wide 

Components

Ventilation 

subsystems

PO NC NC N/A N/A 

50686 4/4/2007 Containment 

(PWR)

Transients and 

hotwork (LPSD)

RF U 3P Containment 2

50700 5/13/2000 Plant-Wide 

Components 

Transient fires 

caused by welding 

and cutting 

RF PC 24 Welding 2

50701 5/24/2000 Transformer 

Yard 

Transformer –

Catastrophic

PO CH 27 Transformer 

Yard

Exclud

50703 8/22/2000 Exclude or 

Transformer 

Yard 

Exclude or 

Transformer –

Catastrophic

PO CH SB4 NA 85 
Data 

A-31

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

sion 

Time

50728 1/20/2009 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical 5

50732 11/7/2002 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

RF NC N/A N/A 10 

50733 4/23/2004 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF U 36 Welding 2

50740 5/16/2000 Plant-Wide 

Components

Lighting, ballast, 

or electric outlet

PO U SB1 N/A N/A 

50744 8/3/2001 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO PC SB4 N/A 10 

50754 1/23/2009 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical N/A 

50763 11/14/2008 Plant-Wide 

Components

Transformers PO NC NC N/A N/A 

50768 1/1/2002 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical N/A 

50771 5/6/2003 Plant-Wide 

Components

Dryers PO PC 13 Transients 2
Appendix A

Data From the FEDB

A-32

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

sion 

Time

50784 11/20/2005 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical 0

50796 11/4/2009 Control/Aux/

Reactor 

Building 

Transients RF PC 7 Transients 2

50809 11/9/2000 Control/Aux/

Reactor 

Building 

Transients RF PC 7 Transients 2

50811 1/9/2001 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical N/A 

50820 10/23/2008 Plant-Wide 

Components

Junction box PO PC 18 Electrical 7

50821 10/30/2008 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding 18

50825 10/1/2009 Plant-Wide 

Components 

Transients PO U (NCPC)SB1 NA Indete

nate

50829 9/11/2004 Plant-Wide 

Components

Transformer 

(plant-wide 

components) 

PO PC 23 Electrical 45

50833 9/23/2008 Turbine 

Building

Transients RF PC 37 Transients N/A 
Data 

A-33

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

sion 

Time

50866 3/28/2001 Plant-Wide 

Components

Lighting, ballast, 

or electric outlet

PO PC SB1 N/A 8 

50871 1/24/2002 Plant-Wide 

Components

Pumps PO PC 21 Electrical 13

50874 7/12/2002 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

CD PC 15 Electrical 2

50876 11/13/2002 Plant-Wide 

Components

Junction box RF PC 18 Electrical 25

50878 11/12/2002 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting 

RF PC 6 Welding 13

50884 2/23/2004 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO U 36 Welding 8

50893 12/2/2005 Plant-Wide 

Components

Transformers PO PC 23 Electrical 13

50895.1 5/13/2007 Turbine 

Building

Transient fires 

caused by welding 

and cutting 

RF PC 36 Welding 40 

50895.2 5/13/2007 Turbine 

Building

Transient fires 

caused by welding 

and cutting 

RF PC 36 Welding 35 
Appendix A

Data From the FEDB

A-34

Table A-1 (continued)

Fire event data for 2000–2009

Fire ID Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppr

ssion 

Time

50896 5/13/2007 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF U 3B Containment 2 

50898 2/29/2008 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC SB4 NA 2 

50899 10/27/2008 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO CH SB4 N/A 2 

 Special Bin Designation Applicable to Table A-1 and Table A-2

Special Bin Bin Name Description

SB1 Lighting ballast and 

electric plug

This is for lighting, ballast, outlet/electric plug. If the fire was propagated, it will be re-evaluated la

SB2 Crane This is for fires related to intermittent maintenance in a particular crane (but it may other equipmen

harm the operation. If the fire was propagated, it will be re-evaluated later. If the fire involved a cra

belong to motor bin.

SB3 Under capacity event This bin is for motor, pump, or ventilation subsystems with motors under 5 kV or dry transformers 

SB4 Doesn’t belong to any bin The ignition source and the location of the event are known, but this event cannot be mapped to any 
Data 

A-35

Table A-2

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

2 1/5/1999 Transformer 

Yard

Transformer –

Catastrophic

PO CH 27 Transformer 

Yard

14

3 1/14/1999 Plant-Wide 

Components

Hydrogen tanks PO CH 17 Flammable 

Gas

52 

5 5/18/1999 Transformer 

Yard

Transformer – Non 

Catastrophic

RF PC 28 Transformer 

Yard

22 

6 7/13/1999 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

PO PC 6 Welding 40

7 10/9/1999 Plant-Wide 

Components

Yard transformers 

(others)

PO U 29 Excluded N/A 

9 1/3/1990 Plant-Wide 

Components

Transformers PO PC 23 Electrical 13 

14 5/24/1990 Transformer 

Yard

Yard Transformer 

(Others)

PO PC SB4 Excluded N/A 

17 6/28/1990 Plant-Wide 

Components

Ventilation 

subsystems

RF PC 26 Containment 29 
Appendix A

Data From the FEDB

A-36

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

18 7/13/1990 Plant-Wide 

Components

HEAF for mediumvoltage electrical 

cabinet (>1000 V)

CD PC 16.b HEAF 10 

19 8/4/1990 Plant-Wide 

Components

Dryers CD CH 13 Excluded N/A 

20 8/25/1990 Transformer 

Yard

Transformer – Non 

Catastrophic

PO CH 28 Transformer 

Yard

90 

21 9/22/1990 Transformer 

Yard

Transformer –

Catastrophic

PO CH 27 Transformer 

Yard

29 

22 12/3/1990 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF CH 3B Containment 76 

23 12/19/1990 Turbine 

Building

Transients PO PC 37 Transients 40 
Data 

A-37

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

24 12/22/1990 Turbine 

Building

Main feedwater 

pumps

PO PC 32 Oil 20 

25 1/11/1991 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO U 36 Welding 85

26 2/14/1991 Containment 

(PWR)

Transient and 

hotwork (LPSD)

RF CH 3P Containment 8 

29 2/23/1991 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

HS PC 15 Electrical 6

30 4/29/1991 Turbine 

Building

T/G hydrogen 

(Turbine Building)

PO CH 34 Excluded N/A 

31 6/15/1991 Transformer 

Yard

Transformer – Non 

Catastrophic

PO U 28 Transformer 

Yard

23

32 6/27/1991 Transformer 

Yard

Yard transformers 

(others)

PO PC 29 Excluded N/A 

33 8/1/1991 Transformer 

Yard

Yard transformers 

(others)

PO PC SB4 Exclude 183 

34 8/11/1991 Turbine 

Building

Main feedwater 

pumps

PO PC 32 Oil 11
Appendix A

Data From the FEDB

A-38

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

36 11/9/1991 Turbine 

Building

T/G hydrogen PO CH 34 Turbine 

Generator

15

38 3/21/1992 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

CD CH 15 Electrical 8

41 6/17/1992 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 14

42 7/3/1992 Plant-Wide 

Components

Transients PO PC SB4 Excluded 12 

43 7/4/1992 Transformer 

Yard

Transformer – Non 

Catastrophic

PO CH 28 Transformer 

Yard

23

44 7/13/1992 Turbine 

Building

Main feedwater 

pumps

PO CH 32 Oil 13

45 7/29/1992 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 16 

46 8/4/1992 Plant-Wide 

Components

Battery chargers PO PC 10 Electrical 13

48 9/4/1992 Transformer 

Yard

Transformer – Non 

Catastrophic

PO CH 28 Transformer 

Yard

27

49 9/15/1992 Transformer 

Yard

Yard transformers 

(others)

PO CH SB4 Excluded 77 
Data 

A-39

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

50 11/24/1992 Transformer 

Yard

Yard transformers 

(others)

PO PC SB4 Excluded N/A 

52 6/19/1993 Plant-Wide 

Components

Pumps RF PC 21 Electrical 10

55 10/13/1993 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

RF PC 6 Welding 8

56 10/21/1993 Turbine 

Building

T/G oil PO PC 35 Turbine 

Generator

10

58 12/25/1993 Turbine 

Building

T/G hydrogen PO CH 34 Turbine 

Generator

2 

59 1/29/1994 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

CD CH SB4 N/A 20 

61 4/3/1994 Turbine 

Building

T/G hydrogen PO CH 34 Turbine 

Generator

167
Appendix A

Data From the FEDB

A-40

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

63 6/15/1994 Turbine 

Building

T/G oil CD PC 35 Turbine 

Generator

85

64 6/1/1994 Transformer 

Yard

Transformer – Non 

Catastrophic

PO CH 28 Transformer 

yard

10 

65 7/2/1994 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO CH SB4 Excluded 31 

66 7/11/1994 Containment 

(PWR)

Reactor coolant 

pump

PO PC 2 Containment 10

67 7/29/1994 Turbine 

Building

T/G oil PO PC 35 Turbine 

Generator

10

68 8/10/1994 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

PO PC 24 Welding 30 

69 8/29/1994 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical 10

71 3/1/1995 Turbine 

Building

Main feedwater 

pumps

PO PC 32 Oil 23
Data 

A-41

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

72 4/14/1995 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

RF CH 6 Welding 19

74 6/10/1995 Plant-Wide 

Components

HEAF for mediumvoltage electrical 

cabinet (>1000 V)

PO CH 16.b HEAF 136

75 8/22/1995 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

RF PC 6 Welding 8

76 10/21/1995 Transformer 

Yard

Transformer –

Catastrophic

RF CH 27 Transformer 

Yard

30 

78 1/24/1996 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

RF CH 6 Welding 13

79 2/5/1996 Transformer 

Yard

Transformer – Non 

Catastrophic

RF CH 28 Transformer 

Yard

37 

80 2/29/1996 Turbine 

Building

Transients fires 

caused by welding 

and cutting

CD PC 36 Welding 23
Appendix A

Data From the FEDB

A-42

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

81 3/25/1996 Plant-Wide 

Components

Transients PO U 25 Transients 23

82 3/27/1996 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

RF PC 36 Transients 14 

83.1 4/4/1996 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF PC 15 MCR 9 

83.2 4/4/1996 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF NA NA Electrical 25 

84 4/19/1996 Control 

Room

Main control board PO PC 4 Control 

Room

10

86 6/23/1996 Transformer 

Yard

Yard transformers 

(others)

PO CH 29 Transformer 

Yard

18 

87 8/19/1996 Plant-Wide 

Components

Pumps PO PC 21 Oil 2
Data 

A-43

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

88 10/5/1996 Transformer 

Yard

Yard transformers 

(others)

PO CH 29 Transformer 

Yard

16 

89 10/15/1996 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 10 

90 10/17/1996 Containment 

(PWR)

Reactor coolant 

pump

HD CH 2 Containment 16

91 11/19/1996 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

PO U 24 Welding 19 

92 11/22/1996 Transformer 

Yard

Yard transformers 

(others)

PO PC 29 Exclude N/A 

93 3/4/1997 Plant-Wide 

Components

RPS MG sets PO PC 22 Electrical 10

94 8/1/1997 Turbine 

Building

T/G excitor PO PC 33 Turbine 

Generator

18

95 10/9/1997 Diesel 

Generator 

Room

Diesel generators PO PC 8 Oil 2 
Appendix A

Data From the FEDB

A-44

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

96 10/28/1997 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

RF PC 24 Transients 19

97 6/10/1998 Plant-Wide 

Components

RPS MG sets PO PC 22 Electrical 29

98 10/8/1998 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF PC 15 Electrical 46

159 1/16/1990 Plant-Wide 

Components

Pumps PO PC 21 Electrical 13 

181 2/13/1997 Plant-Wide 

Components

Pumps PO PC 21 Electrical 10

184 6/27/1997 Plant-Wide 

Components

Battery chargers PO CH 10 Excluded N/A 

187 8/16/1999 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 8 

188 8/24/1999 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 13
Data 

A-45

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

194 5/22/1990 Transformer 

Yard

Transformer – Non 

Catastrophic

PO PC 28 Excluded N/A 

199 1/22/1990 Plant-Wide 

Components

Pumps RF PC 21 Excluded N/A 

200 2/6/1990 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

CD PC SB4 Excluded 7 

201 3/8/1990 Plant-Wide 

Components

Pumps CD PC 21 Electrical N/A 

202 3/23/1990 Control 

Room

Main control board PO PC 4 Control 

Room

2

203 4/6/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF CH 15 Electrical 24 

206 6/11/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

CD U 15 Electrical 2 

207 7/15/1990 Plant-Wide 

Components

Cable run (selfignited cable fires)PO(1), 

RF(2)

PC 12 Excluded N/A 
Appendix A

Data From the FEDB

A-46

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

208 8/8/1990 Turbine 

Building

Transients PO PC 37 Transients 2

209 8/22/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 2

210 10/16/1990 Containment 

(PWR)

Transient and 

hotwork (LPSD)

RF U 3P Excluded N/A 

211 11/2/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF PC 15 Electrical 2

214 3/8/1991 Turbine 

Building

Boiler RF PC 30 Oil 6 

216 7/12/1991 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical N/A 

217 7/19/1991 Plant-Wide 

Components

Pumps PO PC 21 Oil N/A 

218 9/12/1991 Turbine 

Building

T/G oil PO U 35 Turbine 

Generator

2

219 9/27/1991 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 10
Data 

A-47

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

220 10/20/1991 Plant-Wide 

Components

Transformers RF PC 23 Electrical N/A 

224 3/8/1992 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF U 15 Electrical 10

226 4/17/1992 Diesel 

Generator 

Room

Diesel generators PO U 8 Oil 2

228 8/14/1992 Plant-Wide 

Components

Pumps PO PC 21 Excluded N/A 

229 8/21/1992 Control/Aux/

Reactor 

Building

Cable fires caused 

by welding and 

cutting

PO CH 5 Welding N/A 

230 8/31/1992 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

PO PC 20 Exclude N/A 

231 10/22/1992 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO PC 36 Welding N/A 

233 11/29/1992 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical 2 
Appendix A

Data From the FEDB

A-48

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

235 12/30/1992 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical 25 

236 1/6/1993 Control/Aux/

Reactor 

Building

Transients PO U 7 Control room 2

237 3/19/1993 Containment 

(PWR)

Transient and 

hotwork (LPSD)

RF PC 3P Containment 2

238 4/1/1993 Control/Aux/

Reactor 

Building

Transients PO PC 7 Transients 2

239 7/14/1993 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO PC 36 Welding 25

240 7/19/1993 Containment 

(PWR)

Transient and 

hotwork (LPSD)

RF PC 3P Containment N/A 

241 11/3/1993 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF PC 3B Containment 2

242 11/13/1993 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO U SB4 N/A 10 
Data 

A-49

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

243 12/1/1993 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF PC 3B Containment 2

244 12/7/1993 Turbine 

Building

Transients RF PC 37 Transients 2 

246 1/12/1994 Control/Aux/

Reactor 

Building

Transients RF(1), 

SD(2)

CH 7 Transients 2

247 1/12/1994 Plant-Wide 

Components

Pumps PO PC 21 Electrical 22 

248 3/5/1994 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding 2

249 3/7/1994 Plant-Wide 

Components

Ventilation 

subsystems

RF PC 26 Electrical 2

250 7/19/1994 Transformer 

Yard

Transformer – Non 

Catastrophic

PO PC 28 Excluded N/A 

251 10/11/1994 Plant-Wide 

Components

Transformers CD PC 23 Electrical 2
Appendix A

Data From the FEDB

A-50

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

252 3/18/1995 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

RF U 6 Excluded N/A 

253 7/6/1995 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 10

254 9/25/1995 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF(1), 

PO(2)

PC 15 Electrical 4 

255 11/19/1995 Plant-Wide 

Components

Transformers RF(1), 

PO(2)

CH 23 Electrical 10

256 7/22/1996 Plant-Wide 

Components

Cable fires caused 

by welding and 

cutting

Decom 

(1), 

SD(2an

d3)

U 11 Welding 2

258 11/3/1997 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF PC 36 Welding 2

259 12/26/1997 Control/Aux/

Reactor 

Building

Transients PO PC 7 Excluded N/A 

260 2/3/1998 Plant-Wide 

Components

Pumps PO PC 21 Oil N/A 
Data 

A-51

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

262 2/19/1999 Plant-Wide 

Components

Air compressors PO PC 9 Electrical 2

20264 1/19/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO/SD U 15 Electrical 10

20265 2/2/1990 Turbine 

Building

Main feedwater 

pumps

PO U 32 Oil 5 

20266 2/19/1990 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF U 3B Containment 2

20267 3/12/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

CD U 15 Electrical N/A 

20268 4/19/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical N/A 

20269 4/30/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical N/A 

20270 6/7/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF U 15 Electrical 2

20271 7/9/1990 Plant-Wide 

Components

Transformers PO U 23 Electrical 3 

20272 9/10/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO(1), 

SD(2)

U 15 Electrical 5 
Appendix A

Data From the FEDB

A-52

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20273 9/18/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical N/A 

20274 10/9/1990 Plant-Wide 

Components

RPS MG sets PO PC 22 Excluded N/A 

20275 10/11/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO(1),. 

SD(2)

U 15 Electrical N/A 

20276 10/12/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF U 15 Excluded N/A 

20277 11/16/1990 Control/Aux/

Reactor 

Building

Transients RF U 7 Transients 6 

20278 11/24/1990 Plant-Wide 

Components

Ventilation 

subsystems

PO U 26 Electrical 2 

20279 11/28/1990 Plant-Wide 

Components

Transformers PO U 23 Electrical N/A 

20280 12/5/1990 Transformer 

Yard

Yard transformers 

(others)

CD PC 29 Transformer 

Yard

N/A 
Data 

A-53

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20281 6/24/1991 Plant-Wide 

Components

Ignition source is 

specified but does 

not belong to any 

bin

PO U 25 Excluded N/A 

20282 9/17/1991 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical N/A 

20283 10/3/1991 Plant-Wide 

Components

Electric motors PO U 14 Electrical 2

20284 10/14/1991 Plant-Wide 

Components

HEAF for mediumvoltage electrical 

cabinet (>1000 V)

RF U 16.b HEAF 2 

20287 2/29/1992 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF(1), 

PO(2)

U 15 Electrical 5 

20288 3/9/1992 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF U 3B Containment N/A 

20289 3/16/1992 Control/Aux/

Reactor 

Building

Transients RF(1), 

PO(2)

U 7 Transients 10

20291 4/28/1992 Plant-Wide 

Components

Pumps RF PC 21 Electrical N/A 
Appendix A

Data From the FEDB

A-54

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20292 6/25/1992 Turbine 

Building

T/G hydrogen PO U 34 Excluded N/A 

20293 9/1/1992 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO U 36 Welding 2

20294 10/5/1992 Plant-Wide 

Components

Transients fires 

caused by welding 

and cutting

PO U 24 Welding N/A 

20295 10/12/1992 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical 2

20296 10/23/1992 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

RF U 6 Welding 10

20297 11/17/1992 Control/Aux/

Reactor 

Building

Transients RF U 7 Transients N/A 

20298 1/11/1993 Plant-Wide 

Components

Electric motors PO(1), 

RF(2)

U 14 Electrical 2

20300 3/30/1993 Turbine 

Building

Transients RF U 37 Transients N/A 

20301 4/13/1993 Turbine 

Building

Transients PO U 37 Transients 2
Data 

A-55

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20302 7/25/1993 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical 35 

20303 10/14/1993 Plant-Wide 

Components

Transients RF PC 25 Transients 2

20304 11/2/1993 Control/Aux/

Reactor 

Building

Transients CD PC NC Excluded 2 

20306 12/30/1993 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF U 3B Containment 2

20308 3/9/1994 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF U 36 Welding N/A 

20310 3/26/1994 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF U 3B Containment N/A 

20311 4/4/1994 Containment 

(PWR)

Transient and 

hotwork (LPSD)

RF U 3P Containment N/A 

20312 7/27/1994 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical N/A 
Appendix A

Data From the FEDB

A-56

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20313 9/29/1994 Plant-Wide 

Components

Transients PO(1), 

PO(2)

U 25 Transients 25 

20314 12/19/1994 Plant-Wide 

Components

Electric motors PO U 14 Electrical 10 

20316 2/24/1995 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO U 36 Welding N/A 

20317 4/10/1995 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

RF U 6 Welding 2

20319 8/15/1995 Plant-Wide 

Components

Pumps RF U 21 Exclude 2 

20320 3/21/1996 Plant-Wide 

Components

Pumps PO U 21 Electrical 2

20321 7/10/1996 Exclude Exclude CD NC SB4 N/A N/A 

20322 9/13/1996 Turbine 

Building

Main feedwater 

pumps

PO U 32 Oil 46
Data 

A-57

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20323 1/8/1997 Plant-Wide 

Components

RPS MG sets PO NC NC Exclude 46 

20324 8/12/1997 Plant-Wide 

Components

Ventilation 

subsystems

PO U 26 Electrical 2

20325 1/16/1998 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical 10

20326 10/12/1998 Turbine 

Building

Transients RF U 37 Transients 2

20328 5/6/1999 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical 2

20329 9/1/1999 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical 2

20330 10/3/1999 Plant-Wide 

Components

Electric motors RF U 14 Electrical N/A 

20334 2/20/1990 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO U 15 Electrical N/A 

20336 2/14/1991 Plant-Wide 

Components

Transients PO U 25 Transients N/A 
Appendix A

Data From the FEDB

A-58

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20337 4/21/1991 Turbine 

Building

Transients fires 

caused by welding 

and cutting

PO U 36 Welding N/A 

20338 10/11/1991 Plant-Wide 

Components

Pumps CD U 21 Electrical N/A 

20340 12/1/1992 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

CD U 6 Welding 2

20341 3/31/1993 Plant-Wide 

Components

Transients RF U 25 Transients 15 

20342 4/30/1993 Control/Aux/

Reactor 

Building

Transient fires 

caused by welding 

and cutting

RF U 6 Welding N/A 

20344 2/20/1994 Plant-Wide 

Components

Electric motors RF U 14 Electrical 10

20346 3/30/1994 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

RF U 15 Excluded N/A 

20348 4/16/1994 Containment 

(BWR)

Transients and 

hotwork (LPSD)

RF U 3B Containment 2

20349 4/23/1994 Turbine 

Building

Transients fires 

caused by welding 

and cutting

RF U 36 Welding 2
Data 

A-59

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20350 6/9/1994 Plant-Wide 

Components

Crane CD U SB2 N/A 8 

20351 6/21/1994 Control 

Room

Main control board PO U 4 Control 

Room

N/A 

20352 6/23/1994 Transformer 

Yard

Transformer – Non 

Catastrophic

PO PC 28 Transformer 

yard

2

20353 7/13/1994 Diesel 

Generator 

Room

Diesel generators PO PC 8 Electrical 2 

20354 10/8/1994 Containment 

(PWR)

Transients and 

hotwork (at power)

PO PC SB1 N/A N/A 

20356 2/19/1995 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 5 

20357 5/24/1995 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Excluded N/A 

20358 1/23/1996 Plant-Wide 

Components

Air compressors PO U 9 Electrical N/A 

20359 3/3/1996 Plant-Wide 

Components

Air compressors RF NA NA Excluded N/A 
Appendix A

Data From the FEDB

A-60

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20360 5/25/1996 Plant-Wide 

Components

Transformers PO/SD(

2), 

SD(3)

PC 23 Electrical 13 

20361 1/7/1997 Plant-Wide 

Components

Transients PO U 25 Transients N/A 

20362 3/2/1997 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO PC 15 Electrical 2

20363 7/27/1997 Plant-Wide 

Components

Junction boxes PO PC 18 Electrical N/A 

20364 12/4/1997 Plant-Wide 

Components

Electric motors PO U 14 Electrical 2 

20365 1/13/1998 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

PO PC 20 Flammable 

gas

20 

20366 2/6/1998 Plant-Wide 

Components

Pumps PO U 21 Oil N/A 

20367 2/24/1998 Plant-Wide 

Components

Pumps PO PC 21 Oil 2
Data 

A-61

Table A-2 (continued)

Fire event data for 1990–1999

Fire 

ID

Event 

Date

Location Ignition Source Power 

Mode

Fire 

Severity

Bin 

Designation

NSP 

Category

Suppre

ssion 

Time

20368 6/7/1998 Plant-Wide 

Components

Air compressors PO U 9 Electrical 2

20369 6/14/1998 Plant-Wide 

Components

Transformers PO PC 23 Excluded N/A 

20370 7/1/1998 Plant-Wide 

Components

Transformers PO U 23 Electrical 10

20371 9/9/1998 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

PO U 20 Excluded N/A 

20372 11/23/1998 Plant-Wide 

Components

Electric motors CD PC 14 Electrical 2

20373 3/16/1999 Plant-Wide 

Components

Transients PO PC 25 Excluded N/A 

20374 3/19/1999 Plant-Wide 

Components

Ventilation 

subsystems

PO PC 26 Electrical 2

50607 3/1/1997 Plant-Wide 

Components

Electrical cabinets 

(non-HEAF)

PO NC NC Excluded N/A 

50608 5/28/1997 Control/Aux/

Reactor 

Building

Transients RF U 7 Transients 2
Appendix A

Data From the FEDB

A-62

Table A-3

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

2 2/7/1968 Plant-Wide 

Components

Cable run Power operation Challenging 12 

3 3/9/1968 Plant-Wide 

Components

Cable run Power operation Challenging 12 

4 3/12/1968 Plant-Wide 

Components

Cable run Power operation Challenging 12 

5 12/30/1969 Plant-Wide 

Components

Electrical cabinets Low Power 

operation

Challenging 15.1 

6 7/7/1970 Containment 

(PWR)

Reactor coolant 

pump

Low Power 

operation

Challenging 2 

7 8/15/1970 Containment 

(PWR)

Reactor coolant 

pump

Power operation Undetermined 2 

8 8/19/1970 Turbine Building Main feedwater 

pumps

Power operation Challenging 32 

9 9/15/1970 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Low Power 

operation

Challenging 20 

10 12/15/1970 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

11 2/19/1971 Turbine Building Transient fires 

caused by welding 

and cutting

Low Power 

operation

Challenging 36 
Data 

A-63

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

12 3/24/1971 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

14 8/15/1971 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

16 11/15/1971 Turbine Building Transient fires 

caused by welding 

and cutting

Low Power 

operation

Undetermined 36 

20 6/15/1972 Plant-Wide 

Components

Pumps Power operation Challenging 21 

21 6/16/1972 Plant-Wide 

Components

Pumps Power operation Challenging 21 

22 6/27/1972 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

24 9/13/1972 Turbine Building Main feedwater 

pumps

Power operation Challenging 32 

25 11/8/1972 Transformer Yard Transformer –

Catastrophic

Low-power 

operation

Challenging 27 

26 11/12/1972 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3P 

29 12/22/1972 Plant-Wide 

Components

Pumps Power operation Undetermined 21 
Appendix A

Data From the FEDB

A-64

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

32 3/15/1973 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Power operation Undetermined 24 

33 3/15/1973 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Low-power 

operation

Challenging 20 

34 3/27/1973 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

35 6/10/1973 Turbine Building T/G oil Power operation Challenging 35 

36 8/15/1973 Turbine Building T/G oil Power operation Challenging 35 

37 1/23/1974 Plant-Wide 

Components

Pumps Power operation Challenging 21 

38 2/15/1974 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

39 3/15/1974 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

40 4/19/1974 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Challenging 6 

41 5/13/1974 Plant-Wide 

Components

Transformers Power operation Undetermined 23 

42 6/15/1974 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 
Data 

A-65

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

43 6/15/1974 Turbine Building Transient fires 

caused by welding 

and cutting

Power operation Undetermined 36 

46 9/20/1974 Turbine Building Transients Power operation Challenging 37 

47 10/15/1974 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Power operation Undetermined 24 

48 11/15/1974 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

50 12/15/1974 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

52 1/31/1975 Containment 

(PWR)

Reactor coolant 

pump

Power operation Undetermined 2 

54 3/15/1975 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

55 3/22/1975 Control/Aux/

Reactor Building

Transients Power operation Challenging 7 

56 3/31/1975 Control/Aux/

Reactor Building

Transients Low-power 

operation

Undetermined 7 

57 4/2/1975 Transformer Yard Transformer –

Catastrophic

Power operation Challenging 27 
Appendix A

Data From the FEDB

A-66

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

60 5/22/1975 Turbine Building Main feedwater 

pumps

Low-power 

operation

Challenging 32 

62 6/27/1975 Turbine Building T/G Oil Power operation Challenging 35 

63 9/15/1975 Diesel Generator 

Room

Diesel generators Power operation Undetermined 8 

64 9/15/1975 Turbine Building T/G oil Power operation Undetermined 35 

65 11/4/1975 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

66 11/5/1975 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

67 12/4/1975 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

68 12/21/1975 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

69 1/7/1976 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

70 1/19/1976 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

72 3/4/1976 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

73 3/18/1976 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 
Data 

A-67

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

74 3/24/1976 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

75 4/1/1976 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

76 4/15/1976 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

77 4/15/1976 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

79 4/17/1976 Diesel Generator 

Room

Diesel generators Power operation Undetermined 8 

80 5/4/1976 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3B 

81 5/15/1976 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

82 6/11/1976 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

83 6/15/1976 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

84 8/16/1976 Plant-Wide 

Components

RPS MG sets Power operation Undetermined 22 
Appendix A

Data From the FEDB

A-68

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

85 9/1/1976 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

86 9/15/1976 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

87 10/15/1976 Diesel Generator 

Room

Diesel generators Power operation Undetermined 8 

89 11/4/1976 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

90 11/15/1976 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

92 12/15/1976 Containment 

(PWR)

Reactor coolant 

pump

Power operation Undetermined 2 

94 3/3/1977 Containment 

(PWR)

Transients and 

hotwork

Power operation Challenging 3 

96 3/14/1977 Containment 

(PWR)

Reactor coolant 

pump

Low-power 

operation

Challenging 2 

97 3/15/1977 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

99 3/24/1977 Transformer Yard Transformer – Non 

Catastrophic

Power operation Undetermined 28 

100 4/3/1977 Turbine Building T/G hydrogen Power operation Challenging 34 
Data 

A-69

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

101 4/4/1977 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

102 4/7/1977 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

103 4/14/1977 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

106 5/7/1977 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

107 5/13/1977 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 36 

108 5/15/1977 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Undetermined 15.1 

110 6/9/1977 Turbine Building Cable fires caused 

by welding and 

cutting

Power operation Challenging 31 

111 6/15/1977 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

112 6/15/1977 Containment 

(PWR)

Reactor coolant 

pump

Low-power 

operation

Undetermined 2 

113 6/30/1977 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 
Appendix A

Data From the FEDB

A-70

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

115 7/11/1977 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

116 7/15/1977 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

117 7/15/1977 Turbine Building Cable fires caused 

by welding and 

cutting

Power operation Undetermined 31 

118 7/17/1977 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

121 8/15/1977 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

122 8/15/1977 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

123 9/3/1977 Turbine Building Transients Low-power 

operation

Challenging 37 

124 9/15/1977 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

125 9/15/1977 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

127 12/10/1977 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 
Data 

A-71

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

128 12/13/1977 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

131 2/10/1978 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

132 3/15/1978 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

134 3/20/1978 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

135 4/13/1978 Plant-Wide 

Components

Electrical cabinets Power operation N/A 15.1 

138 7/4/1978 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

139 7/5/1978 Turbine Building Boiler Power operation Undetermined 30 

142 7/28/1978 Transformer Yard Transformer –

Catastrophic

Power operation Challenging 27 

143 8/11/1978 Plant-Wide 

Components

Hydrogen tanks Power operation Challenging 17 

144 8/15/1978 Diesel Generator 

Room

Diesel generators Power operation Undetermined 8 

145 8/16/1978 Plant-Wide 

Components

Pumps Low-power 

operation

Challenging 21 
Appendix A

Data From the FEDB

A-72

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

148 10/27/1978 Containment 

(PWR)

Transients Low-power 

operation

Challenging 3P 

149 11/13/1978 Turbine Building T/G hydrogen Low-power 

operation

Challenging 34 

150 11/15/1978 Diesel Generator 

Room

Diesel generators Low-power 

operation

Undetermined 8 

151 12/12/1978 Transformer Yard Transformer – Non 

Catastrophic

Power operation Undetermined 28 

153 12/23/1978 Transformer Yard Transformer – Non 

Catastrophic

Low-power 

operation

Undetermined 28 

155 1/15/1979 Plant-Wide 

Components

Transformers Power operation Undetermined 23 

157 2/23/1979 Transformer Yard Transformer – Non 

Catastrophic

Power operation Undetermined 28 

158 4/4/1979 Battery Room Batteries Power operation Challenging 1 

159 4/15/1979 Plant-Wide 

Components

Pumps Power operation Challenging 21 

162 6/12/1979 Plant-Wide 

Components

Dryers Power operation Challenging 13 

163 7/12/1979 Control Room Main control board Low-power 

operation

Challenging 4 
Data 

A-73

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

164 7/15/1979 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

166 7/24/1979 Diesel Generator 

Room

Diesel generators Power operation Undetermined 8 

167 8/15/1979 Containment 

(PWR)

Reactor coolant 

pump

Low-power 

operation

Undetermined 2 

168 9/4/1979 Containment 

(PWR)

Reactor coolant 

pump

Power operation Undetermined 2 

169 9/30/1979 Containment 

(PWR)

Reactor coolant 

pump

Power operation Challenging 2 

170 9/30/1979 Containment 

(PWR)

Transients and 

hotwork

Power operation Undetermined 3 

172 10/15/1979 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

175 11/27/1979 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

176 12/7/1979 Plant-Wide 

Components

Electric motors Low-power 

operation

Undetermined 14 

177 12/15/1979 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

178 12/27/1979 Containment 

(PWR)

Transients and 

hotwork

Power operation Undetermined 3 
Appendix A

Data From the FEDB

A-74

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

179 1/2/1980 Plant-Wide 

Components

Transients Low-power 

operation

Undetermined 25 

180 1/16/1980 Containment 

(PWR)

Reactor coolant 

pump

Power operation Undetermined 2 

181 1/21/1980 Plant-Wide 

Components

Cable run Low-power 

operation

Challenging 12 

183 2/1/1980 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Undetermined 6 

186 2/22/1980 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

192 3/20/1980 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

195 4/15/1980 Plant-Wide 

Components

Bus duct Power operation Challenging 16.1 

198 4/16/1980 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Power operation Challenging 24 

201 4/22/1980 Turbine Building Main feedwater 

pumps

Power operation Challenging 32 

202 4/30/1980 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Power operation Challenging 24 
Data 

A-75

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

204 5/5/1980 Diesel Generator 

Room

Diesel generators Low-power 

operation

Undetermined 8 

209 5/21/1980 Plant-Wide 

Components

Pumps Power operation Challenging 21 

211 6/3/1980 Plant-Wide 

Components

Transformers Power operation Challenging 23 

214 7/6/1980 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

215 7/15/1980 Diesel Generator 

Room

Diesel generators Power operation Undetermined 8 

217 8/8/1980 Plant-Wide 

Components

RPS MG sets Power operation Challenging 22 

219 8/23/1980 Plant-Wide 

Components

Pumps Low-power 

operation

Challenging 21 

222 9/23/1980 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

223 10/2/1980 Plant-Wide 

Components

Electric motors Power operation Challenging 14 

224 10/5/1980 Plant-Wide 

Components

Pumps Power operation Challenging 21 

226 10/14/1980 Containment 

(PWR)

Transients Low-power 

operation

Undetermined 3P 
Appendix A

Data From the FEDB

A-76

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

230 11/21/1980 Turbine Building Transient fires 

caused by welding 

and cutting

Power operation Challenging 36 

231 11/28/1980 Plant-Wide 

Components

Cable run Low-power 

operation

Undetermined 12 

232 12/9/1980 Containment 

(PWR)

Transients Low-power 

operation

Undetermined 3P 

234 12/15/1980 Turbine Building T/G excitor Power operation Undetermined 33 

236 12/31/1980 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

238 1/24/1981 Plant-Wide 

Components

Pumps Power operation Challenging 21 

240 2/2/1981 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

242 2/24/1981 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Challenging 6 

244 3/9/1981 Diesel Generator 

Room

Diesel generators Power operation Undetermined 8 

247 5/1/1981 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3P 
Data 

A-77

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

250 5/12/1981 Turbine Building T/G hydrogen Power operation Challenging 34 

257 6/3/1981 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Challenging 6 

258 6/15/1981 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Undetermined 6 

260 6/30/1981 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

261 7/3/1981 Transformer Yard Transformer –

Catastrophic

Power operation Challenging 27 

262 7/14/1981 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

263 7/16/1981 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

264 7/17/1981 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

Power operation Challenging 19 

266 7/24/1981 Plant-Wide 

Components

Pumps Power operation Challenging 21 

269 8/10/1981 Plant-Wide 

Components

Pumps Power operation Challenging 21 
Appendix A

Data From the FEDB

A-78

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

270 8/15/1981 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

279 10/26/1981 Turbine Building Transients Power operation Challenging 37 

282 10/30/1981 Plant-Wide 

Components

Cable Run Low-power 

operation

Undetermined 12 

286 11/7/1981 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

287 11/7/1981 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3B 

288 11/11/1981 Turbine Building Main feedwater 

pumps

Power operation Undetermined 32 

289 11/15/1981 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 

291 11/23/1981 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

293 11/29/1981 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3B 

294 12/17/1981 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Undetermined Undetermined 24 
Data 

A-79

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

296 1/9/1982 Plant-Wide 

Components

Ventilation 

subsystems

Low-power 

operation

Undetermined 26 

297 1/12/1982 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3P 

299 1/19/1982 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

300 1/19/1982 Plant-Wide 

Components

Transformers Low-power 

operation

Challenging 23 

304 2/4/1982 Turbine Building T/G hydrogen Power operation Challenging 34 

316 4/9/1982 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 3B 

319 4/14/1982 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Challenging 6 

322 5/19/1982 Plant-Wide 

Components

Pumps Power operation Challenging 21 

323 5/27/1982 Plant-Wide 

Components

Dryers Power operation Challenging 13 

324 5/27/1982 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 
Appendix A

Data From the FEDB

A-80

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

326 6/11/1982 Turbine Building T/G excitor Power operation Challenging 33 

328 8/11/1982 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

330 8/15/1982 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

333 9/2/1982 Plant-Wide 

Components

Transformers Power operation Challenging 23 

334 9/9/1982 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 

337 9/13/1982 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 

339 9/19/1982 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 

343 9/28/1982 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 

344 10/1/1982 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 
Data 

A-81

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

345 10/4/1982 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 

347 10/7/1982 Plant-Wide 

Components

Electric motors Power operation Challenging 14 

349 10/15/1982 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

352 11/3/1982 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

353 11/9/1982 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

354 11/11/1982 Plant-Wide 

Components

Electric motors Power operation Challenging 14 

357 11/27/1982 Plant-Wide 

Components

Battery chargers Power operation Challenging 10 

359 12/26/1982 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 36 

363 2/2/1983 Plant-Wide 

Components

Transformers Power operation Undetermined 23 

368 2/16/1983 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 
Appendix A

Data From the FEDB

A-82

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

369 3/12/1983 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

370 3/16/1983 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Undetermined 15.1 

371 3/18/1983 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3P 

373 3/21/1983 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3B 

376 4/26/1983 Plant-Wide 

Components

Transformers Low-power 

operation

Undetermined 23 

384 5/20/1983 Turbine Building T/G excitor Power operation Challenging 33 

385 5/25/1983 Plant-Wide 

Components

Cable fires caused 

by welding and 

cutting

Power operation Challenging 11 

387 6/10/1983 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3B 

388 6/19/1983 Plant-Wide 

Components

Pumps Power operation Challenging 21 
Data 

A-83

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

389 6/20/1983 Plant-Wide 

Components

Transformers Low-power 

operation

Challenging 23 

391 7/8/1983 Plant-Wide 

Components

Cable fires caused 

by welding and 

cutting

Power operation Challenging 11 

397 9/7/1983 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

398 9/7/1983 Plant-Wide 

Components

Cable run Low-power 

operation

Undetermined 12 

401 9/19/1983 Turbine Building T/G oil Power operation Challenging 35 

402 9/25/1983 Turbine Building T/G oil Power operation Challenging 35 

403 10/9/1983 Plant-Wide 

Components

Ventilation 

subsystems

Low-power 

operation

Challenging 26 

405 11/14/1983 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

407 12/23/1983 Transformer Yard Transformer –

Catastrophic

Power operation Challenging 27 

410 1/15/1984 Diesel Generator 

Room

Diesel generators Low-power 

operation

Undetermined 8 
Appendix A

Data From the FEDB

A-84

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

413 2/13/1984 Turbine Building Transient fires 

caused by welding 

and cutting

Power operation Challenging 36 

415 3/19/1984 Turbine Building T/G hydrogen Power operation Challenging 34 

418 4/28/1984 Plant-Wide 

Components

Battery chargers Low-power 

operation

Challenging 10 

421 5/21/1984 Plant-Wide 

Components

Transformers Low-power 

operation

Challenging 23 

426 6/6/1984 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3B 

429 6/29/1984 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 3B 

431 7/11/1984 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

433 7/20/1984 Plant-Wide 

Components

Hydrogen tanks Power operation Challenging 17 

434 8/2/1984 Plant-Wide 

Components

Electrical cabinets 

with HEAF

Power operation Undetermined 16.a 

435 8/6/1984 Plant-Wide 

Components

Pumps Power operation Undetermined 21 
Data 

A-85

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

436 8/7/1984 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

444 10/29/1984 Plant-Wide 

Components

Pumps Undetermined Challenging 21 

445 11/4/1984 Transformer Yard Transformer –

Catastrophic

Power operation Challenging 27 

448 11/20/1984 Turbine Building Transient fires 

caused by welding 

and cutting

Power operation Challenging 36 

450 11/27/1984 Control/Aux/

Reactor Building

Transients Low-power 

operation

Challenging 7 

454 12/18/1984 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

455 12/19/1984 Turbine Building T/G hydrogen Power operation Challenging 34 

464 3/29/1985 Control/Aux/

Reactor Building

Transients Undetermined Challenging 7 

465 4/8/1985 Turbine Building T/G hydrogen Power operation Challenging 34 

469 5/2/1985 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

471 5/8/1985 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3P 
Appendix A

Data From the FEDB

A-86

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

474 6/14/1985 Turbine Building Transient fires 

caused by welding 

and cutting

Power operation Challenging 36 

475 6/25/1985 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

476 6/26/1985 Turbine Building Main feedwater 

pumps

Power operation Challenging 32 

477 6/29/1985 Turbine Building Main feedwater 

pumps

Power operation Challenging 32 

480 7/14/1985 Control Room Main control board Power operation Challenging 4 

484 8/14/1985 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

485 8/24/1985 Containment 

(PWR)

Reactor coolant 

pump

Power operation Challenging 2 

486 9/7/1985 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

487 9/12/1985 Turbine Building T/G excitor Power operation Challenging 33 

490 10/11/1985 Plant-Wide 

Components

Electric motors Undetermined Undetermined 14 

491 10/15/1985 Plant-Wide 

Components

Pumps Power operation Challenging 21 
Data 

A-87

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

492 10/28/1985 Plant-Wide 

Components

Electrical cabinets Undetermined Undetermined 15.1 

493 10/31/1985 Plant-Wide 

Components

Electrical cabinets Power operation N/A 15.1 

494 10/31/1985 Plant-Wide 

Components

Transformers Power operation Challenging 23 

495 11/2/1985 Plant-Wide 

Components

Pumps Low-power 

operation

Challenging 21 

498 12/3/1985 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

499 12/3/1985 Plant-Wide 

Components

Dryers Undetermined Undetermined 13 

502 12/15/1985 Containment 

(BWR)

Transients Low-power 

operation

Challenging 3B 

505 1/8/1986 Plant-Wide 

Components

Pumps Low-power 

operation

Undetermined 21 

506 1/20/1986 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 6 

508 1/25/1986 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 
Appendix A

Data From the FEDB

A-88

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

509 2/1/1986 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

510 2/1/1986 Plant-Wide 

Components

Cable run Power operation Challenging 12 

511 2/7/1986 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Challenging 6 

512 2/17/1986 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

Power operation Challenging 19 

513 2/19/1986 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Undetermined 15.1 

515 3/6/1986 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

516 3/8/1986 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Undetermined 15.1 

518 3/22/1986 Plant-Wide 

Components

Pumps Low-power 

operation

Undetermined 21 

522 4/17/1986 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

524 5/10/1986 Containment 

(BWR)

Main feedwater 

pumps

Power operation Challenging 32 
Data 

A-89

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

529 6/22/1986 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

531 7/23/1986 Turbine Building T/G oil Power operation Challenging 35 

532 7/24/1986 Plant-Wide 

Components

RPS MG sets Low-power 

operation

Undetermined 22 

535 8/13/1986 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

541 9/19/1986 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

544 10/14/1986 Plant-Wide 

Components

Ventilation 

subsystems

Undetermined Challenging 26 

545 10/24/1986 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 24 

551 12/16/1986 Plant-Wide 

Components

Transformers Power operation Challenging 23 

552 12/23/1986 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 24 

554 1/2/1987 Turbine Building T/G oil Power operation Challenging 35 
Appendix A

Data From the FEDB

A-90

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

557 1/31/1987 Plant-Wide 

Components

RPS MG sets Low-power 

operation

Challenging 22 

559 2/8/1987 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

562 2/16/1987 Turbine Building T/G oil Power operation Challenging 35 

566 3/1/1987 Plant-Wide 

Components

Pumps Low-power 

operation

Challenging 21 

567 3/2/1987 Plant-Wide 

Components

Transients Power operation Challenging 25 

570 3/5/1987 Plant-Wide 

Components

Hydrogen tanks Power operation Challenging 17 

572 3/14/1987 Plant-Wide 

Components

Pumps Power operation Challenging 21 

575 3/19/1987 Plant-Wide 

Components

Bus duct Power operation Challenging 16.1 

577 3/27/1987 Turbine Building Transients Power operation Challenging 37 

580 4/7/1987 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 36 

582 4/10/1987 Turbine Building Transients Low-power 

operation

Undetermined 37 
Data 

A-91

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

583 4/11/1987 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 36 

586 4/15/1987 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 36 

587 4/20/1987 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

588 4/20/1987 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 36 

589 4/22/1987 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 36 

590 4/22/1987 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 36 

591 4/25/1987 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 36 

601 5/28/1987 Turbine Building T/G oil Low-power 

operation

Challenging 35 

608 6/17/1987 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 
Appendix A

Data From the FEDB

A-92

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

611 7/2/1987 Plant-Wide 

Components

RPS MG sets Low-power 

operation

Challenging 22 

613 7/9/1987 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 36 

614 7/10/1987 Plant-Wide 

Components

Transformers Power operation Challenging 23 

625 9/17/1987 Plant-Wide 

Components

Ventilation 

subsystems

Power operation Challenging 26 

626 9/19/1987 Turbine Building Boiler Low-power 

operation

Undetermined 30 

631 10/9/1987 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

632 10/13/1987 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

633 10/13/1987 Plant-Wide 

Components

Ventilation 

subsystems

Power operation Challenging 26 

634 10/14/1987 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

636 10/16/1987 Turbine Building T/G oil Power operation Challenging 35 
Data 

A-93

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

638 10/30/1987 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3P 

639 10/31/1987 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3P 

640 11/2/1987 Containment 

(BWR)

Cable fires caused 

by welding and 

cutting

Low-power 

operation

Challenging 11 

641 11/2/1987 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 6 

642 11/4/1987 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

643 11/10/1987 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 36 

644 11/10/1987 Diesel Generator 

Room

Diesel generators Undetermined Challenging 8 

646 11/18/1987 Plant-Wide 

Components

Battery chargers Power operation Undetermined 10 

648 11/24/1987 Containment 

(BWR)

Transients Low-power 

operation

Undetermined 3B 
Appendix A

Data From the FEDB

A-94

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

650 11/30/1987 Control/Aux/

Reactor Building

Transients Power operation Undetermined 7 

651 12/3/1987 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

653 12/10/1987 Plant-Wide 

Components

Transients Power operation Challenging 25 

654 12/11/1987 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

656 12/17/1987 Plant-Wide 

Components

RPS MG sets Power operation Challenging 22 

659 12/30/1987 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

660 12/30/1987 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

662 1/8/1988 Turbine Building Main feedwater 

pumps

Power operation Challenging 32 

665 1/19/1988 Plant-Wide 

Components

Junction boxes Low-power 

operation

Challenging 18 

667 1/28/1988 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

668 1/28/1988 Turbine Building T/G oil Power operation Undetermined 35 
Data 

A-95

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

669 2/1/1988 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

670 2/1/1988 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

673 2/8/1988 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

676 2/16/1988 Turbine Building T/G excitor Power operation Undetermined 33 

677 2/27/1988 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

678 3/2/1988 Plant-Wide 

Components

Bus duct Power operation Challenging 16.1 

681 3/9/1988 Plant-Wide 

Components

Cable run Low-power 

operation

Challenging 12 

682 3/9/1988 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3P 

683 3/12/1988 Plant-Wide 

Components

Dryers Low-power 

operation

Undetermined 13 

700 4/15/1988 Turbine Building Transient fires 

caused by welding 

and cutting

Power operation Challenging 36 
Appendix A

Data From the FEDB

A-96

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

704 4/20/1988 Plant-Wide 

Components

Dryers Power operation Challenging 13 

708 5/10/1988 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Undetermined 15.1 

710 5/10/1988 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

713 5/21/1988 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 24 

715 5/24/1988 Plant-Wide 

Components

Dryers Power operation Challenging 13 

717 5/27/1988 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 24 

718 5/27/1988 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 24 

720 5/28/1988 Plant-Wide 

Components

RPS MG sets Low-power 

operation

Challenging 22 

722 6/4/1988 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3B 
Data 

A-97

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

724 6/6/1988 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 24 

726 6/11/1988 Plant-Wide 

Components

Electric motors Low-power 

operation

Challenging 14 

732 7/6/1988 Plant-Wide 

Components

Bus duct Power operation Challenging 16.1 

734 7/17/1988 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

735 7/21/1988 Plant-Wide 

Components

Pumps Power operation Challenging 21 

736 7/24/1988 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

737 7/29/1988 Turbine Building Main feedwater 

pumps

Power operation Challenging 32 

738 7/29/1988 Transformer Yard Transformer – Non 

Catastrophic

Low-power 

operation

Undetermined 28 

739 7/30/1988 Turbine Building Main feedwater 

pumps

Power operation Challenging 32 

740 8/2/1988 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 24 
Appendix A

Data From the FEDB

A-98

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

743 8/11/1988 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Challenging 6 

745 8/17/1988 Plant-Wide 

Components

Junction boxes Power operation Challenging 18 

747 9/4/1988 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Challenging 20 

751 9/27/1988 Turbine Building Transient fires 

caused by welding 

and cutting

Undetermined Challenging 36 

752 9/28/1988 Turbine Building T/G oil Power operation Undetermined 35 

755 10/5/1988 Plant-Wide 

Components

Pumps Power operation Challenging 21 

756 10/14/1988 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

763 11/11/1988 Transformer Yard Transformer –

Catastrophic

Power operation Challenging 27 

765 11/27/1988 Diesel Generator 

Room

Diesel generators Low-power 

operation

Undetermined 8 

770 2/21/1980 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Undetermined 6 
Data 

A-99

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

772 2/14/1981 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 3B 

773 1/21/1989 Plant-Wide 

Components

Transients Low-power 

operation

Undetermined 25 

777 5/11/1989 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

778 7/11/1989 Plant-Wide 

Components

Pumps Power operation Undetermined 21 

781 4/27/1989 Plant-Wide 

Components

Pumps Power operation Undetermined 21 

785 5/19/1989 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Undetermined 15.1 

792 7/15/1988 Plant-Wide 

Components

Iso-phase ducts Power operation Challenging 16.2 

794 3/31/1989 Plant-Wide 

Components

RPS MG sets Power operation Undetermined 22 

795 8/28/1989 Containment 

(PWR)

Reactor coolant 

pump

Power operation Undetermined 2 

797 2/3/1989 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Undetermined 15.1 
Appendix A

Data From the FEDB

A-100

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

801 11/6/1988 Plant-Wide 

Components

RPS MG sets Low-power 

operation

Undetermined 22 

805 4/12/1989 Plant-Wide 

Components

Battery chargers Low-power 

operation

Undetermined 10 

808 3/24/1989 Diesel Generator 

Room

Diesel generators Undetermined Undetermined 8 

809 12/23/1989 Turbine Building T/G oil Power operation Challenging 35 

831 11/1/1988 Diesel Generator 

Room

Diesel generators Low-power 

operation

Undetermined 8 

832 10/7/1989 Plant-Wide 

Components

Transformers Power operation Undetermined 23 

835 11/18/1989 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 24 

842 12/8/1988 Plant-Wide 

Components

Pumps Power operation Undetermined 21 

845 5/29/1989 Transformer Yard Transformer –

Catastrophic

Low-power 

operation

Challenging 27 

846 9/16/1989 Plant-Wide 

Components

Transformers Power operation Undetermined 23 
Data 

A-101

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

848 1/7/1989 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

Low-power 

operation

Undetermined 19 

853 12/1/1989 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

Undetermined Undetermined 19 

864 11/28/1989 Diesel Generator 

Room

Diesel generators Low-power 

operation

Undetermined 8 

870 1/29/1988 Plant-Wide 

Components

Electric motors Power operation Undetermined 14 

872 11/19/1989 Transformer Yard Transformer – Non 

Catastrophic

Power operation Undetermined 28 

886 7/10/1980 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

887 8/27/1980 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

888 3/28/1981 Plant-Wide 

Components

Electric motors Power operation Undetermined 14 

891 3/15/1982 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

893 4/20/1982 Plant-Wide 

Components

Pumps Power operation Challenging 21 

897 3/8/1983 Plant-Wide 

Components

Pumps Power operation Challenging 21 
Appendix A

Data From the FEDB

A-102

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

901 5/7/1983 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

902 5/15/1983 Diesel Generator 

Room

Diesel generators Power operation Undetermined 8 

905 8/27/1983 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

907 12/9/1983 Plant-Wide 

Components

Pumps Low-power 

operation

Challenging 21 

908 7/3/1984 Plant-Wide 

Components

Cable Run Power operation Challenging 12 

914 11/20/1985 Plant-Wide 

Components

Pumps Low-power 

operation

Challenging 21 

916 1/7/1986 Plant-Wide 

Components

Transformers Power operation Undetermined 23 

919 7/17/1986 Transformer Yard Yard transformers 

(others)

Low-power 

operation

Challenging 29 

922 7/10/1987 Plant-Wide 

Components

Bus duct Power operation Challenging 16.1 

926 1/20/1989 Turbine Building T/G hydrogen Power operation Challenging 34 

928 3/1/1989 Control Room Main control board Power operation Challenging 4 
Data 

A-103

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

929 10/9/1989 Plant-Wide 

Components

Iso-phase ducts Power operation Challenging 16.2 

934 4/13/1986 Transformer Yard Transformer – Non 

Catastrophic

Power operation Undetermined 28 

935 8/2/1985 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

940 10/2/1987 Turbine Building T/G oil Power operation Challenging 35 

941 9/1/1989 Transformer Yard Transformer –

Catastrophic

Low-power 

operation

Challenging 27 

942 3/5/1989 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

944 10/7/1989 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

945 9/16/1989 Diesel Generator 

Room

Diesel generators Undetermined Undetermined 8 

947 1/3/1989 Plant-Wide 

Components

Electrical cabinets 

with HEAF

Power operation Challenging 16.b 

949 1/9/1982 Plant-Wide 

Components

Pumps Low-power 

operation

Challenging 21 
Appendix A

Data From the FEDB

A-104

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

955 2/12/1988 Plant-Wide 

Components

Pumps Power operation Challenging 21 

957 10/27/1989 Turbine Building T/G excitor Power operation Challenging 33 

963 6/11/1988 Containment 

(PWR)

Transients and 

hotwork

Undetermined Undetermined 3 

968 4/3/1989 Plant-Wide 

Components

Transients Undetermined Challenging 25 

969 5/2/1989 Turbine Building Transient fires 

caused by welding 

and cutting

Undetermined Challenging 36 

971 9/19/1989 Plant-Wide 

Components

Electrical cabinets Undetermined Undetermined 15.1 

972 9/27/1989 Turbine Building Transients Undetermined Undetermined 37 

975 11/9/1989 Plant-Wide 

Components

Pumps Undetermined Undetermined 21 

1050 1/1/1989 Turbine Building Transients Power operation Challenging 37 

1051 2/12/1989 Turbine Building Transients Low-power 

operation

Undetermined 37 

1052 8/16/1989 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

Power operation Undetermined 19 

1053 8/19/1989 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 
Data 

A-105

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

1054 9/28/1989 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 

1094 11/4/1983 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 

1095 9/8/1986 Turbine Building Transient fires 

caused by welding 

and cutting

Power operation Undetermined 36 

1097 11/15/1986 Plant-Wide 

Components

Ventilation 

subsystems

Low-power 

operation

Undetermined 26 

1098 2/7/1989 Plant-Wide 

Components

Transients Power operation Undetermined 25 

1099 2/11/1989 Plant-Wide 

Components

Pumps Low-power 

operation

Undetermined 21 

1100 4/18/1989 Plant-Wide 

Components

Ventilation 

subsystems

Power operation Undetermined 26 

1108 6/6/1989 Plant-Wide 

Components

Air compressors Power operation Undetermined 9 

1109 10/28/1989 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 
Appendix A

Data From the FEDB

A-106

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

1117 2/16/1980 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 24 

1119 2/23/1989 Turbine Building Transients Power operation Undetermined 37 

1120 10/28/1989 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 3B 

1121 11/5/1989 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 24 

1124 10/7/1986 Plant-Wide 

Components

Electric motors Undetermined Undetermined 14 

1128 3/10/1988 Turbine Building Transients Power operation Undetermined 37 

1129 2/15/1989 Plant-Wide 

Components

Transformers Low-power 

operation

Undetermined 23 

1132 11/6/1989 Plant-Wide 

Components

Dryers Undetermined Undetermined 13 

1133 11/7/1989 Plant-Wide 

Components

Electrical cabinets Undetermined Undetermined 15.1 

1134 12/16/1989 Plant-Wide 

Components

Transformers Low-power 

operation

Undetermined 23 
Data 

A-107

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

1143 2/28/1975 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Undetermined Undetermined 24 

1144 3/26/1975 Turbine Building Transients Undetermined Undetermined 37 

1145 5/2/1975 Turbine Building Transient fires 

caused by welding 

and cutting

Undetermined Undetermined 36 

1147 6/2/1975 Plant-Wide 

Components

Electrical cabinets Undetermined Undetermined 15.1 

1149 12/2/1975 Turbine Building Transients Undetermined Challenging 37 

1151 3/10/1977 Diesel Generator 

Room

Diesel generators Low-power 

operation

Undetermined 8 

1153 10/16/1977 Turbine Building Transients Low-power 

operation

Undetermined 37 

1154 3/10/1978 Turbine Building Transient fires 

caused by welding 

and cutting

Undetermined Undetermined 36 

1155 4/26/1978 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

Power operation Undetermined 19 

1157 11/5/1983 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 36 
Appendix A

Data From the FEDB

A-108

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

1178 4/29/1975 Plant-Wide 

Components

Pumps Power operation Undetermined 21 

1179 7/7/1975 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

1180 10/18/1975 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 3B 

1181 3/30/1976 Plant-Wide 

Components

Transients Power operation Undetermined 25 

1182 8/17/1976 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Undetermined 6 

1184 9/2/1976 Plant-Wide 

Components

Pumps Power operation Undetermined 21 

1185 1/8/1977 Plant-Wide 

Components

Ventilation 

subsystems

Power operation Undetermined 26 

1186 2/17/1977 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Challenging 6 

1191 7/19/1979 Plant-Wide 

Components

Off-gas/H2

recombiner (BWR)

Power operation Undetermined 20 
Data 

A-109

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

1235 2/3/1975 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation 

Undetermined 3B 

1238 10/9/1975 Plant-Wide 

Components

Cable run Undetermined Undetermined 12 

1239 5/24/1976 Plant-Wide 

Components

Pumps Low-power 

operation

Undetermined 21 

1240 9/11/1976 Turbine Building Main feedwater 

pumps

Power operation Undetermined 32 

1242 11/3/1976 Turbine Building Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 36 

1243 12/3/1976 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Undetermined Undetermined 24 

1244 2/8/1977 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

1245 2/24/1977 Turbine Building Transient fires 

caused by welding 

and cutting

Power operation Undetermined 36 

1246 4/25/1977 Plant-Wide

Components

Electrical cabinets Undetermined Undetermined 15.1 
Appendix A

Data From the FEDB

A-110

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

1247 4/27/1977 Plant-Wide 

Components

Transients Undetermined Undetermined 25 

1249 10/27/1977 Containment 

(BWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 3B 

1252 6/7/1978 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Undetermined Undetermined 24 

1253 6/25/1978 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

1254 8/24/1978 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Power operation Undetermined 24 

1258 12/19/1978 Plant-Wide 

Components

Transformers Power operation Undetermined 23 

1259 1/25/1979 Plant-Wide 

Components

Electrical cabinets Power operation Undetermined 15.1 

1260 4/29/1979 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Undetermined 15.1 

1297 11/18/1989 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Power operation Undetermined 6 
Data 

A-111

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

1308 8/7/1984 Transformer Yard Transformer – Non 

Catastrophic

Power operation Challenging 28 

1311 3/31/1988 Control/Aux/

Reactor Building

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 6 

1315 12/12/1989 Plant-Wide 

Components

Electrical cabinets Undetermined Undetermined 15.1 

1317 4/13/1978 Plant-Wide 

Components

Miscellaneous 

hydrogen fires

Power operation Undetermined 19 

1337 3/31/1989 Plant-Wide 

Components

Ventilation 

subsystems

Low-power 

operation

Challenging 26 

1482 1/22/1986 Turbine Building Main feedwater 

pumps

Power operation Challenging 32 

1483 3/13/1986 Diesel Generator 

Room

Diesel generators Power operation Challenging 8 

1485 7/20/1986 Diesel Generator 

Room

Diesel generators Low-power 

operation

Challenging 8 

1487 4/17/1987 Plant-Wide 

Components

Ventilation 

subsystems

Power operation Challenging 26 

1488 10/21/1987 Containment 

(PWR)

Reactor coolant 

pump

Power operation Undetermined 2 
Appendix A

Data From the FEDB

A-112

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

1489 10/26/1987 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Challenging 15.1 

2361 3/10/1986 Plant-Wide 

Components

Cable run Power operation Undetermined 12 

2367 12/13/1983 Plant-Wide 

Components

Electrical cabinets Power operation Challenging 15.1 

2368 10/16/1983 Plant-Wide 

Components

Electrical cabinets Low-power 

operation

Undetermined 15.1 

2370 11/19/1976 Plant-Wide

Components

Electrical cabinets Undetermined Undetermined 15.1 

2373 12/2/1976 Control Room Main control board Undetermined Undetermined 4 

2374 12/31/1975 Diesel Generator 

Room

Diesel generators Undetermined Undetermined 8 

2445 10/5/1987 Plant-Wide 

Components

Pumps Undetermined Undetermined 21 

2447 8/1/1987 Plant-Wide 

Components

Electrical cabinets Undetermined Undetermined 15.1 

2456 2/3/1987 Turbine Building Main feedwater 

pumps

Power operation Undetermined 32 

2463 10/16/1988 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 3P 
Data 

A-113

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

2465 9/23/1988 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 3P 

2466 9/12/1988 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Challenging 3P 
Appendix A

Data From the FEDB

A-114

Table A-3 (continued)

Fire event data for 1968–1989

Incident 

Number

Event Date Location Ignition Source Power Condition Fire Severity Bin 

Designation

2467 7/27/1988 Containment 

(PWR)

Transient fires 

caused by welding 

and cutting

Low-power 

operation

Undetermined 3P 

2469 7/14/1988 Plant-Wide 

Components

Transient fires 

caused by welding 

and cutting

Undetermined Challenging 24 

2476 1/23/1989 Plant-Wide 

Components

Ventilation 

subsystems

Undetermined Undetermined 26 





UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON, DC 20555-0001

------------------

OFFICIAL BUSINESS
NUREG-2169 Nuclear Power Plant Fire Ignition Frequency and Non-Suppression Probability 

Estimation Using the Updated Fire Events Database