NUREG/CR-5384

SAND89-1359

A Summary of

Nuclear Power Plant

Fire Safety Research at

Sandia National Laboratories,

1975-1987

Prepared by S. P. Nowlen

Sandia National Labor.

Prepared for

U.S. Nuclear Regulatorq

'S

atories

y Commission

_ -4
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.1-

/
NUREG/CR-5384

SAND89-1359

RP

A Summary of

Nuclear Power Plant

Fire Safety Research at

Sandia National Laboratories,

1975-1987

Manuscript Completed: December 1989

Date Published: December 1989

Prepared by

S. P. Nowlen

Sandia National Laboratories

Albuquerque, NM 87185

Prepared for

Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

NRC FIN A1010
A"'

Is

I.i
ABSTRACT

This report summarizes the results and conclusions generated by the U. S.

Nuclear Regulatory Commission sponsored Fire Protection Research Program

at Sandia National Laboratories. Efforts conducted from the programs

inception in 1975 through 1987 are discussed. The individual efforts are

discussed within a framework based on specific areas of investigation.

Early efforts are presented in the context of investigations of specific

regulatory concerns. Later efforts are presented within the context of

an integrated investigation of fire safety issues. This integrated

approach considers the fire safety issue in terms of (1) source fire

characterization, (2) detection and suppression system effectiveness, (3)

room effects, (4) equipment response, and (5) room-to-room fire effects.

The report provides a complete bibliography of reports and journal

articles generated as a result of these efforts with a cross-reference

listing of major reports to specific efforts.

Among the topics investigated by various experimental efforts are the

effectiveness of fire retardant cable coatings and cable tray fire

barrier systems in the prevention of fire spread and fire induced damage,

the effectiveness of suppression methods for cable tray fires, testing of

cable penetration seals, transient fuel fire characterization testing,

investigation of electrical cabinet and control room fires, equipment

damageability testing, and large scale enclosure fire testing for the

validation of computer fire simulation codes. Topics investigated as a

part of analytical efforts include a review of the fire regulations which

bear relevance to nuclear plants, investigation of the standards and

strategies invoked in the design of various fire protection subsystems,

the modeling of cable fire behavior, the identification of reported

transient fuel sources, and the development of a fire occurrence data

base.

iii/iv

TABLE OF CONTENTS

Section

EXECUTIVE SUMMARY ..................................................

1.0 INTRODUCTION

1.1. overview of the Fire Protection Research Program ........

1.2 Format for Presentation ................................

2.0 INVESTIGATION OF SPECIFIC REGULATORY CONCERNS

2.1 Scope of This Chapter ..................................

2.2 Fire Protection Systems Study ..........................

2.3 Fire Protection Subsystems Study ........................

2.3.1 Ventilation Subsystems Study .....................

2.3.2 Fire Detection Subsystems Study ..................

2.3.3 Fire Barrier Subsystems Study ....................

2.3.4 Fire Hazards Analysis Subsystems Study ...........

2.4 Cable Tray Fire Testing ................................

2.5 Investigation of Fire Stop Test Parameters ..............

2.6 Fire Suppression System Effectiveness Investigations ....

2.7 Cost Analysis of Fire Protection Systems ................

2.8 Detector Siting Criteria Requirements Study .............

2.9 Twenty-Foot Separat.on Adequacy Investigations ..........

3.0 FIRE CHARACTERIZATION STUDIES

3.1 Introduction ...........................................

3.2 General Studies and Experience Base Reviews .............

3.2.1 Review of Fire Characterization Data .............

3.2.2 Identification and Classification of Transient

Combustible Fuel Sources ........................

3.2.3 Development of Nuclear Power Plant Fire

Occurrence Data Base ...........................

3.3 Transient Fuel Source Fire Characterization Efforts ...

3.3.1 Trash/Pool Fire Correlation Tests ................

3.3.2 Transient Fuel Source Fire Tests .................

3.4 Investigation of Cable Tray Fire Behavior ...............

3.4.1 Cable Use Screening Survey .......................

3.4.2 Electrically Initiated Cable Fire Tests ..........

3.4.3 Exposure Cable Tray Fire Testing .................

3.4.4 Cable Tray Fire Retardant Coatings Tests .........

3.4.5 Cable Tray Fire BarrierjTests ....................

3.4.6 Cable Tray Fire Corner Effects Tests .............

3.4.7 Burn Mode Analysis of Cable Fires ................

3.5 Investigation of Electrical Control Panel Fires .........

3.5.1 Development of an Electrical Fire Initiation

Apparatus ..................................

3.5.2 Experimental Evaluation of Electrical Panel

Fires ..........................................

Pag~e

1

6

10

13

13

14

14

15

15

16

16

is

19

20

20

21

22

23

23

24

30

32

32

33

34

35

35

36

40

46

47

49

52

52

53

v
TABLE OF CONTENTS (Continued)

Section

4.0 DETECTION AND SUPPRESSION SYSTEM EFFECTIVENESS STUDIES ......... 55

4.1 Introduction ............................................ 55

4.2 Fire Detection Systems Investigations .................... 55

4.2.1 Fire Protection Subsystems Study; Fire Detection, 55

4.2.2 Detector Siting Criteria Requirements Study.,..,. 58

4.3 Investigation of the Effectiveness of Fire Suppression

Systems ........................ . 59

4.4 Detection and Suppression Insights Based on Actual

Experience ............................................. 60

5.0 ROOM EFFECTS STUDIES ........................................... 64

5.1 Introduction ............................................ 64

5.2 Twenty-Foot Separation Tests ............................ 65

5.3 Base Line Validation Enclosure Fire Tests ................. 72

5.4 Cabinet and Control Room Fire Tests ...................... 80

6.0 EQUIPMENT RESPONSE STUDIES ...................................... 87

6.1 Introduction ............................. ..... ......... 87

6.2 Investigations of Cable Fire Vulnerability .............. 87

6.2.1 Cable Tray Fire Testit. ................ ........ 88

6.2.2 Twenty-Foot Separation Tests ...................... 93

6.2.3 Cable Radiant and Convective Damage Tests ......... 94

6.2.4 Cable Steady State Thermal Damage Tests .......... 97

6.2.5 Cable Transient Thermal Damage Tests............. 99

6.3 Equipment Damage Sensitivity Ranking Study.............. 102

6.4 Relay Thermal Damage Tests .............................. 103

6.5 Component Testing in Secondary Fire Environments ........ 103

7.0 ROOM-TO-ROOM FIRE ISSUES STUDIES ............................... 108

7.1 Introduction.................................1-........ 108

7.2 Fire Protection Subsystems Study; VentilationSystems... 108

7.3 Fire Protection Subsystems Study; Fire Barriers ......... 109

7.4 Investigation of Fire Stop Test Parameters ............. 110

8.0 AN OVERVIEW OF THE FIRE RISK SCOPING STUDY ..................... 112

8.1 Introduction ........................................... 12

8.2 A review and Updating of the Fire Risk Perspective ...... 112

8.3 Identification and Assessment of Unaddressed Fire

Risk Issues ....................................... .... 114

8.4 Summary ........................................ ........ 116

9.0 SUMMARY ....................................................... 119

10.0 REFERENCES .................................................... 122

APPENDIX A: BIBLIOGRAPHY OF FIRE PROTECTION RESEARCH PROGRAM

REPORTS WITH CROSS-REFERENCE OF REPORTS TO SPECIFIC

RESEARCH EFFORTS ....................................... 125

vi
LIST OF TABLES

Table Pae

3.1 Cable Types Selected for Initial Cable Fire Testing .......... 36

3.2 Matrix of Cable Fire Retardant Coatings Tests ................ 41

3.3 Summary of Principal Single Tray Gas Burner Cable

Fire Retardant Coatings Test Results ...................... 43

3.4 Summary of Principal Two Tray Diesel Fuel Fire Cable

Fire Retardant Coatings Tests Involving Nonrated

3-Conductor Cables ........................................ 45

3.5 Matrix of Cable Tray Fire Barrier Tests ...................... 46

3.6 Summary of Principal Two Tray Gas Burner Cable Tray

Fire Barrier Tests Involving Nonrated 3-Conductor

PE/PVC Cables .................................... ....... 47

3.7 Summary of Corner Effects Test Results For Upper of Two

Cable Trays............................................... 51

4.1 Summary of Fire Suppression System Effectiveness Study

Results ................................................... 61

5.1 Summary of Principal Fire Environment Characterization

Results for Experiments 1-6 of the Twenty-Foot

Separation-Tests .......................................... 67

5.2 Summary of Principal Fire Environment Characterization

Results for Tests 1-4 of the Twenty-Foot Separation

Tests ..................................................... 68

5.3 Matrix of Simple Fuel Base Line Validation Tests ............. 76

5.4 Summary of Principal Result for the Simple Fuel Base

Line Validation Tests ..................................... 77

5.5 Matrix of Control Room Fire Tests ............................ 82

6.1 Summary of Single Tray Gas Burner Cable Fire Retardant

Coatings Test Results ..................................... 90

6,2 Summary of Two Tray Diesel Fuel Cable Fire Retardant

Coatings Test Results ..................................... 91

6.3 Summary of Single Tray Gas Burner Cable Fire Barrier

Test Results .............................................. 92

6.4 Summary of Experimental Conditions Varied in Each of the

Twenty-Foot Separation Tests .............................. 95

8.1 Summary of Scenario Requantification Results Prior to

the Incorporation of Plant Appendix R Modifications ....... 113

8.2 Summary of Appendix R Plant Modification Risk Impact ......... 113

8.3 Summary Unaddressed Issues Investigation Findings ............ 118

vii
LIST OF FIGURES

Figure: aum

3.1 Typical Quantity Transient Fuel Source Histograms ............ 25

3.2 Upper and Lover Bound Quantity Transient Fuel Source

Histograms ................................................ 27

3.3 Yearly History of Fire Events as Documented in the

SNL Data Base ............................................. 31

3.4 Pre-Test Cable Tray Configuration Used in July 6, 1977

RGI.75 Separation Criteria Adequacy Test .................. 38

3.5 Burn Mode Analysis for Nonrated Cable Fire ................... 50

3.6 Burn Mode Analysis for Rated Low Flame Spread Cable

Fire ................................... : .................. 50

4.1 Fire Suppression Probability Curve Based on Incidents

In the SNL Fire Occurrence Data Base for Which a Time

to Fire Suppression is Reported ........................... 63

5.1 Instrumentation Placement Used in the Twenty-Foot Tests ...... 69

5.2 Average Temperatures Measured Near the Redundant Train

Cable Trays During Experiments 1-4 of the Twenty-Foot

Separation Tests .......................................... 71

5.3 Average Temperatures Measured Near the Redundant Train

Cable Trays During Tests 1-6 of the Twenty-Foot

Separation Tests ........................................... 71

5.4 Estimated Heat Release Rates for Experiments 2 and 3,

and for Tests 1 and 2 of the Twenty-Foot Separation

Tests ..................................................... 73

5.5 Instrumentation Placement Used in the Base Line

Validation Tests .......................................... 75

5.6 Temperature Versus Time with Elevations as the Curve

Parameter at the Room Center Instrument Tree (Sector 2)

During Base Line Validation Test 5 ........................ 78

5.7 Temperature Versus Elevation with Time as The Curve

Parameter at the Room Center Instrument Tree (Sector 2)

During Base Line Validation Test 5 ........................ 78

5.8 Heat Release Rate for Control Room Fire Test 21 .............. 83

5.9 Heat Release Rate for Control Room Fire Test 22 .............. 83

5.10 Heat Release Rate for Control Room Fire Test 23 .............. 84

5.11 Heat Release Rate for Control Room Fire Test 24 ............... 84

5.12 Heat Release Rate for Control Room Fire Test 25 .............. 85

6.1 Radiant Thermal Heating Cable Tray Damageability Test

Results ................................................... 98

6.2 Radiant Thermal Heating Cable Nonpiloted Ignition

Test Results .............................................. 98

6.3 Cable Steady State Thermal Damageability Results for

a Nonrated PE/PVC 3-Conductor Power Cable ................. 100

6.4 Cable Steady State Thermal Damageability Results for

a Rated Low Flame Spread XPE 3-Conductor Power Cable ...... 100

viii
Acknowledgements

The results and conclusions summarized here were generated as a result of

several years of research performed by a number of investigators, both

within Sandia and at other organizations. Many individuals have

contributed to the performance of these efforts. The contributions of

each of these individuals are acknowledged as the foundations upon which

this work is based.

ix
NOMENCILATURE

ASTM - American Society for Testing and Materials...

AWG - American Wire Gage

BTP - Branch Technical Position

CDF - Core Damage Frequency

CFR - Code of Federal Regulations

EPR - Ethylene-propylene Rubber

FMRC - Factory Mutual Research Corporation

FPRP - Fire Protection Research Program

I&E - Inspection and Enforcement

IEEE - Institute of Electrical and Electronics Engineers

NBS - National Bureau of Standards

NFPA - National Fire Protection Association

PE - Polyethylene

PMMA - Polymethyl-methacrylate

PRA - Probabilistic Risk Assessment

PVC - Polyvinyl Chloride

RG - Regulatory Guideline

RMIEP - Risk Methodologies Integration and Evaluation Program

SNL - Sandia National Laboratories

TAP-A45 - Task Action Plan A45

UL - Underwriters Laboratories

USNRC - United States Nuclear Regulatory Commission

XPE - Cross-Linked Polyethylene (also XLPE)

x
EXECUTIVE SUMMARY

This report presents a consolidation of the results and conclusions

generated through numerous individual efforts conducted under the U. S.

Nuclear Regulatory Commission (USNRC) sponsored Fire Protection Research

Program (FPRP) at.Sandia National Laboratories (SNL). This program was

initiated in fiscal year 1975 (FY-75) and the report covers efforts from

program inception through the termination of efforts as of the end of

FY-87. The individual efforts conducted under this program involved both

analytical and experimental efforts associated with a broad range of

nuclear power plant fire safety issues.

As initially conceived, the early FPRP investigated specific regulatory

concerns. These concerns were raised in large part by the cable tray

fire at the Browns Ferry Plant in 1975, though the program actually

predates that fire by approximately 3 months. As a result of this fire,

awareness of the potential impact of fire on the operability of a nuclear

power plant increased. The early FPRP investigations focused on the

identification of areas of weakness in the fire regulations and on the

defintion of a new set of fire protection guidelines.

In more recent years, the focus of the FPRP has shifted towards an

integrated investigation of more general fire safety concerns and fire

phenomena. The individual efforts performed as a part of this integrated

approach to fire safety can be grouped into five areas of investigation.

These areas are:

1. Source Fire Characterization,

2. Detection and Suppression System Effectiveness,

3. Room Effects,

4. Equipment Response, and

5. Room-to-room Fire Effects.

Source fire characterization is associated with the identification of

potential fire initiation sources and the characterization of the burning

behavior of these sources. Detection and suppression system

effectiveness includes consideration of the degree of additional safety

afforded by such systems, and the adequacy of current guidelines for

system implementation in nuclear power plant applications. Room effects

issues ate associated with the mechanisms for the transport of fire

products (heat, smoke, etc.:) within the room of fire origin. Equipment

response issues are associated with the effects of a fire environment on

the operability of plant components. The final area, room-to-room fire

effects, is associated with the potential adverse effects of a fire

beyond the room of origin. These effects include fire spread through

barriers, the management of fire products and fire suppression agents,

manual fire brigade accessibility issues, and spurious suppression system

operation in uninvolved areas.

-1-
A major objective of the more recent investigations has been the support

of efforts to assess plAnt risk due to fires. Each of the five areas of

investigation can be associated with one or more of the steps performed

in such risk assessments. An adequate understanding of the phenomena

involved in a fire is critical to the appropriate modeling of the effects

of a fire on plant systems.

Listed below are the specific areas of research conducted under the FPRP.

The studies have been grouped to indicate their applicability to either

specific regulatory issue investigations, and/or the specific areas of

investigation identified as a part of the integrated approach to fire

safety. It will be noted that several of these efforts provide insights

into more than one area of investigation.

Investigations of Specific Regulatory Concerns:

1975 Cable Use Screening Survey

1976 Fire Protection Systems Study

1979 Fire Protection Subsystems Study

1976-81 Cable Tray Fire Testing:

1976 Electrically Initiated Cable Fire Tests

1977 Exposure Fire Cable Fire Tests

1978 Fire Retardant Cable Coating Tests

1978 Cable Tray Fire Barrier Tests

1979 Cable Tray Fire Corner Effects Tests

1981 Cable Radiant and Convective Heating Damage Tests

1981 Burn Mode Analysis of Cable Fires

1980 Investigation of Fire Stop Test Parameters

1980-83 Fire Suppression System Effectiveness Investigations:

1980 Halon Suppression Effectiveness Tests

1981 Water Sprinkler Suppression Effectiveness Tests

1982 Directed Water Spray Suppression Effectiveness

Tests

1983 Carbon Dioxide Suppression Effectiveness Tests

1981 Cost Analysis of Fire Protection Systems

1982 Detector Siting Criteria Requirements Study

1982 Twenty-Foot Separation Adequacy Investigations

Source Fire Characterization Studies:

1975 Cable Use Screening Survey

1976-81 Cable Tray Fire Testing:

1976 Electrically Initiated Cable Fire Tests

1977 Exposure Fire Cable Fire Tests

1978 Fire Retardant Cable Coating Tests

1978 Cable Tray Fire Barrier Tests

1979 Cable Tray Fire Corner Effects Tests

1981 Burn Mode Analysis of Cable Fires

1981 Trash/Pool Fire Correlation Tests

1984 Identification and Classification of Transient Fuel

Ignition Sources

-2-
1985

1985

1985

1985

1986

Review of Fire Characterization Data

Development of Electrical Ignition Apparatus

Transient Fuel Source Fire Tests

Electrical Cabinet and Control Room Fire Tests

Development of Nuclear Power Plant Fire Occurrence

Data Base

Detection and Suppression Effectiveness Studies:

1980-83 Fire Suppression System Effectiveness Investigations:

1980 Halon Suppression Effectiveness Tests

1981 Water Sprinkler Suppression Effectiveness Tests

1982 Directed Water Spray Suppression Effectiveness

Tests

1983 Carbon Dioxide Suppression Effectiveness Tests

1982 Detector Siting Criteria Requirements Study

Room Effects

1982

1985

1985

Studies:

Twenty-Foot Separation Tests

Base Line Validation Enclosure Fire Tests

Electrical Cabinet and Control Room Fire Tests

Equipment Response Studies:

1976-81 Cable Tray Fire Testing:

1978 Fire Retardant Cable Coating Tests

1978 Cable Tray Fire Barrier Tests

1981 Cable Radiant and Convective Heating Damage Tests

1984 Cable Steady State Thermal Damage Tests

1985 Cable Transient Thermal Damage Tests

1985 Equipment Damage Sensitivity Ranking Study

1985 Relay Thermal Damage Tests

1985 Component Testing in Secondary Fire Environments

Room-to-Room

1979

1980

Fire Issue Studies:

Fire Protection Subsystems Study

Fire Barriers

Ventilation Systems

Investigation of Fire Stop Test Parameters

The results and conclusions of each of these individual efforts are

discussed in the chapters which follow. The discussions are presented in

a format consistent with the grouping of efforts presented immediately

above. The reports, papers, and journal articles generated by the

SNL/USNRC FPRP that document the various efforts are listed in Appendix A

both in chronological order and with a cross referencing of major reports

to specific efforts.

As a result of the investigations undertaken through the FPRP, a number

of insights have been gained. Early investigations were intended to

address specific regulatory questions and concerns, and as a result, have

-3-
had a significant impact on the formulation of fire safety guidelines for

commercial nuclear reactors. In particular, experimentation under the

FPRP demonstrated that the redundant train separation criteria of RG-l.75

were inadequate for the protection of cable trays, even considering the

use of low flame spread cables and a variety of passive cable tray

protective features. Testing also demonstrated that even, the more

stringent requirement for redundant train separation, stipulated in

Appendix R fire regulations is not sufficient in and of itself to prevent

redundant train damage due to a single fire. Rather, the, degree of

safety afforded by such measures will depend on, case specific factors

involving the magnitude of the fire hazard, the interaction between the

fire and the enclosure, and the adequacy, of fire detection and

suppression systems.

As a result of more recent efforts, a greater overall understanding of

fire phenomena and fire risk has developed. Experimentation demonstrated

the relative effectiveness of various fire suppression systems, and

illustrated potential drawbacks to each system. The behavior of a fire

in various transient fuel source packages, anda fire confined, to a

single electrical control panel were quantitatively evaluated. In an

effort to provide data against which to validate computer fire simulation

models, a series of 25 large-scale enclosure fire. tests was performed.

Recent analytical efforts include a review and -documentation of the

experience base associated with fires in nuclear power plants, a review

of available quantitative fire characterization data, the re-analysis of

certain past cable fire test efforts, and the support of efforts to

estimate the risk of core damage due to fire.

It should also be noted that the efforts described here are related to a

number of other efforts associated with the problem of_ fire -safety in

nuclear facilities. In particular, the TAP-A45 efforts represented one

of the first attempts to quantify nuclear powerplant fire risk. More

recently, the Risk Methodology Integration and Evaluation Program (RMIEP)

and the NUREG-1150 risk analyses have both contributed to the

understanding of fire risk and have advanced the methodololgies used in

fire risk assessment. Each of these efforts has drawn upon FPRP results

as a source of relevant data. In turn, the FPRP has drawn upon these

risk studies as a source of insights which have often been used to

establish the direction and objectives of new efforts. FPRP efforts hav6

also benefited from and contributed to Department of Energy fire safety

investigations both within Sandia and at other national laboratories.

While many insights have been gained through the FPRPI efforts, a number

of areas remain in which a greater understanding is required., A one year

study was initiated at the termination of the FPRP to identify

outstanding unaddressed fire safety issues. This study, known as the

Fire Risk Scoping Study, identified several areas in which a greater

understanding is needed. These issues were examined in the context of

fire risk assessment, and many of the issues raised were associated with

-4-
the adequacy of current fire risk assessment methodologies. However,

resolution of many of the unaddressed issues raised will require' a

greater understanding of fire phenomenology than that currently

available.

There are a number of questions associated with the modeling of fire

growth and fire effects in nuclear power plant situations which are -in

need of further understanding. For the fuel types and geometries

encountered in nuclear power plants, and in particular cable tray arrays,

currently employed analytical models used to predict fire growth behavior

have not been validated. While data on the impact of a fire on the

environment of a large enclosure was gathered under the FPRP, this data

was not fully processed because of the termination of efforts. Hence,

this data has not been generally applied in the validation of enclosure

fire simulation models. Thus, the accuracy with which analytical

predictions of fire growth behavior and the impact of a fire on the

surroundings can be made has yet to be demonstrated.

Significant shortcomings also remain in the available base of knowledge

regarding the operability of plant equipment in a fire environment.

Efforts were initiated to investigate these effects, and certain limited

insights were gained. However, very little is known about the mechanisms

and thresholds of fire damage for most types of plant equipment. In

particular, the data base on cable thermal damageability' is quite

limited. Also, concerns for the potential impact of smoke on high

voltage equipment, the impact of low level thermal exposure and gaseous

suppression systems on sensitive control circuitry, and the potential

adverse effects of manual fire fighting efforts have not been addressed.

Also not yet investigated are a number of issues associated with the

potential adverse effects of a fire and fire products beyond the room of

fire origin. These issues include assessment of the reliability of fire

barrier systems under actual fire conditions, the investigation of

potential mechanisms for the spread of smoke, the effectiveness of fire

suppressant management measures, the potential for spurious operation of

suppression systems in nonfire areas, and manual fire fighting

accessibility issues.

Under the Fire Aging of Electrical Components Program (reference USNRC

FIN A-1833), an investigation of plant aging and fire safety has'been

initiated. The identified issues being investigated include the impact

of aging on the fire damageability and flammability of cables and other

types of class 1E equipment and the impact of aging on passive fire

protection features such as cable wraps and coatings and fire barrier

penetration seals.

-5-
1.0 INTRODUCTION

1.1 Overview of the Fire Protection Research Program

This report presents a consolidation of the results and conclusions

generated through numerous individual efforts conducted under the U. S.

Nuclear Regulatory Commission (USNRC) sponsored Fire Protection Research

Program (FPRP) at Sandia National Laboratories (SNL). This program was

initiated in fiscal year1 1975 (FY-75) and the report covers efforts

from program inception through termination at the end of FY-87. The

individual efforts conducted under this program involved both analytical

and experimental efforts associated with a broad range of nuclear power

plant fire safety issues.

Since the programs inception in 1975 a number of significant changes in

the regulatory approach to the fire safety issue have occurred. With

these changes in the regulatory environment came changes in the approach

and objectives of the FPRP as well. This section provides a brief

overview of the historical development of the fire program. Each of the

topics introduced below will be discussed in greater detail in the

sections to follow.

On March 22, 1975, shortly after inception of the FPRP program, a severe

cable tray fire occurred at the Brown's Ferry nuclear power plant.

Largely as a result of this fire a new set of regulations related to fire

safety was instituted. This development of new fire regulations began

with the release of the first draft of Branch Technical Position (BTP)

APCSB 9.5-1 and its associated Appendix A in August of 1976. The main

body of this document was intended to cover plants already into the

construction phase, while the Appendix was intended to cover plants still

in the planning phase. Following a period of review and public comment,

these guidelines were modified somewhat and formalized as Appendix R to

10CFR50 which was 'adopted February 19, 1981. Following adoption of

Appendix R, BTP 9.5-1 was reissued as a part of the Standard Review Plan.

In this reissue Appendix A to the BTP was eliminated.

During this period from 1975 through 1982 FPRP investigations were

designed to address very specific regulatory questions. The emphasis of

the FPRP was placed initially on the identification of areas of weakness

in the fire regulations. Emphasis later shifted towards the

investigation of the technical adequacy of the new guidelines generated.

As the regulatory environment for fire protection settled following the

institution of Appendix R (to 10CFR50), the fire program underwent a

transition to a more integrated, generalized research effort. This

difference is clearly reflected in the objectives of efforts conducted

under the two approaches.

One of the first efforts performed under the FPRP was a review of the

regulations and standards that governed, either explicitly or implicitly,

1. Fiscal years for USNRC sponsored efforts begin October 1 of the

previous calender year and extend through the following September 30.

-6-
the implementation of fire protection in nuclear power plants. This

review identified explicit guidance documents in the form of regulations

and regulatory guidelines (RGs), and implicit documents in the form of a

plethora of national fire standards generated by various standards

organizations. In general it was concluded that these documents

represented a confusing and often contradictory set of guidelines which

did not consider certain unique aspects of nuclear power plants.

With the adoption of Appendix R and its supporting documents the USNRC

resolved much of the uncertainty and confusion resulting from the

existence of contradictory standards by endorsing a specific set of

standards for each of the issues of fire protection relevant to the

nuclear power situation. These new regulations included consideration of

the unique character of the nuclear power plant situation and included

general requirements for the protection of certain plant safety features

from the damaging effects of fires.

In parallel with these reviews experiments were performed to evaluate the

adequacy of the cable separation guidelines of RG-I.75, the then current

design guide. This guideline established redundant train minimum

separation distances for cable trays of five feet vertically and three

feet horizontally. Testing demonstrated that under exposure fire

conditions this guide was inadequate to prevent the spread of fire to

redundant cable trays, even considering the use of low flame spread

cables certified by the IEEE-383-74 flame test. The final test in this

series was conducted on July 6, 1977.

As a result, certain additional measures for the protection of cables

were experimentally evaluated. These included fire retardant coatings,

and protective barriers. While each of these measures resulted in a

degree of increased protection, a wide variability in the effectiveness

of similar measures developed by various manufacturers was demonstrated.

In general, none of these measures was considered adequate to completely

insure protection of vital cable trays from exposure fires under the

separation criteria of RG-1.75.

One of the principal provisions of BTP 9.5-1, which was also incorporated

into the Appendix R guidelines, requires that redundant trains of

equipment must maintain a separation of 20 feet horizontally with no

intervening combustibles and with inclusion of automatic fire detection

and suppression systems. Following release of BTP 9.5-1, an

investigation of the adequacy of t•hk 20-foot separation criteria was

initiated. In a series of experiments, it was demonstrated that for a

small room where hot layer effects could become significant, 20 feet of

separation was not in and of itself sufficient to insure that cabling so

separated from the source fire would remain undamaged. These tests did

not investigate the additional measure of safety afforded by' the

requirement for the use of automatic fire detection and suppression

systems in such situations.

As a result of these findings, additional research was undertaken to

further assess the degree of safety afforded by the 20 foot separation

-7-
criteria. These investigations focused on continuation of the protective

coatings and barriers tests for cable trays, and on investigations of the

effectiveness of various fire suppression systems when applied to cable

fires.

Following the institution of the Appendix R fire safety regulations,

investigations shifted towards a more integrated approach to the

investigation of fire safety. This shift was partially motivated by a

need to support the analysis of fire risk. More recent efforts conducted

between 1983 and 1987 were based on five specific areas of concern.

These five areas are:

- Source Fire Characterization,

- Detection and Suppression System Effectiveness,

- Room Effects Issues,

- Equipment Response Issues, and

- Room-To-Room Fire Effects Issues.

Characterization of the source fire includes the identification of the

anticipated fuel sources and the characterization of ignition and fire

growth behavior for these fuel sources. Specific concerns in this area

include the rate of release of both heat and combustion products to the

environment and the eventual extent of fire growth. Considerations in

the effectiveness of detection and suppression include the adequacy, in

the context of nuclear power plant applications, of general national and

industry guidelines for system design, installation, and maintenance and

the effectiveness of common fire suppressants when applied to the

combustible fuels found in a power plant, especially cables. Room

effects issues are associated with the mechanisms of transport of heat

and combustion products within the room of fire origin. Equipment

response issues are those associated with the potential damaging effects

of fire environments, including the effects of manual or automatic fire

suppression efforts, on plant components that may not be directly

involved in the fire itself. The final area is concerned with potential

room-to-room fire effects including the transport of fire products to

remote areas, the spread of fire through fire barrier systems, the

spurious actuation of fire suppression systems in remote areas, fire

brigade accessibility issues that may compromise barrier integrity, and

the management of combustion products and fire suppression agents.

It was during the early stages of this phase of the program that further

work was halted through the termination of funding as of the end of

FY-87. No new investigations have been initiated under this program

since FY-86, and subsequent efforts have been entirely directed at

closing out outstanding portions of prior investigations.

Actual investigations performed under this integrated approach focused

primarily on source fire characterization, detection and suppression

effectiveness, and room effects. Only preliminary and quite limited

efforts associated with equipment response and room-to-room issues have

been performed. Efforts that have been performed include the

characterization of typical fire ignition sources, support of efforts to

-8-
develop computer models for the prediction of fire behavior and

environmental effects, limited cable and component fire environment

vulnerability testing, characterization of electrical panel fires, and

the development of a fire occurrence data base.

Because these more recent efforts were intended to provide a measure of

the degree of safety afforded by the regulations, the work was directed

towards providing information useful to PRA analyses. This included the

support of efforts to develop analytical fire simulation models for use

in risk assessment analyses. In the development and application of such

models, an understanding of the phenomenology involved in each of the

areas described above is required. Thus, it is often in these models

that the various elements of fire research are drawn together. While the

actual development of fire simulation models was not undertaken as a part

of the Sandia FPRP, the support of such efforts at various other

institutions was always a consideration in the formulation of program

plans.

The efforts described here are also directly related to a number other

efforts associated with the problem of fire safety in nuclear facilities.

In particular, the TAP-A45 efforts represented one of the first efforts

that quantified nuclear power plant fire risk. More recently, the Risk

Methodology Integration and Evaluation Program (RMIEP) and the NUREG-1150

risk analyses have both contributed to the understanding of fire risk and

have advanced the methodololgies used in fire risk assessment. Each of

these efforts has drawn upon FPRP results as a source of relevant data.

In turn, the FPRP has drawn upon these risk studies as a source of

insights which have often been used to establish the direction and

objectives of new efforts. FPRP efforts have also benefited from and

contributed to Department of Energy fire safety investigations both

within Sandia and at other national laboratories.

As a result of the FPRP efforts undertaken over the years a list of

issues which were unaddressed in the context of a fire PRA and which were

perceived to represent potentially significant risk contributors was

formulated. Based on this list of issues an effort known as the Fire

Risk Scoping Study was undertaken. This effort performed a review of the

current perception of fire risk for nuclear power plants and an initial

evaluation of the potential significance of six identified unaddressed

issues. These issues were:

- Fire Induced Control Systems Interactions,

- The Effectiveness of Manual Fire Fighting, Including the

Effectiveness of Smoke Control Measures,

- Equipment Vulnerability in the Total Fire Environment, Including

the Adverse Effects of Spurious Suppression System Actuation,

- Seismic/Fire Interactions,

- The Adequacy of Fire Barrier Qualification Standards, and

- The Adequacy of Analytical Tools for Fire.

This effort was completed concurrent with the writing of this report and

the findings of that study will be discussed briefly at the close of this

report.

-9-
1.2 Fo-rmat for ?resentation

The presentation of results and conclusions generated by the various

individual analytical and experimental efforts performed under the FPRP

has been formulated to conform to the historical development of program

objectives. As described above, early efforts in the FPRP were intended

to specifically address certain regulatory questions, whereas later

efforts were based on a more broadly based, integrated investigation of

fire phenomenology. As the primary format for presentation, efforts will

be described within these two contexts. For most of the early

investigations of specific regulatory questions the results can also be

applied within the framework of the integrated fire phenomena

investigations. Thus, where appropriate these early efforts will be

described both in the context of the investigation of specific regulatory

concerns and in the context of the investigations in each of the five

areas of interest described above.

Listed below are the specific areas of -research conducted under the

USNRC/Sandia FPRP. The studies have been segregated indicating their

applicability to either specific regulatory issue investigations, and/or

the specific areas of investigation identified as a part of the

integrated approach to fire safety. Typically, each effort focused on a

particular area of investigation, though it will be noted that many of

the efforts provide insights into more than one area of investigation.

Investigations of Specific Regulatory Concerns:

1975 Cable Use Screening Survey

1976 Fire Protection Systems Study

1979 Fire Protection Subsystems Study

1976-81 Cable Tray Fire Testing:

1976 Electrically Initiated Cable Fire Tests

1977 Exposure Fire Cable Fire Tests

1978 Fire Retardant Cable Coating Tests

1978 Cable Tray Fire Barrier Tests

1979 Cable Tray Fire Corner Effects Tests

1981 Cable Radiant and Convective Heating Damage Tests

1981 Burn Mode Analysis of Cable Fires

1980 Investigation of Fire Stop Test Parameters

1980-83 Fire Suppression System Effectiveness Investigations:

1980 Halon Suppression Effectiveness Tests

1981 Water Sprinkler Suppression Effectiveness Tests

1982 Directed Water Spray Suppression Effectiveness

Tests

1983 Carbon Dioxide Suppression Effectiveness Tests

1981 Cost Analysis of Fire Protection Systems

1982 Detector Siting Criteria Requirements Study

1982 Twenty-Foot Separation Adequacy Investigations

Source Fire Characterization Studies:

1975 Cable Use Screening Survey

1976-81 Cable Tray Fire Testing:

1976 Electrically Initiated Cable Fire Tests

-10-
1977

1978

1978

1979

1981

1981

1984

1985

1985

1985

1985

1986

Exposure Fire Cable Fire Tests

Fire Retardant Cable Coating Tests

Cable Tray Fire Barrier Tests

Cable Tray Fire Corner Effects Tests

Burn Mode Analysis of Cable Fires

Trash/Pool Fire Correlation Tests

Identification and Classification of Transient Fuel

Ignition Sources

Review of Fire Characterization Data

Development of Electrical Ignition Apparatus

Transient Fuel Source Fire Tests

Electrical Cabinet and Control Room Fire Tests

Development of Nuclear Power Plant Fire Occurrence

Data Base

Detection and Suppression Effectiveness Studies:

1980-83 Fire Suppression System Effectiveness Investigations:

1980 Halon Suppression Effectiveness Tests

1981 Water Sprinkler Suppression Effectiveness Tests

1982 Directed Water Spray Suppression Effectiveness

Tests

1983 Carbon Dioxide Suppression Effectiveness Tests

1982 Detector Siting Criteria Requirements Study

Room Effects

1982

1985

1985

Studies:

Twenty Foot Separation Tests

Base Line Validation Enclosure Fire Tests

Electrical Cabinet and Control Room Fire Tests

Equipment Response Studies:

1976-81 Cable Tray Fire Testing:

1978 Fire Retardant Cable Coating Tests

1978 Cable Tray Fire Barrier Tests

1981 Cable Radiant and Convective Heating Damage Tests

1984 Cable Steady State Thermal Damage Tests

1985 Cable Transient Thermal Damage Tests

1985 Equipment Damage Sensitivity Ranking Study

1985 Relay Thermal Damage Tests

1985 Component Testing in Secondary Fire Environments

Room-to-Room

1979

1980

Fire Issue Studies:

Fire Protection Subsystems Study

Fire Barriers

Ventilation Systems

Investigation of Fire Stop Test Parameters

The sections that follow provide summary discussions of each of these

efforts within the framework presented above. The report focuses on the

principal insights and conclusions of each effort as applicable to the

particular topic of discussion for each section, as well as the

applicability of these insights to fire risk assessment. For a more

complete description of a particular effort refer to the reports, papers,

-11-
and journal articles that document the various efforts. These reports are listed in Appendix A both in chronological order and with a cross referencing of major reports to specific efforts.

-12-
2.0 INVESTIGATION OF SPECIFIC REGULATORY CONCERNS

2.1 Scope of This ChaRter

Early efforts conducted under the FPRP were primarily intended to address

specific regulatory concerns and questions. These efforts are discussed

in brief in this chapter. Many of these efforts will also be discussed

in following chapters as they also provide insights into the phenomena

associated with the five areas of investigation identified as a part of

the integrated approach to fire safety research applied in more recent

years. The discussions presented in this chapter will focus on the

issues of concern that led to each of these early research efforts and

the regulatory insights gained as a result. Later chapters will provide

more detail on the actual experimental results for these efforts as

appropriate.

The studies performed, which were primarily intended to address specific

regulatory concerns, are listed below:

1976 Fire Protection Systems Study

1979 Fire Protection Subsystems Study

1976-81 Cable Tray Fire Testing:

1976 Electrically Initiated Cable Fire Tests

1977 Exposure Fire Cable Fire Tests

1978 Fire Retardant Cable Coating Tests

1978 Cable Tray Fire Barrier Tests

1979 Cable Tray Fire Corner Effects Tests

1981 Cable Radiant and Convective Heating Damage Tests

1981 Burn Mode Analysis of Cable Fires

1980 Investigation of Fire Stop Test Parameters

1980-83 Fire Suppression System Effectiveness Investigations:

1980 Halon Suppression Effectiveness Tests

1981 Water Sprinkler Suppression Effectiveness Tests

1982 Directed Water Spray Suppression Effectiveness

Tests

1983 Carbon Dioxide Suppression Effectiveness Tests

1981 Cost Analysis of Fire Protection Systems

1982 Detector Siting Criteria Requirements Study

1982 Twenty Foot Separation Adequacy Investigations

Each of these studies is described in turn within this chapter.

2.2 Fire Protection Systems Study

One of the first efforts undertaken as a part of the FPRP was a review of

the then current fire protection practices and perceptions.[l] This

review investigated a number of aspects of protecting nuclear power

plants from the adverse effects of fires. As a part of this review the

environment of regulation as embodied in the various national and

international regulatory and insurance standards was reviewed. It was

concluded that "(t)here exists an abundance of overlapping and often

contradictory standards, guides, codes and criteria for nuclear power

-13-
plants fire protections systems. Additionally, many of the requirements

are not founded on adequate experimental and analytical information."

As an additional aspect of this study, the findings and recommendations

resulting from investigations of the 1975 Browns Ferry cable fire

incident were reviewed. This was coupled to an initial attempt to

establish probabilistic fire safety goals and to assess the impact of

specific fire protection improvements on overall plant fire safety.

The principal conclusions of the study were that (1) a need existed to

establish a consistent set of regulations and guidelines for fire

protection in nuclear power applications, and (2) that rather than invoke

a number of individual plant fire protective measures, an integrated

approach involving the overall identification, quantification, and

resolution of the primary plant fire hazards should be undertaken.

2.3 Fire Protection Subsystems Study

As a follow-up to the Fire Protection Systems Study an effort called the

Fire Protection Subsystems Study was undertaken. Four specific fire

subsystems were identified and relevant information for each subsystem

was reviewed and evaluated. The four subsystems investigated were:

- Ventilation Systems

- Fire Detection Systems

- Fire Barriers

- Hazards Analysis

Investigations performed in each of these four areas of study are

discussed in turn in the following sections.

2.3.1 Ventilation Subsystems Study

The objective of the ventilation subsystems study was to examine the role

of internal plant ventilation systems on fire safety in a nuclear power

plant.J21 Under this effort, the standards for the installation of

ventilation systems were reviewed. Based on an assessment of the

adequacy with which these standards addressed nuclear power plant fire

safety issues, the study also developed technical bases for ventilation

system functions and performance in fire emergencies. Finally, changes

and additions to the guidelines to clarify intent and to define design

criteria were recommended.

As a result of these efforts, it was concluded that the standards were

generally insufficiently detailed and did not provide for the design of

the ventilation system as an integral part of the fire protection system.

Four potential fire ventilation strategies were considered. These were

(1) smoke removal (smoke purging); (2) smoke control (or containment);

(3) fire control (limiting fire intensity by limiting oxygen

availability); and (4) temperature control (or heat removal). It was

concluded that the most desirable approach to ventilation design for fire

emergencieswas the temperature control strategy. This approach provides

-14-
for limited smoke removal and smoke control functions as well. Fire

control was considered inappropriate in that this strategy would

complicate fire response actions and enclosure accessibility.

It was also recommended that ventilation systems be considered as an

integral part of the fire protection system and that appropriate local

control capability be provided. This would allow fire fighters to

realign ventilation flow under the specific fire conditions to attain the

desired configuration.

To the knowledge of the author, these recommendations have not been

incorporated into the industry standards and have not been generally

incorporated into plant designs. Ventilation system design and

installation continues to be governed by essentially the -same standards

as those considered in the subsystem study.

2.3.2 Fire Detection Subsystems Study

Fire detection subsystems were evaluated from the standpoint of overall

plant fire safety considering the technical bases for detection system

design, the adequacy of design guidance, and the effectiveness of

qualification testing in simulating actual fire performance.[3] It was

found that the industry and regulatory guidelines were inconsistent and

often provided conflicting requirements. This resulted from an observed

inconsistency by which plant areas were identified, and resulted in

recommendations for different levels of detector protection for the same

plant areas. It was also found that the technical bases upon which

choices of detector type and detector siting criteria were determined

were inadequate. This resulted from differences in detector

qualification standards and from a lack of test methods to evaluate

detector siting strategies. Installation and maintenance procedures were

also found to have no uniformly applied set of guidelines or procedures.

Certain of these issues, in particular the issue of detector siting, were

recognized as being difficult to standardize. It was recommended that a

firm technical basis for the selection of detectors be established, that

a uniform qualification methodology for different detector types be

adopted, and that installation and maintenance standards be developed.

To the knowledge of the author, the issues of installation and

maintenance have to some degree been addressed by national fire standards

organizations. However, different detector types continue to be

qualified under different conditions, and detector selection and siting

continue to be largely dependent on the use of engineering judgment.

2.3.3 Fire Barrier Subsystems Study

The examination of fire barriers was intended to (1) study and evaluate

the standards for the qualification of fire barrier elements, (2) perform

thermal analyses of typical three-hour fire barrier systems to determine

their response under various conditions, and (3) assess the need for

further understanding of barrier performance factors.[4]

-15-
The study concluded that the guidelines for the qualification of fire

barrier elements provided for an adequate exposure fire intensity and no

changes were recommended in this area. Two areas of potential weakness

were identified. The first was with respect to the use of a hose stream

test as a part of the qualification standards. This test was considered

to have poor repeatability, to be imprecise, and to be difficult to

control. It was recommended that a more precise methodology be developed

for application of tangential loads following fire exposure. The second

area was the failure of U.S. standards to incorporate a positive furnace

pressure during fire exposure testing of doors and penetration seal

systems. This was considered to be an easily corrected shortcoming in

the test procedures which, if not corrected, could result in

nonconservative estimates of fire barrier endurance under actual exposure

conditions. In each of these two areas, no relevant changes have since

been made in the national standard tests.

In the second area, that of the pressure questions, a follow-up study of

the effects of positive pressure exposure on cable barrier penetration

fire stop systems was undertaken. [5,6] These efforts, which are

described below in Section 2.5, confirmed the nonconservative nature of

negative pressure test schemes for fire barrier penetration seals.

2.3.4 Fire Hazards Analysis Subsystems Study

In the final area of study, fire hazards analysis, the efforts were

limited to a review of the fire hazards analysis methodologies and an

assessment of the degree of applicability of those methodologies to the

evaluation of nuclear power plants.[7] On the basis of this review, it

was concluded that each of the identified methodologies was deficient in

meeting at least one of the analysis criteria set forth. It was further

concluded that refinements to the existing methodologies were needed. An

overall approach was proposed.

Since the performance of this work significant improvements in fire

probabilistic risk assessment (PRA) methodologies have been made. Many

of the shortcomings identified in the study have been addressed. In a

recently completed study, the Fire Risk Scoping Study, the state of the

art in fire risk assessment for nuclear power plants was reviewed.[8]

This review identified the principal sources of uncertainty in a fire

risk analysis, and also investigated the potential risk impact of a

number of issues which had been identified subsequent to the performance

of several risk analyses. Thus, risk assessment methodologies continue

to evolve and mature.

2.4 Cable Tray Fire Testing

In the wake of the 1975 Brown's Ferry cable spreading room fire a number

of actions were considered as potential approaches to the reduction of

plant fire vulnerability. During the years between 1976 and 1981 a

number of efforts were conducted to evaluate the effectiveness of several

of these proposed measures. These investigations represented a

significant portion of the early fire research efforts. The specific

related efforts were:

-16-
1975 Cable Use Screening Survey

1976 Electrically Initiated Cable Fire Tests

1977 Exposure Fire Cable Fire Tests

1978 Fire Retardant Cable Coating Tests

1978 Cable Tray Fire Barrier Tests

1979 Cable Tray Fire Corner Effects Tests

1981 Cable Radiant and Convective Heating Damage Tests

1981 Burn Mode Analysis of Cable Fires

One of the first of the potential cable fire mitigation measures

evaluated was the adequacy of the newly instituted IEEE-383-74 cable

flame spread test standard in reducing the potential for the spread of

fire among cable trays.f 9,101 Several experiments were conducted in

which cable tray arrays which conformed to the then current cable

separation criteria of Regulatory Guide 1.75 (RG-l.75) were subjected to

fires. These guidelines specify physical separation distances for both

single train and redundant train cable tray installations. For single

train trays, minimum separation is 10.5 inches vertically and eight

inches horizontally. For independent, redundant safety trains, minimum

separation distances are five feet vertically and three feet

horizontally.

Both electrically initiated and exposure (external fire source) fires

were used. It was concluded that while cables which passed the

IEEE-383-74 flame test were less likely to propagate electrically

initiated fires, exposure fires still posed a threat of redundant train

involvement in a single fire. This test series culminated in the test of

July 6, 1977, in which full involvement of a large array of trays

containing qualified cables, including the involvement of the simulated

redundant trays, was observed.

With this determination that RG-l.75 was insufficient to prevent the fire

involvement of redundant cable trains, even considering the use of

IEEE-383-74 low flame spread cables, other potential protective features

were experimentally evaluated. These additional features were the

protection of cable trays with insulating wraps and fire retardant

coatings, and the use of flame barriers for cable tray arrays.[ll-14]

While each of these features afforded some additional measure of safety,

wide variability between protective features of different types, and even

between similar protective features produced by different manufacturers,

was observed.[151 In the final analysis, none of the features evaluated

was considered sufficient in and of itself to insure fire safety under

the separation criteria of RG-I.75.

With the findings described above, it became of increasing interest to

provide tools with which one might assess the level of safety provided by

various protective features without undertaking extensive testing. This

is reflected in the final three efforts, the Cable Tray Fire Corner

Effects Tests, the Cable Radiant and Convective Damage Testing, and the

Burn Mode Analysis of Cable Fires, which were directed towards providing

more broadly based insights into the phenomena involved in cable fire

growth and fire induced cable damage. The Corner Effects Tests explored

-17-
the effects of thermal reradiation from walls and ceilings on the

intensity of cable fires.[16] The Cable Radiant and Convective Damage

Tests involved initial cable fire environment damageability

assessments.J17] The Burn Mode Analysis effort developed a methodology

for predicting the mode of burning (i.e. open flaming, smoldering, fire

ball behavior, or transitional) based on measurements of a cables surface

and internal temperatures.[18] It was in these later cable fire research

efforts that a transition to the integrated approach to fire safety

research first began to emerge. The results of these efforts are

described in more detail in Chapter 3 as a part of the discussions of

fire characterization efforts, and in Chapter 6 as a part of the

discussion of equipment damageability studies.

2.5 Investigations of Fire Stop Test Parameters

As a part of the Fire Protection Subsystems Study described above (see

Section 2.3.3), questions were raised regarding the adequacy of U. S.

fire barrier qualification tests. One of the two potential weaknesses

identified was that the U.S. standard tests did not address exposure

furnace pressure. It is a commonly observed phenomena that enclosure

pressures under fire conditions will increase above ambient conditions,

particularly for rooms with forced ventilation such as those typical of a

nuclear power plant. It was concluded that failure to apply a positive

pressure across a barrier element during fire exposure testing could

result in nonconservative estimates of the actual fire barrier

performance. In practice, barrier elements have often been qualified

with negative furnace pressures, which could result in cool air being

drawn into the furnace from outside the furnace through air passages in

or around a barrier. This could potentially mask a vulnerability of

barrier elements to the passage of hot gases from within the furnace, or

fire enclosure, out past the barrier to the outside.

As a follow up to these findings, efforts were initiated to examine the

standards for the qualification of barrier elements, and to perform a

limited number of tests on certain cable penetration fire stops.[5,6]

While certain pressure effects were noted for some seal systems resulting

in premature failure, the results were not considered sufficient to

demonstrate a generic vulnerability for cable penetration seals. This

issue was also raised again as a part of the recently completed Fire Risk

Scoping Study. Here again it was found that no generic vulnerability has

been demonstrated, and recommended actions included a review of actual

fire barrier performance.

The question of the significance of pressure on barrier performance

continues to be a point of debate within the general fire research

community as well. For example, the American Society for Testing and

Materials (ASTM) committee responsible for the relevant ASTM standard for

fire doors (ASTM E-05.21.2) recently considered and rejected a proposal

to modify those standards to include a positive pressure requirement for

fire exposure testing, even though scientific evidence that pressure

effects have been documented for at least some barrier systems was

presented. Of the industrialized nations, only the U.S. and Canada

-18-
continue to endorse barrier qualification test standards which do not

require the imposition of a positive pressure furnace exposure condition.

2.6 Fire Suppression System Effectiveness Investigations

In addition to physical separation of redundant safety trains, Appendix R

also requires the use of automatic fire detection and suppression systems

where physical separation short of rated three-hour fire barriers is

available. It was assumed that provisions for the prompt suppression of

a fire would provide an additional measure of safety by limiting the

extent of fire damage. For a nuclear power plant, the most common

combustible fuel source is cable insulation. This fuel is not typical of

fuel loadings in most nonnuclear industry situacions for which the

existing national standards had been established. Thus, the

effectiveness of the commonly available fire suppression systems and of

the guidelines for their design and installation had not been

demonstrated for the nuclear industry.

During the years 1978-83, a series of experiments was conducted to

evaluate the effectiveness of Halon, carbon dioxide, and water based fire

suppression systems in suppressing fully developed cable tray

fires.[I0,19] The individual efforts associated with these

investigations were:

1978-80 Halon Suppression Effectiveness Tests

1979-81 Water Sprinkler Suppression Effectiveness Tests

1980-82 Directed Water Spray Suppression Effectiveness Tests

1980-83 Carbon Dioxide Suppression Effectiveness Tests

These tests demonstrated that properly applied suppression system of each

type were capable of extinguishing a fully developed cable tray fire.

However, proper application for the gaseous systems, Halon and C02 ,

required that suppressant concentrations recommended in the design

standards must be maintained for up to 15 minutes to insure that deep

seated cable fires did not reignite. It was also found that the gaseous

systems allowed enclosure temperatures to remain fairly high as compared

to water based systems. This resulted from the fact that the gaseous

suppressants did not represent as significant a thermal sink as did

water. This raised a potential concern for the impact of longer term

lower level thermal damage to sensitive equipment. The use of water was

also identified as a potential source of damage in that equipment wetting

could result if the water is not properly drained, or vulnerable

equipment not properly protected.

As a result of these investigations, it was concluded that the general

industry design standards for the use of fixed fire suppression systems

were adequate for application to nuclear power plants.. However, it was

recommended that certain additional considerations unique to the nuclear

industry should also be factored into system designs. In particular,

questions were raised regarding the effects of lower level thermal

exposure on particularly sensitive equipment, such as integrated

circuits, and over the adequacy with which implementation practices for

-19-
water suppression systems have provided for the management of the applied

water and for the protection of equipment vulnerable to damage due to

wetting.

2.7 CostiAnalysis of Fire Protection Systems

Following the March 1975 cable fire at the Brown's Ferry plant there was

an increased awareness of the importance of fire protection to overall

plant safety. As a part of the efforts undertaken in response to this

increased awareness, a limited study was undertaken to assess the costs

associated with the implementation of certain active and passive fire

protective measures.[20] Considerations included the installation of

Halon or water spray suppression systems, upgrading of passive barriers

to full three-hour rated fire barriers, and the protection of cable trays

with one-hour fire barrier systems. In addition, plant areas were

examined in order to determine the feasibility of installing fixed fire

suppression systems, and in order to develop cost estimates for

installation of fire detection systems where fixed fire suppression

systems were not feasible.

It was concluded that a number of factors contributed to the cost of fire

protection system installations. These factors included the congestion

of equipment, scheduling, seismic considerations, quality assurance

considerations, and other special considerations of the working

environment (e.g., special protective gear requirements and security

considerations). The subjectivity of before the fact assessments of

these factors was determined to result in considerable uncertainty in the

estimates of final implementation costs.

2.8 Detector Siting Criteria Requirements Study

Consistent with the goal of providing for the prompt suppression of plant

fires as a method for minimizing the extent of fire damage, the proposed

Appendix R regulations included requirements that automatic fire

detection systems be provided for areas housing redundant trains of

safety equipment. As with the case fixed suppression systems, the USNRC

was largely dependant on existing general industry guidelines for the

selection, installation, and maintenance of fire detection systems.

However, as with suppression systems, the adequacy of the general

industry detector guidelines in the context of a nuclear power plant had

not been assessed. Thus, an effort was performed to review the relevant

guidelines and practices, and to identify potential shortcomings in these

guidelines as applied to the nuclear industry.[21]

It was found that, in practice, the selection and siting of fire

detectors was based largely on engineering judgement. It was also

concluded that general industry guidelines did not realistically take

into account a number of environmental and plant safety requirements that

are unique to nuclear facilities. In particular, shortcomings were

identified in that fuller accountability was required for (1)

environmental factors such as ventilation, congestion, and background

radiation, (2) the flammability characteristics of power plant

-20-
combustibles, particularly cables, and (3) the need to limit fire damage

to assure continued plant operability.

It was recognized that these factors would be difficult to incorporate

into standard test procedures. In particular, it was concluded that very

little technical basis existed upon which appropriate test criteria might

be selected. Since the performance of this review, very little change in

the national guidelines has been made. The selection and siting of fire

detectors continues to be heavily dependent on engineering judgment.

2.9 Twenty-Foot Separation Adequacy Investigations

One of the principal provisions set forth in BTP 9.5.1, and later in

Appendix R to 1OCFR50, requires that redundant trains of equipment,

including cables, be separated by 20 feet of horizontal space with no

intervening combustibles. The regulations also specify that in

situations were such separation is employed, automatic fixed fire

detection and suppression systems must also be installed.

In an effort to assess the effectiveness of the twenty-foot separation

criteria, a series of ten full-scale fire tests was performed.[42] In

these tests a pair of cable trays was used to simulate each of two

redundant equipment trains. One pair of cable trays was subjected to an

exposure fire and the other pair, separated from the source fire by 20

feet, was monitored for electrical integrity. No suppression of the test

fires was employed.

In a number of these tests, damage to the simulated redundant equipment

train was observed. For older style cables that would not pass the

IEEE-383-74 flame spread test, even fire retardant coatings and passive

insulating fire barrier systems were not sufficient to prevent fire

induced electrical failure. For the newer IEEE-383-74 certified low

flame spread cables, electrical failure was observed in unprotected

cables, though for those tests in which both cable trains were protected

by cable coatings or cable wraps, no electrical failures were observed.

These results demonstrated that even for cables which passed the

IEEE-383-74 flame test, damage to the redundant, non-fire-involved cables

could result from hot layer effects alone. Thus, it was concluded that

20 feet of horizontal separation was not, in and of itself, sufficient to

insure the continued operation of redundant equipment trains during a

fire. This places more reliance on the additional provisions for the

inclusion of automatic fire detection and fire suppression systems in

such situations. In a deterministic sense the Appendix R requirements

will proclude fire induced redundant train damage under most fire

conditions. However, these deterministic criteria do not address the

residual risk associated with the potential for very large fires or fire

suppression system failure.

-21-
3.0 FIRE CHARACTERIZATION STUDIES

3.1 Introduction

One of the fundamental questions associated with the assessment of fire

safety or fire risk is the question of defining the fire threat itself.

This definition requires an identification of anticipated ignition

sources and the combustible fuel types, loadings, and geometries present.

It also requires an analysis of the fundamental fire behavior of those

combustible fuels of concern including the frequency of fire initiation,

the fire growth and development behavior of the end configuration of

these fuel sources, and the intensity of the input, in terms of heat and

combustion products, to the surrounding environment. Each of these

questions falls within the scope of fire characterization investigations.

A number of FPRP efforts have focused on the characterization of fires on

both an analytical and an experimental basis. These efforts have

involved generalized reviews of fire characterization information

including the nuclear plant operating experience, the evaluation of

transient fuel fire sources, characterization of both self-ignited and

exposure cable tray fires, and the examination of fires in electrical

control panels. The specific efforts that will be discussed in this

chapter are:

General Studies and Experience Base Reviews:

1985 Review of Fire Characterization Data

1984 Identification and Classification of Transient Fuel

Ignition Sources

1986 Development of Nuclear Power Plant Fire Occurrence Data

Base

Transient Fuel Source Fire Characterization Efforts:

1981 Trash/Pool Fire Correlation Tests

1984 Identification and Classification of Transient Fuel

Ignition Sources

1985 Transient Fuel Source Fire Tests

Cable Fire Characterization Efforts:

1975 Cable Use Screening Survey

1976 Electrically Initiated Cable Fire Tests

1977 Exposure Fire Cable Fire Tests

1978 Cable Tray Fire Retardant Coatings Tests.

1978 Cable Tray Barrier Tests

1979 Cable Tray Corner Effects Tests

1981 Burn Mode Analysis of Cable Fires

Electrical Panel Fire Investigations:

1985 Development of Electrical Ignition Apparatus

1985 Cabinet and Control Room Fire Tests

-22-
3.2 General Studies and Experience Base Reviews

Three FPRP studies have focused on a general investigation of nuclear

power plant fire characterization, including reviews of the nuclear plant

operating experience base.

3.2.1 Review of Fire Characterization Data

In a review of fire characterization data, the knowledge base of

quantitative data on the fire behavior of typical nuclear power plant

combustibles was examined.[23] This review identified the available data

on the full range of nuclear power plant fuels including various

transient fuel sources, liquid fuel pool fires, and cable insulation. A

fairly large data base in many areas was identified. In particular,

liquid fuel pool fires and trash fires have been explored quite

extensively. However, certain critical areas of shortcoming were also

identified.

The most significant shortcoming with respect to the nuclear industry is

that the quantitative data base on cable fire behavior was identified as

inadequate. A large base of data gathered from small-scale tests (i.e.,

samples on the order of several square inches only) does exist. However,

the applicability of this small-scale data to the behavior of a largescale cable fire has not been demonstrated. While a significant number

of large-scale cable fire tests have been performed, both within and

outside the FPRP, the principal objectives of these tests have not been

to explore fire growth behavior. Hence, detailed fire characterization

data was not typically gathered, and the available data is not

appropriate to the validation of small-scale cable flammability test

results.

The dependency of fire risk analyses on the ability to accurately predict

cable fire growth behavior makes this shortcoming particularly important.

Typically, many of the most significant fire scenarios center on the

potential for fire spread and fire induced damage in arrays of cable

trays. Enclosure fire simulation model predictions used in the analysis

of nuclear plant fire scenarios depend heavily on the predicted growth

rate of the fire source. As not enough is known about full-scale cable

fires to a-priori establish the expected fire growth behavior, predictive

models of this growth behavior are often employed. These fire growth

models are, in turn, dependant on the availability of the type of data

generated by small-scale tests. This data includes ignition parameters,

heat of combustion, mass loss rate as a function of exposure intensity,

and combustion products yield rates. A lack of adequate large-scale test

data, coupled with uncertainties as to the applicability of small-scale

test results to full scale conditions has prevented the validation of

currently employed cable fire simulation correlations.

-23-
3.2.2 Identification and Classification of Transient Combustible Fuel

Sources

Fuel sources in a nuclear power plant are generally divided into

transient and in-situ fuels. In-situ fuels are"'those combustible fuel

sources which exist within a plant as a result of as designed plant

systems and structures. These fuels can be well defined for particular

plant areas based on inspections of the areas in q'uestion. The transient

fuel sources are those combustible materials that exist within a plant on

a shorter term basis. These materials are often Associated with such

activities as plant construction, house keeping,' ard plant maintenance.

As these fuels come and go in a plant it is. much more difficult to

quantify the transient fuel source threat for most plant areas.

In an attempt to overcome this difficulty, the experiences of USNRC plant

inspectors was reviewed through both interviews and examination of

Inspection and Enforcement (I&E) reports. The objective was to

characterize the classes and quantities of transient fuel sources which

have been encountered in nuclear power plants.. This work was performed

in conjunction with the USNRC sponsored Risk Methodologies Integration

and Evaluation Program (RMIEP). 2 -

It was found that the I&E reports were not adequate to accurately

quantify the amounts of various types of combustible materials found at

plants. These reports also often did not identify the specific area of

the plant in which a particular item was found. In addition, 35 I&E

inspectors were polled and several responses were received. Based on

this review five general categories of transient- fuels were identified.

Based on the inspector responses the typical quantities of material found

for each of the five categories are as follows:

Oil: 1 to 5 gallons

Solvents: 1 gallon

Paint: 1 gallon

Untreated Wood: From 10 pounds up

Paper/Trash: 30 to 55 gallon containers

These results must be considered subjective as they are based on an

individual's recall, and as such may be biased. For four of these five

fuel types, histograms were developed to identify the frequency with

which a given quantity of the fuel was reported-as a "typical" inspection

finding. These histograms are presented in Figure 3.1. For the category

of untreated lumber no typical quantity could be established. In

addition, for each of the five fuel types, similar histograms were

developed for the upper and lower bounds of reported fuel quantities.

These histograms are presented in Figure 3.2.

2. This work has not been previously published, though has been

documented in a letter report to the USNRC dated June 29, 1984.

-24-
s0

25 FI

20

1i10 -

5 F

0

7 I 

I -

.1 - <• 80 so 55

BIN SIZE (UNITS: gal)

>56

Figure 3.1a: Paper/Trash

sO

25 I20

isI10

5

iiILIL,

<1 1 2 S 4 5 10 15 2050 75100>100

BIN SIZE (UNITS: goa)

Figure 3.1b: Oil

Figure 3.1: Typical Quantity Transient Fuel Source Histograms

-25-
30

25

w 20

Is

10

5

0

30

25

20

15

10

5

a

• I •

lpt 1 qt Ig 9 S gal >5 gMl

BIN SIZE

Figure 3.1c: Solvents

aw

a,w

I

F

I L

I pt I qt 1g8 Sga >Sga9

BIN SIZE

Figure 3.1d: Paint

Figure 3.1: Typical Quantity Transient Fuel Source Histograms (cont).

-26-
30

C

'U

<5 <30 s0 55 >55

BIN SIZE (UNITS: goa)

Figure 3.2a: Paper/Trash

30

25

20

15

I10

<1 1 2 4 15 1015205075100>100

BIN SIZE (UNITS: 0)

Figure 3.2b: Oil

Figure 3.2: Upper and Lover Bound Quantity

Transient Fuel Source Histograms

-27-
I

30

25

20

15

10

5

0

BIN SIZE

Figure 3.2c: Solvents

30

25

20

Uj 15

CaC

10

S

I pt I qt I gal 3gml >5 ga

BIN SIZE

Figure 3.2d: Paint

Figure 3.2: Upper and Lover Bound Quantity

Transient Fuel Source Histograms (cont)

-28-
33

30 - oUwnv&

25

S20'

15

10 '

to -

Is

10

0 <10 10-50 50-100 >200

BIN SIZE (uNIT: b)

Figure 3.2e: Untreated Wood

Figure 3.2: Upper and Lover Bound Quantity

Transient Fuel Source Histograms (cont)

-29-
3.2.3 Development of Nuclear Power Plant Fire Occurrence Data Base

One of the most valuable sources of information on the frequency of

fires, the sources of fire initiation, the eventual extent of fire

involvement, and the extent of impact of fires on plant operations is the

nuclear power plant operating experience base itself. At the time of

this work commercial nuclear reactors in the U.S. had logged several

hundred years of combined operating experience. In an effort to

characterize the actual history of fires in nuclear power plants, a

review of the past experience base in this regards was performed in

conjunction with the RMIEP study. The results of this review were

utilized as the basis for the development of a data base of U.S. nuclear

power plant fire occurrences.[24]

This review of fire incidents included fires from as early as 1965

through June of 1985. Incidents were identified through both the USNRC

incident reporting system and certain insurance industry data bases. A

total of 364 events are identified in the data base. To the extent

possible, incident reports include identification of the source of the

fire, the extent of fire growth, the extent of fire damage, the impact on

plant systems, fire detection and suppression methods and times, as well

as several other factors.

One of the difficulties encountered in the formulation of this data base

was that fire reports are quite inconsistent in the level of detail

provided. Reports can vary in detail from a mere few words stating that

a fire occurred, to quite complete descriptions of a fire event. This

inconsistency is reflected in differences in the level of detail provided

for each fire event.

The data base itself has been designed to be accessed using a standard

International Business Machines (IBM) Personal Computer (PC) or

compatible systems with commercially available software. The data base

files are contained on three 360 kbyte 51⁄4-inch floppy diskettes available

in the public domain. This ready availability and ease of application

have made the data base a quite useful tool in the assessment of plant

fire risk. It is routinely utilized to estimate fire ignition

frequencies for specific plant areas, to classify anticipated fire

initiation sources, and to assess the anticipated effectiveness of

detection and suppression efforts. The data base also provides some

limited insights into the types of equipment most vulnerable to fire

initiation and to fire damage.

Based on this listing of fire experiences, a given nuclear power plant

can expect to encounter a significant fire, on average, once every 6-10

years of operation. In this context, a significant fire is one which can

or will result in the degradation of one or more safety systems.

Further, the U. S. nuclear industry as a whole experiences on the order

of 10-15 reportable fires each calender year. The yearly history of fire

occurrences documented in the data base is illustrated in Figure 3.3.

Based on an informal collection of more recent fire incident reports this

-30-
0-Power Oper. -Hot Shutdown

-Pre-op Test. im -Cold Shutdown -Refuel ing

-,a

0

CU

0,

ICU

25

20

15

10

5

0

E

K

!-

I

M

DOCK

DW

LNUCY D004

/I" I

01= D004 DOOý

ýOw

Doug

D009

D004

389 DOO(

A d I.

69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84

Calender Year

Figure 3.3 Yearly History of Fire Events as Documented in the SNL Data Base
rate of fire occurrences appears to be continuing at approximately the

same rate in more recent years.

As a part of the recently completed Fire Risk Scoping Study (8], those

incidents within this data base for which asuppression time is reported

were utilized as the basis for the development of a suppression

probability distribution. A total of 69 such events were identified.

These results are described in more detail in Chapter 4 of this report,

which describes fire detection and suppression system effectiveness

related efforts.

3.3 Transient Fuel Source Fire Characterization Efforts

A transient fuel source is any combustible fuel source that is not a part

of the as-designed plant systems and structures. Thus this definition

includes such items as trash, construction and maintenance materials, and

spills of liquid fuels such as oil and solvents. Two experimental

efforts conducted as a part of the FPRP provide direct insights into

phenomena of interest in the definition of the fire threat, which certain

of these potential fire sources represents. These are:

1981 Trash/Pool Fire Correlation Tests

1985 Transient Fuel Source Fire Tests

3.3.1 Trash/Pool Fire Correlation Tests

The Trash/Pool Fire Correlation Tests were performed during the early

stages of the FPRP during which specific regulatory concerns were being

investigated.[22] It was considered desirable to establish an

equivalency between a liquid fuel pool fire and other transient fuel

packages, and in particular trash fires. The investigation of these two

transient fuel sources was motivated by two factors. First, in

experimental fire work there is a great deal of uncertainty in the

anticipated behavior of a particular fuel package because the

repeatability observed in many fuel packages is quite poor. Liquid fuel

pool fires have been observed to represent one of the most repeatable

fire sources. The second factor was the capability of existing fire

simulation models to predict the behavior of liquid fuel pool fires based

on certain fundamental fuel properties (for example see Reference 25),

whereas, such predictions can not be accurately and reliably made for a

fuel package made up of trash.

In an attempt to establish a basis for equivalency, the assessment of

several experimental fires involving both simulated trash and liquid fuel

pools was undertaken. The fire characteristic considered of primary

interest was the rate of thermal radiation heat flux emitted by the fire

source. This parameter was assumed to most nearly represent the degree

of threat a given fuel package represented as an exposure fire source.

In each test the rate of thermal heat flux received at certain locations,

near the fire was monitored, along with several other parameters

characterizing the severity of the resulting enclosure environment.

-32-
As a result of these tests, it was concluded that a liquid fuel pool fire

involving 5 gallons of heptane burned in a 5 square foot fuel pan did not

appear to be more likely to cause ignition of secondary fuel sources than

certain of the trash-fueled fires tested. (This heptane fuel source had

been previously used as a cable tray fire exposure source.) It was also

concluded that no true equivalency could be established between the trash

fires and the liquid fuel pool fires. This resulted from observed

differences between the highly transient behavior of the solid fuel

packages and the relatively steady burning in the liquid fuel packages.

Some basis for comparison was established, though no true one-to-one

correspondence could be demonstrated in all aspects simultaneously. It

was also confirmed that the transient fire behavior of the solid fuel

packages would be hard to predict without first characterizing fuel

behavior through experimentation.

3.3.2 Transient Fuel Source Fire Tests

In a subsequent effort a number of "typical" transient fuel fire sources

were experimentally evaluated to determine the rate of heat release

observed for each fuel package.[26] Five fuel packages were tested

ranging from a small bucket with cleaning solvent and paper rags to a

single large plastic trash container filled with paper and cotton rags.

The selection of the fuel packages tested was based in part on the

results of the transient fuels experience base review described above in

Section 3.2.2.

Peak heat release rates observed during testing ranged from 12 to 145 kW.

Typical heat release rates were in the range from 20 to 50 kW. It was

also found that fires were quite long lasting with open flaming

continuing for as long as 65 minutes. Flame heights ranged from as

little as 10 inches to as high as 3 feet, with transient bursts as high

as 8 feet. Plume temperatures, measured with bare bead thermocouples, at

approximately 3 feet above the base of the fire peaked in the range of

250 to 800"C. At a height of six feet above the base of the fire typical

plume temperatures ranged from 40 to 100°C. The highest measured plume

temperature at six feet was approximately 250°C for a test involving a

cardboard box and cleaning solvent.

Comparison of these FPRP tests to tests previously conducted by other

investigators [27] involving similar fuel packages also provided useful

insights. In these previous tests, the trash fuel configuration used

included a highly flammable waxed paper fuel configured in a manner such

that fire growth rates would be maximized. In these previous tests peak

heat release rates of as high as 600 kW had been recorded. In the FPRP,

tests a similarly sized fuel package involving plain paper and cotton

rags displayed a peak heat release of only 145 kW. As a result, the

previously tested fuel packages were concluded to represent worst case

configurations for such fuel packages. The FPRP packages were considered

to represent more realistic best estimate configurations.

-33-
3.4 Investigation of Cable Tray Fire Behavior

As has been stated above, cable insulation dominates the combustible fuel

loading in most nuclear power plant areas. Most of this cable insulation

is present in the form of cables routed in extensive cable tray arrays.

Thus, the characterization of the fire behavior of cables in tray arrays

and of the role of various passive fire protective features in preventing

fire spread is of critical importance to the overall understanding of the

problem of fires in nuclear facilities.

This critical role of cable insulation as the primary fuel source of

interest is further amplified when one considers the results of past fire

risk assessments. For many such assessments, the dominant fire scenarios

focus on plant areas where power, control, and instrumentation cabling

for redundant trains of safety equipment are routed through single fire

areas and can thus represent single point multiple system fire

vulnerabilities.[8] For these scenarios the rate of fire growth

predicted for the cable tray arrays effectively competes with the

probability of fire suppression within a given time frame to determine

the significance of the given scenario in the overall risk perspective.

In actuality, relatively little fundamental research on the fire behavior

of cable tray installations has been performed. As a part of the early

work conducted under the FPRP, a number of experimental efforts

associated with the investigation of various cable tray fire safety

issues were performed. The primary objectives of these efforts were to

address specific regulatory questions and concerns, as has been described

in Chapter 2 of this report. However, these efforts also provide

insights into the general behavior of cables under fire conditions as

well. It is these more broadly based insights which will be discussed

here.

The specific experimental efforts of interest in this context are:

1975 Cable Use Screening Survey

1976 Electrically Initiated Cable Fire Tests

1977 Exposure Fire Cable Fire Tests

1978 Cable Tray Fire Retardant Coatings Tests

1978 Cable Tray Barrier Tests

1979 Cable Tray Corner Effects Tests

In more recent years, initial efforts to utilize the broader insights

gained as a result of these cable tray fire tests in the formulation of

cable fire growth simulation models were undertaken. These efforts met

with only limited success as the narrow scope of these early cable fire

tests resulted in only limited quantitative data being gathered. The

particular study of interest in this context is:

1981 Burn Mode Analysis of Cable Fires

-34-
3.4.1 Cable Use Screening Survey

As an initial step in the performance of cable fire testing, a survey was

conducted in 1975 to determine the commercial nuclear industry design

practices regarding the selection of cable insulation materials. This

review was not intended to determine the characteristics of cables in

existing plants, but rather, to obtain an indication of the

characteristics of cables in new installations and for existing plant

cable upgrade and replacement activities.

Responses to the survey were obtained from 13 architect-engineering

firms, 13 utility companies, and 13 cable manufacturers. The respondents

identified 20 different cable types which were being considered for use.

The most popularly cited cable types were cross-linked polyethylene (XPE

or XLPE) with or without some jacketing material (34% of the

respondents), ethylene-propylene rubber (EPR) with a Hypalon jacket

(23%), and EPR with a Neoprene jacket (19%).

On the basis of this survey, five cable types were selected for initial

screening. All five types were #12 AWG single or multi-conductor cables.

This size selection was based in part on the anticipation of the

Electrically Initiated Cable Fire Tests (described immediately below) and

an understanding that the electrical initiation of fires experimentally

would be difficult to achieve. As cable size increases, the power

requirements to initiate combustion also increase. Cables of the #12 AWG

size were considered an appropriate selection as these are generally the

smallest power cables found outside of containment in most power plants.

The five cable types selected are described in Table 3.1.

3.4.2 Electrically Initiated Cable Fire Tests

Electrical faults represent one potential source for the initiation of

cable fires. As a part of early fire research efforts, an examination of

the potential for the development of electrically initiated fires in

IEEE-383-74 rated low flame spread cables was performed. As a result

several, insights were gained.

It was found that for the #12 AWG cables tested, currents of from 120 to

130 amperes were required to induce open flaming. This compared

favorably to pretest analytical predictions that currents in the range of

100-120 amperes would be required to initiate combustion. In full-scale

testing, the intense period of fire activity persisted for between 40 and

240 seconds after which rapid reduction to self-extinguishment of the

fire was observed.

Also included as a part of these tests was an examination of the adequacy

of RG 1.75 cable tray separation criteria in'preventing the spread of an

electrically initiated cable tray fire. In no case involving

electrically initiated fires in rated low flame spread cables was

propagation of the fire beyond the tray of fire origin observed. Thus,

RG 1.75 was judged adequate to prevent the spread of electrically

-35-
initiated fires involving IEEE-383-74 rated low flame spread cables. (As

will be discussed immediately below, RG 1.75 was judged inadequate when

the threat of exposure fires was considered.)

Table 3.1: Cable Types Selected for Initial Cable

Fire Testing

Cable #1 Single Conductor #12 AWG, 45 mil (1.14 mm) EPR,

30 mil (0.76 mm) Hypalon jacket, 600 V.

Cable #2 Single Conductor #12 AWG, 47 mil (1.19 mm)

chlorinated rubber (proprietary), 47 mil (1.19 mm)

chlorinated polymer (proprietary) jacket, 600 V.

Cable #3 Single Conductor #12 AWG, 47 mil (1.19 mm) EPR,

15 mil (0.38 mm) Neoprene jacket, 600 V.

Cable #4 Single Conductor #12 AWG, 30'mil (0.76 mm) XPE, no

jacket, 600 V.

Cable #5 Three Conductor #12 AWG, 30 mil (0.76 mm) XPE,

silicone glass tape, 65 mil (1.65 mm) XPE jacket,

600 V.

Note: Cables 4 and 5, though similar, were supplied by

different manufacturers.

3.4.3 Cable Tray Exposure Fire Testing

In subsequent testing, two of the cables evaluated in the electrical

ignition study were tested under exposure fire conditions. The cable

types selected for this subsequent testing were those considered to be

the least flame resistant of those evaluated previously. These two cable

types were both of the XPE type and are those designated as cables #4 and

#5 in Table 3.1.

The fire source used in the first series of exposure tests was comprised

of two propane ribbon burners, each identical to those used in the

IEEE-383-74 flame spread test, placed under the horizontal cable trays.

These ribbon burners were each driven at the fuel rates specified for the

IEEE-383-74 test burner. Note that the IEEE-383-74 test specifies the

use of a single burner so that the total exposure fire source intensity

was twice that of the standard test. This increase in exposure intensity

was intended to compensate for the horizontal configuration of the cable

trays used in the exposure tests, as compared to the vertical tray

-36-
configuration of the standard test. In a horizontal configuration, self

sustaining cable tray fires are more difficult to induce.

It was observed that under this exposure the XPE cables tested required a

minimum exposure time of approximately 300 seconds to establish self

sustaining combustion in a single cable tray. Note that the IEEE-383-74

standard burner intensity is 70,000 BTU/Hr (20.5 kW). The use of two

such burners produces a fire equivalent in intensity to a small, low

intensity trash fire or to a heptane pool fire approximately ten inches

(0.26 m) in diameter.

The final test in this series of exposure fire tests was conducted on

July 6, 1977.[10] In this test one division of safety related cables was

simulated using 14 filled horizontal cable trays in a two tray wide by

seven tray high array. The lower trays were filled with the single

conductor XPE cable' described in Table 3.1 as Cable #4, while the upper

trays were filled withi the three conductor XPE cable described in Table

3.1 as Cable #5. These 14 cable trays were separated by eight inches

horizontally and by 10.5 inches vertically, as allowed by RG 1.75. A

second, redundant train of safety related cables was simulated by two

filled cable trays each located five feet above the highest of the

simulated division one cable trays, again consistent with the RG 1.75

guidance. Figure 3.4 provides a photograph of the pre-test

configuration. This particular test provides a number of insights into

the growth behavior of a cable tray array fire.

A five minute exposure to two standard IEEE-383-74 ribbon burners under

one of the lowest two trays produced a fully developed fire within this

one cable tray. During this' initial five minute period, a barrier was

used to shield the remaining trays from the fire. The propane burners

then were extinguished and the barrier was removed. The fire eventually

propagated through not only the closely stacked division one cable trays,

but the simulated redundant division cables as well.

It was also noted, based on infrared thermography, that the fire grew

primarily in an upward direction, spreading horizontally only as it

progressed from level to 'level. The rate of fire spread was observed to

accelerate as the fire progressed. The angle of this horizontal spread

from level to level was estimated at 35* to either side of the vertical.

Very little horizontal flame spread in any given tray beyond this angle

of flame progression was noted.

Due to the build-up of a dense layer of smoke in the test enclosure,

visual observation of the test fire was very difficult. Based on

thermocouple measurements, and on a review of infrared thermovision

images taken during the fire, the progress of the flames has been

estimated. The exposed tray on the first level was observed to be

burning intensely, though in a very localized region, after the five

minute burner exposure. Within. approximately five minutes of removal of

the barrier, the second and third level trays appeared to be involved in

the fire. Within ten minutes of the barrier removal, the fourth level

trays were also involved. The sixth level of cable trays was involved

-37-
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-38'
within 18 minutes of barrier removal. The simulated redundant cable

train was observed to be burning within 22 minutes of the removal of the

fire barrier.

It is interesting to note that probabilistic risk assessment activities

for fire have resulted in the development of a fire suppression

probability distribution based on historical experiences of nuclear power

plant fires in the U.S.[8] This suppression probability distribution is

described in detail in Chapter 4 as a part of the discussion of detection

and suppression system effectiveness investigations. Based on this

distribution, the median probability that the July 6, 1977, test fire

would have been suppressed prior to the involvement of the redundant

cable trays would have been estimated at only 58 percent (including

credit for the five minute burner exposure).

At approximately 34 minutes into the test, seven minutes after ignition

of the simulated redundant train cables, the cable tray array collapsed.

This collapse was attributed to the melting of aluminum structures which

had been used to support the steel cable trays. The aluminum used in the

support structure had an estimated melting point of 1220°F (660°C). Peak

temperatures in the vicinity of the cable tray array were measured at up

to 16009F (871 0 C). The peak temperature measured near the ceiling of the

test enclosure approximately six feet (1.8 m) above the highest of the

cable trays was approximately 1300°F (704°C).

For all of the cable tray fire tests performed, the height of a cable

tray flame was found to be strongly dependant on the nature and intensity

of the fire source. For the electrically initiated fires, the flames

observed during the peak of fire intensity fluctuated rapidly in heights

from 4 to 10 inches. For tests involving exposure of a single cable tray

to a propane gas burner, the flames were observed to fluctuate from 10 to

12 inches in height. When a single tray was exposed to a liquid fuel

pool fire, cable tray flame heights fluctuated between 30 and 50 inches

in height. In the July 6, 1977, test flame heights in the cable tray

array were difficult to judge, though as the fire grew in intensity the

flame heights also increased. Indications were that the flames from the

lower array of division one cables bridged the five foot vertical gap to

ignite the division two cables.

Significant differences were also noted in the heat transfer processes

observed for self-ignited and for exposure fire conditions. In all cases

the flame temperature was roughly 1900°F (1027°C). However, the luminous

flame zone for the electrically initiated fires was optically thin with

an apparent emissivity on the order of 0.1 measured. This is quite low

in comparison to typical values for larger fires, and implies a

correspondingly lower intensity thermal radiation output from such fires.

It was noted that the transfer of heat to immersed objects was convection

dominated in the electrically initiated fires and radiation dominated in

the larger exposure fires.

Estimates of the upward velocity of gases in the region of the flame were

made by tracking the progress of small luminous eddies shed from the

-39-

I
flames. On this basis it was estimated that the average upward gas

velocity in the area of the flames was from 3 to 4 feet per second.

Variations from this range were quite small, even over a large number of

measurements made in different tests.

3.4.4 Cable Tray Fire Retardant Coatings Tests

As a result of the July 6, 1977 test's demonstration that RG 1.75 cable

tray separation criteria were insufficient to insure the protection of

redundant train cable trays under exposure fire conditions, the

investigation of additional fire protective features for cable trays was

initiated. These protective features included fire retardant coatings

for cable trays. A series of tests was performed to evaluate the

effectiveness of a variety of coatings features in (1) reducing material

flammability, (2) preventing the spread of fire and (3) preventing fire

induced cable failures.

For the fire retardant coatings, tests on both a small- and large-scale

were conducted. The small-scale tests evaluated certain fundamental

flammability characteristics while the large-scale tests evaluated the

effects of the coatings on the spread of fire and on preventing or

delaying fire induced damage. (For the purposes of this section, the

discussion of the large scale tests will focus on the flammability and

fire spread results. Damageability results from these tests will be

discussed in Chapter 6, which describes FPRP equipment damageability

studies.) In all, a total of seven different coatings were evaluated.

These coatings were identified in the test reports only by a letter

designation. Thus the coatings are referred to only as coatings 'A'

through 'G'. The names of the actual manufacturers of these coatings

have not previously been published, and will not be published here. The

full matrix of tests performed is presented in Table 3.2.

In the small-scale tests the effects on the flammability of small

sections of cable resulting from application of cable fire retardant

coatings produced by six of the seven different manufacturers were

investigated. These small-scale tests used two types of rated low flame

spread cables which are described as cables #4 and #5 in Table 3.1. The

flammability of the samples was evaluated through measurements of the

time to ignition of the cables themselves, time to maximum heat release

rate, and cumulative heat release at given times after initiation of

exposure. Each of these parameters was measured at each of four exposure

heat flux levels ranging from 1.0 to 4.0 W/cm2.

As a result, it was found that the coatings were all effective at

reducing the materials flammability. However, the effectiveness observed

for the different coatings varied dramatically. For example, at an

exposure heat flux of 4.0 W/cm2 with the unprotected cables open flaming

was observed within 0.8 minutes and the peak heat release rate was

measured after 6.0 minutes of exposure. For the coated samples at this

same exposure flux, the time to observed open flaming of the cables

themselves varied from a low of 5.0 minutes to a high of 24 minutes. It

-40-
Table 3.2: Matrix of Cable Fire Retardant Coatings Tests.

I

Small-Scale Tests Single Tray Tests Two Tray Tests

Gas Burners Gas Burners Oil Pool

383-Rated Cables 383-Rated Non-383 383-Rated Non-383 Non-383

Single Three Single Three Three

Coating Cond. Cond. Cond. Cond. Cond.

None X X X X X X X

A X X X X X X X

B X X X X X

C X X X X X X X

D X X X X X

E X X X X X X X

F X X

G X X X X X X X
should be noted that, in certain cases, open burning of the coating

materials was observed in significantly shorter times. The time to

maximum heat release similarly varied from a low of 12 minutes to a high

of 34 minutes. (Note that for these two parameters a longer time

indicates lesser flammability.)

In terms of the cumulative heat release, significant variations were also

noted. For the unprotected cables at an exposure of 4.0 W/cm2, the

cumulative heat release after 15 minutes of exposure was 78.0 MJ/m2. For

the coated cables, this parameter varied from a low of only 8.1 Mi/in 2 to

a high of 60.4 Mi/in 2. (In this case, higher cumulative heat releases

indicate a higher flammability.)

While in overall terms the small-scale test results were relatively self

consistent, certain inconsistencies did appear. For example, the best

delayer of cable ignition was the coating identified in the tests as

coating E, which delayed cable ignition to 24 minutes. Thie next best

performer in this sense was coating D which delayed ignition to 14

minutes. However, in terms of cumulative heat release after 15 minutes

of exposure coating E allowed 22.5 MjI/i 2 while coating D allowed only

8.1 MJ/rn2.

It is also of interest to note that for both of these samples no open

flaming of the cables had been observed for most or all of this 15 minute

period. Thus, the released heat is presumably accounted for as (1)

combustion of the coating itself, and (2) smoldering combustion in the

cables prior to open flaming. This observation of smoldering combustion

also implies that even though open flaming may be delayed or prevented,

significant cable degradation, and possibly electrical failure, may be

observed. Thus, these small-scale tests demonstrated that no one single

parameter should be used to judge the effectiveness of a given coating.

The full-scale cable coatings tests were performed using cable trays

loaded with either IEEE-383-74 rated low flame spread cables or with a

nonrated cable. The rated cable used was the three conductor XPE cable

used in previous testing and described as Cable #5 in Table 3.1. The

nonrated cable used was a 12 AWG three conductor cable with a 20/10

PVC/PE insulation and a PVC jacket. A total of 33 tests on five of the

seven coatings was performed. Fifteen of these 33 tests involved the

exposure of a single cable tray to a gas burner f ire. Thirteen tests

involved the exposure of a two tray stack to a gas burner. In all of the

gas burner exposure fire tests two of the standard IEEE-383-74 propane

ribbon burners were used as in previous RG-l.75 cable fire tests

described above. For the coatings tests repeated burner cycles of five

minutes on and five minutes off up to a maximum test duration of 60

minutes (six full cycles) or until ignition of the cable samples was

observed were utilized. The final five tests involved the exposure of a

two tray stack to a diesel fuel liquid pool fire.

Table 3.3 summarizes some of the principal results of the single tray gas

burner cable coatings tests. Note that the time to ignition for

uncoated, low flame spread cables was 5 minutes. (That is to say,

-42-
ignition occurred during the first burner cycle.) For the coated cables,

ignition times varied from 5 minutes (coating C) to no observed ignition

within 60 minutes (coatings D and E). The times to electrical failure of

the coated cable were also significantly affected in most cases. Several

of the coatings prevented electrical failure entirely. These results are

discussed further in Chapter 6 as a part of the discussion of equipment

damageability investigations.

Table 3.3: Summary of Principal Single Tray Gas Burner

Cable Fire Retardant Coatings Test Results.

Time to Burn Burn

Cable Type: Ignition Duration Length

Coating (min) (min) (in)

3-Conductor, IEEE-383-74 Rated Cables:

None 5 13 27

A 10 15 30

B 15 7 40

C 5 40 43

D No 0 0

E No 0 0

1-Conductor, IEEE-383-74 Rated Cables:

None 5 10 34

A 10 6 35

B 20 7 43

C 10 15 58

D No 0 0

E No 0 0

One result of particular interest is the effect of the coating 'C' on the

duration of burning after ignition, and the length of the burned area.

For the uncoated low flame spread cables, burn durations for the

3-conductor and 1-conductor cables were 13 and 10 minutes respectively.

The corresponding burn distances were 27 and 34 inches respectively. For

the coating designated 'C' the burn durations for the 3-conductor and

1-conductor cableg actually increased to 40 and 15 minutes respectively.

Similarly, the length of the burned area increased to 43 and 58 inches

respectively. Thus, for this coating, while the times to electrical

shorting were delayed somewhat, the duration of burning and extent of

fire spread were both increased significantly.

-43-
For the two tray gas burner coatings tests, both rated and nonrated

cables were used. The primary result of interest from these tests is the

effects of the fire on the upper of the two trays. The only case in

which propagation of the fire to the upper tray was observed involved

coating 'C' with unqualified cables. In no case was propagation of the

fire to the upper tray observed for coated low flame spread cables. It

should be noted that, as in previous tests, an insulating barrier was

placed between the two trays during the times when the gas burners were

on. This barrier was removed during cycle periods when the burners were

off. This limited the effects of the exposure fire on the upper tray to

that produced by the burning of the lower tray only.

The two tray diesel fuel coatings tests differed from the gas burner

tests in three important respects. First, the exposure fire involving

the diesel fuel pool was more intense than that involving the gas

burners. Second, no barrier was placed between the two trays during the

burning of the diesel fuel exposure fire. Third, the diesel fuel pool

fire burned continuously for approximately 13 minutes as opposed to the

use of 5 minute on, 5 minute off burner cycles. The diesel fuel fire

tests are indicative of the actual response of a coated two tray stack to

a relatively severe exposure fire situation. Only five of the seven

coatings were evaluated in this configuration.

All of the diesel fuel pool fire coatings test involved the use of the

nonrated PE/PVC 3-conductor cable. The results of these tests are

summarized in Table 3.4. Note that the times to electrical failure

varied from 3-11 minutes for the lower tray, and from 7-19 minutes for

the upper tray. Three of the five coatings evaluated, coatings 'A', 'B',

and 'E', prevented the propagation of fire to the second upper tray even

under these fairly severe conditions. For the other two coatings tested

in this series, significant fire spread within the upper tray was

observed.

In summary, the Cable Tray Fire Retardant Coatings Tests demonstrated a

wide variability in the effectiveness of the different cable coatings

evaluated. This variability was noted in virtually every parameter

investigated including (1) the delay in the onset of cable burning, (2)

the delaying or prevention of fire induced electrical failure, and (3)

the rate and extent of fire spread. Certain of the cable coatings

performed very well under all of the conditions evaluated. The coating

identified as 'E' would be judged the overall best performer. The

coatings identified as 'A' and 'B' also performed well in that they

prevented the propagation of fire to the upper cable tray under the

relatively severe exposure conditions of the two-tray diesel fuel fire

tests. The coating identified as 'C' would be judged the poorest

performer. In some instances, this coating actually resulted in more

severe fire conditions than did uncoated cables.

-44-
Table 3.4: Summary of Principal Two Tray Diesel Fuel

Fire Cable Fire Retardant Coatings Tests

Involving Nonrated 3-Conductor Cables.

Time to Burn Burn

Ignition Duration Length

Coating (min) (min) (in)

Lower Tray Response:

A 13 42 72

B 13 31 20

C 12 37 84

E No 0 36

G 12 42 66

Upper Tray Response:

A No 0 72

B No 0 72

C 12 43 96

E No 0 0

G 12 46 84

However, these tests also demonstrated that the use of any of the fire

retardant coatings evaluated would not prevent the onset of electrical

failure under the diesel fire exposure conditions. Thus, the use of such

coatings can not'be, in and of itself, considered sufficient to prevent

fire induced cable degradation.

One should also note that these tests did not address certain other

aspects of the use of such coatings on cable performance which should be

considered in the practical application of such measures. In particular,

no investigation was performed of the impact of application of such

coatings on the ampacity rating of the cables, or of the potential

degradation of these coatings due to aging or other effects. Nor were

the coatings examined for material composition. In these tests, all

coatings were applied to thickness recommended by the individual

manufacturers. These recommended thicknesses varied considerably from a

light coating to quite thick, trowel on coatings. This thickness almost

certainly would play a role in the effectiveness of all aspects of the

coating performance. The effects of either increasing or decreasing the

recommended thickness was not investigated.

-45-
3.4.5 Cable Tray Fire Barrier Tests

As a second potential method for reducing the severity of cable tray

fires, and for reducing the likelihood of fire induced damage, the use of

protective passive fire barrier systems for cable trays was

experimentally investigated. These tests were conducted in a manner

identical to that used in the single tray and two tray gas burner cable

coatings tests described immediately above. The same cable types and the

same gas burner exposure fire source were used. Five potential fire

barrier systems were tested. These were:

1 -

2-

3-

4-

5-

ceramic wool blanket wrap,

solid tray bottom covers,

solid tray top cover with no vents,

solid tray bottom cover with vented top cover, and

1-inch insulating barrier between cable trays.

of cable tray fire barrier tests is presented in Table 3.5.

system identifiers in this table are those number codes given

above.

The matrix

The barrier

immediately

Table 3.5: Matrix of Cable Tray Fire Barrier Tests.

Single Tray Tests Two Tray Tests

Barrier 383-Rated Non-383 Non-383

System Single Three Three Three

Identifier* Cond. Cond. Cond. Cond.

1 X X

2 X X X X

3 X X

4 X X X X

5 X

* Defined in text.

The most telling of these tests are the two tray gas

five of the barrier systems were evaluated using

exposure. These tests can also be compared to the

case in which a two tray configuration of unprotected

exposed to the same ignition source. The results

summarized in Table 3.6.

burner tests as all

a consistent fire

previously reported

nonrated cables was

of these tests are

-46-
Table 3.6: Summary of Principal Two Tray Gas Burner

Cable Tray Fire Barrier Tests Involving

Nonrated 3-Conductor PE/PVC Cables.

Barrier Time to Burn Burn

System Ignition Duration Length

Identifier* (min) (min) (in)

Lower Tray Response:

None 5 39 67

1 15 45 108

2 20 4 43

3 10 68 120

4 10 55 66

5 5 42 120

Upper Tray Response:

None 3 59 84

1 No 0 0

2 No 0 0

3 No 0 0

4 No 0 0

5 No 0 0

* Defined in Text.

In all cases, the propagation of fire to the upper tray was prevented.

In only two cases were electrical faults in the upper tray observed, and

in one of these two cases (involving barrier system #5), the fault

resulted from fire propagating in the lower tray beyond the end of the

insulating fire barrier placed below the upper tray. However, in no case

was electrical failure prevented in the lower of the two trays. In fact,

the barriers (with the exception of barrier system #2) generally

increased both the duration and eventual extent of fire development in

the lower tray.

3.4.6 Cable Tray Fire Corner Effects Tests

In a fire, the intensity of the thermal feedback delivered to a fuel

element can dramatically affect that fuel elements burning rate and fire

growth rate. Sources of thermal feedback include hot layer effects, heat

transfer from other burning fuel elements, and the re-radiation of heat

from enclosure surfaces. In cable fire testing, it has often been

-47-
observed that the presence or absence of thermal feedback can determine

whether or not a fire will self extinguish or continue to burn and grow.

This is illustrated by the observation that while it is difficult to

establish self-sustaining combustion in a single strand of cable, cables

laid up in a cable tray array or placed in a cabinet configuration burn

much more easily, and much more intensely. In these latter cases, the

presence of other combustible fuel sources, and/or the proximity of the

cables to a surface contribute to the intensity of combustion.

Under the FPRP, an effort was conducted to investigate the effects of

proximity to enclosure surfaces on the burning of a cable tray. In these

tests, known as the Corner Effects Tests, a room ceiling-wall corner was

simulated using insulating wallboard panels. In a series of six tests,

pairs of cable trays were positioned at various distances from the

simulated corner and then subjected to a gas burner exposure fire. The

distance from the cable tray to the simulated corner was varied from 12

inches (5 inches horizontal and 10.5 inches vertical) to 134 inches (60

inches horizontal and 120 inches vertical). These tests involved both an

IEEE-383-74 rated low flame spread cable and a nonrated cable (identical

to those used in the fire retardant coatings tests described above). The

gas burner exposure fire source used was physically identical to that

used in previous tests described above. As in the previous tests a

burner operation time of five minutes was used, though in the corner

effects tests repeated burner cycles were not used. During the cycle

period in which the burners were on, the upper tray was shielded from the

gas burner fire. After five minutes the gas burner was extinguished and

the barrier removed, exposing the upper tray to only the fire established

in the lower tray.

As a result of these tests, a pronounced effect on the fire behavior was

observed. One of the parameters measured was the total weight loss for

the cables in the upper of the two trays. The nonrated cables

experienced a 62% increase in total weight loss, from approximately 30.5

to 49.5 pounds, as the distance between the upper tray and the corner was

decreased from 134 to 12 inches. For the rated cables an even more

pronounced increase was observed with upper tray weight loss increasing

from 3.75 to 39.75 pounds, or an equivalent increase of more than 960% of

base value.

A second parameter measured was the average rate of mass loss for the

upper tray. En the case of the nonrated cables this mass loss rate

increased from 0.78 to 0.92 lbs/min as the distance from the upper tray

to the corner decreased from 134 to 12 inches. For the rated cables the

increase in upper tray mass loss rate was from 0.15 to 1.99 lbs/mmn for

this same change in distance from the upper tray to the corner.

A third parameter measured was the total length of fire involvement for

the upper cable tray. For the nonrated cables at a distance between the

upper tray and the corner of 134 inches the length of fire involvement

prior to self extinguishment was 96 inches. At distances of both 21 and

12 inches full tray fire involvement was observed (total tray length was

144 inches). For the rated cables at a distance of 134 inches, only 16

-48-
inches of the upper tray burned prior to self extinguishment. When the

distance to the corner was decreased to 21 inches, the length of

involvement increased to 72 inches. At a distance of 12 inches to the

corner the length of fire involvement increased to 120 inches.

These results are summarized in Table 3.7. It is clear from these tests

that thermal feedback will profoundly impact the development of a cable

fire. In particular, for the rated low flame spread cables while in a

relatively open condition away from the surfaces, combustion conditions

were marginal with very little spread of fire in the second tray.

However, when the thermal feedback was increased through proximity to the

surfaces, self-sustaining combustion continued much longer and the fire

progressed much farther along the upper cable tray. (Similar marginal

combustion conditions for rated cables were also noted in the fire

testing of control panel cable configurations as described in Section 3.5

below. Here again the presence or absence of significant thermal

feedback was sufficient to determine whether the fire would grow or self

extinguish in low flame spread cables.) For the cables not rated as low

flame spread, combustion was much more vigorous in an open configuration

than was that involving rated cables. Even so, thermal feedback

contributions to increased fire severity are apparent.

3.4.7 Burn Mode Analysis of Cable Fires

As a result of the insights gained from the various cable tray fire

tests, an effort to formulate an empirical correlation between certain

characteristic cable thermal parameters and the mode of cable combustion

was performed. Under this approach, a cable's surface and subsurface

temperatures were used to predict the mode of cable combustion. The

combustion modes considered were (1) continuous use range, (2)

accelerated aging, (3) pyrolosis, (4) deep seated or smoldering fire, (5)

interior gas combustion, (6) surface fire, (8) fire ball flaming, (9)

deflagration, and <10) flashover. Each of these modes was associated

with a given combination of interior and surface temperature for a given

fuel element or cable type.

Using these fire mode definitions the progression of certain of the cable

fires observed in past testing were plotted. The data was taken from the

cable tray fire retardant coatings and fire barrier tests described

above. Two fire tests had been conducted using unprotected cables in

order to establish a base line for cable fire behavior. One of these

tests involved an IEEE-383-74 rated low flame spread cable, while the

other involved an nonrated cable. Figure 3.5 and 3.6 provide examples

of the fire development observed for these two different cable types

based on experimental measurements of the cable temperatures, and on

observations of the actual fire burning mode.

-49-
1800

OEFLAGRATSON

1600

.*1400 FNBL

1200 SUM FV

A 0

0 200 400 800 800 1000 1200 1400 1800 1800

FEL. T TEMP (F)

Figure 3.5: Burn Mode Analysis of Non-Rated Cable Fire

1800 -

- •.'LOanATIIM

1600-

0- 1200

80

400 Jtq•

200

00 200 400 8O0 800 1000 1200 1400 1800 1800

FUEL ?4TERNAL TEMP CF)

Figure 3.6: Burn Mode Analysis of Rated Low Flame Spread Cable Fire

-50-
Table 3.7: Summary of Corner Effects Test Results

for Upper of Two Cable Trays.

Cable Type/ Total Weight Average Mass Length of

Distance to Loss (lbs) Loss Rate Fire Area

Surfaces (in.) (lbs/mmn) (inches)

IEEE-383-74 Cables:

Side - 5.0 39.75 1.99 120

Top - 10.5

Side - 10.5 1.23 72

Top - 18.0

Side - 60.0 3.75 0.15 16

Top - 120.

Nonrated Cables:

Side - 5.0 49.5 0.92 144*

Top - 10.5

Side - 10.5 Top 

Top -

- 18.0 18.0 44.75 0.89 144*

Side - 60.0 30.5 0.78 96

Top - 120.

* Total length of cable tray.

The development of this burn mode analysis technique was limited in that

only cable fire data available from previously conducted tests was used.

No further confirmatory testing was undertaken. The available data had

been gathered in pursuit of quite different objectives, and hence, was

not ideally suited for use in this analysis methodology. However, the

technique did display a potential for addressing cable fire growth

modeling limitations by providing a basis for the prediction of cable

fire burning modes, and hence, cable fire growth modes.

The modeling of cable fire growth behavior remains a source of

considerable uncertainty in the modeling of nuclear power plant fire

scenarios, and in the analysis of fire risk. Should further experimental

investigations of cable tray fire behavior be undertaken, it would be of

utility to provide for the investigation of the adequacy of the burn mode

analysis technique as a part of these investigations. The technique, if

adequately validated, is well suited to incorporation into fire

simulation models as it depends only on a prediction of the fuel surface

and subsurface temperatures. Such predictions could be generated by a

simulation model by using one-dimensional or composite transient thermal

-51-
targets as fuel models rather than using lumped parameter element models

as are typically employed in current models.

3.5 Investigations of Electrical Control Panel Fires

In recent years an investigation of electrical control cabinet fires was

performed. There are two aspects of this work relevant to the issues of

source fire characterization. First, an apparatus for electrically

initiating fires through the simulation of a faulty electrical connection

was developed. Second, the effects of various cabinet parameters on the

development of a cabinet fire were investigated. Each of these two

aspects of the cabinet fire investigations are discussed in turn in the

two sections which follow.

3.5.1 Development of an Electrical Fire Initiation Apparatus

Historically, a large number of electrical control panel fires have

occurred in commercial U. S. reactors. The Sandia Fire Occurrence Data

Base [24] includes 39 reported cabinet fire incidents occurring between

12/16/72 and 8/2/84.[8] Nearly all of these fires resulted from selfgenerated electrical faults within the panel. The remainder resulted

from electrical faults generated by an external source (e.g., rodents,

water, etc.). Thus, in the experimental investigation of electrical

panel fires it was of interest to investigate the behavior of an

electrically initiated fire. However, as was found in previous tests

involving cable trays, described above, the experimental inducement of an

electrically initiated fire is quite difficult to achieve.

As a part of the cabinet fire investigations an apparatus was developed

which could reliably and repeatably induce a self-sustaining fire in

nonrated (i.e., not qualified by the IEEE-383-74 flame spread

qualification test) cables in a control panel configuration.[28] The

criteria for the development of this 'apparatus included the restriction

that the fault should not be detectable by a 15 ampere fault current

breaker.

The apparatus developed simulates a faulty terminal block connection.

Ignition of nonrated electrical cables was achieved using a power source

of less than 200 watts. In full scale cabinet fire tests this apparatus

was used to initiate fires in cable arrays 'within actual electrical

control panels. With the unqualified cables, propagation was observed

which eventually resulted in the complete involvement of the subject

cabinet. The most intense of the electrically initiated fires grew to a

peak intensity of 1.3 MW within approximately 10 minutes of ignition.

These tests are described in more detail below.

One of the concerns which was raised by these tests was that in practice

cables in electrical control panels are often stripped of their

protective outer jacket. In the IEEE-383-74 flame spread test cables are

tested with the cable jacketing intact. The standard test does include a

requirement for the flammability testing of the individual conductors,

though this requirement is significantly less stringent than the testing

-52-
for the full cable configuration. It was of potential concern that if a

qualified cable were stripped of its jacket it may be more susceptible to

fire than initial qualification testing might indicate.

Attempts were initiated to electrically induce ignition and propagation

of fire in IEEE-383-74 rated low flame spread cables. These efforts were

terminated before conclusive results were obtained. While the qualified

cables appeared more resistant to the development of a self-sustained

fire, ignition of the cables was achieved readily, and it was the

impression of the investigators that under the proper conditions a self

sustaining fire would result. Efforts to investigate this potential were

terminated in the early stages as a result of the termination of the Fire

Protection Research Program and the Cabinet Fire Testing Program.

3.5.2 Experimental Evaluation of Electrical Panel Fires

The experimental evaluation of electrical panel fires investigated two

aspects of the cabinet fire question. First, the program investigated

the effects of a number of cabinet parameters on the development of a

fire within a single control panel.[29] Second, the program investigated

the environmental impact of a fire confined to a single control panel on

a very large, near control room sized enclosure.[30] For the purposes of

the discussion of fire characterization efforts being presented here,

only the first of these two aspects is of direct interest. Results of

the investigation of the impact of a cabinet fire on the environment of

an enclosure will be deferred to the discussion of room effects issues

presented in Chapter 5.

In the first series of tests the effects of cabinet parameters including

the style of cabinet (i.e., benchboard versus vertical cabinets), the

fuel loading density, the fuel configuration, cable type, open versus

closed cabinet doors, the presence of ventilation grills, the presence of

internal cabinet partitions, and the intensity of the ignition source on

the rate and eventual extent of fire growth were investigated. In all,

22 cabinet effects tests were conducted, of which six involved fully fuel

loaded full-scale cabinet fire tests. The remaining 16 tests involved

partially fuel loaded, or nonfuel loaded cabinet fire tests investigating

very specific fire growth questions. The conclusions resulting from

these 22 cabinet effects tests are summarized as follows:

1. Cabinet fires can be ignited and will propagate in either

qualified or unqualified electric cables. It was found that

it was much more difficult to establish a self-sustaining fire

in the qualified cables, though in certain configurations,

quite intense fires in qualified cables were observed.

2. Once ignited, the cabinet fires observed often developed quite

rapidly, growing from fire ignition to peak fire intensities

of up to 1.3 MW in as little as 5-8 minutes. The electrically

initiated fires involved significant pre-ignition heating

times, and it is suspected that in-cabinet smoke detectors

-53-
would have detected these faults prior to ignition, though no

tests were performed to confirm this suspicion.

3. The observed rapid fire growth rates are expected to make the

suppression of cabinet fires by plant personnel using handheld extinguishers quite difficult. Such suppression

activities cannot be expected to be effective under most

circumstances if suppression activity is not initiated within

approximately five minutes of ignition.

3. The propagation of a fire from cabinet to cabinet under the

conditions tested was considered unlikely. These conditions

were comprised of a solid steel, double wall barrier with no

through penetrations. No conclusions can be drawn regarding

the effectiveness of other barrier systems in preventing the

spread of fire.

4. Adjacent cabinet temperatures, while below those expected to

result in nonpiloted ignition, may be severe enough to cause

failure and/or calibration shifts in electronic components.

It is important to note that in all the cases tested the fire was

confined to a single control panel. A number of questions remain

unanswered regarding the potential for a cabinet fire to spread beyond

the cabinet of origin. Potential fire spread mechanisms not investigated

include the effectiveness of single wall steel fire barriers, the

reliability of cable penetration seals, and the spread of fire to either

overhead or below cabinet cable trays and raceways. The only fire

barrier system which was evaluated was the effectiveness of a solid,

double wall steel barrier with no through penetrations such as that

between two stand-alone fully enclosed cabinets. This configuration was

found to be quite effective in reducing the adjacent cabinet temperatures

below those expected to cause nonpiloted ignition of the cabinet fuel

materials. The temperatures observed may, however, cause failure and/or

calibration shifts in electronic components for these adjacent cabinets.

Another aspect of this issue not yet investigated is the effectiveness of

fire suppression systems when applied to a burning cabinet. General room

area fire suppression systems may be inhibited by the presence of the

cabinet walls, especially water sprinkler systems. Also unresolved are

questions associated with the use of in-cabinet gaseous suppression

systems. The use of such systems could compromise the operability of

electronic equipment housed in the cabinet.

-54-
4.0 DETECTION AND SUPPRESSION SYSTEM EFFECTIVENESS STUDIES

4.1 Introduction

As a part of the guidance provided in 10CFR50 Appendix R, the USNRC has

endorsed a variety of national fire standards. Among those standards are

several associated with the design and installation of fire detection and

fire suppression systems. However, during the formulation of the

Appendix R guidelines it was recognized that these standards had been

developed for application to typical industrial, occupancy, and storage

facilities. It was concluded that the applicability of these national

standards to the circumstances of a nuclear power plant had not been

demonstrated. Two factors of particular concern were identified. The

first was the applicability of detector system selection and installation

guidelines given the congestion of equipment, ventilation ducts, and

cable trays typical of nuclear power plants. Second, the effectiveness

of the various fire suppressants when applied to deep seated cable fires

had not been investigated.

As a result of these concerns, investigations into certain aspects of

fire detection and fire suppression systems were performed as a part of

the USNRC/Sandia FPRP. The specific studies of interest in this context

are:

Fire Detection Systems Investigations:

1979 Fire Protections Subsystems Study; Fire Detection

1982 Detector Siting Criteria Requirements Study

Fire Suppression System Effectiveness Investigations:

1980 Halon Suppression Effectiveness Tests

1981 Water Sprinkler Suppression Effectiveness Tests

1982 Directed Water Spray Suppression Effectiveness Tests

1983 Carbon Dioxide Suppression Effectiveness Tests

In addition, as a result of the development of the Fire Occurrence Data

Base, certain insights have been gained based on the historical

experience with respect to the detection and suppression of actual fires.

4.2 Fire Detection Systems Investigations

4.2.1 Fire Protection Subsystems Study; Fire Detection

One of the four subsystems investigated as a part of the Fire Protection

Subsystems Study was fire detection systems. The regulatory implications

of this study have been discussed in Chapter 2 above. The discussion

presented here will focus on the technical aspects of the work performed,

and the principal conclusions generated.

The Fire Detection Subsystems Study [31 examined the adequacy of fire

detection in the context of nuclear power plant applications. The

specific aspects of fire detection systems considered were (1)

establishing area detection requirements, (2) selecting specific detector

-55-
types, (3) locating and spacing detectors, and (4) performing

installation tests and maintenance.

The study found that the traditional approach to the design and

installation of fire detection systems included the use of a combination

of fire codes (regulations), test standards, fire consultant

recommendations, insurance agency requests, and detector vendor

suggestions as inputs to the design process. This approach had been

developed as a result of installation experiences primarily gained

through fire detection implementation in residential and general

commercial applications. In a nuclear power plant a number of factors

are present which were identified as somewhat unique, and hence, not

necessarily accounted for in this traditional design approach. These

factors are ventilation conditions, ceiling heights, ceiling

construction, and the types of combustibles present.

The first step in the detection system design process is the

determination of area fire detection requirements. That is to say, one

must establish which areas within a plant require the installation of an

automatic fire detection system. Seven criteria were set forth upon

which such assessments should be made:

I. Importance of the area to overall plant safety,

2. Susceptibility of the area to surrounding fire hazards,

3. Degree of fire hazard within the area,

4. Potential of fire spreading to other areas,

5. Type of available fire suppression (e.g., manual or

automatic, inert gas or water),

6. Cost of added fire detection capability, and

7. Normal occupancy of the area.

It was found that in practice, it is not always possible to assess all of

these factors objectively for each area of a power plant. As a result,

detector requirements have generally been established on the basis of the

importance of an area to plant safety, regardless of the level of

associated fire risk.

The standards and guidelines for the determination of area fire detection

needs were identified as providing confusing, and often contradictory

requirements. This resulted from (1) differences in the principal

concerns of the standards organizations (e.g., plant safety versus

property protection) and (2) inconsistency in the terminology used to

identify specific plant areas (e.g., remote shutdown rooms versus

auxiliary panel rooms, or emergency/standby cooling equipment versus

safety related pump room).

The second step in the design of detection systems is the selection of

specific detector types, or combinations of detector types, for use in a

given area. Five types of fire detectors were considered in this study.

These five types represented the selection of devices with a proven

-56-
record of operability outside the laboratory environment. These five

types are:

1. Area heat detectors,

2. Continuous line heat detectors,

3. Ionization products of combustion detectors,

4. Photoelectric smoke detectors, and

5. Ultraviolet flame detectors.

Although other types of detectors were being developed, none had been

proven outside the laboratory environment. To a large extent this

remains true, and the five detector types cited above remain the most

popularly selected fire detector types.

It was found that the available fire detection system design standards

provided very little guidance upon which to base fire detector type

selections. Eight factors were identified which should be considered in

the selection of detector types. These factors are:

1. Anticipated nature of the combustion products to be

developed by the fuels in the area of concern,

2. Anticipated rate of development of a fire in the area of

concern and the acceptable ultimate extent of fire

involvement,

3. Characteristics of the area's ventilation system,

4. Room congestion which may reduce "visibility" of the fire

or combustion products,

5. Room geometry factors, and in particular, ceiling height,

6. Operational activities expected for the area which may

compromise the effectiveness or spuriously actuate

the fire detection system,

7. Detector maintenance requirements, and

8. The cost of detector system implementation.

The next step in the design process is to determine the appropriate

placement and spacing of fire detectors within the area of concern. Here

again, it was found that the standards for the design and installation of

detector systems provided very little guidance. Five factors were

identified as important to the placement of fire detectors. These five

factors are:

1. Ventilation conditions,

2. Ceiling height,

3. Ceiling construction factors such as solid joists

and sloping surfaces,

4. Room congestion, and

5. Detector zoning.

The consideration of these factors was recognized as requiring the

extensive use of engineering judgment.

-57-
The final step in the design and installation of fire detection systems

is the performance of installation tests and maintenance. This step was

identified as particularly important as actual applications seldom

resemble the conditions used in the qualification testing of detectors.

Furthermore, the subjective nature of the design process leaves

considerable uncertainty as to the actual effectiveness to be expected of

the installed system. Four factors were identified as criteria upon

which installation testing should be performed. These four factors are:

1. Visual inspection to insure detectors are installed as

designed,

2. Verification of the proper wiring and operation of each

individual detector,

3. Monitoring of the stability of the detector system over a

period of several weeks, and

4. The evaluation of the detector system response to an

actual test fire under typical conditions of operation.

With respect to maintenance activity, three criteria were set forth.

These are:

1. Periodic testing of the operability of each individual

detector,

2. Periodic cleaning of detectors, and

3. Restoration of detector operation promptly upon completion

of periodic testing and cleaning.

In summary, the study found that the design and installation of fire

detection systems was based largely on the use of engineering judgment.

Furthermore, the available standards for detection systems provided

inadequate guidance upon which to base decisions associated with a number

of important and fundamental design and implementation factors. A number

of design, installation, testing, and maintenance criteria were

identified. It was concluded that the fire detection operating

principles and qualification tests did not permit the prediction of

detector response characteristics. Furthermore, it was considered

doubtful that any theory would be developed and proven in the near future

to describe the complex interaction of each physical parameter affecting

detector operation. It was recommended that the best approach to solving

the uncertainties associated with the design and installation process

would be the implementation of in-place testing of detector response

under environmental conditions anticipated to occur normally in each area

being protected.

4.2.2 Detector Siting Criteria Requirements Study

The Detector Siting Criteria Requirements Study [21] performed a review

of relevant research associated with the implementation of fire detection

in a nuclear power plant. Of particular concern to the study was

research on the characteristics of cable tray fires which had been

performed at a number of organizations, and the implications of that

-58-
research to the problem of fire detection for a nuclear power plant. The

study cited and reviewed work performed at Factory Mutual Research

Corporation (FMRC), the National Bureau of Standards (NBS), and efforts

sponsored by Underwriters Laboratory (UL).

The principal finding of the study was that the evaluation of a cable

fire situation is a complex problem requiring the use of many types of

inter-related data. It was found that the various studies each provided

considerable and significant insights. However, it was concluded that

further experimental evaluations of cable fires would be required in

order to bring together the various pieces of the cable fire problem. In

particular, the state of knowledge regarding the behavior of cable fires

was insufficient to provide for the determination of fire detector siting

requirements. It was recommended that an effort be initiated to

establish criteria for the determination of fire detection system

effectiveness as a part of the design process. It should be noted that

such efforts have not, to date, been undertaken.

4.3 Investigations of the Effectiveness of Fire Suppression Systems

As stated above, the guidelines for the implementation of fire protection

in nuclear power plants include provisions for the installation of fire

suppression systems under certain conditions. It is intended that such

provisions would limit the extent of damage from a single fire through

the prompt suppression of the fire itself. However, it was recognized

that the standards upon which the design and installation of suppression

systems were based had been developed as a result of experience in the

application of such systems to residential and general commercial

installations. Thus, the adequacy of the common suppression systems as

applied to the nuclear power plant situation had not been assessed. In

particular, the effectiveness of these systems in suppressing a deep

seated cable tray fire had not been demonstrated.

As a part of the FPRP, efforts were performed to evaluate the

effectiveness of the most common of the fire suppression systems in

suppressing a fully developed cable tray fire.[19] Four fire suppression

systems were evaluated. These four systems are:

1. Halon3 1301 room flooding gaseous suppression systems,

2. Carbon dioxide room flooding gaseous suppression systems,

3. Water sprinkler suppression systems, and

4. Directed water spray suppression systems.

Each of these systems was evaluated in a configuration consistent with

the design and installation guidelines provided in the relevant National

Fire Protection Association (NFPA) fire standards. In all, 37 full-scale

cable tray fire tests were performed. The primary objective of these

tests was, for the gaseous systems, to determine the minimum "soak time"

required to suppress a fully developed cable fire at the suppressant

3. Halon is a registered trademark of the DuPont Corporation.

-59-
concentrations recommended in the relevant design standards. The "soak

time" is that length of time in which suppressant concentration must be

maintained in order to insure that the fire would not reignite upon the

reintroduction of oxygen or the dilution of the suppressant. For the

water based systems, the objective was to determine the minimum spray

time required to fully suppress the test fires.

In these tests both IEEE-383-74 rated low flame spread cables and

nonrated cables were used. Cable trays were arranged in both vertical

and horizontal configurations. Each test fire involved either two or

five cable trays. In each case sufficient fire growth time was allowed

to insure that a fully developed, deep seated fire resulted.

Table 4.1 summarizes the findings of these tests. The soak times or

spray times required to extinguish a cable tray fire involving either

vertical or horizontal cable trays and either rated or nonrated cables

are reported for each type of suppression system investigated. The most

effective of the systems evaluated was the directed water spray system.

The sprinkler system was also quite effective for vertical cable trays.

However, for horizontal trays the blockage of lower trays by the upper

trays meant that somewhat longer spray times were required. Both the

Halon and carbon dioxide systems were effective at extinguishing the

cable tray fires when concentrations of 7% and 50% by volume respectively

were used. However, soak times of up to 15 minutes were required to

prevent reignition.

One observation made was that while the rated low flame spread cables

were more difficult to ignite, and fires grew more slowly than in the

case of the nonrated cable, once a fully developed fire is present the

rated cables are mcre difficult to extinguish than are the nonrated

cables. This is reflected in the increased soak time required for the

gaseous systems to extinguish, and prevent reignition, of fires involving

the rated cables.

Water was more effective as a suppressant than were either of the two

gaseous systems tested. With the application of water, a significant

heat sink is introduced which quickly acts to cool both the burning

cables and the general enclosure environment. With the gaseous systems

this heat sink is not as great, and consequently, both the cables and the

room air can remain at elevated temperatures for extended periods of

time. While the gaseous systems eventually extinguished the test fires,

if concentrations were not maintained for fairly long periods, up to 15

minutes, then reignition of the fire was likely upon the reintroduction

of oxygen (in the case of carbon dioxide) or the dilution of the

suppressant (in the case of Halon). This results from the failure of the

gaseous systems to quench the smoldering combustion process typical of

deep seated cable fires.

4.4 Detection and Suppression Insights Based on Actual Experience

In conjunction with the Risk Methodologies Integration and Evaluation

Program (RMIEP), a data base was compiled documenting the history of

-60-
I

ON

Table 4.1: Summary of Fire Suppression System Effectiveness Study Results.

(This table provides the minimum gaseous system soak times and water based system spray times required to suppress a fully developed cable tray fire and prevent reignition.)

Cable Tray Fire Suppression System Type Orientation Halon (6%) Carbon Dioxide Sprinklers Directed Spray

NFPA-12A NFPA-12 NFPA-13 NFPA-15

IEEE-383 Horizontal 15 min 15 min 5 min 5 min

Rated Low

Flame Spread Vertical 15 min 15 min 5 min 5 min

Horizontal 10 mmn 10 min 5 min 5 min

Nonrated

Vertical 10 min 10 min 5 mmn 5 min
reported fire events for commercial nuclear reactors in the U.S.[24] The

data base included incidents reported both under the reporting

reuqirements of the USNRC, and incidents reported to certain of the

nuclear industry insurance interests. While the level of detail provided

in the original incident reports varies considerably, for many of the

incident reports the method of fire detection and fire suppression is

identified. Also included in this data base are 69 incidents in which

the actual time required to suppress the fire was included. These

incident reports have provided a number of insights into actual

circumstances of fire detection and suppression under actual fire

conditions.

For those incidents for which the method of detection and suppression is

reported, the vast majority involved both manual detection and manual

suppression of the subject fire. Only a few fires, the remainder of

those events which include such information, have been automatically

detected and automatically suppressed. The time required to suppress

those fires for which a suppression time is reported ranged from two

minutes to over seven hours. These 69 suppression time data points are

well represented by a lognormal probability distribution curve. The

parameters of this curve, based on a least-squares fit to the linearized

log-normal data, are a mean suppression time of 42 minutes, a median

suppression time of 20 minutes, a 5th percentile value of 3 minutes, and

a 95th percentile value of 150 minutes. The data and the fitted lognormal curve are presented in Figure 4.1 in cumulative probability versus

time form.

It should be noted that this suppression probability curve lumps all of

the reported incidents into a single curve. This presentation does not

include consideration of a number of factors which will influence actual

fire detection and suppression times. Among others, these factors

include the presence of automatic fire detection and suppression systems

in the fire area, the level of training received by the manual fire team,

the type of fire source, the location of the fire, and the level of

activity associated with the fire area. Such factors can be expected to

play a significant role in the actual fire response times to be expected

in a given situation. However, there is insufficient data available upon

which to base an assessment of the actual impact of these, and other,

factors on the probability of fire suppression within any given time

frame. This derives largely from the observation, noted above, that most

of the fires included in the formulation of this suppression model were

manually detected and suppressed. In the performance of a fire risk

assessment, one is largely dependent on the use of judgment in the

evaluation of such factors.

-62-
90

!'

C!

70

G 50

a-

~40

4-)30

3 20

E

Z3 U 10

0

1 2 5 10 20 50 100 200 5

Time (min)

Figure 4.1 Fire Suppression Probability Curve Based On Incidents In the SNL

Fire Occurrence Data Base for Which a Time to Fire Suppression is Reported.
5.0 ROOM EFFECTS STUDIES

5.1 Introduction

The adverse impact of a fire can extend well beyond the area of immediate

burning and fuel involvement. A fire represents a source of heat, smoke,

toxic and corrosive gases, water vapor, and other combustion products.

Once released, these products will disperse within the enclosure in which

the fire occurs. (These products can also be distributed to other nearby

enclosures, though this aspect of the fire problem will be addressed in

Chapter 7 of this report.) The various fire products can, in turn, induce

damage in equipment not directly involved in the fire. Traditional

concerns have focused on the problem of heat, though equipment damage

concerns extend to the potential adverse impact of the other combustion

products as well.

An understanding of the damaging impact of a fire on equipment operability

will be dependant on two factors. First is the behavior of the combustion

products in distributing themselves within (and outside) the fire

enclosure, and second is the susceptibility of the equipment to damage.

This chapter focuses on efforts associated with the characterization of the

behavior of fire products in distributing themselves about the fire

enclosure. Expressed somewhat differently, this chapter focuses on efforts

to characterize the impact of a fire on the environment within the fire

enclosure. The investigation of equipment vulnerability issues is

discussed separately in Chapter 6.

Three FPRP efforts have, either directly or indirectly, addressed the

characterization of enclosure environments during a fire. These three

efforts are:

1982 Twenty-Foot Separation Tests

1985 Base Line Validation Enclosure Fire Tests

1985 Electrical Cabinet and Control Room Fire Tests

The principal insights associated with the characterization of enclosure

fire environments resulting from each of these three efforts are discussed

in turn in the sections which follow.

It should be noted that enclosure fire environment characterization testing

is closely linked to efforts to numerically simulate fire environments

through the application of computer models. The validation of a fire

simulation model is entirely dependant on the availability of appropriate

test data. The actual development of fire simulation models has not been a

part of the past Sandia FPRP. However, the USNRC did support efforts to

develop a complex, three-dimensional, finite difference type "field" model

for the evaluation of fire. These efforts were conducted under an

independent contract between the USNRC and Brookhaven National

-64-
Laboratories. The role of the Sandia FPRP in this code development effort

was one of experimental support for code validation. In particular, the

Base Line Validation Tests, described below, were performed primarily to

provide validation data for use in benchmarking this, and other, fire

models. For a further description of the model development effort refer to

Reference 31.

5.2 Twenty-Foot Separation Tests

The Twenty-Foot Separation Tests were performed during the early stages of

the FPRP in which the primary focus was placed on the investigation of

specific regulatory concerns. One of the principal provisions of the

BTP 9.5-1, and later of the Appendix R fire protection regulations,

requires that equipment associated with redundant safety trains must be

separated by a minimum of 20 feet of horizontal space with no intervening

combustibles. In addition, under such circumstances, automatic fire

detection and suppression systems must be employed as an additional measure

of protection. (Exceptions to this regulation are considered on a case by

case basis.) A total of 10 large-scale enclosure fire tests were performed

in order to assess the adequacy of 20 feet of spatial separation as a fire

protection measure.

The regulatory implications of these tests have been discussed in detail in

Chapter 2 of this report. The findings of these tests related to the

damageability of cables due to hot layer effects are discussed in Chapter 6

below. The discussions which are presented here will focus on the

technical aspects of the data gathered as related to the problem of

enclosure fire environment characterization.

A test enclosure constructed of concrete block and measuring 25x14xlO feet

(LxWxH) with an open door of variable size was used in all tests. (This is

with exception to experiment 1, in which the room length was 30 feet, and

experiment 4, in which the door was closed.) Four preliminary

"Experiments" were 'performed in order to provide base line information on

the enclosure environments to be expected. The source fire in these

"Experiments" was comprised of a liquid fuel pool fire measuring ix5 feet

and filled with ten gallons of heptane. Six "Tests" were then performed to

evaluate the effectiveness of 20 feet of spatial separation as a means of

protecting cables from fire induced damage.

In each of Tests 1-6 two vertical cable trays (representing one of two

trains of equipment) were exposed to the same liquid fuel pool fire

described above, except that only five rather than ten gallons of fuel were

used. A second pair of cables (representing a second equipment train) was

located above the door at the opposite end of the test enclosure. These

second train cables were not involved in actual combustion.

-65-
Testing involved the use of both rated low flame spread and nonrated

cables. Each of the two cable types used were tested in each of three

modes of cable protection. These three modes of protection were (1) no

passive cable protection, (2) protection of the cables with a fire

retardant coating, and (3) protection of the cables with an insulating wrap

and solid tray covers. In each case both simulated trains of cable were

similarly protected.

An extensive array of instrumentation was placed within the test enclosure.

Measurements included air temperatures, enclosure surface temperatures,

doorway air flow conditions, and heat flux conditions. Figure 5.1

illustrates the placement of instrumentation within the test enclosure.

Table 5.1 summarizes the principal enclosure fire environment severity

results for Experiments 1-4. Table 5.2 summarizes these same results for

Tests 1-6. Figure 5.2 illustrates the average near ceiling air

temperatures measured near the simulated redundant cable trays during

Experiments 1-4. Figure 5.3 provides similar information for Tests 1-6.

For Experiments 1-4 the maximum recorded air temperatures in the vicinity

of the redundant cable trays ranged from 470°F to 660°F (243-349°C). For

Tests 1-6 the source fires were somewhat more intense as a result of the

additional involvement of the two cable trays simulating the first

equipment train. Maximum hot layer temperatures in the vicinity of the

simulated redundant cable trays during Tests 1-6 ranged from 660°F to

1050 0 F (349-566-C).

During the original experiments, no instrumentation was provided for the

measurement of the fire heat release rates. However, in the utilization of

many enclosure fire simulation models, the heat release rate of the source

fire is required as an input. Developers of certain of the fire simulation

models had expressed a desire to utilize the data from these tests in the

validation of their enclosure fire response models as the enclosure

environment characterization data gathered was somewhat unique. This

uniqueness results from the construction of the test enclosure, the

inclusion of cable trays as a part of the fire source, and the extent of

instrumentation included within the enclosure.

In order to facilitate these validation efforts, posttest data analysis was

performed to estimate the rate of heat release for certain of the

experimental fires. This analysis considered the rates of energy loss from

the test enclosure based on measurements of the doorway air flow conditions

and the enclosure surface response data in the formulation of an overall

enclosure energy balance. In all, data from Experiments 2 and 3, and Tests

1 and 2 was reprocessed. 4

4. This is an account of previously unpublished work which has been

documented in a letter report to the USNRC dated May 8, 1984.

-66-
Table 5.1: Summary of Principal Environment Characterization

Results for Experiments 1-4 of the 20-Ft Separation Tests.

Experiment Number

1 2 3

Door Size (WxH, ft)

Room Length (ft)

8x8 8x8 4x8

4

no door

30 25 25 25

App. Fire Duration (min) 25.4 22.5 21.9

App. Max Near Cable Tray"*

Hot Layer Temperature (F)

App. Max Lower Cable Tray**

Heat Flux (kW/m 2)

Time to Short Circuit" (min)

App. Max Doorway Air Velocity

2 ft Below Top (ft/sec):

2 ft Above Bottom (ft/sec):

470

5.5

NT

2.9

1.3

620 660

14.0

500

10.0 13.0 8.0

10.2* NF 12.3'

4.4

1.6

5.6

3.0

NT

NT

* -Failures in Non-IEEE-383 rated cables

** - Refers to Simulated Redundant Trays Above Doorway

NT - Data Not Taken

NF - No Failure Noted

-67-
Table 5.2: Summary of Principal Environment Characterization

Results for Tests 1-6 of the 20-Ft Separation Tests.

Cable Protection*

Cable Type

Test Number

1 2 3 4 5 6

None None Sys 2 Sys 2 Sys 3 Sys 3

UQ Q UQ Q UQ Q

1050 850 660 670 710 740

36 23 12 14 15 14

App. Max Near Cable Tray**

Hot Layer Temperature (F)

App. Max Lower Cable Tray**

Heat Flux (kW/m 2)

Time to Short Circuit (min)**

Upper Tray:

Lower Tray:

Sprinkler Head Response

Time (min):

App. Max Doorway Air Velocity

2 ft Below Top (ft/sec):

2 ft Above Bottom (ft/sec):

4.1 12.9 NF NF

4.4 NF 17.4 NF

10.7 NF

12-.9 NF

1.9 3.3 2.8 3.0 2.0 3.2

7.4 6.7 5.6 6.0 5.7 5.5

2.9 1.2 2.8 2.3 3.7 4.0

* -Cable Protection Systems Described in Text

** - Refers to Simulated Redundant Trays Above Doorway

NF - No Failure Noted

UQ - Cable Not Qualified by IEEE-383-74

Q - Cable Qualified by IEEE-383-74

-68-
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Figure 5.1 Instrumentation Placement Used in the Twenty-Foot Tests

-69-
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Figure 5.1 Instrumentation Placement Used in the Twenty-Foot Tests (cont)

-70-
TEMPERATURE,* C TEMPERATURE,o

500.

400

300

200

100

F

932

752

572

398

212

Pt

S ' ' ''32

0 300 600 900 1200 1500 1800

TIME,SEC.

TEMPERATURES ARE THE AVERAGE OF

THERMOCOUPLES 69, 73, AND 77.

(1 FT. BELOW CEILING AND 2 FT. FROM THE TRAY)

Figure 5.2 Average Temperatures

Cable Trays During Experiments 1-4

Measured Near the Redundant Train

of the Twenty-Foot Separation Tests

TI MRATURE, OC TEMPERATURE, a F

600

500

400

300

200

100

0

1112

932

752

572

392

212

32

0 300 600 900 1200 1500 1800

TIME, sem

TEMPERATURES ARE THE AVERAGE OF THE

THERMOCOUPLES 69, 73 AND 77

(1 ft BELOW CEIUNG AND 2 ft. FROM THE TRAY)

Figure 5.3 Average Temperatures Measured Near the Redundant Train

Cable Trays During Tests 1-6 of the Twenty-Foot Separation Tests

-71-
Figure 5.4 provides plots of the estimated heat release rates for

Experiments 2 and 3, and for Tests 1 and 2. The estimated heat release

rates for Experiments 1 and 2 were approximately 550 to 600 kW. As these

experiments involved only the liquid fuel pool fire, the heat release rates

were relatively constant. The results of the energy balance analysis for

these simple liquid fuel pool fires compared well with both analytical

predictions of the anticipated pool fire intensity (using the methodology

presented in Reference 25), and with separate pool fire tests involving the

same fuel source, but for which the actual heat release rates were

measured. These results lent confidence to the overall validity of the

energy balance method, and to the specific formulation developed.

For Tests 2 and 3, which included the additional fire involvement of two

vertical trays of nonrated and rated low flame spread cables respectively,

peak heat release rates were estimated to be approximately 850 to 900 kW.

Relatively little difference in fire behavior was noted between Test 1,

involving nonrated cables, and Test 2, involving rated low flame spread

cables. In fact, contrary to what one might expect, the fire in Test 2

grew at nearly the same rate, peaked at a higher intensity, and released

more heat overall than did the fire in Test 1. This result reiterates

other test results (e.g. the suppression effectiveness tests, and cabinet

fire tests described above) in which it has been observed that while more

difficult to ignite, once a fire is established in the rated cables, that

fire is often more intense, and more difficult to extinguish than a similar

fire in nonrated cables.

These tests represent a rather unique data set regarding nuclear power

plant enclosure fire behavior. However, the results'are limited in several

respects. First, heat release rate estimates are available for only four

of the ten experimental fires. Second, the room size is typical of only

the. smallest of enclosures encountered in a power plant. Third, all of the

tests were conducted under conditions of natural ventilation (i.e. and open

doorway) whereas in a power plant forced ventilation conditions are nearly

universal. Each of these limitations was resolved in the performance of

the Base Line Validation Tests, which are described immediately below.

5.3 Base Line Validation Enclosure Fire Tests

As a part of the FPRP a series of large-scale enclosure fire tests was

performed to provide enclosure fire environment characterization results

for use in the validation of computer fire simulation models. These tests

differed from previous tests performed, both within and outside the FPRP,

in several important respects. First, the test enclosure utilized was

considerably larger than any previously used fire test enclosure for which

extensive environment characterization information had been gathered. This

test enclosure measured 60x40x20 feet (LxWxH) (18.3x12.2x6.lm). Second,

all of the tests utilized conditions of forced ventilation typical of those

encountered in nuclear power plant enclosures. These ventilation

-72-
0

0

0

0

900

800

700

600

500

400

300

200

100

0

0 4 8 12 16 20

Time (MIN)

* *iPt 2 s - expi 3 1 4 test I o 0 list 2

Figure 5.4 Estimated Heat Release Rates for Experiments 2 and 3,

and for Tests 1 and 2 of the Twenty-Foot Separation Tests

-73-
conditions were varied during testing, and simulated conditions including

those typical of control room smoke purging ventilation rates. Third, the

tests included the use of a full-scale control room mock-up physical

configuration to investigate the effects of internal room partitioning on

the room environment. Fourth, the density and variety of instrumentation

included as a part of the test program was significantly greater than

previously performed fire tests had utilized. This instrumentation density

was intended to provide adequate data upon which to base the validation of

even the most complex, three-dimensional fire simulations models being

developed. Finally, the source fires included a variety of fuels ranging

from quite simple liquid fuel pool fires and gas burners to simulated

electrical control panels loaded with cable insulation.

Figure 5.5 illustrates the placement of instrumentation within the test

enclosure. Measurements included air temperatures based on both bare-bead

and aspirated thermocouples, slug calorimeter heat fluxes, concentrations

of carbon dioxide, oxygen,' carbon monoxide, and total hydrocarbons both

within the enclosure and in the exhaust gases, smoke optical densities, and

enclosure inner and outer surface temperatures. En all a total of over 300

channels of data were installed. The data for each channel was logged at

five second intervals for periods from fire initiation, through natural

f ire extinguishment, and including a period of post fire cool-down.

A total of 20 Base Line Validation Tests involving simple fuel fire sources

were performed. (As will be described below an additional five tests

involving a fire source located within a control room panel were also

conducted.) Table 5.3 provides a matrix of the simple fuel fire tests

performed as a part of the Base Line Validation test effort. Parameters

varied during testing were the rate of enclosure ventilation, the intensity

of the source fire, the type of fire source, location of the fire source,

and the presence or absence of the control room panels.

These tests were performed in the later stages of the FFRP. As a result of

the termination of FPRP efforts shortly after the completion of these

tests, full processing of the test data has not, to date, been undertaken.

Data processing routines have been developed and certain limited data

processing has been performed. Table 5.4 provides a summary of certain of

the principal results obtained from the limited data processing which has

been completed. In addition to these general results, three tests, Tests

4, 5, and 21, have been examined in some detail.[32]

The temperature measurements made within the enclosure illustrate a

significant degree of vertical thermal stratification as shown in Figures

5.6 and 5.7. No true hot layer effect was observed in these tests in that

the vertical stratification presented a relatively smooth transition from

high ceiling temperatures to lower floor temperatures, rather than a near

discontinuous jump from the hot to cold layer. This is believed to be at

least in part due to the presence and configuration of the forced

-74-
-60'

A

N

0-

0-

Sectors E[ - Corner Rakes

Expanded Stations - Exhaust Port

Stations Is - Vent Inlet Ports

Sectors

Expanded

Stations

Corner

Rakes Stations

000 W1o00 --II.0~

o00

-NO000

-U

- NOo0

-U

-0

-0

- .S8XH (19"7") -

- .9XH (18') -

- .?XH (14') -

- .5XH (1M') -

- .3XH (6W) -

0 [ 0l

0 i

3 ---

U -

0 -- _

- A Aspirated Thermocouple

0 - Bare-Dead Thermocouple

0 - Large Sphere Calorimeter

0 - Small Sphere Calorimeter

0

0

O - Gas Sample Port

- Velocity Flow Probe

- Smoke Turbidlmeter

Figure 5.5: Instrumentation Placement Used in the Base

Line Validation Tests

-75-
Table 5.3: Matrix of Simple Fuel Base Line Validation Tests.

Test # 112 13 14 15 117 119 1111 1112113114115116117118

Propylene Burners X X X X X X X X I

Fuel Heptane Pool XX XX XXX

Type Methanol Pool I X

PMMR Solid Slabs _ _ I _ _ _ _ X 

Nominal 588 kW XIX XIXX X X JX Xx

Peak Fire 1000 kH I I X XXI I I XI

Intensity 2000 kW X XX

Fire Room Center XXX XX XXX I I I

Loaion South Wall I XI I lXlx X X x X I X

S-W Corner I IXX

-I

Nominal I ch/hr (800 CFM) X X X X IX X X X

Enclosure 4.4 ch/hr (3500 CFM) -t X X

Ventilation 8 ch/hr (8400 CFM) X X

Rate 18 ch/hr (8008 CFM) X X . X X jX

Burner Steady State Mode XIXIXI Ii X Fire Mode Growing Fire Mode I I I.X X ŽX
Table 5.4: Summary of Principal Results for the

Base Line Validation Tests

1 P 10 5 E0 2 .0 C

P 1 50 12 0

3 P 1 200 68 3.00

0. ~ ) C 0 ) L.C5 4- 0: C 11 C I0.0>

0 f .

? P 1 5 I00 14 .

a 0 a 020 8, 0 - L& > a. I-- a.I- I-a- C

9 P 10 500T 120 3.0

2 P 16 500 123 3.0

3 P 10 2000 368 3.0

4 P 1 500 T 133 7.5

5 P 10 500T 115 6.6

6 H 1 580 106 5.5

7 P 1 500 146 4.5

8 P 1 1000T 290 8.0

9 P e 16 0T 229 7.0

10 H 4.4 1000 210 6.5

11 M 4.4 500 121 -

12 H 4.4,2000 332 3.0

13 ,H 8 2000 304 2.5

14 M 1 500 140 -

15 H 1 1000 121 6.0

16 H 1 500 114 5.5

17 H 18 500 95 4.5

18 S 1 100 T 130 -

19 H ~1 1000 206 3.0

20 H 8 1000 245 3.0

21 P 1 SoOdT 146 6.2

22 P 1 100 oT 164 7.2

.23 .C 1 1250T 262 7.8

124 1C 1 1350 T 23? 5.0

12 1 8 80TI 82 5.0

*-P - Propylene Burner

H - Heptane Pool

M - Methanol Pool

S - PMMR Solid Slabs

C - Cable Loaded Cabinet

-77-
100

U / .?xH (14')

60

L

4. •._: ._• --- -'-S.--

EL 40/

E / .3xH (6")

.5xH (10')

20

0 2 4 6 8 .10 12 14

Time (min)

Figure 5.6 Temperature Versus Time with Elevations as the Curve

Parameter at the Room Center Instrument Tree (Sector 2)

During Base Line Validation Test 5

min 2 3 4 5 6

20- I II

15

4-

C

o 10

LI

5

0

20 40 so 80 100

Temperature (C)

Figure 5.7 Temperature Versus Elevation with Time as The Curve

Parameter at the Room Center Instrument Tree (Sector 2)

During Base Line Validation Test 5

-78-
ventilation system, which presumably enhanced the level of mixing within

the enclosure. Furthermore, it was observed that the level of the

ventilation inlets represented somewhat of a physical layer boundary in

that temperatures above the level of the ventilation inlet ports were

significantly higher than those below the inlets as shown in Figures 5.6

and 5.7. This observation would tend to imply that in the application of

zone or layered fire models, it might be more accurate to provide for a

dividing of the hot layer itself into two separate layers. The level of

this division would be determined by the configuration of the ventilation

system.

A second important observation was that in virtually all of the tests, a

dense layer of smoke was observed to fill the test enclosure from floor to

ceiling within 5-15 minutes of fire initiation. This smoke layer

completely obscured any visibility in the room. Even the fire could not be

seen once this smoke layer had descended, and in some cases the fire source

was as little as 12 feet from an observation window. Forced ventilation

rates as high as 10 room air changes per hour were not sufficient to

maintain visibility in the test enclosure. These conditions can be

expected to severely hamper manual fire fighting efforts, as well as limit

the ability to perform plant operations (either in the control room or in

remote fire areas) even given that a self contained breathing apparatus is

available. (The only tests in which a smoke layer did not form were those

involving a methanol pool or the PMMA 5 solid, both of which are very clean

burning fuels.)

Processing of the data from these tests has also led to the development of

an extension to the traditionally employed carbon dioxide calorimetry heat

release rate calculation methodology. The rate of heat release is one of

the most important characteristics of a fire. In experimentation the rate

of carbon dioxide generation by a fire has been used extensively to provide

an estimate of the rate of heat release based on a thermal balance for the

exothermic conversion of a carbon chain to carbon dioxide. However, the

large size of the test enclosure used in these tests introduces unique

difficulties in the application of carbon dioxide generation calorimetry

techniques. The technique requires that one accurately estimate the time

dependant rate of carbon dioxide generation. Under most typical test

conditions, this rate is estimated based on measurements of the composition

of the gases exiting the test enclosure. However, with the large test

enclosure utilized here, accumulation of fire products within the room

would result in the underestimation of fire intensity by as much as 60%

under this simplistic approach.

As a part of the data processing, a methodology was developed in which the

measurement of gas concentrations made at nine locations within the test

enclosure were utilized to estimate the time dependent rate of fire

5. Poly-methyl-methacrylate, or more commonly, plexiglass.

-79-
products accumulation within the test enclosure. The heat release rates of

the test fires can then be estimated based on both the outflow gas

conditions, and the rate of enclosure accumulation. Figure 5.8, described

below, illustrates the results obtained using this enhanced methodology.

The enhanced carbon dioxide generation based calculations follow closely

the expected burner profile during both the transient and steady state

periods of combustion. Of particular interest is the accuracy with which

the sudden cut off of the gas burner is reflected in the carbon dioxide

calorimetry based intensity estimates. One should also note that the

methodology developed would be equally applicable to estimation of heat

release rates by oxygen consumption calorimetry as well.

The data available from these tests represents a truly unique data set. No

other large-scale enclosure fire experimental effort, either within or

outside the FPRP, has provided the level of instrumentation in an enclosure

of the size used in these tests, nor explored the variety of nuclear power

plant enclosure fire issues which were investigated here. The available

data could go a long way towards resolving many of the uncertainties

currently associated with the simulation of nuclear power plant fire

enclosure fire effects. However, a number of enclosure fire questions

would still remain unaddressed. These include room to room spread of fire

and/or smoke though ventilation connections and open doorways, the effects

of room partitioning and ceiling soffits on the fire environment, the

effectiveness of dedicated smoke removal and smoke control systems (such

systems are not currently employed in U.S. reactors), the impact of smoke

on operator and fire brigade performance, and the responsiveness of fire

detection and suppression systems in very large enclosures.

5.4 Cabinet and Control Room Fire Tests

The cabinet fire test program was conducted in two phases. The tests

conducted under the first phase investigated the effects of various cabinet

parameters on the development of an electrical control panel fire

(reference A-56). These tests were conducted at the SNL Fire Test

Facility, which measures 24x25x18 feet (7.3x7.6x5.5 meters) (LxWxH). In

the second phase of the cabinet fire test program [30] a series of five

electrical control panel fire tests were conducted using the same test

enclosure and test instrumentation as that described in Section 5.3 above

in conjunction with the Base Line Validation Tests. The enclosure used for

these second phase tests was quite large, measuring 60x40x20 feet

(18.3x12.2x6.1 meters).

Of particular interest to the present discussion is the data associated

with characterization of the enclosure environment which was gathered

during these tests. The discussions which follow will focus on the second

phase tests for several reasons. First, the density and variety of

enclosure instrumentation provided in the second phase tests was much more

extensive than that of the first phase tests. Second, the test enclosure

-80-
for the second phase tests was much larger than that used in the first

phase tests, and was more typical of nuclear power plant enclosure

dimensions. Third, the second phase tests were conducted with a full-scale

control room panel physical mock-up in place in the test enclosure.

Fourth, the ventilation configuration used in the second phase tests was

more typical of that found in a nuclear power plant. It was, in fact, the

specific objective of the second phase tests to explore the impact of a

cabinet fire on the environment of a typical nuclear power plant enclosure.

Five cabinet fire tests were conducted as a part of the second phase tests.

Two of these five tests, Tests 21 and 22, involved the use of a gas burner

placed within a cabinet shell. The gas burners were controlled with a preprogrammed burning rate. The remaining three tests involved the burning of

an electrical control panel loaded with cable. Two of these three cable

tests utilized a benchboard cabinet, Test 23 involving IEEE-383-74 rated

low flame spread cables, and Test 24 involving nonrated cables. The third

cable test, Test 25, involved nonrated cables in a vertical cabinet. In

both of the nonrated cable fire tests, the fire was electrically initiated

using the apparatus described in Section 3.5.1. (This apparatus simulates

a faulty terminal block connection generating 200 watts of heat at less

than 15 amperes.) The single test involving rated low flame spread cables

was initiated using a simulated transient fuel source comprised of a small

plastic bucket, laboratory wipes, and one quart of acetone. The

experimental conditions for each of these five cabinet fire tests are

summarized in Table 5.5. Figures 5.9 through 5.13 illustrate the measured

rate of heat release for each of the five cabinet fire tests.

The findings with respect to the enclosure environment observed during the

second phase cabinet fire tests can be summarized as follows:

1. Peak temperatures at the ceiling of the enclosure directly above

the cabinet fire were observed to reach as high as 262*C (504*F).

2. Outside of the immediate vicinity of the fire plume enclosure

temperatures for a fire confined to a single cabinet were observed

to reach no higher than 150*C in this large test enclosure.

(Caution must be exercised in extrapolating these results to

smaller enclosures, or to situations in which electrical panels

form the equivalent of a smaller enclosure through internal room

partitioning often employed as a part of ventilation system

design).

3. The build-up of smoke in the test enclosure was in all cases found

to be a significant problem. Typically, within 6-15 minutes smoke

had totally obscured visibility throughout the test enclosure from

ceiling to floor. Smoke purge ventilation rates as high as 10

room air changes per hour were ineffective at maintaining even

minimal visibility.

-81-
Table 5.5: Matrix of Control Room Fire Tests.

Test * 192012 1122123 24125

*Propylene Burner X X

Fuel Type Heptane Pool X X

Cable Loaded Cabinet X X X

500 kW X1

Nominal Peak 800 kN X

Fire Intensity .1000 k_ XX X

1300 kW J Xx

Room Center X

Fire Location South-Nest , Corner X

Benchboard Cabinet 'A' X X X X

Vertical Cabinet 'C" X

Nominal Enclosure I ch/hr (800 CFM) XJ X X J Xix

Ventilation Rate 8 ch/hr (6400 CFM) X I I X

Gas Burner Steady State Mode

Fire Mode Growing Fire Mode
700

600

500

400

300

200

100

0

0 5 10 15 20 25 30

TIME (min)

Figure 5.8 Heat Release Rate for Control Room Fire Test 21

cc

1200

1000

800

600

400

200

0

0 5 10 15 20 25 30

TIME (min)

Figure 5.9 Heat Release Rate for Control Room Fire Test 22

-83-
2000

cc

cc

1500

1000

500

0

0

Figure 5. 10

10 20 30 40 50 60

TIME (min)

Heat Release Rate for Control Room Fire Test 23

cc

1400

1200

1000

800

600

400

200

0

0 10 20 30 40 50 60

TIME (min)

Figure 5.11 Heat Release Rate for Control Room Fire Test 24

-84-
1000

800 -

3 600 -

200 -

0 10 20 30 40 50 60

TIME (min)

Figure 5.12 Heat Release Rate for Control Room Fire Test 25

4. Heavy depositions of soot were observed throughout the test

enclosure, including within closed cabinets not involved directly

in the fire. In the case of fires involving polyvinyl chloride

(PVC) cables, this soot was found to be heavily laden with

chlorides. If the soot deposits are wetted, possibly by

suppression water, equipment could be exposed to a conductive, and

highly corrosive solution. (This is discussed in more detail in

Chapter 6 below.)

These tests explored the impact of a fire confined to a single cabinet on

the environment of a large enclosure. In general it was found that the

enclosure environments experienced would not represent a thermal threat to

most types of plant equipment, with the possible exception of sensitive

electronic equipment. However, other adverse environmental effects were

noted. In particular, smoke buildup and deposition within the enclosure

was quite severe. These tests did not explore the potential for the spread

of fire to more than a single cabinet, nor to cable trays either above or

below a burning cabinet. The presence of such fire spread paths may be

likely, and hence, a cabinet fire may grow well beyond the bounds to which

the fires in these tests were confined. Such fire growth would result in

fire environments much more severe than those encountered here.

-85-
The available data from the Cabinet and Control Room Fire Tests is of equal

quality and completeness to that gathered during the Base Line Validation

Tests. Thus, this data represents a unique source of enclosurq fire

environment characterization information. The Cabinet and Control Room

Fire Tests, in particular, provide data on the response of a large forced

ventilated enclosure to a fire which is confined within a metal cabinet,

and hence, produces relatively little radiative thermal input into the fire

environment. Three out of the five cabinet tests involved the uncontrolled

burning of actual lengths of insulated cables and can be considered

characteristic of the behavior to be expected of an actual cabinet fire,

which remains confined to a single cabinet. The level of instrumentation

employed in these tests has provided for the accurate estimation of the

actual heat release rates experienced during these tests. The availability

of this heat release rate information will provide for the minimization of

actual fire growth and fire intensity modeling uncertainties. This will

allow fire modelers to focus on the other aspects of the fire model, such

as the distribution of heat within the enclosure and the modeling of hot

layer effects, somewhat independent of the estimation of fire intensity.

-86-
6.0 EQUIPMENT RESPONSE STUDIES

6.1 Introduction

The concerns of fire safety in a nuclear power plant extend beyond the

actuarial and life safety concerns which dominate traditional applications.

For a nuclear power plant the ability to maintain safe operation or to

achieve and maintain safe shut down of the reactor itself is of paramount

concern. This operational ability will be dependant on the availability of

undamaged plant equipment and systems during and after a fire event. Thus,

in the consideration of fire protection measures, and in the analysis of

fire risk, an understanding of the impact of a fire on the operability of

plant equipment is needed. From this perspective, a fire represents a

source of adverse environmental effects which may degrade the operability

of plant equipment. Equipment operability concerns are broader in context

and extent than the traditionally considered issues of material

ignitability and flammability. The impact of secondary fire effects (e.g.,

heat, smoke, corrosive products, suppression effects) are also of potential

concern. These secondary effects hold the potential to render plant

equipment inoperable, even though that equipment may not actually burn.

As a part of the FPRP, only limited equipment vulnerability investigations

have been undertaken. Many of the early investigations do provide certain

limited insights into equipment vulnerability, though this was not

typically the primary concern of these early, i.e., regulatory issues,

investigations. As a part of more recent efforts, initial attempts were

undertaken to investigate equipment vulnerability issues. The specific

efforts which provide such insights, and which will be discussed in the

sections which follow, are:

1976-81 Cable Tray Fire Testing:

Fire Retardant Cable Coating Tests

Cable Tray Fire Barrier Tests

1981 Cable Radiant and Convective Heating Damage Tests

1982 Twenty-Foot Separation Tests

1984 Cable Steady State Thermal Damage Tests

1985 Cable Transient Thermal Damage Tests

1985 Equipment Damage Sensitivity Ranking Study

1985 Relay Thermal Damage Tests

1985 Component Testing in Secondary Fire Environments

6.2 Investigation of Cable Fire Vulnerability

Data on the thermal damageability of cables represents the majority of

information which has been gathered with regards to the vulnerability of

equipment to fire induced damage. This holds true for both efforts

conducted within and outside the SNL/USNRC FPRP. Cables have been the

focus of research for a number of reasons. Two to the most significant of

-87-
these reasons are (1) the high level of interest in the overall problem of

fire safety for cable installations which developed in the wake of the 1975

cable fire at the Browns Ferry Reactor site, and (2) the fact that fire

vulnerabilities at cable pinch points such as the cable spreading room or

cable tunnel often represent significant contributors to fire risk and to

overall plant risk.

Under the FPRP, data on cable thermal damageability has been gathered,

either directly or indirectly, as a part of several efforts. These efforts

are:

1976-81 Cable Tray Fire Testing:

Fire Retardant Cable Coating Tests

Cable Tray Fire Barrier Tests

1981 Cable Radiant and Convective Heating Damage Tests

1982 Twenty-Foot Separation Tests

1984 Cable Steady State Thermal Damage Tests

1985 Cable Transient Thermal Damage Tests

The 1976-81 Cable Tray Fire Tests were conducted during the early stages of

the FPRP during which specific regulatory concerns were being investigated.

As a part of these tests some information on the limits of thermal

operability for a limited selection of cable types was gathered. This is

also true of the Twenty-Foot Separation Tests. The 1981 Cable Radiant and

Convective Heating Damage Tests were the first FPRP effort to specifically

investigate the operability limits of cables. The 1984 Steady State

Thermal Damage Tests were conducted as a part of more recent FPRP efforts,

and investigated the limits of thermal damage under constant temperature

exposure conditions. The final effort, the 1985 Cable Transient Thermal

Damage Tests, were performed in an attempt to reproduce, in a simulation

chamber, the damage conditions which had been observed in the Twenty-Foot

Separation Tests. These tests also assessed the impact that initiation of

fire suppression would have had on the observed damage had active

suppression been employed.

6.2.1 Cable Tray Fire Testing

As originally conceived, the FPRP investigated a variety of regulatory

questions associated with nuclear power plant fire safety. Many of the

questions raised were associated with the general problem of fire safety

for cable tray installations. As a part of certain of these early cable

tray fire test efforts, the vulnerability of cables to fire induced damage

was also investigated. It should be noted that the damageability aspect of

these tests was only a secondary concern. These tests were primarily

concerned with issues of fire initiation and fire growth in cable tray

installations. However, certain insights were gained from the limited

damageability information which was gathered. Those cable tray fire

efforts which did include some investigation of fire induced cable damage

-88-
were the Fire Retardant Cable Coating Tests, and the Cable Tray Fire

Barrier Tests.

Testing under each of these two programs involved the use of three cable

types. The first was an XPE insulated IEEE-383-74 rated low flame spread

cable (described as cable #5 in Table 3.1 above). The second was a PE/PVC

insulated cable which was nonrated (described in Section 3.4.4 above).

Both of these cables were 12AWG 3-conductor power cables. The third cable

was a single conductor 12AWG XPE insulated rated low flame spread power

cable (described as cable #4 in Table 3.1 above).

Of the Fire Retardant Cable Coatings Tests conducted, those of interest

here are the single tray gas burner exposure tests and the two tray diesel

fuel fire exposure tests. In the single tray gas burner tests, a single

horizontal loaded cable tray was exposed to an external fire source

comprised of a pair of IEEE-383 type standard gas burners. These two

burners were cycled in five minute on-five minute off burner cycles until a

sustained fire was established in the exposed cable tray. In the two tray

diesel fuel fire tests, a stack of two horizontal loaded cable trays was

exposed to an external fire source comprised of a diesel fuel pool fire.

These fire exposure conditions have been described previously (see Chapter

3).

Of the fire barrier tests, those of interest here are the single tray gas

burner exposure fire tests. These tests were performed in essentially the

same manner as the single tray fire retardant coatings tests. However,

rather than fire retardant coatings, five types of passive fire protective

barrier systems were evaluated.

The two tray gas burner fire retardant coatings and barrier tests performed

are of limited interest to the current discussions due to the constraints

placed on the fire exposure of the upper tray (as described in Chapter 3

above). In these tests the upper tray was protected from exposure to the

external fire source by a nonflammable barrier during the repeated gas

burner fire cycles. It was intended that this limitation to the upper tray

exposure would simulate the conditions of a self-ignited cable tray fire,

rather than exposure fire conditions. As a result of this limitation to

upper tray exposure, only one case of electrical faulting was observed.

Tables 6.1, 6.2, and 6.3 summarize the damageability results for the single

tray gas burner fire retardant coatings tests, the two tray diesel fuel

fire retardant coatings tests, and the single tray fire barrier tests,

respectively. Presented are the times to observed electrical failure for

each test, and in the case of the two tray tests, for each cable tray.

These results illustrate that the various passive fire protective measures

employed did delay the onset of electrical damage. This is with the

exception of the nonrated cable tests involving the various fire barrier

systems in which no delaying of electrical failure was noted. The

-89-
effectiveness of the different measures varicd significantly. Even for a

given measure, e.g. coatings, different products performed differently.

For the less severe gas burner exposure tests, many of the protective

measures successfully prevented electrical faulting completely. However,

as illustrated by the diesel fuel fire tests, none of the measures can be

expected to prevent electrical faulting under more severe exposure fire

conditions.

Table 6.1: Summary of Single Tray Gas Burner Cable

Fire Retardant Coatings Test Results. (Note that these

tests used 3 different types of cables as described in text.)

Cable Type: Failure

Coating Designator Time*

(min)

IEEE-383 Rated XPE 3-Conductor:

No Coating 9

Coating A 26

Coating B NF

Coating C 15

Coating D NF

Coating E NF

IEEE-383 Rate XPE Single Conductor:

No Coating 5

Coating A NF

Coating B NF

Coating C 24

Coating D NF

Coating E NF

Nonrated PE/PVC 3-Conductor:

No Coating 6

* 'NF' Indicates no failure observed within 60 minutes.

-90-
These tests illustrate that some measure of operability protection can be

gained for cable tray installations through the application of passive fire

protective features. However, these measures do not entirely eliminate the

problem of potential electrical damage for cable tray installations. The

testing clearly demonstrates the variability between various protective

features, and the continued potential for damage even when passive

protection is employed. These tests did not consider such factors as

coating thickness, ampacity, durability, aging, asbestos content, potential

chemical interactions with the cable materials, ease of application, and

cost. In practical applications all of these factors must be considered.

Table 6.2: Summary of Two Tray Diesel Fuel Cable

Fire Retardant Coatings Test Results. (Note that these

tests used a nonrated PE/PVC 3-conductor cable.)

Coating: Failure

Tray: Time

(min)

Coating A:

Lower Tray: 10

Upper Tray: 11

Coating B:

Lower Tray: 6

Upper Tray: 11

Coating C:

Lower Tray: 3

Upper Tray: 7

Coating E:

Lower Tray: 10

Upper Tray: 19

Coating G:

Lower Tray: 11

Upper Tray: 11

-91-
Table 6.3: Summary of Single Tray Gas Burner Cable

Fire Barrier Test Results. (Note that these tests used

three different types of cables as described in text.)

Cable Type: Failure

Barrier Designator* Time**

(min)

IEEE-383 Rated XPE 3-Conductor:

No Barrier*** 9

Barrier 2 NF

Barrier 4 NF

IEEE-383 Rate XPE Single Conductor:

No Barrier*** 5

Barrier 2 NF

Barrier 4 NF

Nonrated PE/PVC 3-Conductor:

No Barrier*** 6

Barrier 1 2

Barrier 2 4

Barrier 3 3

Barrier 4 5

* Barrier designators correspond to the following:

1 - Ceramic wool blanket over open ladder tray,

2 - Solid tray bottom with no cover,

3 - Solid tray cover with no bottom,

4 - Vented tray cover and solid tray bottom,

** "NF" Indicates no failure observed within 60 minutes.

***Reported previously in Table 6.1, reproduced here for

reference.

-92-
6.2.2 Twenty-Foot Separation Tests

The objective of the Twenty-Foot Separation Tests was to determine the

technical adequacy of the proposed USNRC Twenty-Foot separation criteria.

This criteria required that equipment associated with redundant safety

trains must maintain a horizontal separation of Twenty-Foot with no

intervening combustibles. It was intended that spatial separation would

minimize the likelihood of fire damage to redundant equipment trains. The

adequacy of this criteria as a means of fire protection was assessed

through the performance of a series of enclosure fire tests. In each test,

the continued operability of a simulated redundant train of cables

separated from a source fire in accordance with Appendix R was monitored,

and electrical faults noted.

This effort involved the performance of four preliminary "Experiments" and

six "Tests." In the four preliminary "Experiments" the fire source was

comprised of only a liquid heptane fueled pool fire. This pool consisted

of ten gallons of heptane in a five-by-one foot fuel pan. In each case the

fire was located along the rear wall of the compartment. Two horizontal

cable trays were located above the doorway at the front of the compartment.

In Experiments 2 and 4, only, energized cables were monitored for

electrical failure.

In the six "Tests" two trains of equipment were each simulated by two

loaded cable trays separated by the mandated Twenty-Foot. One of the

simulated trains of equipment was located at the back of the test enclosure

and subjected to a liquid fuel pool, the same as that described above

though using only five gallons of heptane, as an exposure fire source. The

second train was located above and just inside of an open doorway at the

front of the test enclosure. Certain of the cables within this simulated

second train were monitored for electrical integrity throughout the test.

In several cases, electrical failure was observed in the -second train

cables (those located above the doorway). The damage observed was

attributed entirely to hot layer effects. The simulated redundant cables

were not subjected to either direct flame or fire plume impingement.

Heating of the cables was entirely due to the flow of hot gases across the

room and out the open doorway. In no case was ignition of the second train

of cables observed.

Two types of cabling were utilized in these tests. The first was a three

conductor, 12AWG, polyethylene (PE) insulated and jacketed cable. This

cable was not an IEEE-383 rated low flame spread cable. The second cable

was a three conductor, 12AWG, cross-linked polyolefin insulated and jacked

cable. This second cable was a rated low flame spread cable.

For each of these two cable types, three cable protection configurations

were evaluated. These were (1) no protection of the cables, (2) protection

-93-
with a ceramic blanket wrap and solid tray covers, and (3) protection

with a fire retardant coating. (In each test both of the simulated

trains of cable received identical protection.) For the nonrated PE

cable, damage was observed in all three of the cable protection

configurations tested. For the rated low flame spread cable, failure was

observed only in the case in which no cable protection was employed.

Table 6.4 summarizes the test conditions utilized in each of the four

"Experiments" and six "Tests." Figure 5.2, presented above, illustrates

the temperature profiles measured in the vicinity of the cable trays near

the doorway for Experiments 1-4. Figure 5.3, presented above,

illustrates the same information during Tests 1-6. The time at which

electrical failure was observed is also indicated on these figures for

each of the tests in which such failures were observed. (As stated

above, no damage information was gathered during experiments 1 and 3.)

These results are of limited quantitative value as measurements of the

thermal conditions of the cables at the time of failure were not

considered reliable. Also, as the temperature profiles observed are

highly transient, it is difficult to extrapolate these results to other

fire situations. However, these tests did dramatically illustrate the

potential impact of indirect fire effects on the operability of cables in

particular, and plant equipment in general. The tests also indicated

that in some cases, longer term failures may be observed even though the

most severe part of a fire's growth history may have passed. This is

illustrated by the failure time observed in Tests 2 and 3. In both of

these cases electrical failure was observed well after the time at which

the peak air temperatures were reached. In Test 2 temperatures had

dropped from the peak value of approximately 500*C at 6 minutes, to a

value of approximately 300*C by the observed time of electrical failure

at 13 minutes. Later analyses showed that the fire in Test 2 had

essentially self -extinguished due to the consumption of the available

fuel by the time electrical damage was observed. This "delayed" failure

illustrates that damage may occur following the peak intensity, or

possibly even the extinguishment, of the fire itself.

6.2.3 Cable Radiant and Convective Heating Damage Tests

In conjunction with the Twenty-Foot Separation Tests described

immediately above, a series of independent cable damageability tests was

conducted (reference A-37). These tests investigated the damageability

limits of the two cable types used in the Twenty-Foot tests (the PE and

polyolefin cables described above) under conditions of either convective

or radiative heating.

-94-
Table 6.4: Summary of Experimental Conditions Varied in Each

of the Twenty-Foot Separation Tests. (Note that the ten tests

are identified as Experiments 1-4 and Tests 1-6.)

Experiments 1-4:*

Experiment Room Length: Door Size

Number (w-14ft. h-10ft) (w x h)

1 30 ft 8ft x 8ft

2 25 8 x 8

3 25 4 x 8

4 25 Closed

Tests 1-6:"

Test # Cable Type: Cable Tray Protection:

1 Nonrated None

2 Rated None

3 Nonrated Ceramic Blanket and Steel Covers

4 Rated Ceramic Blanket and Steel Covers

5 Nonrated Fire Retardant Coating, 1/8 inch

6 Rated Fire Retardant Coating, 1/8 inch

* All experiments used a 1x5 ft. pan with 10 gal. of heptane,

only, as the fire source.

** All tests used the 25 ft. length room with a 4x8 ft door.

The fire source was a 5 gallon heptane pool plus two

vertical cable trays, protected as indicated, simulating

one of two equipment trains.

-95-
In the convective heating tests, samples of each of the two cable types

were subjected to an elevated, steady temperature in a convective oven.

The cables were exposed using four different cable configurations as

described below:

1. Cable segments placed on a metal mesh shelf (12 tests),

2. Cable segments placed on a cable tray with a downward 90° bend

over one rung of the tray and a weight hung from the end of

this downward section (to simulate additional cable) (12

tests),

3. Cable segments placed in a cable tray with a distributed weight

placed on top of the cable (to simulate the bottom cable in a

loaded tray) (2 tests), and

4. Cable segments wrapped around an 18 inch (46 cm) aluminum

mandrel (3 tests).

Cables in each of these configurations were exposed to a variety of

elevated temperatures ranging from 130°C to 450°C for a predetermined

length of time ranging from 10 to 60 minutes. Following exposure the cable

samples were removed from the oven and allowed to cool. They were then

tested for the presence of conductor to conductor shorts and open

conductors. A total of 29 tests were performed.

It should be noted at the outset that this methodology can allow for the

masking of actual failures. In subsequent testing, described below, it has

been found that monitoring of a cable during the exposure period is

critical to the accurate identification of cable failures. It has been

observed that cables which develop shorts during exposure will often "heal"

once cooled. This healing has been observed up to the point were actual

ignition of the cable insulation occurs. It has also been noted that for

energized cables a short will often act as a fire ignition source as well,

and that the resulting fire will often completely consume all cable

insulation and jacketing materials near the location of the fault. Thus, a

lack of post exposure shorting in the tests described here can not be

considered conclusive evidence that the subject cables would actually

survive the exposures without shorting.

With the cables in the first configuration, no cases of electrical shorting

were observed. In many tests the cable jacketing and insulation materials

suffered severe discoloration, embrittlement, and shrinkage. With the

cables in the second configuration, the weighted bend, nonrated cable

shorting was observed at exposure temperatures as low as 150*C. At

temperatures of 170*C, shorting was observed after as little as 30 minutes

of exposure. No shorting was observed in the rated low flame spread cable

following 60 minute exposures at 250°C. In the third configuration,

distributed weighting, shorting of the nonrated cable was observed after a

60 minute exposure at 1700C. No samples of the rated low flame spread

cable were tested in this configuration. In the final configuration,

mandrel wrapped, following a 60 minute exposure at 275*C the rated low

-96-
flame spread cable would not pass a voltage withstand test. (This is a

more stringent failure criteria than that used for the previous

configurations.) Based on these results, the threshold of thermal damage

for the two cable types were estimated to be 130*C for the nonrated cable

and 250°C for the rated cable.

As an independent part of this test program, a number of radiative

heating cable tray tests were also performed. These tests utilized three

banks of quartz heaters to expose a loaded cable tray to predetermined

heat flux conditions. These heat flux levels varied from 5 to 40 kW/m 2 .

In each test the subject cables were energized to 320 VDC and powered to

5 amperes AC. The failure criteria used was the presence of a cable to

cable tray short as indicated by the presence of a cable to cable tray

current. No monitoring of conductor to conductor shorts was performed.

A total of 10 experiments, 5 each on the rated and nonrated cables, was

performed. The observed times to electrical failure, and the observed

times to nonpiloted ignition, versus the exposure heat flux level were

analyzed using a methodology developed at Factory Mutual Research Center

(FMRC).[33,34] Under this methodology the inverse time to electrical

failure, or ignition, is plotted as a linear function of the exposure

heat flux. Recently, the adequacy of this critical flux methodology has

been questioned.[8] While this correlation works fairly well for higher

heat flux levels, as one approaches the threshold values, the correlation

breaks down. Thus, the extrapolation of this data back to the abscissa,

and the interpretation of the extrapolated value as a critical heat flux

for damage, or for ignition, is inappropriate.

Figures 6.1 and 6.2 illustrate the results obtained for the onset of

cable to tray shorts and nonpiloted ignition of the cable samples,

respectively. In the original test report extrapolation of this data to

the abscissa was performed, and critical heat flux values were reported.

However, as described above, the more recent information indicates that

the interpretation of these values as threshold exposure values was

inappropriate. Thus, these results have not been reproduced here.

6.2.4 Cable Steady State Thermal Damage Tests

In a more recent effort an additional series of convective thermal

exposure cable damageability tests was performed. Two types of cabling

were exposed to steady state elevated temperature environments in a

convective oven. One of the cable types tested was a non-low-flamespread, 3 conductor, 12AWG, 20/10 PE/PVC insulated, PVC jacketed cable

rated to 600V. The second cable was an IEEE-383-74 rated low flame

spread, 3 conductor, 12AWG, cross-linked polyethylene (XPE or XLPE)

insulated and jacketed cable. 6

6. This is an account of previously unpublished work which has been

documented in a letter report to the USNRC dated July 14, 1984.

-97-
70'

*o4

0

0

q

EIEEE 383 Qualified Cable

PS/PVC Unqualified Cable

7

a

to

. . q Test .! 4 I l I

0.0 5.0 10.0 15.0 20.0 2 M35O :30.0 0

External Heat Flux, kW/ma

4M0 4W. 50.

Figure 6.1 Radiant Thermal Heating Cable Tray Damageability Test Results

?0

-4

*0

E0 IEEE 383 Qualified Cable

o PB/PVC Unqualified Cable

10

Test 3

0.0 5.0 10.0 1.0 M. 5. 30 35.0

External Heat Flux, kW/ma

40.0 45.0 5O0

Figure 6.2 Radiant Thermal Heating Cable Non-Piloted Ignition Test Results

-98-
These tests differed from the previous tests, described immediately above,

in two important respects. First, conductor to conductor shorts were

monitored throughout the period of exposure, not just following the

exposure. Second, in certain respects the cable configuration was less

severe than that used previously. In these tests a segment of cable was

routed into the oven onto a cable tray and back out of the oven. In the

previous tests, cable configurations included weighted bends, the use of

distributed weights pressing down on the samples, and mandrel bends. The

configuration used in these tests is most similar to the first

configuration used in the previous tests in which cable segments were

simply placed on a mesh shelf.

The results of these tests provided data, for each cable type, on both the

threshold of thermal damageability, and the time to damage versus exposure

temperature at higher temperatures. For the rated cable, electrical

shorting was observed within approximately 40 minutes at temperatures as

low as 270*C. Failures in the nonrated cables were observed at

temperatures as low as 250"C. The time to failure versus exposure

temperature data are presented in Figures 6.3 and 6.4.

These tests provide an important first step in the quantitative evaluation

of cable vulnerability in a convective environment. The ability to

analytically predict cable failures under convective conditions can play a

significant role in the'evaluation of fire risk as many fire risk scenarios

involve the exposure of cables to hot layer conditions in which convection

is the dominant mode of heat transfer. The recording of time to failure

versus the steady state exposure temperatures provides information of use

in the analytical prediction of time to electrical failure for transient

thermal exposures as well. The use of a simple threshold exposure

temperature value may not be appropriate as a criteria for cable failure.

Short term exposures at much higher temperatures will not necessarily

result in electrical failure. These tests also demonstrated that in the

performance of experiments, the monitoring of a cable during the exposure

period is important as "healing" of electrical faults was in some cases

observed. These tests represent only an initial step towards the analysis

of cable failure. Only two types of cables were tested, and only under a

limited range of thermal exposures. Also, no criteria for the onset of

cable electrical failure has yet been demonstrated.

6.2.5 Cable Transient Thermal Damage Tests

In the Twenty-Foot Separation Tests it was demonstrated that 20 feet of

horizontal separation was not, in and of itself, sufficient to insure the

safety of redundant equipment trains. However, the Appendix R fire

regulations require that in addition to 20 feet of separation with no

intervening combustibles, one must also provide automatic fire detection

and suppression systems in plant areas were such separation is employed as

a protective measure. In the Twenty-Foot Separation Tests active

-99-
0~

CL

a

a.J

500

480

300

200

31880

Unqualified PE/PVC Cable

0 a * I * I

8

Figure 6.3

20 40 68 80

Time to Electrical Failure (Min)

Cable Steady State Thermal Damageability Results for

a Non-Rated PE/PVC 3-Conductor Power Cable

Q.

x

aL

500

480

3880

200

•100

IEEE-383 Qualified XLPE/XLPE Cable

0 -t - * . I

8 20

Time

40

to Electrical

S . I-|

68

Failure (Min)

88

Figure 6.4 Cable Steady State Thermal Damageability Results for

a Rated Low Flame Spread XPE 3-Conductor Power Cable

-100-
suppression of the test fire was not employed. Nonpressurized sprinkler

heads were placed within the test enclosure and were monitored for

activation of the fusible link. The Cable Transient Thermal Damage Tests

investigated the possibility that the actuation of the sprinkler system and

active suppression of the test fires might have prevented the observed

cable failures.[35]

The observed exposure temperature profiles which, during the Twenty-Foot

tests, had resulted in the failure of the unprotected rated and nonrated

cables were experimentally reproduced in a transient thermal exposure

chamber. These profiles were those observed during Tests 1 and 2, which

have been described previously. In each of these two tests the cables were

not protected by any passive coating or barrier system. Test 1 involved

the nonrated cable and Test 2 involved an IEEE-383-74 rated low flame

spread cable. The observed temperature profiles in the vicinity of the

cables for each test were reproduced in full to simulate the actual test

conditions, and in part to simulate the onset of active fire suppression

and the resultant cooling of the enclosure environment. This simulation of

the cooling effects of suppression system activation was achieved through

interruption of the transient temperature profile at the observed time of

sprinkler head actuation. As a result a number of insights were gained.

It was found that cables with unprotected terminations in the test chamber

were much more susceptible to damage than were those which did not

terminate in the chamber. This was attributed to the fact that the

insulation materials would shrink upon heating, thus exposing unprotected

conductor. Careful measures needed to be taken in order to insure that the

presence of a cable termination did not in itself induce a premature cable

failure. It was also found that the geometry of the cable samples played

an important role in the time to observed damage. Shielding of a monitored

sample by other cables, as in a simulated loaded cable tray, delayed, and

often prevented the onset of electrical damage. Convection was also found

to significantly effect cable damage times. In single cable tests the

level of visible damage (e.g. cracking, blistering, discoloration) was

directly related to the magnitude of the velocities near the cable, and

hence the magnitude of the convective heat transfer coefficient. This

clearly indicates that convective, as well as radiative, damage mechanisms

must be considered, both in testing and in analytical fire modeling.

In the tests involving the simulation of fire suppression it was found that

damage was, in fact, prevented. However, in the case of the nonrated cable

in particular, significant cracking, and blistering of the jacket and

insulation material was still observed. This raises a potential concern in

that if suppression with water were actually employed, high humidity

-101-
environments and wetting of the cables would result. Thus, the presence of

significant cracks and blisters in the insulation could allow water to

induce shorting. It was intended that a second phase of this effort would

be initiated to investigate this potential. These second phase tests were,

however, not undertaken due to the termination of FPRP efforts.

6.3 Equipment Damage Sensitivity Ranking Study

As a lead-in to anticipated component fire environment damageability

testing, a study was performed to rank the fire damage significance of

safety-related nuclear power plant equipment. This ranking considered 33

types of plant equipment. In the initial screening the performance

requirements and potential sensitivity to fire induced damage were

considered. This screening resulted in the identification of the following

list of plant equipment as the highest ranking equipment in terms of the

decreasing sensitivity to fire damage:

Recorders

Logic Equipment

Controllers

Power Supplies

Meters

.Relays (solid state and electrical/mechanical)

Hand Switches

As a second screening step equipment was further examined based on system

significance, relative prevalence, and potential for affecting the loss of

a complete safety function. The LaSalle Nuclear Power Plant was used as

the basis for evaluation of these criteria. This screening found that at

LaSalle the prevalence of each type of equipment throughout the plant was

as follows:

Number in LaSalle

Total Number Front Line Systems

Recorders 25 3

Logic Equipment 114 33

Controllers '93 1

Power Supplies 40 10

Meters 127 102

Relays 771 524

Hand Switches 446 322

As can be seen, relays and hand switches are much more prevalent, both in

the plant in general and in front line safety systems, than are the other

types of equipment identified as potentially the most sensitive to fire

damage. On this basis relays and hand switches were identified as the

first choices for the performance of fire damageability testing. Other

-102-

a
likely candidates identified include logic equipment, power supplies,

transmitters, and motor control centers.

6.4 Relay Thermal Damage Tests

As described immediately above, relays were identified as the first

candidate for fire damageability testing based on both the vulnerability to

fire damage and on the prevalence of relays in front line safety systems.

Thus, as an initial step in the performance of damageability testing on

equipment other than cables, two types of relays were tested to thermal

failure (reference A-49).

The two relays tested were the Agastat GPI relay and the General Electric

HMA relay (model 12HMAlllB9). In each test a single relay was powered and

placed inside of a controlled environment thermal exposure chamber. The

initial temperature in the chamber was typically 50°C, and was increased in

incremental steps of 10°C every ten minutes until failure of the relay to

function was observed.

The Agastat relay uses an external socket connector. Two types of

connectors are available, and one relay was tested with each of the two

sockets. Failures in the Agastat relay were observed between 160*C and

210°C. Failure modes included shorts in the sockets, open circuits between

the relay terminals and the socket, apparent shorting of the external

socket connection screws to the metal base plate, and melting of a contact

support internal to the relay. Severe warping of the relay socket was

observed, and many of the failures are attributed to this warping.

The General Electric relay used direct connections rather than a socket.

Failure of the relay system was observed above 350°C. However, this

failure was caused by the initiation of a fire in the coil lead wires

resulting from two of the lead wires shorting together. The relay itself

was still functional at the time of cable failure. The resulting fire

badly damaged the relay.

These tests clearly demonstrated that even equipment of a similar nature,

i.e. relays, can exhibit significantly different failure thresholdis and

modes. The failure temperatures for the Agastat relay were near or below

those typically assumed for even unqualified cables. Thus, the

consideration of damage to equipment other than cables, and in particular

in the analysis of a control room, may play a significant role in the

analysis of fire risk. These tests demonstrated that the vulnerability of

such equipment will be dependant on many factors.

6.5 Component Testing in Secondary Fire Environments

In an attempt to explore the impact of an actual fire environment on the

operability of plant equipment, a series of component exposure tests were

performed in conjunction with the Cabinet Fire Tests described above.

-103-
During cabinet fire testing a number of components were placed at various

locations within the test enclosure. These components were subjected to

the uncontrolled environment which developed during the tests. Component

exposures were performed during both the first phase Cabinet Effects Tests,

and the second phase Room Effects Tests. These two phases differed primary

in that the first phase tests were performed in a 10,000 cubic foot

enclosure while the second phase tests were performed in a 48,000 cubic

foot enclosure.

Qualified nuclear power plant components subjected to these uncontrolled

fire environments included switches, meters, relays, and chart recorders.

In addition, certain other equipment which was not typical of that used in

a nuclear power plant were also tested. These were electronic counters, a

power supply, and an oscilloscope amplifier. These components do represent

equipment of a similar nature to other types of electronic equipment. Many

of these components were powered, and certain of the components were

monitored for operability. In all, components were included in five of the

cabinet fire tests. All five of these fire tests involved the burning of

cables within a control panel. In most cases the components were

positioned such that they were not involved in the actual fire itself.

Thus, the environments are described as secondary fire environments, and

did not include such effects as flame impingement or actual component

burning. As a result of these experiments a number of insights were

gained regarding the potential modes of failure one might expect for the

various types of equipment tested.

Switches were tested in various orientations with some panel mounted in a

cabinet with an open back, some mounted on their sides, and some placed

upright on a horizontal surface. None of the switches tested experienced

any gross failure due to secondary fire effects. In several cases the

switches did experience moderate to heavy depositions of soot on the

working parts and contact surfaces. In one case, a switch which was closed

during exposure had a contact resistance of approximately 100 kohm. The

application of a 15VAC stress across contact points was sufficient to

reduce the contact resistance to essentially that measured prior to

exposure (in the milli-ohm range). During two of these tests, one switch

was powered and monitored. The peak temperatures experienced by these

switches were approximately 60*C and 30*C respectively. These two

switches continued to carry their load currents without apparent

difficulty. No detectable leakage currents were experienced (0.25 mA AC

sensitivity).

Two of the exposed switches were subsequently placed in a 27"C, 70%

relative humidity environment for 12 days. These switches were not cleaned

and the soot deposits were left intact. Following this humidity exposure,

one of the two switches displayed visible evidence of fairly extensive

corrosion. This switch, when first closed, displayed a high contact

resistance. This condition was quickly corrected by the application of a

low DC voltage stress across the contact points. Neither of the switches

experienced any gross adverse functionality effects.

-104-
Samples of the same type of relays which had been tested to failure

previously, as described immediately above, were also used in this effort.

The maximum thermal environments experienced by the relays were

approximately 60*C. Other than slight corrosion on the metal surfaces of

relays whose covers had been removed during exposure, no adverse impact on

the functionality of the relays was noted. As with the switches, several

of the relays experienced moderate to heavy deposition of smoke

particulate. One relay placed in a 27*C, 70% relative humidity environment

for 12 days following exposure also showed no adverse functionality impact.

A total of 13 meters of different types were also tested. These meters

were not powered during exposure, though pre- and post-exposure

calibrations were performed. None of the meters experienced any apparent

damage due to this exposure, with the exception of two meters which became

involved in the fire and were destroyed. The most severe environment

experienced, short of fire involvement, reached a peak temperature of

approximately 1000 C.

Two strip chart recorders were also tested. In the first case, the

recorder's front cover was removed and the recorder was placed on a surface

in the enclosure approximately 8 feet from the burning cabinet. In the

second case, the recorder's cover was left intact and the recorder was

panel mounted in an open backed cabinet not involved in the fire. In the

first case, heavy deposition of soot on the strip chart pen sliders

completely blocked pen movement. Attempts to clean this deposition and

restore functionality were unsuccessful. In the second case, only a light

deposition of soot was noted. This soot prevented one of the three

recording pens from traveling over its full range under the input of a

slowly changing voltage source as one would expect during normal operation.

This failure was successfully cleared by applying a sudden step change in

voltage.

Two solid state electronic counters were tested. In the most severe

exposure, one of the two counters experienced a peak temperature of 167*C

with temperatures remaining above 150% for about five minutes. This

counter was not powered nor monitored during exposure, though post-exposure

evaluation showed the counter to be working normally. A heavy deposition

,of soot was found on the circuit board. This counter was subsequently

powered and placed, without cleaning, into an environment of 32*C and 90%

relative humidity for 5.5 hours. The environment was then modified to a

95% relative humidity and the exposure continued. After 17.5 hours of this

exposure the counter was found with the front display deactivated and the

its power supply fuse blown. The counter was removed from the chamber, the

.fuse replaced, and before the mode of failure could be diagnosed counter

function returned to normal. The counter was again placed in the humidity

.chamber at 40*C and 95% relative humidity for an additional 18 hours. At

the end of this period the counter was again found with the same failure

symptoms. In this case the failure was traced to the build-up of a

conductive medium which allowed excessive leakage currents near the power

-105-
supply transistor. This medium was removed, and counter function returned.

The counter was again checked, some hours later, and was found to have

malfunctioned as a result of another problem. This problem was eventually

traced to corrosion related bridging of a series of four closely spaced

current paths on the printed circuit board.

One final piece of equipment tested for which an interesting result was

observed was an oscilloscope amplifier. This amplifier was fed a nominal

one volt input, set to a factor of 5 amplification, and the output

monitored. The environment in the vicinity of the amplifier reached a peak

temperature of 110°C, and included a direct exposure to the thermal

radiation from the back of the open fire cabinet. During the exposure a

severe calibration drift in the output signal was noted. Eventually the

output signal was lost entirely. This loss of output was attributed to the

actuation of a thermal cut-out protection breaker which was set to 58°C.

Once this cut-out was reset, and the component cooled, the function

returned to normal.

One additional finding which resulted from these tests was that the soot

which was deposited throughout the enclosure was found, in the case of

burning PVC insulated cables, to be heavily laden with chlorides. It was

estimated that the soot deposits were comprised of as much as 33% by weight

water soluble chlorides. As much as 60% of the chloride generation

expected from the cable fires was accounted for by chloride bound to the

soot, rather than airborne chloride gases. These chlorides, when combined

with water, can be highly corrosive and conductive. This is considered the

most likely cause of both the leakage current and corrosive bridging

failures noted in the case of the electronic counter.

These tests have illustrated a number of mechanisms by which various types

of electrical/mechanical equipment might be damaged in a fire environment.

The results include quantitative assessments of the thermal environment to

which the components were subjected. In other respects, the results are

relatively qualitative in that no attempt was made to determine damage

thresholds, nor to quantitatively evaluated the relative degradation of

functionality in the context of a control circuit. This makes it difficult

to extrapolate the results to other equipment and other fire environments,

except to say that equipment of a similar type to that tested would be

expected to display similar vulnerabilities.

The failure mechanisms observed include melting, high temperature

electronic failures, thermally induced calibration shifts, leakage currents

induced by conductive smoke or smoke and water combinations, leakage

currents on open contact pairs, particulate build-up on moving parts,

corrosion of moving parts, and high contact resistance. The presence of

corrosive and conductive deposits also raises a potential for high voltage

breakdown in equipment such as switchgear and motor control centers, though

-106-
these effects have not been investigated. Other potential damage

mechanisms which have not been investigated include the impact of water

sprays (either alone or in combination with other fire effects), and the

impact of gaseous suppressant application on equipment operability.

-107-
7.0 ROOM-TO-ROOM FIRE EFFECTS STUDIES

7.1 Introduction

Room-to-room fire effects involve the potential for a fire or fire

products to spread beyond the room of fire origin. The primary

mechanisms for fire and fire products spread is the failure of fire

barrier elements to contain a fire. Such failures could result from

either design inadequacies, inadequate barrier maintenance, barrier aging

degradation, or from personnel actions. The spread of fire products,

such as smoke and heat, to remote locations may also occur through the

plant ventilation system. Fire or fire products spread could induce

significant increases in plant risk since the fire barriers form the

first and foremost plant feature which is expected to limit the extent of

fire damage and protect redundant trains of plant equipment.

As a part of the FPRP, only limited investigations of room-to-room fire

effects have been undertaken. The particular studies which provide

insights applicable to this aspect of fire safety are:

1979 Fire Protection Subsystems Study; Ventilation Systems

1979 Fire Protection Subsystems Study; Fire Barriers

1980 Investigation of Fire Stop Test Parameters

7.2 Eire Protection Subsystems Study: Ventilation Systems

As a part of the Fire Protection Subsystems Study, a review of the role

played by plant ventilation systems in fire protection was performed

(reference A-15). The primary focus of this study was a review of the

guidelines for the design and installation of ventilation systems as

related to fire protection strategies and design. The principal purpose

of this study was to formulate recommendations for the modification of

these regulations for application to nuclear power plants.

With respect to of room-to-room fire effects, ventilation systems

represent a potential conduit for the spread of fire products to nonfire

areas. It was found that the guidelines and regulations for the design

and installation of ventilation systems were not sufficiently detailed to

allow for the design of ventilation systems as an integral part of the

fire protection systems. No provisions were included to provide such

desirable features as local control and alignment of the ventilation

system to meet the needs of fire products control or containment.

In practice, ventilation systems are typically installed with fire

dampers at those locations where the ventilation duct work penetrates a

rated fire barrier. These dampers are designed to close when either

smoke or sufficient heat is detected in the ventilation ductwork.

However, these dampers are typically designed to contain the spread of

fire and flames rather than smoke or heat. Thus, many damper systems

allow significant amounts of heat and smoke to pass even when fully

closed. While one would expect that unrealistically large quantities of

-108-
heat must be passed to represent a threat of fire spread, experimental

evidence indicates that even relatively low level heat may cause

calibrations shifts in certain types of plant equipment such as

integrated circuitry. In addition, while not yet investigated

experimentally, it is to be expected that smoke itself will represent a

potential source of equipment damage for certain types of plant equipment

such as high voltage switchgear.

As the design and installation of ventilation systems continues to, be

governed by essentially the same guidelines as those considered in this

study, ventilation systems continue to represent a potential conduit for

the spread of fire products to nonfire areas. To date no experimental

investigations of this have been undertaken. Also, as noted in Chapter 6

above, very little is known about the vulnerability of plant equipment to

relatively low thermal exposures, nor the impact of smoke on the

operability of plant equipment. Thus, the significance of fire products

spread to nonfire areas remains largely unassessed.

It should also be noted -that the significance of room-to-room fire

effects will be dependant on the thresholds of equipment vulnerability to

fire induced damage. In particular, it is to be expected that the

environments in nonfire locations will be less severe than those in the

room of fire origin. " Should it be determined that equipment will survive

relatively harsh fire enclosure environments, then concerns for room-toroom equipment damage may be limited to suppression system actuation

problems. However, to date there is insufficient data upon which to base

such suppression induced equipment vulnerability assessments.

7.3 .Fire Protection Subsystems Study: Fire Barriers

In the considerationd of room-to-room fire effects, fire barrier systems

play a key role. In particular, one is dependent on the integrity and

durability of sealsinstalled in cable, conduit, ducting, and other fire

barrier through. penetrations and the integrity and durability of fire

doors to prevent the spread of fire and fire products from the room of

fire origin. As'a part of the Fire Protection Subsystems Study, a review

of the regulations governing the qualification of fire barrier elements

was conducted.[4]

As a' result of this study, two potential weaknesses were identified. The

first was the use of a'hose stream test as a part of such qualifications-.

This test was judged to have poor repeatability. The second *was the

failure of qualification standards in the U.S. to specify the a positive

pressure differential across the barrier element during the fire exposure

testing. It is this second potential weakness which was considered of

greater importance.

In an actual enclosure fire, the heating of the enclosure air will result

in an increase in the enclosure pressure. Thus, should a fire barrier

element or penetration seal have cracks or gaps which would allow for the

passage.'of air, during an' actual enclosure fire the elevated pressure

-109-
could force hot air, or even flames, out past the barrier element. Such

cracks or gaps may result from improper installation, inadequate

maintenance, aging effects, or may actually be a part of the as designed

barrier element (as in the case of doors). The failure of the, U. S.

standard tests to impose a positive differential pressure during

qualification testing could mask this potential barrier failure

mechanism.

This question of pressure effects on barrier elements was investigated

further in the Fire Stop Test Parameters investigation. It was also

raised as a part of the Fire Risk Scoping Study.[8] The results of these

investigations are described in Section 7.4 and in Chapter 8

respectively.

7.4 Investigation of Fire StoR Test Parameters

As a follow up to the Fire Protection Subsystems Study, a limited series

of cable tray fire barrier penetration seal positive pressure fire

exposure-tests were performed.[5] These tests also explored the impact

of such factors as the loading density of cable in the penetration, the

diameter of the penetrating cables, and the type of conductor (i.e.

aluminum or copper) on the response of the seal system to the standard

exposure test. This test series was limited in that (1) only a very few

penetration seal systems were investigated, and (2) none of the seal

systems tested were specifically qualified for use, nor verified to

actually be in use, in nuclear power plants.

It was found that for those seal material which remained integral during

the test and did not allow a path for gas flow, the effects of changes in

pressure differential were not significant. For tests with a pressure

differential from 2 to 125 Pa (0.008 to 0.5 inches of water), no

significant change in the transmission of heat nor the onset of flaming

on the unexposed side were noted. However, for one type of silicone

elastomer seal system installed with through opening, a significant

degradation in performance was note when the differential pressure in the

furnace was made positive. Within 15 minutes of the initiation of the

exposure tests, hot gas issuing through the passages was melting the

cable insulation materials near these passages. While these cables were

already electrically failed due to the fire on the exposure side, the

onset of insulation melting is a good indicator that ignition thresholds

are being approached. In all probabilility, any type of pilot flame

would have been sufficient to ignite these cables. When the standard

test was performed for this same penetration type Without the pressure

imposition, no hot gas passage nor insulation melting was observed.

It was also found that the construction of the fire stop would affect its

response to the exposure test. Increasing the number or diameter of the

cables or conduits penetrating the seal would result in more rapid

increases in the unexposed surface temperature. Different cable

insulation materials, and different conductor materials would also affect

the seal response.

-110-
This investigation provided only a limited and rather qualitative

assessment of the effects of various fire stop physical parameters and

qualification test parameters on the exposure response. It was

recommended that a further study of these effects be undertaken to

determine whether the observed effects were significant for typically

employed nuclear power plant fire seal systems.

-111-
8.0 AN OVERVIEW OF THE FIRE RISK SCOPING STU6Y

8.1 Introduction

As a result of the various efforts which were undertaken as a part of the

FPRP a list of six issues was developed which represented potential

contributors to fire risk, and yet, had not been addressed in previously

completed fire: risk assessments. In response, an effort known as the

Fire Risk Scoping Study was undertaken. It was the purpose of this study

to (1) review and update the perspective of fire risk in light of the

information developed through the FPRP, and (2) to identify and perform,

initial investigations of any potential unaddressed issues of fire risk.

While performed as a separate and independent project, the findings of

this study will be discussed briefly because (1) the efforts were a

direct outgrowth of the FPRP, and (2) the study generated a number of

conclusions and recommendations which are relevant to any future fire

safety research which may be undertaken.

8.2 A Review and Updating of the Fire Risk Perspective

As an initial step in the performance of the Fire Risk Scoping Study, a

review of four previously completed fire probabilistic risk assessments

(PRAs) was performed. In each PRA the data and information made

available as a result of the FPRP since the performance of the original

work was used as the basis for requantification of the risk scenarios.

In addition, plant modifications made in response to implementation of

Appendix R since performance of the original PRA was also incorporated,

and risk estimated again re-calculated. The objective of these

reassessments was to assess the impact of the updated information, fire

modeling techniques, and Appendix R implementation on fire risk.

The four plant fire PRAs which were reviewed were those for Limerick,

Indian Point II, Seabrook, and Oconee. In each case only the dominant

fire risk areas were re-examined. The requantifications were performed

within a limited scope. No reassessment of the fundamental fault

scenarios was performed, except in the cases where Appendix R

modifications were made. The requantifications were performed following,

as closely as possible, the methodology of the original analyses.

Finally, judgmental factors used in the quantification process were not

revised. The results of the requantification analyses prior to

incorporation of Appendix R plant modifications are presented in Table

8.1. Table 8.2 illustrates the impact of identified Appendix R plant

modifications on the updated risk estimated.

In each case, fire was found to represent a dominant contributor to plant

core damage risk. This had been consistently demonstrated by risk

analyses performed by a variety of analysts for a number of commercial

reactors, and was not altered by the use of the updated information and

modeling techniques. While the results of the NRC fire protection

-112-
Table 8.1 Summary of Scenario Requantification Results Prior

to the Incorporation of Plant Appendix R Modifications

Original CDF Reguantified CDF

Limericka 2.3E-5 1.6E-4

Indian Point 2 b 6.5E-5 2.OE-4

Oconee& 1.3E-5 2.OE-5

Seabrookb 2.1E-5 4.6E-5

a - Point Estimate

b - Mean Value Estimate

Table 8.2 Summary of Appendix R Plant Modification Risk Impact*

Plant: Reouantified Without With AUpendix R

Appendix R Mod's Modifications

Limerick8 1.6E-4 5.9E-5

Indian Point 2b 2.OE-4 8.8E-6

Seabrookb ** 4.6E-5 4.6E-5

a

b

- Oconee Analysis Already Considered Appendix R Changes - Seabrook Appendix R Changes Did Not Affect The Dominant

Scenarios

- Point Estimate

- Mean Value Estimate

-113-
research program have reduced fire risk estimate uncertainties, the

overall perception of fire as a source of risk was not significantly

altered. Even considering the improvements in fire protection which have

resulted from the implementation of the Appendix R fire regulations, fire

continues to represent a dominant core damage risk contributor.

Implementation of Appendix R fire protection guidelines was demonstrated

to have reduced fire risk at certain reactors by an order of magnitude.

However, for other reactors the implemented plant modifications did not

affect the dominant fire risk scenarios.

It was concluded that little or no basis for comparison of risk estimates

from analysis-to-analysis existed. This primarily resulted from

differences in how five factors, which were identified as the principal

sources of fire risk analysis uncertainty, were determined. These are

(1) estimation of fire occurrence frequency and fire size, (2) screening

methodology differences, (3) modeling of fire detection and suppression,

(4) estimation of of equipment damage thresholds; and (5) modeling of

fire growth and environment response. It was recommended that

standardized methodologies be developed in each of these areas in order

to provide a basis for analysis-to-analysis comparison. In addition, the

available fire growth models were identified as inadequate, and the

adequacy of fire analysis tools in general was further examined as a part

of the investigation of unaddressed fire risk issues.

8.3 Identification and Assessment of Unaddressed Fire Risk Issues

The Fire Risk Scoping Study was initiated on the basis of a list of fire

risk issues developed as a part of the FPRP. This list was comprised of

fire safety issues which had been identified subsequent to the

performance of several plant fire PRAs. Using this list as the starting

point, a number of plant designers, fire researchers, industry

representative, fire protection consultants, and regulators were polled

to insure that, to the degree possible, the list of unaddressed risk

issues was eomplete. As a result a final list of six issues was

developed. The potential impact of each of these issues on fire risk was

assessed. The issues investigated are:

Control Systems Interactions

Total Environment Equipment Survival

Manual Fire Fighting Effectiveness

Fire Modeling Adequacy

Seismic/Fire Interactions

Fire Barrier Reliability

The evaluation of control systems interactions focused on the examination

of the LaSalle Station control room. This work was performed in

conjunction with the RMIEP analysis of that plant. The risk contribution

due to a fire in one section of one control panel in the control room,

the electrical distribution panel, was estimated at 8.lE-6/yr. This can

be compared to an estimated risk for all internal events of 2.OE-5/yr to

4.OE-5/yr. The design evaluated in this analysis does meet the criteria

-114-
of Appendix R. However, the deterministic reviews of control system

independence performed as a part of Appendix R fire safety reviews can

leave probabilisticly significant control systems interaction

vulnerabilities unresolved. In the case examined, it was found that the

level of indication and control provided on the remote shutdown panel was

instrumental in reducing the estimated core damage frequency by an order

of magnitude through operator recovery actions. It was recommended that

a review of industry practices on the implementation of remote shutdown

capability be performed and that control systems be examined on both

deterministic and probabilistic bases.

In the evaluation of the importance of manual fire fighting to plant fire

risk, two approaches were taken. First, a review of current plant

practices was performed. This review found that a wide plant-to-plant

variability exists. Fire brigade staffing and training varied from the

minimum requirements of Appendix R to training far in excess of the

regulations. The study identified a potential weakness in the Appendix R

fire regulations in that training for members of manual fire fighting

teams need not include training on actual fires. Thus, personnel

assigned as fire fighters may never have faced a smoke filled room nor an

actual fire.

The second approach involved the variation of assumed manual fire

suppression probabilities and the assessment of the impact of this

variation on risk estimates. It was found that for many dominant fire

risk scenarios, the estimated time to fire induced critical failures is

quite short making it unlikely that manual fire fighting efforts will be

successful prior to damage. It was also found that relatively small

variations in fire suppression times can result in order of magnitude

changes in fire risk estimates. It was recommended that a review of

manual fire fighting provisions be performed on a plant specific basis

and that plant areas for which manual suppression is the only available

fire fighting system be reexamined to determine whether predicted fire

damage times are consistent with realistic manual brigade response times.

The currently available tools for use in fire analysis were also

examined. It was found that these tools are, in general, inadequately

validated. This results in large part from a lack of appropriate

experimental data for situations typical of nuclear power plants against

which to base validation. While many fire tests of various types have

been performed, the objectives of these tests has not generally been

nuclear power plant fire model validation. One notable exception to this

is the Base Line Validation Tests and the Cabinet and Control Room Fire

Tests performed under the FPRP. These tests were specifically performed

to provide enclosure fire model validation results under conditions

typical of nuclear power plant fire situations. However, these tests

were performed shortly before the termination of the Fire Protection

Research Program and planned efforts to process and make this data

available were cancelled.

-115-
Another area investigated under this effort was the adequacy of the

available data on the vulnerability of plant equipment to fire, or fire

suppression induced damage. Very few efforts have been conducted to

specifically examine the impact of a fire on the operability of plant

equipment. Most of the available data, both from within and outside the

FPRP, has focused on cables. However, even for cables, relatively little

is known about the mechanisms and thresholds of fire induced damage. In

addition, certain of the publicly available cable damageability data was

identified as having been extrapolated in a nonconservative manner and is

considered inappropriate for use in fire risk assessments. For other

types of plant equipment, and for damage mechanisms other than direct

thermal heating, very little information is available. It was determined

that insufficient data existed upon which to base an assessment of the

risk impact of this issue. It was recommended that equipment

damageability studies be undertaken. In particular, the impact of fire

suppression systems on control circuitry, the damageability of electrical

cables, the effects of smoke and/or water on high voltage equipment, and

the impact of smoke and/or water on control circuitry were identified as

potentially significant equipment damage mechanisms.

Also investigated was the potential impact of seismic/fire interactions

on plant risk. While it was determined that risk significant

seismic/fire interactions can be identified, it was also concluded that

such vulnerabilities will be more easily corrected than quantified. It

was recommended that an effort be undertaken to develop guidelines upon

which plants could base a comprehensive walkdown to identify and resolve

these vulnerabilities.

The final area investigated was the reliability of fire barrier elements.

This issue is directly related to the questions raised in past efforts

regarding the reliability of fire barriers under actual fire conditions.

The study found that there was insufficient data upon which to base

actual risk estimates. A simple screening analysis showed that should

barrier reliability be on the order of 99%, then no significant risk

impact is expected. However, should barrier reliability be on the order

of 90% then an order of magnitude increase in fire risk'could result. It

was recommended that a comprehensive review of fire barrier performance

in the U.S. be performed in order to determine whether any fire barrier

designs are particularly vulnerable to premature failure. It is

anticipated that such a review would demonstrate that most barrier

systems function well in actual fires, and hence, no significant risk

impact would be expected.

8.4 Summary

The Fire Risk Scoping Study performed a review and requantification of

past fire risk scenarios. This review demonstrated that while fire risk

estimate uncertainties have been reduced, the overall perception of fire

as a significant risk contributor has not changed. Recommendations were

made to develop standardized methodologies for the performance of a

-116-
number of fire risk assessment steps in order to provide a basis for

analysis-to-analysis comparison of results.

In addition, six unaddressed fire risk issues were examined. The results

of this examination are summarized in Table 8.3. A number of

recommendations were made for follow-on efforts associated with these six

issues. Of the six risk issues, control systems interactions and manual

fire fighting effectiveness are considered the plant issues of the

highest importance. Each is estimated to have a potential order of

magnitude impact on plant risk. (Note that this impact is not expected

to be multiplicative when more than one issue is considered

simultaneously.) Also considered important are the issues of the

adequacy of fire analysis tools and total environment equipment survival.

In each of these two areas, a greater understanding of the phenomena is

needed. The issue of barrier reliability is identified as potentially

significant; however, it is anticipated that a comprehensive review of

fire barrier performance in the U.S. would demonstrate that barrier

reliability is adequate. For the final issue, seismic fire interactions,

potential vulnerabilities were identified. However, these

vulnerabilities are considered to be more easily resolved than

quantified.

-117-
Table 8.3 Summary Unaddressed Issues Investigation Findings

Issue: CDF Impact*-

Control Systems Interactions

Manual Fire Fighting Effectiveness

Adequacy of Fire Analysis Tools

Total Environment Equipment Survival

Fire Induced Effects

Spurious Suppression Effects

0(10)

0(10)

0(10)

Generic Difficult to Quantify,

Probabilistic Issue Not

Deterministic

Generic

Generic

I- Unknown

Small-0(l0)

Small-0(10)

Generic

Plant Specific

Not A Plant Issue

Not Quantified,

Insufficient Data

Not Quantified,

Insufficient Data

Vulnerability Not

Assessed, No Data

Easily Resolved on

Plant Specific Basis

Barrier Reliability Generic

Seismic/Fire Interactions Small Generic

* - 0(10) Is a mathematical representation for order of magnitude.

Note: The core damage frequency (CDF) impacts are not expected to display multiplicative

character when more than one issue is considered, rather, the effects will be additive.
9.0 SUMMARY

During the years 1975-1987 the Fire Protection Research Program has

investigated a variety of issues 'associated with fire safety in

commercial nuclear power plants. The efforts performed have been

conducted on both analytical and experimental bases. Investigations of

fire ignition, fire.growth, fire induced damage, fire detection and

suppression, the modelling of fire, and fire risk have* been performed.

These investigations have led to a better understanding of the adequacy

of past and present fire protection regulations, as well as a greater

understanding of fire overall. The following lists some of the major

results and conclusions which have resulted from these efforts:

- Fire retardant cable insulation, cable coatings, cable tray

covers, and other passive cable tray protective measures reduce fire

severity. However, such measure do not insure that fire induced

damage will not occur and wide variability in relative effectiveness

of different systems and products was demonstrated.

- While cables certified by the IEEE-383-74 flame spread test are

more difficult to ignite and spread fire more slowly, even these

rated low flame spread cables can be ignited, burned, and/or

damaged. It has also been observed that once a self-sustaining fire

is developed in such cables, these fires tend to be more intense and

more difficult to extinguish.

- If properly designed and installed carbon dioxide,: and Halon

suppression systems will eventually extinguish even deep seated

fires such as those encountered with cable tray installations.

However, the maintenance of proper concentrations of suppression

agents for sufficient periods of time is critical to prevent

reignition.

Gaseous suppression agents applied during a fire permit enclosure

temperatures to remain higher than do water based suppression

systems. Sensitive control circuitry may experience loss of

function and/or calibrations shifts during extended exposures at

even relatively temperature elevations.

- Water is the most effective fire suppressant for suppressing even

deep seated cable fires. The use of water does, however, produce

severe moisture environments which may lead to equipment damage,

even beyond the region of immediate fire involvement. The proper

management *of fire suppression water must also be considered as a

part-of. system design.

Cable and ducting wall penetration seals can allow hot gases and

flame to pass through prematurely under conditions of positive

pressure differential if the seal system is such that air passages

are incorporated, even though such penetration seal systems may pass

standard fire qualification tests.

-119-
- 'Hot gas layers from fires have, during testing, been observed to

cause damage to cables spatially separated in accordance with the

provisions of the Appendix R fire regulations and not directly

involved in the fire. (In these tests no active suppression of the

room fires was attempted. Appendix R doeA specify the use 'of

automatic-fire detection and suppression where, spatial'separation is

uted'as a'fire protection measure.)

- Failure mechanisms identified for electrical components include

high temperatures melting, calibration shifts due to relaively low

elevations in temperature, smoke deposition" moisture, *and/or

corrosive gases. Thermal cut-out protective featur'e4 activation has

also been observed. Such cut-out may require operator action to

restore equipment operability. -

- Testing has shown that cables can fail at temperatures well below

the nonpiloted ignition temperatures., "

- Room environments in control room sized enclosures induced by a

firet in a single control cabinet can be severely degraded by the

rapid development of thick, toxic, and corrosive smoke. In terms of

the thermal environment, for the configurations tested (i.e. a

single cabinet burning in a large open room)' temperatures remained

below those expected to cause damage to most plant equipment

including cables.

- Electrical cabinet fires which consumed all of the available

combustible materials within approximately 15 minutes of ignition

were observed for both IEEE-383-74 rated low flame spread cables and

for nonqualified cables.

- For the nonqualified cables, full involvement cabinet fires can

be electrically initiated as a result of a low intensity (less than

15 Ampere) simulated electrical fault.

- The determiniitic criteria of the Appendix R guidelines do not

address the residual risk associated with probabilistic events such

as multiple faults, multiple spurious operations, and multiple

random equipment failures.

- Manual fire fighting and operator control actions may be severely

hampered by smoke from cable fires, even in very large rooms having

high forced ventilation rates. Typical ventilation configurations

used in practice can not be expected to purge smoke from a fire

enclosure adequately to insure either visibility nor habitability.

- Chlorides released during PVC cable insulation fires were

observed to become bound to smoke particulate which was subsequently

deposited on surfaces throughout a fire enclosure. These chlorides,

when combined with water, can form a highly corrosive deposit.

-120-
The Fire Protection Research Program has fostered a greater understanding

of the behavior of fires, the adequacy of fire related regulations and

guidelines, the adequacy of various fire protection measures, and fire

risk. Historical evidence indicates that significant plant fires occur,

on average, once every seven to ten years of operation. Thus, most

plants can expect to experience a number of significant fires during

their design life. Fire risk, as estimated by several risk assessments,

consistently represents one of the dominant contributors to overall risk

even when consideration of Appendix R plant modifications is included.

The Appendix R regulationsare deterministic in nature and do not address

the residual risk associated with probabilistic combinations of multiple

fire induced failures and random plant equipment failures.

While the understanding of fire phenomena has significantly improved and

the risk due to fire has been reduced by Appendix R implementation, a

number of areas remain in which our knowledge base is relatively poor.

In particular, fire modeling, equipment vulnerability to fire suppression

induced damage, the effects of smoke on high voltage equipment, the

impact of fire environments on control circuitry,, fire induced control

systems interactions, the effectiveness of manual fire fighting efforts,

and room-to-room fire effects are all areas in which a greater

understanding is needed. These areas are particularly important in that

each has a direct. impact on the perception of fire as a source of risk.

-121-
10.0 REFERENCES

1. Report on Task I. Fire Protection System Study, SAND 76-0630,

NUREG76-6516, Albuquerque: Sandia National Laboratories, February

1977.

2. Nuclear Power Plant Fire Protection-Ventilation (Subsystems Study

Task 0), SAND79-0263, NUREG/CR-0636, Albuquerque: Sandia National

Laboratories, August 1979.

3. Nuclear Power Plant Fire Protection-Fire Detection (Subsystems Study

Task 2), SAND78-1373, NUREG/CR-0488, Albuquerque: Sandia, National

Laboratories, March 1979.

4. Nuclear Power Plant Fire Protection-Fire Barriers (Subsystems Study

Task 3), SAND78-1990, NUREG/CR-0468, Albuquerque: Sandia National

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5. Investigation of Fire Stop Test Parameters: Final Report,

SAND81-7144, NUREG/CR-2321, September 1981.

6. Tests and Criteria for Fire Protection of Cable Penetrations,

SAND81-7160, NUREG/CR-2377, Albuquerque: Sandia National

Laboratories, October 1981.

7. Nuclear Power Plant Fire Protection-Fire Hazards Analysis

(Subsystems Study Task 4), SAND79-0324, NUREG/CR-0654, Albuquerque:

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NUREG/CR-5088, Albuquerque: Sandia National Lýboratories, December

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9. "Nuclear Power Plant Fire Protection Research," SAND 77-0389A, ANS

Topical Meeting, Chattanooga, TN, August 1977.

10. A Preliminary Report on Fire Protection Research Program (July 6.

1977), SAND77-1424, Albuquerque: Sandia National Laboratories,

October 1977.

11. A Preliminary Report on Fire Protection Research Program Fire

Retardant Coatings Tests (December 7. 1977 - January 31. 1978),

SAND78-0518, Albuquerque: Sandia National Laboratories, March 1978.

12. Fire Protection Research Quarterly Progress Report (October -

December 1977), SAND78-0477, NUREG/CR-0366, Albuquerque: Sandia

National Laboratories, August 1978.

-122-
13. A Preliminary Report on Fire Protection Research Program Fire

Barriers and Fire Retardant Coatings Tests, SAND78-1456, NUREG/CR0381, Albuquerque: Sandia National Laboratories, September 1978.

14. A Preliminary Report on Fire Protection Research Program Fire

Barriers and Suppression (September 15, 1978 Test), SAND78-2238,

NUREG/CR-0596, Albuquerque: Sandia National Laboratories, December

1978.

15. Fire Protection Research Program for The Nuclear Regulatory

Commission, 1975-1981, SAND82-0431, NUREG/CR-2607, Albuquerque:

Sandia National Laboratories, April 1983.

16. Fire Protection Research Program Corner Effects Tests, SAND79-0966,

NUREG/CR-0833, Albuquerque: Sandia National Laboratories, December

1979.

17. Nuclear Power Plant Electrical Cable Damageability Experiments,

SAND82-0236, NUREG/CR-2927, Albuquerque: Sandia National

Laboratories, October 1982.

18. Burn Mode Analysis of Horizontal Cable Tray Fires, SAND81-0079,

NUREG/CR-2431, Albuquerque: Sandia National Laboratories, December

1981.

19. Evaluation of Suppression Methods for Electrical Cable Fires,

SAND83-2664, NUREG/CR-3656, Albuquerque: Sandia National

Laboratories, October 1986.

20. Cost Estimates for Providing Active and Passive Fire Protection

Measures in Nuclear Power Plants, SAND81-7169, Albuquerque: Sandia

National Laboratories, November 1981.

21. Reguirements fbr Establishing Detector Siting Criteria in Fires

Involving Electrical Materials, SAND8I-7168, NUREG/CR-2409,

Albuquerque: Sandia National Laboratories, July 1982.

22. Investigation of Twenty-Foot Separation Distance as a Fire

Protection Method as Specified in 10 CFR 50, Appendix R,

SAND83-0306, NUREG/CR-3192, Albuquerque: Sandia National

Laboratories, October 1983.

23. Ouantitative Data on the Fire Behavior of Combustible Material Found

in Nuclear Power Plants, A Literature Review, SAND86-0311, NUREG/CR4679, Albuquerque: Sandia National Laboratories, February 1987.

24. Users Guide for a Personal-Computer-Based Nuclear Power Plant Fire

Data Base, SAND86-0300, NUREG/CR-4586, Ajbuquerque: Sandia National

Laboratories, August 1986.

-123-
25. V. Babrauskas, "Estimating Large Pool Fire Burning Rates," Fire

Tech., Vol 19 No 4, 1983.

26. Heat and Mass Release Rates for Some Transient Fuel Source Fires. A

Test Report, SAND86-0312, NUREG/CR-4680, Albuquerque: Sandia

National Laboratories, October 1986.

27. D.R. VonVolkinburg, et.al., "Towards a Standard Ignition Source,"

Lawrence Berkeley Laboratory, LBL-8306, Oct 1978.

28. Description and Testing of an Apparatus for Electrically Initiated

Fires Through Simulation of a Faulty Connection, SAND86-0299,

NUREG/CR-4570, Albuquerque: Sandia National Laboratories, June 1986.

29. An Experimental Investigation of Internally ignited Fires in Nuclear

Power Plant Control Cabinets. Part I - Cabinet Effects Tests,

SAND86-0336, NUREG/CR-4527/Vl, Albuquerque: Sandia National

Laboratories, April 1987.

30. An Experimental Investigation of Internally Ignited Fires in Nuclear

Power Plant Cabinets, Part II - Room Effects Tests, SAND86-0336,

NUREG/CR-4527/V2, Albuquerque: Sandia National Laboratories, October

1988.

31. Safety Research Programs Sponsored by Office of Nuclear Regulatory

Research, Brookhaven National Laboratories, BNL-NUREG-51454 Vol 7

No. 2 and 3, NUREG/CR-2331, June 1988.

32. Enclosure Environment Characterization Testing for Base Line

Validation of Computer Fire Simulation Codes, SAND86-1296, NUREG/CR4681, Albuquerque: Sandia National Laboratories, March 1987.

33. A. Tewarson, et.al., "Categorization of Cable Flammability Part I:

Laboratory Evaluation of Cable Flammability Parameters,", Electrical

Power Research Inst., EPRI NP-1200, Oct 1979.

34. J.L. Lee, et.al., "A Study of Damageability of Electrical Cables in

Simulated Fire Environments," EPRI NP-1767, March 1981.

35. Transient Fire Environment Cable Damageability Test Results.

Phase I, SAND86-0839, NUREG/CR-4638, Albuquerque: Sandia National

Laboratories, September 1986.

-124-
APPENDIX A

BIBLIOGRAPHY LISTING OF SNL/USNRC FIRE PROTECTION RESARCH

PROGRAM.PUBLICATIONS WITH CROSS REFERENCE LISTING OF

MAJOR REPRORTS TO SPECIFIC RESEARCH EFFORTS

-125-

APPENDIX A-I

LISTING OF FORMAL REPORTS, JOURNAL ARTICLES, AND PUBLISHED CONFERENCE

PAPERS GENERATED BY THE USNRC/SNL FIRE PROTECTION RESEARCH PROGRAM

BETWEEN THE YEARS 1975 AND 1988

A-I. Report on Task I. Fire Proteetion System Study, SAND76-0630,

NUREG76-6516, Albuquerque: Sandia National Laboratories, February

1977.

A-2. "Nuclear Power Plant Fire Protection Research," SAND 77-0389A, ANS

Topical Meeting, Chattanooga, TN, August 1977.

A-3. A Preliminary Report on Fire Protection Research Program (July 6.

1977), SAND77-1424, Albuquerque: Sandia National Laboratories,

October 1977.

A-4. "Cable Tray Fire Tests," SAND77-1125C, National Academy of Sciences

Conference on Electrical Insulation and Dielectric Phenomena, Albany,

NY, October 1977.

A-5. "Fire Protection Research Project," SAND77-1768C, Albuquerque: Sandia

National Laboratories, Fifth Water Reactor Safety Research

Information Meeting, Gaithersburg, MD, November 1977.

A-6. A Preliminary Report on Fire Protection Research Program Fire

Retardant Coatings Tests (December 7. 1977 - January 31, 1978),

SAND78-0518, Albuquerque: Sandia National Laboratories, March 1978.

A-7. Fire Protection Research Ouarterly Progress Report (October -

December 1977), SAND78-0477, NUREG/CR-0366, Albuquerque: Sandia

National Laboratories, August 1978.

A-8. A Preliminary Report on Fire Protection Research Program Fire

Barriers and Fire Retardant Coatings Tests, SAND78-1456,

NUREG/CR-0381, Albuquerque: Sandia National Laboratories, Septembe'r

1978.

A-9. "Status of the Fire Protection Research (FPR) Program," SAND78-2025C,

Albuquerque: Sandia National Laboratories, Sixth Water Reactor Safety

Research Information Meeting, Gaithersburg, MD, November 1978.

0

A-10. A Preliminary Report on Fire Protection Research Program Fire

Barriers and Suppression (September 15. 1978 Test), SAND78-2238,

NUREG/CR-0596, Albuquerque: Sandia National Laboratories, December

1978.

-127-
A-Il. "Cable Tray Fire Tests," SAND78-1810C, Albuquerque: Sandia National

Laboratories, PES-IEEE.1979 Winter Power Meeting, New York, NY,

February 1979.

A-12. "Fire Research on Grouped Electrical Cables," SAND79-0031A,

Albuquerque: Sandia National Laboratories, Sixth Annual Energy

Conference and Exhibition, WATTec, Knoxville, TN, February 1979.

A-13. Nuclear Power Plant Fire Protection-Fire Detection (Subsystems Study

Task 2), SAND78-1373, NUREG/CR-0488, Albuquerque: Sandia National

Laboratories, March 1979.

A-14. "Status of Fire Protection Research Program," SAND79-0882A,

Albuquerque: Sandia National Laboratories, Nuclear Power Industry

Symposium, Houston, TX, June 1979.

A-15. Nuclear Power Plant Fire Protection-Ventilation (Subsystems Study

Task 1), SAND79-0263, NUREG/CR-0636, Albuquerque: Sandia National

Laboratories, August 1979.

A-16. Nuclear Power Plant Fire Protection-Fire Barriers (Subsystems Study

Task 3), SAND78-1990, NUREG/CR-0468, Albuquerque: Sandia National

Laboratories, September 1979.

A-17. Nuclear Power Plant Fire Protection-Fire Hazards Analysis (Subsystems

Study Task 4), SAND79-0324, NUREG/CR-0654, Albuquerque: Sandia

National Laboratories, September 1979.

A-18. "Fire Protection Research Program," SAND79-1593A, Albuquerque: Sandia

National Laboratories, Institute of Electrical Engineers of Japan,

October 1979.

A-19. "Status of the Fire Protection Research (FPR) Program," SAND79-2020C,

Albuquerque: Sandia National Laboratories, Seventh Water Reactor

Safety Research Information Meeting, Gaithersburg, MD, November 1979.

A-20. "Burning Characteristics of Horizontal Cable Trays," Seventh Water

Reactor Safety Research Information Meeting, Gaithersburg, MD,

November 1979.

A-21. Fire Protection Research Program Corner Effects Tests, SAND79-0966,

NUREG/CR-0833, Albuquerque: Sandia National Laboratories, December

1979.

A-22. "Fire Protection for Grouped Electrical Cables," SAND80-0244A,

Albuquerque: Sandia National Laboratories, Seventh Annual Energy

Conference and Exhibition, WATTec, Knoxville, TN, February 1980.

-128-
A-23. "Fire Protection Research Program at Sandia Laboratories,"

SAND80-0880C, Albuquerque: Sandia National Laboratories, ANS/ENS

Topical Meeting, Thermal Reactor Safety, Knoxville, TN, April 1980.

A-24. Nuclear Power Plant Fire Protection - Philosophy and Analysis,

SAND80-0334, Albuquerque: Sandia National Laboratories, May 1980.

A-25. "Fire Protection Research Program at Sandia National Laboratories,"

SAND80-2422C, Albuquerque: Sandia National Laboratories, Eight Water

Reactor Safety Research Information Meeting, Gaithersburg, MD,

October 1980.

A-26. "Analysis of Fire Barriets Within Nuclear Power Plants," Nuclear

Technology, 53:204, May 1981.

A-27. "A Network Analysis of Fire Protection," SAND8l-0528J, Albuquerque:

Sandia National Laboratories, June 1981.

A-28. "Nuclear Power Plant Electrical Cable Burn Modes," SAND80-2816C,

Albuquerque: Sandia National Laboratories, American Nuclear Society

Annual Meeting, Miami, FL, June 1981.

A-29. Investigation of Fire Stop Test Parameters: Final Report,

SAND81-7144, NUREG/CR-2321, September 1981.

A-30. Tests and Criteria for Fire Protection of Cable Penetrations,

SAND81-7160, NUREG/CR-2377, Albuquerque: Sandia National

Laboratories, October 1981.

A-31. Cost Estimates for Providing Active and Passive Fire Protection

Measures in Nuclear Power Plants, SAND81-7169, Albuquerque: Sandia

National Laboratories, November 1981.

A-32. Burn Mode Analysis of Horizontal Cable Tray Fires, SAND81-0079,

NUREG/CR-2431, Albuquerque: Sandia National Laboratories, December

1981.

A-33. FIRE: A Subroutine for Fire Protection Network Analysis, SAND81-1261,

Albuquerque: Sandia National Laboratories, December 1981.

A-34. Requirements for Establishing Detector Siting Criteria in Fires

Involving Electrical Materials, SAND8l-7168, NUREG/CR-2409,

Albuquerque: Sandia National Laboratories, July 1982.

A-35. Aging Effects on Fire-Retardant Additives in Organic Materials for

Nuclear Plant Applications, SAND82-0485, NUREG/CR-2868, Albuquerque:

Sandia National Laboratories, August 1982.

-129-
A-36. A Systematic Approach to the Identification and Protection from Fire

of Vital Areas Within Nuclear Power Plants, SAND82-0648, Albuquerque:

Sandia National Laboratories, October 1982.

A-37. Nuclear Power Plant Electrical Cable Damageability Experiments,

SAND82-0236, NUREG/CR-2927, Albuquerque: Sandia National

Laboratories, October 1982.

A-38. "Cable Fire Testing to Meet Realistic Design Criteria," International

Conference on Polymer Insulated Power Cables, Paris, France, March

1983.

A-39. "Cable Tray Fire Experimentation," SAND83-0292C, Albuquerque: Sandia

National Laboratories, CSNI Specialist Meeting on Fire and Explosion

with Ventilation Systems in Nuclear Power Plants, Los Alamos, NM,

April 25-28, 1983.

A-40. Fire Protection Research Program for The Nuclear Regulatory

Commission, 1975-1981, SAND82-0431, NUREG/CR-2607, Albuquerque:

Sandia National Laboratories, April 1983.

A-41. Vulnerability of Nuclear Power Plant Structures to Large External

Fires, SAND83-1178, NUREG/CR-3330, Albuquerque: Sandia National

Laboratories, August 1983.

A-42. Investigation of Twenty-Foot Separation Distance as a Fire Protection

Method as Specified in 10 CFR 50, Appendix R, SAND83-0306,

NUREG/CR-3192, Albuquerque: Sandia National Laboratories, October

1983.

A-43. "The Relationship of Fire Protection Research to Plant Safety,"

SAND83-2251C, Albuquerque: Sandia National Laboratories, Eleventh

Water Reactor Safety Research Information Meeting, Gaithersburg, MD,

October 1983.

A-44. "Fire Protection Research for Nuclear Power Plants," SAND83-2353A,

Albuquerque: Sandia National Laboratories, Eleventh Annual WATTec

Conference, February 1984.

A-45. "Nuclear Power Plant Cable Damageability Testing," SAND84-2551A,

Albuquerque: Sandia National Laboratories, Twelfth Annual WATTec

Conference, February 1985.

A-46. "Fire Protection and Hydrogen Burn Equipment Survival Research at

Sandia National Laboratories," SAND85-1818A, Albuquerque: Sandia

National Laboratories, Thirteenth Water Reactor Safety Research

Information Meeting, Gaithersburg, MD, October 1985.

-130-
A-47. Investigation of Potential Fire-Related Damage to Safety- Related

Equipment in Nuclear Power Plants, SAND85-7247, NUREG/CR-4310,

Albuquerque: Sandia National Laboratories": November 1985.

A-48. "Large-Scale Fire Testing," SAND85-2287A, Albuquerque: Sandia

National Laboratories, Thirteenth Annual WATTec Conference, February

1986.

A-49. Screening Tests of Representative Nuclear Power Plant Components

Exposed to Secondary Fire Environments, SAND86-0394, NUREG/CR-4596,

Albuquerque: Sandia National Laboratories, June 1986.

A-50. Description and Testing of an Apparatus for Electrically Initiated

Fires Through Simulation of a Faulty Connection, SAND86-0299,

NUREG/CR-4570, Albuquerque: Sandia National Laboratories, June 1986.

A-51. Users Guide for a Personal-Computer-Based Nuclear Power Plant Fire

Data Base, SAND86-0300, NUREG/CR-4586, Albuquerque: Sandia National

Laboratories, August 1986.

A-52. Transient Fire Environment Cable Damageability Test Results, Phase I,

SAND86-0839, NUREG/CR-4638, Albuquerque: Sandia National

Laboratories, September 1986.

A-53. "Large-Scale Tests to Evaluate Enclosure Fire Environments,"

SAND86-0805C, Albuquerque: Sandia National Laboratories,

International ANS/ENS Topical Meeting, September 1986.

A-54. "Safety Significance of Fires," SAND86-0834C, Albuquerque: Sandia

National Laboratories, International ANS/ENS Topical Meeting,

September 1986.

A-55. "Screening Tests of Component Survivability in Secondary Environments

Produced by Fire," SAND86-0724C, Albuquerque: Sandia National

Laboratories, International ANS/ENS Topical Meeting, September 1986.

A-56. Heat and Mass Release Rates for Some Transient Fuel Source Fires, A

Test Report, SAND86-0312, NUREG/CR-4680, Albuquerque: Sandia National

Laboratories, October 1986.

A-57. Evaluation of SuRpression Methods for Electrical Cable Fires,

SAND83-2664, NUREG/CR-3656, Albuquerque: Sandia National

Laboratories, October 1986.

A-58. Enclosure Environment Characterization Testing for Base Line

Validation of Computer Fire Simulation Codes, SAND86-1296,

NUREC/CR-4681, Albuquerque: Sandia National Laboratories, March 1987.

-131-
A-59. Quantitative Data on the Fire Behavior of Combustible Material Found

in Nuclear Power Plants. A Literature Review, SAND86-0311,

NUREG/CR-4679, Albuquerque: Sandia National Laboratories, February

1987.

A-60. An Experimental Investigation of Internally Ignited Fires in Nuclear

Power Plant Control Cabinets, Part I - Cabinet Effects Tests,

SAND86-0336, NUREG/CR-4527;Vl, Albuquerque: Sandia National

Laboratories, April 1987.

A-61. "Investigation of Smoke Corrosivity in Nuclear Power Plant

Equipment," SAND87-2484C, International Conference on the Corrosive

Effects of Combustion Products, London England, October 13-14, 1987.

A-62. An Experimental Investigation of Internally Ignited Fires in Nuclear

Power Plant Cabinets, Part II - Room Effects Tests, SAND86-0336,

NUREG/CR-4527;V2, Albuquerque: Sandia National Laboratories, October

1988.

A-63. Fire Risk Scoping Study: Investigation of Nuclear Power Plant Fire

Risk, Including Previously Unaddressed Issues, SAND88-0177,

NUREG/CR-5088, Albuquerque: Sandia National Laboratories, December

1988.

-132-
APPENDIX A-2

CROSS REFERENCE LISTING OF MAJOR REPORTS TO SPECIFIC

FIRE PROTECTION RESEARCH PROGRAM EFFORTS

Experirental Studies:

1976 Electrically Initiated Cable Fire Tests

SAND77-1125C, A-4

SAND82-0431, NUREG/CR-2607, A-40

1977 Exposure Fire Cable Fire Tests

SAND77-1424, A-3

SAND82-0431, NUREG/CR-2607, A-40

1978 Fire Retardant Cable Coating Tests

SAND78-0477, NUREG/CR-0366, A-7

SAND78-0518, A-6

SAND78-1456, NUREG/CR-0381, A-8

SAND82-0431, NUREG/CR-2607, A-40

1978 Cable Tray Fire Barrier Tests

SAND78-1456, NUREG/CR-0381, A-8

SAND78-2238, NUREG/CR-0596, A-10

SAND82-0431, NUREG/CR-2607, A-40

1979 Cable Tray Fire Corner Effects Tests

SAND79-0966, NUREG/CR-0833, A-21

SAND82-0431, NUREG/CR-2607, A-40

1980 Investigation of Fire Stop Test Parameters

SAND81-7144, NUREG/CR-2321, A-29

SAND82-0431, NUREG/CR-2607, A-40

1981 Cable Radiant and Convective Heating Damage Tests

SAND82-0236, NUREG/CR-2927, A-37

1981 Trash/Pool Fire Correlation Tests

SAND83-D306, NUREG/CR-3192, A-42

1982 Twenty-Foot Separation Adequacy Investigations

SAND83-0306, NUREG/CR-3192, A-42

ALSO SEE APPENDIX A OF THIS REPORT

1980-83 Fire Suppression System Effectiveness Investigations:

SAND83-2664, NUREG/CR-3656, A-57

1984 Cable Steady State Thermal Damage Tests

SEE APPENDIX B OF THIS REPORT

1985 Cable Transient Thermal Damage Tests

SAND86-0839, NUREG/CR-4638, A-52

1985 Relay Thermal Damage Tests

SAND86-0394, NUREG/CR-4596, A-49

1985 Component Testing in Secondary Fire Environments

SAND86-0394, NUREG/CR-4596, A-49

1985 Development of Electrical Ignition Apparatus

SAND86-0299, NUREG/CR-4570, A-50

-133-
1985 Transient Fuel Source Fire Tests

SAND86-0312, NUREG/CR-4680, A-56

1985 Base Line Validation Enclosure Fire Tests

SAND86-1296, NUREG/CR-4681, A-58

1985 Electrical Cabinet and Control Room Fire Tests

SAND86-0336/V-I, NUREG/CR-4527/V-I, A-60

SAND86-0336/V-II, NUREG/CR-4527/V-II, A-62

Analytical Studies:

1975 Cable Use Screening Survey

SAND82-0431, NUREG/CR-2607, A-40

1976 Fire Protection Systems Study

SAND76-0630, NUREG76-6516, A-1

1979 Fire Protection Subsystems Study

SAND78-1373, NUREG/CR-0488, A-13

SAND79-0263, NUREG/CR-0636, A-15

SAND78-1990, NUREG/CR-0468, A-16

SAND79-0324, NUREG/CR-0654, A-17

1981 Burn Mode Analysis of Cable Fires

SAND8l-0079, NUREG/CR-2431, A-32

1981 Cost Analysis of Fire Protection Systems

SAND81-7196, A-31

1982 Detector Siting Criteria Requirements Study

SAND81-7168, NUREG/CR-2409, A-34

1984 Identification and Classification of Transient Fuel

SEE APPENDIX C OF THIS REPORT

1985 Review of Fire Characterization Data

SAND86-0311, NUREG/CR-4679, A-59

1986 Development of Nuclear Power Plant Fire Occurrence Data Base

SAND86-0300, NUREG/CR-4586, A-5I

1985 Equipment Damage Sensitivity Ranking Study.

SAND85-7247, NUREG/CR-4310, A-47

-134-
DISTRIBUTION:

U. S. Nuclear Regulatory Commission

Attn: William Farmer (10)

Office of Nuclear Regulatory Research

Washington, DC 20555

U. S. Nuclear Regulatory Commission

Attn: John Flack

Office of Nuclear Regulatory Research

Washington, DC 20555

U. S. Department of Energy

Attn: Andrew J. Pryor

Albuquerque Operations Office

PO Box 5400

Albuquerque, NM 87115

U. S. Department of Energy

Attn: Carl A. Caves

Walter W. Maybee

Mail Stop EG-34

Washington, DC 20545

U. S. Department of Energy

Attn: Justin T. Zamirowski

9800 S. Cass Ave.

Argonne, IL 60439

U. S. Department of the Navy

David M. Taylor Naval Ship

Research and Development Center

Attn: M. Allen Matteson

Mail Code 1740.2

Bethesda, MD 20084-5000

U. S. Department of the Navy

Attn: David Satterfield

National Center #4, Room 311

Naval Sea System Command (56Y52)

Washington, DC 20362

Lawrence Livermore National Laboratory

Attn: Harry Hasegawa

Mail Stop L-442

PO Box 5505

Livermore, CA 94550

Brookhaven National Laboratories

Attn: John Boccio

Bld. 130

Upton, NY 11793

Westinghouse Electric Corp.

Bettis Atomic Power Laboratory

Attn: Craig Markus, ZAP 34N

PO Box 79

West Mifflin, PA 15122-0079

Impell Corporation

Attn: Collin A. Lewis

John E. Echternacht

350 Lennon Ln.

Walnut Creek, CA 94598

Impell Corporation

Attn: Stanley J. Chingo

300 Tri-State International

Suite 300

Lincolnshire, IL 60015

Professional Loss Control

Attn: Kenneth Dungan

PO Box 446

Oak Ridge, TN 37830

Electric Power Research Institute

Attn: Jean-Pierre Sursock

Nuclear Power Division

3412 Hillview Ave.

Palo Alto, CA 94303

American Nuclear Insurers

Attn: D. Sherman, Library

Exchange Building, Suite 245

270 Farmington Ave.

Farmington, CT 06032

Underwriters Laboratories

Attn: Leon Przybyla

333 Pfingston Rd.

Northbrook, IL 60062

Patton Fire Suppression Systems

Attn: Richard Patton

5316 Roseville Rd., Suite P

North Highlands, CA 95660

DIST-1
Factory Mutual Research Corporation

Attn: Jeff Newman

1151.Boston-Providence Hwy.

Norwood, MA 02062

American Electric Power Service Corp.

Attn: Jack Grier

Mechanical Engineering Division

19th Floor

PO Box 16631

Columbus, OH 43216

Grinnell Fire Protection Co.

Attn: Joe Priest

10 Dorrance St.

Providence, RI 02903

Edison Electric Institute

Attn: Jim Evans

111 19th St., NW

Washington, DC 20036-3691

Wisconsin Electric Power Co.

Attn: Michael S. Kaminski

Fire Protection Officer, A-543

333 W. Everett St.

Milwaukee, WI 53203

Arkansas Power and Light

Attn: Ron Rospoli

PO Box 137G

Russelville, AR 72801

Gesamthoshschule Kassel

Attn: Ulrich Heinze Schneider

Universitat das Landes Hessen

FB 14, Postfach 101380

3500 Kassel

FEDERAL REPUBLIC OF GERMANY

Koning und Heunisch

Attn: Dietmar Hosser

Lezter Hasenpfach 21

6000 Frankfurt/Main 70

FEDERAL REPUBLIC OF GERMANY

Geselschaft fur Reaktorsicherheit

Attn: Mr. Liemersdorf

Scwertnergasse 1

D-5000 Koln 1

FEDERAL REPUBLIC OF GERMANY

Centre Scientifique et

Technique du Batiment

Attn: Xavier Bodart

Station de Recherche

84 Avenue Jean-Jaures-Champs-sur-Marne

77428 Marne-La-Vallee Cedex 2

FRANCE

Societe Bertin & Cie

Attn: Serge Galant

BP No. 3

78373 Plaisir Cedex

FRANCE

Electricite De France

Attn: Jean Pierre Berthet

Thermal Production Headquarters

EDF-DSRE-6, Rue Ampere

BP 114

93203 Saint Denis Cedex I

FRANCE

HM Nuclear Installations Inspectorate

Attn: Paul A. Woodhouse

St. Peters House

Stanley Precinct

Balliol Road

Bootle

Merseyside L20 3LZ

ENGLAND

NUPEC

Attn: Kenji Takumi

No. 2 Akiyama Building

6-2, 3-Chome, Toranomon

Minatoku, Tokyo 105

JAPAN

Internal SNL:

3141 S. A.

3151 W. I.

6400 D. J.

6410 D. A.

6412 A. L.

6415 R. M.

6416 E. J.

6419 M. P.

6419 S. P.

6419 J. A.

6420 W. B.

6450 T..R.

8524 J. A.

Landenberger (5)

Klein

McCloskey

Dahlgren

Camp.

Cranwell

Bonano

Bohn

Nowlen (25)

Lambright

Gauster

Schmidt

Wackerly

DIST-2
FUS. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

0249) (A-12hfd bY NRC. Add VOL.. B•pýI. Rev.. NRCM ' 102. "•Adclenlum Nwnbe• I| am.)

3201.3202 BIBLIOGRAPHIC DATA SHEET

2TILANSUTTEISO*M~fCI huaxio ono eu NUREG/CR- 5384

.TITLE AND SUBTITLE .... SAND89 -1359

A Summary of Nuclear Power Plant Fire Safety Research 3. DATE REPORT PUBLISHED

at Sandia National Laboratories, 1975-1987 MONTH YEAR

December 1989

4. FIN OR GRANT NUMBER

-FIN AI010

S. AUTHOR(S) 6. TYPE OF REPORT

S. P. Nowlen

7. PERIOD COVERED alncusi. Oevas

S. PERFORMING ORGANIZATION - NAME AND ADDRESS Ul1 NRC. Pwrov Olvhloa. Ofc eorifgio. US Nooke ReZultory Cormn . onda g• address: 1conera•.. Pr.ovide mwn makl 4'dduess.

Sandia National Laboratories

Albuquerque, NM 87185

I. SPONSORING ORGANIZATION - NAME AND ADDRESS OI NRC 'P rVonNRC %. e. Off ict eflan. U-1 Nu-MearguMW'V Commi;sson.

end mek~g addrem)~

Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

10. SUPPLEMENTARY NOTES

11. ABSTRACT lOW wor dsoeru

This report summarizes the results and conclusions generated by the U. S. Nuclear

Regulatory Commission sponsored Fire Protection Research Program at Sandia National

Laboratories. Efforts conducted from the programs inception in 1975 through 1987 are

discussed. The report provides a complete bibliography of reports and journal articles

generated as a result of these efforts with a cross-reference listing of major reports

to specific efforts. Among the topics investigated by various experimental efforts are

the effectiveness of fire retardant cable coatings and cable tray fire barrier systems

in the prevention of fire spread and fire induced damage, the effectiveness of

suppression methods for cable tray fires, testing of cable penetration seals, transient

fuel fire characterization testing, investigation of electrical cabinet and control

room fires, equipment damageability testing, and large scale enclosure fire testing for

the validation of computer fire simulation codes. Topics investigated as a part of

analytical efforts include a review of the fire regulations which bear relevance to

nuclear plants, investigation of the standards and strategies invoked in the design of

various fire protection subsystems, the modeling of cable fire behavior, the

identification of reported transient fuel sources, and the development of a fire

occurrence data base.

12. KEY WORDS/DESCRIPTORS ¢/.wth, etphreset . YerUarchee h loating hon•j 13. AVAILABILITY STATEMENT

Unlimited

Fire Safety, Nuclear Power Plant Fire Safety, •SECURiTY a. CLASSfCATION

Fire Protection, Fire Characterization, Fire Research IThisP

Unclassified

IT~hi Reponi

Unclassified

15. NUMBER OF PAGES

16. PRICE

NRC FORM 335 0249)

'U. S.GOVERNICIENT PRINTING arrICEs¶989-262-436010372


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OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE, $300

SPECIAL FOURTH-CLASS RATE

POSTAGE & FEES PAID

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PERMIT No. G-67 |

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