REFERENCE 2f*' PUBLICAT

NBSIR 85-3195

Heat Release Rate Characteristics

of Some Combustible Fuel

Sources in Nuclear Power Plants

NAT'L INST. OF STAND & TECH

AlllDb D3M31

B.T. Lee

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Gaithersburg, MD 20899

July 1985

QC ^ 100

.056

85-3195

1985

Sponsored in part by

U.S. Nuclear Regulatory Commission

Washington, DC 20555

ITATIONflL BUREAU OF STANDARDS

IIERARY

NBSIR 85-3195

HEAT RELEASE RATE CHARACTERISTICS

OF SOME COMBUSTIBLE FUEL

SOURCES IN NUCLEAR POWER PLANTS

B.T. Lee

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Gaithersburg, MD 20899

July 1985

Sponsored in part by

U.S. Nuclear Regulatory Commission

Washington, DC 20555

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretsry

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Dinctor
I

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Table of Contents

Page

List of Tables iy

List of Figures y

Abstract yj^

1. Introduction 2. 2. Cable Tray Burn Characteristics 2 3. Trash Fire Burn Characteristics 5

4. Wood Fire Burn Characteristics ^

5. Combustible Liquid Burn Characteristics g

5.1 For Combustible Fluid Depth > 20 mm . . g

5.2 Finite Depth Spills Opaque to Thermal Radiation 21

5.3 Finite Depth Spills Transparent to Thermal Radiation .... 22

6. Summary 23

7. References 24

iii
List of Tables

Page

Table 1. Heat Release Rate Per Unit Area and Heat of Combustion

^ for Flaming Fire of Cable Samples in Normal Air at 60 kW/m 17

Table 2. Simulated Trash Fire Experiments at Sandia National

Labortories 18

Table 3. Ignition and Flame Spread Characteristics Under Constant

Irradiance Conditions 19

Table 4. Rate of Heat Release per Unit Area for Selected Wood

Products 20

Table 5. Unconfined Spill Depths for Hydrocarbon Liquids on EpoxyCoated Concrete and Steel 21

Table 6

Data for Large Pool Burning Rate Estimates 22

Table 7. Radiation Fraction of Combustion Energy for Hydrocarbon

Pool Fires 23

IV
List of Figures

Page

Figure 1. Laboratory-Scale Flammability Apparatus 24

Figure 2. Horizontal Tray Test Setup 25

Figure 3. Mixed Tray Test Setup 26

Figure 4. Tray Surface Area Over Fire-Affected Cables Versus

Burning Rate for PE/PVC Cables 27

Figure 5. Versus 28

Figure 6. Fire Involved Area Versus Time 29

Figure 7. Rate of Fire Coverage Versus Rate of Heat Release 30

Figure 8. Trash Fires 31

Figure 9. Trash Fires 32

Figure 10. Fire Tests of Piles of Clothes and Fabrics 33

Figure 11. Heat Release Rate Correlation with Size of Trash Fire 34

Figure 12. Heat Release Rate Correlation with Size of Trash Fire 35

Figure 13. Envelope Containing All of the Observed Heat Release

Rate Curves for Trash Fires 36

Figure 14. Correlation of Velocity with Flux 37

Figure 15. Envelope Containing Velocity Versus Flux Data for

Wood Products 38

Figure 16. Average Maximum Burning Rate vs Pile Height 39

Figure 17. Heat Release Rate for Single Stacks of Wood Pallets 40

Figure 18. Measured Surface Temperature of an Opaque, Semiinfinite Medium Compared with Theory Using Three

Different Values of Net Flux of 13.8, 8.9 and 6.8

2 2

kW/m and An External Flux of 13.8 kW/m

Figure 19. Measured Surface Temperature (Shaded Region) of Four

Semi-transparent, semi-infinite. Hydrocarbon Liquids

2 Compared with Theory Using a Net Flux of 10 kW/m and

2

An External Flux of 13.8 kW/m ^2

Figure 20. Comparison of Theory and Experiment for Net Flux of

2 2 15.6 kW/m and An External Flux of 26 kW/m 43

Figure 21. Comparison of Experiment and the Range Predicted by

two Theoretical Limits for An Unconfined Spill of

Pennzoil 30-HD on a Steel Substrate 44

Figure 22. Unconfined Spill of Pennzoil 30-HD on An EpoxyCoated Concrete Substrate 45

V
Abstract

A major risk to a nuclear power plant is the possibility of serious fire.

There is a need to know the heat release rate behavior of combustible

fuels in the plant in order to help reduce the fire threat to these

facilities. Heat release rate characteristics of cable tray fires

and some of the associated potential external ignition sources are discussed. Existing correlations are given to determining the time

to ignition and the subsequent heat release rate of spills and pools

of flammable liquids. Approximate correlations are developed for heat

release rate for trash fires as a function of fire size and for one particular cable tray array arrangement as a function of the type of

cable. In addition, a scheme is given for calculating the heat release

rate from wood fuel fires.

key words: cable trays; fire safety; flammability; flammable liquids;

heat release rate; ignition, liquid spills; nuclear power

plants; pool fires; small-scale fire tests; trash; wood

VI
1.0 Introduction

Cable fires pose a serious fire hazard to a nuclear power plant. In 1975

a major cable fire shut down the world's largest operating nuclear plant,

the Browns Ferry Nuclear Facility. It is generally agreed that ignition and

subsequent fire involvement of cables in an utility plant would probably occur

as a consequence of exposure to an external fire rather than from self-heating

due to overloading or short-circuiting of the cables. External fires could be

associated with a spill of flammable liquid, with a quantity of trash, with

wood fuel in the form of boards, ladders, scaffolding, pallets, etc., or with

a combination of such combustible sources.

The U.S. Nuclear Regulatory Commission is interested in identifying data and

modeling or predicting techniques that can be used to extend the existing burn

characteristics of cables and of such "first item" burn sources. This is one

of the tasks in support of the Risk Methodology Integration and Evaluation

Program (RMIEP) for the U.S. Nuclear Regulatory Commission. Other tasks of the

RMIEP program involve the identification of usable models for the activation

of detection and suppression devices, the Identification of candidate room

fire models for use in the RMIEP program, and the identification of areas where the modeling capability can be substantially enhanced for future nuclear

power plant risk analyses. These other tasks are not addressed further in this

report

This report summarizes current information on the heat release rate characteristics

of power cables and some of the associated potential external ignition sources.

It includes the development of approximate correlations for heat release rate

for trash fires as a function of fire size and for one particular cable tray

array arrangement as a function of the type of cable. In addition, a scheme

is presented for calculating the heat release rate from wood fuel fires.

1
2.0 Cable Tray Array Burn Characteristics

A review of the literature on cable tray fires indicated that there were no reliable prediction models for the rate of heat release, nor were there direct

heat release rate data available, on the burning of full-scale or intermediatescale cable tray arrays. This finding was consistent with a review of the subject

by Nowlen [1]. Nowlen [2] has estimated the heat release rate from a fire test

of two vertical cable trays burning over a 5 gal heptane fire based on heat loss

measurements from the room. However, he did not separate the relative contribution

due to the cables alone from that portion of the heat release rate due to the

heptane. Hasegawa, et al, [3] attempted unsuccessfully to measure directly the

heat release rate of cables burning in a single vertical array. They were able

to measure weight loss which can be used to calculate the heat release rate.

Unfortunately, extrapolation of data from fire tests of one or two cable trays

to large tray array fires is hopelessly complicated by an inadequate understanding

of fire-spread and themnal feedback among cable trays and the effect of vitiated

air within the array.

Weight loss data have also been measured by Sumitra [4] in a series of intermediatescale fires involving arrays of 12 to 15 cable trays. This data together with

actual heats of combustion for the cables would result in heat release rates for

these fires. The heat of combustion and the unit area heat release rate of a variety of cable samples, including those used in Sumitra 's tests, have been

measured by Tewarson [5] with his laboratory-scale test shown in Figure 1 for

2

the flaming mode of combustion under an irradiance exposure of 60 kw/m . This

data is given in Table 1. With such limited information, the approach adopted

here was to base a prediction scheme on a correlation of Sumitra 's data with

Tewarson’ s laboratory-scale data and to use the latter, in turn, to help predict

array fire behavior for other types of cables.

Sumitra used two test arrangements using open ladder type of trays. For tests

1-14 with just horizontal trays, the array of twelve trays shown in Figure 2 was used. For tests 15-17, a mixed arrangement of twelve horizontal trays and

2
three vertical trays, shown in Figure 3, was used. As indicated in Figures 2

and 3, a pan of heptane served as the ignition source. The estimated area of

fire involvement in the trays at the time of extinguishment was given by

Sumitra for tests 5 to 9 and 13 to 16. Fire affected areas were also given

for tests 10 and 11 where the fire self-extinguished. The fire involved area

reported in each case was not the sum of the affected surface area of each

individual cable but rather the exposed tray surface area over the fire affected

cables. For example, each of the 2.44 x 0.46 m open trays had a maximum fire

2 2

involvement area of 1.12 m on the top, and 1.12 m on the bottom. When the

burning rate at the time of extinguishment was plotted as a function of the fire

involved area for the PE/PVC cables in Figure 4, the burning rate was found to

vary linearly with the area of involvement. The burning rates at extinguishment

were measured between 8 and 15.5 minutes, well beyond the duration of the heptane

ignition source fires which burned out between 6 and 6.8 minutes.

The rate of heat release can be calculated either with the burning rate or with the fire involved surface area using the following equations;

- A HjXa (1)

Qa = q"A (2)

• — Rate of heat release based on mass loss (kw) — Rate of heat release based on pyrolysis area (kw)

m — Rate of mass loss (kg/s) — kJ Net heat of complete combustion (—

)

T g — Combustion efficiency

^ 2 q" — Rate of heat release per unit area from Laboratory test (kW/m ) 2

A — Pyrolysis area (m )

The quantity q" and the product measured by Tewarson are given in Table 1 under the headings of actual heat release rate per unit area and actual heat

of combustion. is plotted against in Figure 5 for tests 5 to 9 and 13

to 16. The correlation shows that

5
(3) m

0.45

The cable materials PE/PVC, Hypalon, and silicone/asbestos indicated in Figure 5

correspond to cable samples 5, 8, and 22 in Table 1. The cable tests with the

PE/PVC and with the silicone/asbestos used an extra tight packing arrangement.

The Hypalon cable tests used packing arrangements ranging from loose (test 11)

to extra tight (test 10). However, both tests 10 and 11 had burning rates of

only about 0.1 kg/min with predominantly scorching rather than pyrolysis of

the fire affected areas by the heptane ignition source. Consequently, these

two tests were not considered for the correlation in Figure 5. Tests 13 and 14

with the Hypalon cables in a different loose arrangement exhibited more vigorous

burning rates of 6.6 and 3.3 kg/min. Sumitra stated that for unknown reasons,

the Hypalon was difficult to ignite. Given this erratic behavior for the

Hypalon cables, it was decided to consider only the worst case, test 13, for

the Hypalon cables in the correlation in Figure 5.

Figure 6 shows the estimated area of fire involvement plotted against time of

extinguishment for the three cable types. The slope of each line from Figure 6, or rate of fire coverage, is then plotted versus Tewarson’s unit area heat release

rate values from his laboratory test apparatus in Figure 7. The approach used for

Figure 7 was similar to that adopted by Parker [6] where it was assumed that the

flame area in the ASTM E 84 tunnel test was proportional to the total rate of

heat production.

Figure 7 can, in turn, be used to estimate the rate of fire coverage for other

types of cables tested in Tewarson's apparatus. The resulting estimated history

for the pyrolyzing area, when multiplied with q” from Table 1, gives Q versus

time. Equation 3 then can be used to obtain as a function of time. This

prediction method applies only to cable array arrangements, cable packing densities,

and exposure fires similar to those tested by Sumitra. Hasegawa, et al, [3]

for instance, found that cable packing density could significantly affect the

burning rate of cable tray fires. Thus, use of the method for significantly

different situations may not be appropriate and would at best give only an approximation for the heat release rate of such cable tray fires.

4
3.0 Trash Fire Burn Characteristics

Trash fires by Van Volkinburg, et al [7], Lee [8], and Cline, et al [9] were

considered for this analysis. The data is given on Figures 8, 9, 10 and Table

2. Van Volkinburg ’s fires were conducted in a room such that re-radiation

from the hot gases and heated surfaces could reinforce the burning behavior

of the fuel. Peak ceiling temperatures ranged from 95 to 390“C for the trash

fires shown in Figures 8 and 9. This reinforcement would make the burning

rate somewhat high and thus conservative for hazard analysis. Excluded from

Figure 8 was a fire involving a 121 liter combustible wastebasket filled with

72 milk cartons, which exceeded a ceiling temperature of 400“C in a little

over 60 s and exceeded 800° C in 180 s. Radiative feedback varies as temperature

raised to the fourth power. At such elevated temperatures, the radiative

feedback would cause the burning rate to be excessively high and would be

too unrealistic for free-burning hazard analysis. It should be noted that the

temperature of 330°C indicated at 120 s for that fire was in error in

Volkinburg ’s report and should have been about 600°C to be consistent with

its heat release rate curve. Discussions with Fisher [10], one of the authors,

verified that conclusion.

In order to relate the heat release rate from the burning trash with the

size of the fire, an effective diameter for each trash fire had to be determined.

Obviously, only data where the size of the container was known could be used.

An examination of three waste container sizes of 30 gal, 20 gal and 8 gal at

the NBS fire test facility indicated an aspect ratio of height to diameter of

about 1.25, This ratio was assumed for Van Volkinburg 's and Cline's data.

Lee's data were for 0.3 m high piles of clothes and fabrics on the floor

and the actual pile diameters were used. For situations where two and three

similar bags were piled together, the effective diameters were taken to be

/2 and ^3 times the diameter of one bag, respectively. Figure 11 gives a correlation of the trash fire data. The quantity A is the area of the

container opening plus the exterior side area of a combustible container.

2 2 For example, a 32 gal container has 0.19 m on the top and 0.96 m on its sides.

The peak unit area heat release rate decreased with increasing diameter much

like that for liquid pool fires [11] in the laminar range of burning. For pool

5
fires, the rates increase with size for diameters between 0.3 and 1.0 m. This

behavior was absent in Figure 11. One important parameter lacking in the

correlation was packing density. The trash fires could be plotted as in

Figure 12 where two curves corresponding to packing densities of about 30 and

3

100 kg/m were observed. Lee's data had rates which were much lower than the

3 curve for the 30 kg/m packing density. The reason for this low rate was that

fire penetration into the piles of clothes and fabrics was limited by the pile

height of 0.3 m. Consequently, pyrolysis of the combustibles at depths greater

than 0.3 m , which certainly happened for the other trash fires, could not occur

and contribute to these fires. Without more experimental data on the role of

packing density, interpolation and extrapolation of the data in Figure 12 are difficult.

Figure 13 shows an envelope containing essentially all of the observed heat release

rate curves for the trash fires in Figure 11. The curve in Figure 13 was somewhat

low between 6 and 12 minutes for the rubbish bag fire and for Lee's data, but

the discrepancies were not serious. Figure 13 and Figure 11 may be used with

the awareness that the correlation was fairly crude and that heat release rates

might increase with diameter when an effective diameter exceeded a value of

about 1.0 m.

4.0 Wood Fire Burn Characteristics

Fires might not propagate or could spread slowly, rapidly, or almost spontaneously

on a wood surface depending on the incident flux environment. The effect of

incident flux on flame spread on simple wood configurations such as boards and even scaffolding is known. Once part of a board has ignited, involvement of

the vertical surface directly above the ignition area would be rapid. As an approximation, such vertical flame involvement could be assumed to be instantaneous.

Flame spread in the horizontal, lateral, and downward directions can not occur unless a critical flux level for that material has been achieved. Qulntiere and

Harkleroad [12] have tabulated this critical flux for flame spread, in

Table 3 for a variety of wood products. They also derived the following

expression for flame spread velocity:

6
where

and where V - flame spread velocity

c - specific heat

C - flame spread parameter

h - heat loss coefficient

k - thermal conductivity

M q . - critical flux for ignition

o,ig

q"(x) - external radiant flux

e b - parameter in equation

t - time

t^ - characteristic equilibrium time

p - density

Use of F(t) accounted for the transient heating of the solid. The quantities

q" , C, q" , , b, and t are given in Table 3 for several wood products. A

o , s o , ig m

typical plot of equation 4 is given in Figure 14, where the above quantities are further described. The quantity q^ can also be obtained by indirect measurement by extrapolating the data in Figure 4 to zero velocity. These extrapolated

values for

q|^ ^ are given in Table 3 under the heading of Number 2. An envelope

covering the flame spread velocity versus flux data for the wood products listed

in Table 3 is given in Figure 15.

Once the area of fire Involvement has been determined from flame spread

considerations, then it can be multiplied by its heat release rate per unit

area. Values for the latter are given by Chamberlain [13] in Table 4. As for
the radiative and convective components of wood fires, Atreya [14] has determined

these to be 23 and 77 percent, respectively, of the total heat release from

the fire.

In many Industrial and power plant facilities more complex configuration wood

fuels such as pallets may be present. Krasner [15] has studied the burning

characteristics of 4 ft x 4 ft x 5. 5 in pallets weighing 70 pounds each individually

as well as in multiple pallets piled in a single stack. The average maximum

burning rate, defined by Krasner to be the observed relatively constant rate

of maximum burning over a four to five minute period, is given in Figure 16 as

a function of height of the stack of pallets. Alpert and Ward [16] presented

the heat release rate histories for several stack heights. Their data is given

in Figure 17. From Figure 16, a 4 foot high stack has a maximum burning rate

of about 43 Ib/min, which when multiplied with a heat of combustion value of

about 7500 Btu/lb, results in the 4 minute average maximum value of about

5400 Btu/s in Figure 17.

5.0 Combustible Liquid Burn Characteristics

Accidental fires with flammable liquids could occur with the liquid exposed

in an opened container or with the liquid spilled on a surface. With a spilled

liquid, the fuel may be confined or unconfined. In general, the liquid depth

in a confined spill is expected to be greater than in an unconfined spill. For

unconfined spills on a perfectly level floor, the time for the liquid to spread

depends on the liquid viscosity and the roughness of the floor. The final

depth depends on the surface tension of the liquid and on the contact angle

between the liquid and the substrate.

Modak [17] has determined unconfined spill depths for hydrocarbon liquids on epoxy-coated concrete and steel floors. This data is given in Table 5. For pools

of flammable liquids, Babrauskas [18] recommended that the burning rate m" for

pools with diameters greater than 0.2 m be given by

8
( 6 )

00

and the heat release rate be given by

q = Ah . m" . A (7)

c

where:

A = pool area (m ) D = pool diameter (m)

Ah = heat of combustion (kJ/kg)

^ -1

k = extinction coefficient (m ) 2

m = pool mass loss rate (kg/m /s)

2

m^ = infinite-diameter pool mass loss rate (kg/m /s)

$ = mean beam length corrector (-)

Values for the above quantities are given in Table 6.

The time to pool ignition (attainment of fire point) can be obtained from

equations by Modak [17], which relate temperature rise of the pool to Incident

flux and exposure time. For ease of reference, the equation numbers and the

numbering of figures used by Modak were adopted for this part of the report.

5 . 1 For combustible fluid depth > 20 mm.

The surface temperature rise is given by

[T^(0,t) - Tq] ^

1/2

erfc (k/a^t) ( 8 )

where: To = the ambient temperature

t = the time

1“Y = the surface layer absorption

k = the absorption coefficient

9
q" = the net flux (approx. 65% of incident flux)

X = the thermal conductivity

p^c^ = the volumetric heat capacity of the fluid

n = 3.14

and

where is the thermal diffusivity of the oil. The first term in

Eq. 8 represents the classical solution for a non-transparent (y = 0 or k -> <») medium

11/2

AT = 2q"

l^l^l

(9)

where AT = (T^(0,t) - T^) is the surface temperature rise above ambient.

In the use of his equations, Modak recommended that the following properties

be used for hydrocarbon liquids and typical concrete or steel floors:

PROPERTIES OF HYDROCARBON LIQUIDS*

(300 - 600 K)

Thermal conductivity 125

X^, mW/(m*K)

Volumetric heat 1.9

3 capacity MJ/(m »K)

Surface layer absorption 0.45

(1-y)

Absorption coefficient, 48

, -1

k, m

*Values representative of most hydrocarbon fluids

10
MEAN THERMAL PROPERTIES OF CONCRETE AND STEEL

Thermal Conductivity Volumetric Heat Capacity

X2,W/(m«K) P2C2,MJ/(m^«K)

Concrete 1.8 2.10

(at 373 K)

Steel 46 3.62

(at 300 K)

In his comparison of theory with experiment, given in Figures 18, 19, and

20, there was good agreement when the net flux q" was assumed to be

approximately 65 percent of the incident flux.

5. 2 Finite depth spills opaque to thermal radiation

The time-dependent temperature rise over ambient, AT, of the liquid surface is

AT = 2q" ( 10 )

Here, d is the depth of the spill and a is the ratio (l-m)/(l-hn) where

m is defined by

m ^^2^2^2^^1^1^1^

1/2

and ^ property of the substrate

Equation 10 shows some familiar features: for large values of the parameter

10 yields the familiar solution for an opaque semi-infinite spill.

11
d

For (thin spills) 0 , Eq. 10 reduces to:

AT = 2q"

1/2

( 11 )

Equation 11 implies that the temperature response of the thin spill is

essentially the same as the surface temperature response of the semi-infinite

substrate over which the (thin) layer of oil is spilled.

5.3 Finite depth spills transparent to thermal radiation

The surface temperature rise is given by

This implies that, for thin spills, both opaque as well as transparent models

yield the same solution. For thick spills, the transparent model is not a very

meaningful model: Eq. 12 shows that for the thick case AT tends to zero. The

semi-transparent, semi-infinite model assumed for equation 8 is more suitable

for thick spills.

Modak compared theory with experiment for finite depth spills in Figures 21

and 22 with the conclusion that the opaque solution is better suited for the

finite spill fires studied.

As for the radiation fraction of the combustion energy for hydrocarbon pool

fires, Mudan [19] has studied the problem with the results given in Table 7.

( 12 )

Not unexpectedly, Eq. 12 reduces to Eq. 11 for thin spills

12
6 . 0 Sunmiary

1. There is currently no direct heat release rate data available on

the burning of full-scale or intermediate-scale cable tray arrays.

However, existing weight loss data, measured in a series of intermediate-scale fires, was used to estimate heat release rate(s). The

latter were used, in turn, to develop a prediction scheme for fullscale fire behavior based on laboratory-scale heat release rate data

for cables. For cable array arrangements, cable packing densities,

and exposure fires significantly different from those used for the

prediction scheme, the use of this method may not be appropriate and

would at best give only an approximation for the heat release rate

of such cable tray fires.

2. Trash fire data was reviewed, and the peak unit area rate of heat

release from these fires was correlated with size of the trash container.

Packing density was shown to be significant in the burning behavior

of trash. A generalized heat release rate history, based on the peak

unit area rate of heat release, was suggested for trash fires.

3. A method for predicting the heat release rate history of simple wood

fuel configurations was given based on existing flame spread data

correlations and unit area rate of heat release data from laboratory

fire tests. For more complex configuration wood fuels, the burning

characteristics of wood pallets could be used as an approximation.

4. A review of the literature on flammable liquid spill fires indicated

that existing theory was adequate for roughly predicting the time to

ignition for spills of varying size, thickness, and opacity and the

subsequent rate of heat release.

13
7.0 References

1. Nowlen, S.P. , "A Literature Review of Quantitative Information on the

Behavior of Materials in Fire as Related to Nuclear Power Plant Fires".

Sandia National Laboratory, Albuquerque, N.M. Rough draft June 29, 1984.

2. Nowlen, S.P., "Heat Release Rates During the Sandia/U.L. 20 Foot Separation

Tests". Sandia National Laboratories, Albuquerque, N.M. Letter Report

June 1984.

3. Hasegawa, H.K. , et al. Fire Protection Research for DOE Facilities: FY 82

Year - End Report. Lawrence Livermore National Laboratory, University of

California, Livermore, California; September 2, 1983.

4. Sumltra, P.S., "Categorization of Cable Flammability. Intermediate-Scale

Fire Tests of Cable Tray Installations". Factory Mutual Research Corporation,

Norwood, Mass. Interim Report NP-1881 Research Project 1165-1; August 1982.

5. Tewarson, A., and Lee, J.L. , and Pion, R.F. , "Categorization of Cable

Flammability. Part I: Experimental Evaluation of Flammability Parameters

of Cables Using Laboratory-Scale Apparatus". Factory Mutual Research

Corporation, Norwood, Mass. EPRI Project RP 1165-1; July 1979.

6. Parker, W. J. , "An Assessment of Correlations Between Laboratory and Full

Scale Experiments for the FAA Aircraft Fire Safety Program, Part 3: ASTM

E84". Nat. Bur. Stand. (U.S.) NBSIR 82-2564; January 1983.

7. Van Volkinburg, D.R. , et al, "Toward a Standard Ignition Source." Lawrence

Berkeley Laboratory, University of California, Berkeley, California. Paper

No. 78-64; October 1978.

8. Lee, B.T., "Effect of Ventilation on the Rates of Heat, Smoke, and Carbon

Monoxide Production in a Typical Jail Cell Fire". Nat. Bur. Stand. (U.S.)

NBSIR 82-2469; March 1982.

14
9. Cline, D.D. and Von Rlesemann, W.A. , and Chavez, J.M. , "Investigation of

Twenty-Foot Separation Distance as a Fire Protection Method as Specified

in 10 CFR 50, Appendix R" Sandia National Laboratories, Albuquerque, N.M.

NUREG/CR-3192 SAND 83-0306 RP; October 1983.

10. Fisher, F.L., Personal Communication. Lawrence Berkeley Laboratory,

University of California, Berkeley, California.

11. Blackshear, P.L. , and Kanury, A.M, , "Some Effects of Size, Orientation,

and Fuel Molecular Weight on the Burning of Fuel-Soaked Wicks". Eleventh

Symposium (International) on Combustion, pp. 545-552, The Combustion

Institute, Pittsburgh, PA; 1967.

12. Quintiere, J.G. , and Harkeleroad, M. , "New Concepts for Measuring Flame

Spread Properties". Symposium on Application of Fire Science to Fire

Engineering, ASTM STP 882, American Society of Testing and Materials,

Philadelphia, PA; (1985?)

13. Chamberlain, D.L. , "Heat Release Rates of Lumber and Wood Products".

Behavior of Polymeric Materials in Fire, ASTM STP 816, pp 21-41, E.L.

Schaffer, Ed., American Society for Testing and Materials, Philadelphia,

PA; 1983.

14. Atreya, A. , "Pyrolysis, Ignition and Fire Spread on Horizontal Surfaces

of Wood". Doctor of Philosophy thesis in Engineering. Harvard University

Cambridge, Mass.; May 1983.

15. Krasner, L. , "Burning Characteristics of Wooden Pallets as a Test Fuel".

Factory Mutual Research Corporation, Norwood, Mass. Progress Report Serial

No. 16437; May 27, 1968.

16. Alpert, R.L. and Ward, E.J., "Evaluation of Unsprinklered Fire Hazards".

Fire Safety Journal, Vol. 7, No. 2, pp 127-143; 1984.

15
17. Kodak, A.T., "Ignitability of High-Fire-Point Liquid Spills". Factory

Mutual Research Corporation, Norwood, Mass. Final Report NP-1731,

Research Project 1165-1; March 1981.

18. Babrauskas, V., "Estimating Large Pool Fire Burning Rates". Fire

Technology, ¥ol. 19, No. 4, pp 251-261; November 1983.

19. Mudan, K.S., "Thermal Radiation Hazards from Hydrocarbon Pool Fires".

Progress in Energy and Combustion Science, Vol. 10, No. 1, pp 59-80; 1984.

16
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rH rH rH rH

v9 O

m rH o o> 0 m 0 0 o m 0 o 04 o m

m

m O'

n (N rH \n 0 0 O' in 0 o r* 04 O' 04

pH rH rH rH rH rH rH rH 04 fH rH

»*> o f*> rH o 0 0 m 0 0 o> 04 04 0 o m o o 04

rH CO

m 04 04 o O 0 0 r* 0 O

m 04 0 in

m

fO 04 04 04 04 rH ro rH 04 04 rH rH rH 04 rH rH 04 n S o rH 0 O' 0 0 0 0 O rH 0 o rH 04 0 0

r~ vD <P 04 <n 0 rH 04

m o> 0 rH rH 0 n O' 0 n rH

v9 04 04 04 rH rH 04 rH rH rH rH rH rH

0) c

06

A

O

•H

O

•P

C « 3

<X) rH X <9PU

•<

«< « 01 o CD in in 0 0 rH

m 'T o 04 (N o O' in 04 O' 0 04 9) u 9 0 04 o O' 04 0 CO 0 0 O' rH 04 O on m o rH 0 0

iH < > m

n 04 iH 04 r-4 rH r-4 rH rH rH rH rH rH r-4 rH rH o 0 in in 0 m 04 04 0 rH 0 rH 0 4T 04 0 O' 0 0 0 O' 0 0 in 9 rH o 0 O' m m rH O 0 O' O' 04 0 0 m m 0 n m 04 04 04 04 CN 04 rH rH rH rH

O'

U1 m c rH (D rH

m (0 CO CD (0 (A 0) O (0 CO

U 0 -r4 H cn •H (A Ui (A 09 0) CA

b6 (A (A in (0

U6 m

u

n P z fl

m z z <0 z IB (Q

m *B Z z (0 IB IB (B Z iB

M <0 06 br Cl. Ou

X Or Or Or

X Or Or Or Or

04

04

0)OP

CO« §0cpoz 0 0 CD 04 X

9) rH rH <0 z < rH * % U Or --r — X E . •o T3

10

B c •rH •H (A 0 rH 0 0 < ^ 

iB 04 04 0 rH m rH rH o U 9

(V ,—,

rH O' * rH >1 >- r--

A rH

A rH rH 04 rH — z z 0 lO A '-r --r rH (A — in >

IB

m

u

u ' lA » U rH u 0 0 u u u — « <

0) 0 « • • 0 > > rH 0 rH •0 >—

.—

c • c 0 0 • 0 0 w 0 rH • 0 o ¥ in 0 0) 0 ro 0) • • 0 \ 0 0 (N Or rH u u • * u o4 Cp • c c • 0 —

• m 0 '—

c. o4 Or

u

u «p o 0 0 0> o4 04

W 04

X 0 u 0 \ CJ rH rH • c u o C 0 U X u o 0) u 04 0 0 \ >, >r ep 0 Pi \ 0 C « u > 0 > > z 0 > z 0 0 M z z U u X 0 u 0 ki cu \ 0 0 \ 0 0 s. 0 •H \ 0 •H rH 04 ul \ \ u - \ u X u ^H u rH Hh > u 0 u u 0 u Cd 0 u u K b) u 0 •M 0 u H 0) r< 0 X 0 0 X 0 0 X 0 0 0 0 0 X {A X 0 0 H «

17
Experiment

No.

Fuel Source

3

4, 11

5, 10

9

Table 2.

Peak Heat

Release Rate

(kW)

9.1 kg computer paper crumpled 109

up in two plastic trash bags.

11.4 kg rags, 7.7 kg paper towels, 119

5.9 kg plastic gloves and tape, 5.9 kg

methyl alcohol. Contents mixed in two

40 gal trash bags.

13.6 kg computer paper crumpled up and 109

divided in two 7.5 kg (50 gal) plastic

trash cans.

4.6 kg crumpled up computer paper 40

and 31.8 kg folded computer paper.

Paper evenly divided into two bags.

Simulated Trash Fire Experiments at Sandia National Laboratories [9]

18
Ignition

and

Flame

Spread

Characteristics

Under

Constant

Irradiance

Conditions

[12]

• • • • • • o m o o 1 CM m

ON Csj ON CM 1 MT ON

iH CM iH Mr 1 cn ro

0 CO 4J ^

O O • • o o

CO in in m

O o 1 o o • • 1 • o o 1 o o

I I

I I

CM ^ .H

I

/-~S CVJ 60 0

•H o

<N r o :s cr X

d c

iH o

4-1 •H

4-1 iH •H

cc! 0 /T-N O 00 CM

•H •H 60 0

•H o

*H O rH r o O 4-4 'w' cr

NX) I I

I I I

CM o CO m NO NO CM

rH r—i iH r—iH rH iH

o

00 m 00 CM 00 CM o CM iH cn

rH rH m CM rH cn CM CM 1—1 1—1

mT CO iH iH CJN NO mT

Td • • • • • • • • •

cc) o O O O o o o o o tH CD /-V

cc) V4 CM

CJ X C4 CD e

•H 3 CO *> CJ

4-1 iH = o TO

•p4 4-] cr IS >4

)-4 o V ^ cO a 4-( 0 o

O 0 0 PQ m o o

CO 0) NO CM /—^ CM 1-H

• • G • O /—s o 1—

G G rH •H ^—N s V—

/

S_r G in N ' 44 rrH 00 m r^ s »4 00 r- 0 c CO 1—

ON T3 cO 1-H 1-4 iH •H •H • • m U p4 i-H C/3 CO cO cO NO CO i-H CO C/3 •H r-l t—

C/3 O )4 /—

^—'

J-i Pu 04 PQ •H B rH

o; T) T3 T3 P<4 o Td 03

4-1 r> #1 l-l >-l 0) >4 C

CO 'O 'O CO CO CO rH CO CN CO CO s o o O O O o /~v cO • o (X, o o -O -O S) •H -X ?-4 rH jd t3 •Td •D 4-t a 00 cx Td U u >4 )4 o d •H o

rH rH cO cO CO CO 4J o -C o

P4 pa pa pa PL4 CO o 3

•u •H

(0C

(U T3&o

T3U

ctJ O

>-i a\

0) <-t »o I—

•H cn

19

-

1/2

*from

Intersect

ofV

vs

q

F(t)
Mean HRR. kW/ni* Tune lo Mtfcnaii

iBd NoBunal Dmenuoiu

Nuinba

of Sample!

Tune lo IfDlUOO,

1

Peak HRR.

t Peak

Firvi |.nun

Average

Fuii 10-miD Total 5-miD Heal Release, Average MJ/m’ (Btu/fd)

Snmhftp pue

2 by 1 is lumba 5 17 60 134 96 109 57.7 (5080) Douglas &r 2 by 1 u tumba 3 14 40 124 89 . 79 43.8 (3860)

fir 2 by 6 ID lumber 4 15 28 98 59 78 45.3 (3990) Redwood

2 by 1 ID lumber 9 11 20 118 95 71 38 1 (3350) Dou^ fir ID plywood 2 12 17 115 90 70 38.8 (3420)

rwMi£i»t fu v; in plywood 3 8 19 119 98 82 43.4 (3820) Pamclc hoard, H ID 3 26 104 132 95 109 58.8 (5180) AoouUical tile A 5 10 62 96 68 61

Acouitical tile B 5 9 41 100 83 65

Hardboard. mxtiiim density, papa-faced,

Vb m 4 25 29 355 150 118

Hardboard,

dc&klt), H 1C 3 21 197 158 94 120

Hardboard,

tufb dCDUI),

¥ll ID 3 33 153 380 112

Table 4. Rate of heat release per unit area for selected

wood products [13]

20
Table 5

UNCONFINED SPILL DEPTHS FOR HYDROCARBON LIQUIDS

ON EPOXY-COATED CONCRETE AND STEEL [17]

Liquid Spill Depth (nra)

#2 Fuel oil 0.22

#6 Residual oil NA

Mobil DTE 797 0.34

Pennzoil 30-HD 0.75

Fyrquel 220 0.84

21
Table 6 Data for Large Pool Burning Rate Estimates [18]

Material

Density

(kg/mT

AA.

(kJ/kg)

Ah.

(UJ/kg}

mi

e) (m*'»

k

Im-)

T,

(K) References

Cryogenics

Liquid Hi 700 442 120.0 0.169 (±0.006) 6.1 (±0.4) — 1600 4.5 LNG (iDosUy CH4) 415 619 60.0 0.078 (±0.018) 1.1 (± 0.8 ) 0.6 1600 1.4.30 LPG UxKMtly C»HJ 685 426 46.0 0.099 (±0.009) 1.4 (±0.5) 0.4 — 80,35

Alcohols

Methanol (CHiOH) 796 1230 20.0 0.017 (±0.001) • 1300 6.22.37

Ethanol (C.H.OHl 794 1000 26.8 0.016 (±0.001 ) • 0.4 1490 7.9,24.31

Simple Organic Fuels

Butane (C«Hio) 673 870 45.7 0.078 (±0.003) 2.7 (±0.3) — — 6

Beniene (C»H(| 874 600 40.1 0.085 (±0.002) 2.7 (±0.3) 4.0 1460 5.31.38

Hexane (CJi.J 650 450 44.7 0.074 (±0.005) 1.9 (±0.4) — 1300 5.38,39

Heptane (C7 H 1 J 675 605 44.6 0.101 (±0.009) 1.1 (±0.3) — — 22.33

Xylene (C*H , 0) 870 555 40.8 0.090 (±0.007) 1.4 (±0.3) — — 5

Acetone (C,H,0) 791 670 25.8 0.041 (±0.003) 1.9 (±0.3) 0.8 — 9.29.37

Dioxane iCJ^tOi) 1035 630 26.2 0.018* 6.4* — — 33

Diethyl ether (C«H •0) 714 385 34.2 0.085 (±0.018) 0.7 (±0.3) — — 3

Petroleum Products

Benzine 740 — 44.7 0.048 (±0.002) 3.6 (±0.4) — — 3

Gasoline 740 330 43.7 0.055 (±0.002) 2.1 (±0.3) 2.0 1450 3.18.24.31.38.39

Kerosene 820 670 43.2 0.039 (±0.003) 3.5 (±0.8) 2.6 1480 3.21 JP-4 760 — 43.5 0.051 (±0.002) 3.6 (±0.1)“ — 1220 3.16.21,34

JP5 810 700 43.0 0.054 (±0.002) 1.6 (±0.3) 0.5 1250 8.14.15,32

Transformer oih

hydrocarbon 760 — 46.4 0039* 0.7* — 1600 22

Fuel oil, heavy 940-1000 — 39.7 0.035 (±0.003) 1.7 (±0.6) — — 3,6

Crude oil 830-880 — 42.5-42.7 0.022-0.045 2.8 (±0.4) — — 3.38

Solids

Polyroethy1- methacrylate 1184 1611 24.9 0.020 (±0.002) 3.3 (±0.8) 1.3 1260 12.26

* Value independent of diameter in turbulent regime

*Only two data pcinta available

22
Table 7 Radiation fraction of combustion energy for hydrocarbon pool fires [19]

Hydrocarbon

Pool size

(m)

Methanol

LNG on land

?l

f r

II LNG on water

LPG on land

Butane

Gasoline

Gasoline

Benzene

Hexane

Ethylene

1.22

18.0

0.4-3.05

1 . 8-6.1

20.0

8.5-15.0

20.0

0.3-0.76

1.22-3.05

1.0-10.0

1.22

*In these cases, the smaller diameter fires were

radiative outputs.

%

Radiative output/

Combustion output

17.0

16.4

15.0-

34.0

20.0-

25.0

36.0

12.0-

31.0*

7.0

19.9-26.9

40.0-

13.0*

60.1-

10.0*

36.0-38.0

40

38

associated with higher

23
24
9 9

41*

40% Fill (typieoM

n'/i h w*-

L J I I 9"Dttp,

4;ii .Zi I I

105*

10 I/I :1

I I

I I

.1 I

17* Leod C«l I Syitwr;

rsTTT^.

L*M«r

7fPf Optf>

Tr«)r«

L

Lead C«ii S)r*t«rrt

END VIEW

1 42 -

»6* $>

I UJ

N

NORTH ELZV

0 I6NIT(0N SOURCE I A SS'k ie*K 4*

Dttp

^

vlth

£gol. Mptont.

Nozzle for Extinguishment

5TO

PLAN VIEW

Figure 2 . Horizontal Tray Test Setup [4]

25
Figure 3 Mixed Tray Test Setup [4]

26
m

OJ

(U!Ui/B)i) 31VU ONINUng

n3oU

>

w

Pm

(MO

UM

0) •u

cO>M

C

•Hc

!-i 3

cO

(U

CJ

cO UMu

3m

CO

>M H

<r

(U

>M3

00

-H

27

TRAY

SURFACE

AREA

(m^)
Qm"

0.46

Q/^

28

versus
PE/PVC

Rate

~

2.3

m^/min

(^uj) V3UV iNdng

29

Figure

6.

Fire

involved

area

versus

time
RATE

OF

FLAME

COVERAGE

(m^/min)

F.M. FLAMMABILITY APPARATUS

RATE OF HEAT RELEASE (kW/m^)

Figure 7. Rate of fire coverage versus rate of heat release

30
700

600

500

400

300

200

100

1. 125 Uter (32 gal.) rubbish bag is polyethylene.

Contents are straw, grass, Eucalyptus duff. Total

weight of 4.1 kg.

2. 6.6 liter (1.75 gal.) container is polyethylene and

weighs 0.23 kg. Contents are twelve 0.95 liter

cardboard milk cartons weighing 0.45 kg.

Figure 8. Trash fires [7]

31
700

-

TRASH

BAG

FIRES

Each

1

gal.

bag

has

1

polyethylene

bag,

600

-

12

polystyrene

cups,

1

7

paper

cups,

and

0.91

kg

of

fluf

fed-up

paper

towels

for a

(MM) asvaiBU 1V3H do aivu

32

Figure

9.

Trash

fires

[7]
600

1

(M)|) 31VU aSVBIBU 1V3H

00

cno

•H

O

0)3

oo

tH

U.

33

TIME

FROM

IGNITION

(min)
600

I

34

EFFECTIVE

DIAMETER

(ft)
eoE

o» o

CD lO ^

CO C4

(M>0

O >IV3d

cJ

CM

CM

CMO

CM

00

X.

CO

rt

4-1

C

(UN

UJ «

[y 5 ^ 2 >

CM

LU ^ > O I-O

LU

00o

CDod co

T-l 4J

CO r—

0)

)-i poo

LU

CO0) X

CMd

(U3

bC

35
«3O

a

<

•O

(v/0) asvaiaa iv3h jo aiva

36

Figure

13.

Envelope

containing

all

of

the

observed

heat

release

rate

curves

for

trash

fires
I

Figure 14. Correlation of velocity with flux [121

37
1/2

6

Figure 15. Envelope containing velocity versus flux data

for wood products [12]

38
39

AVERAGE

MAXIMUM

BURNING

RATE

VS.

PILE

HEIGHT

[15]
Btu /

Sec

Figure 17. Heat release rate for single stacks of wood pallets [16]

40
Surfoct

Timptrofurt

Abovv

AiNbltfit

AT,

K

Figure 18. Measured surface temperature of an opaque, semi-infinite

medium compared with theory using tiiree different values of net flux

2 2 of 13.8, 8.9 and 6.8 k',V/m and an external flux of 13.8 klV/m .

41
Figure 19. Measured surface temperatures (shaded region) of four semitransparent, semi-inf inxte hydrocarbon liquids compared -th

“

using a net flux of 10 hW/m'^ and an_erternal flux of

42
Eipoturt Stc.

Figure 20. Comparison of theory and experiment for net flux of 15.6 kW/m

and an external flux of 26 kW/m .

43
150

Uhconfintd Spill cf Ptctnioil 50»HD en

Steel Subttrote

1

<

t

I

K

c

a

E

I

9

too

50

0

Eiternol Flux; 15.6 KW/fr^

Ambient : 699 K

Spill Depth of Pennzoil 50-tC : 075mm

0 too 200 500

Expowre Time, Sec.

Figure 21. Comparison of experiment and the range predicted by two

theoretical limits for an unconfined spill of Pennzoil 30-HD on a steel substrate.

44
Surface

Temperature

Rise

Above

Ambient,

AT, K

100 200 300

Exposure Time, Sec.

Figure 22 . Dnconfined spill of Petmzoil 30-HD on an epoxy-coated

concrete substrate.

45
NSS»114^ (REV, 2»eo)

4. TITLE AND SUBTITLE

Heat Release Rate Characteristics of Some

Combustible Fuel Sources in Nuclear Power Plants

,

5. AUTHOR(S)

B. T. Lee \

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS r DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered!

WASHINGTON, D.C. 20234

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See Instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR-85/3195

2. Performing Organ. Report No. Publl-catlon Date

July 1985

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State. ZIP)

Nuclear Regulatory Coinmission

Washington, DC 20555

10. SUPPLEMENTARY NOTES

I I Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here) A major risk to a nuclear power plant is the possibility of serious fire. There is

a need to know the heat release rate behavior of combustible fuels in the plant in

order to help reduce the fire threat to these facilities. Heat release rate

characteristics of cable tray fires and some of the associated potential external

ignition sources are discussed. Existing correlations are given for determining thej

time to ignition and the subsequent heat release rate of spills and pools of

flammable liquids. Approximate correlations are developed for heat release rate forj

trash fires as a function of fire size and for one particular cable tray array

arrangement as a function of the type of cable. In addition, a scheme is given for

calculating the heat release rate from wood fuel fires.

12. KEY WORDS (S/x to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) cable trays 5 fire safety 5 flammability; flammable liquids; heat release rate

ignition; liquid spills; nuclear power plants; pool fires; small-scale fxre tests,

trash; wood.

13. AVAILABILITY

Uni imited

I I For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

52

15. Price

$ 10.00

USCOMM-DC 6043-P80]