United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 94-22: Fire Endurance and Ampacity Derating Test Results for 3-Hour Fire-Rated Thermo-Lag 330-1 Fire Barriers

                                 UNITED STATES
                         NUCLEAR REGULATORY COMMISSION
                     OFFICE OF NUCLEAR REACTOR REGULATION
                            WASHINGTON, D.C. 20555

                                March 16, 1994


NRC INFORMATION NOTICE 94-22:  FIRE ENDURANCE AND AMPACITY DERATING TEST 
                               RESULTS FOR 3-HOUR FIRE-RATED THERMO-LAG 330-1  
                               FIRE BARRIERS


Addressees

All holders of operating licenses or construction permits for nuclear power
reactors. 

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to inform licensees of the preliminary results of fire endurance and
ampacity derating tests of Thermo-Lag 330-1 (Thermo-Lag) fire barriers
conducted by the NRC at Underwriters Laboratories, Incorporated (UL).  It is
expected that recipients will review the information for applicability to
their facilities and consider actions as appropriate to avoid similar
problems.  However, suggestions contained in this information notice are not
NRC requirements; therefore, no specific action or written response is
required.

Description of Circumstances

As part of its continuing evaluation of Thermo-Lag fire barrier performance,
the NRC Office of Nuclear Reactor Regulation (NRR) conducted three full-scale
fire endurance tests and one full-scale ampacity derating test of 3-hour 
fire-rated Thermo-Lag fire barriers.  The principal objective of the tests was
to evaluate the performance of the barriers against the results of tests
previously reported by Thermal Science, Incorporated (TSI, the vendor).  

Sandia National Laboratories (SNL), Albuquerque, New Mexico, provided
technical assistance by designing and executing the test program and preparing
the test report.  The base test specimens were constructed and instrumented at
SNL.  The test specimen fire barriers were constructed at UL by trained
Thermo-Lag installers under the direction of SNL during October and
November 1993.  The tests were conducted at UL under the direction of the NRC
and SNL during December 1993.  The NRC staff informed the Nuclear Management
and Resources Council (NUMARC) of the test results during a public meeting at
NRC Headquarters on February 9, 1994.  The final test results will be
documented in SNL Report SAND94-0146, "An Evaluation of the Fire Barrier
System Thermo-Lag 330-1."  The staff will place this report in the NRC Public
Document Room after it is completed.  The staff expects the report to be
completed during April 1994.

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Discussion

Each of the four base test articles was a U-shaped configuration laying
sideways which duplicated configurations, material specifications, dimensions,
orientations, cable types and fills, and instrumentation, previously tested
and reported by the vendor.  A single layer of cables was installed in each of
the fire test articles in accordance with the types and placements reported in
the vendor's test reports.  The cable fill for the ampacity derating test
article is discussed under the "Ampacity Derating Test" section of this
information notice.

Each of the base test articles was protected by a 3-hour fire barrier formed
from two layers of nominal �-inch-thick Thermo-Lag 330-1 preformed panel.  SNL
purchased the Thermo-Lag preformed panels and trowel-grade material used to
construct the test article fire barriers from Texas Utilities Electric Company
(TU Electric).  TU Electric performed a source inspection of the materials at
TSI and the NRR Vendor Inspection Branch conducted a receipt inspection of the
materials at the Comanche Peak Steam Electric Station when TU Electric
delivered the materials to SNL.

The fire barriers for Test Articles 1, 2, and 4, were constructed in
accordance with TSI Technical Note 20684, Revision V, "Thermo-Lag 330 Fire
Barrier System Installation Procedures Manual Power Generating Plant
Application," November 1985.  The fire barrier for Test Article 3 was
constructed in accordance with the methods used by the vendor for Test
Article 4 of TSI Report 82-11-81, "Three Hour Fire Endurance Tests Conducted
on Test Articles Containing Generic Cables Protected with the Thermo-Lag 330-1
Subliming Coating Envelope System," November 1982.  Table 1 summarizes the
test article characteristics. 

The stress skin (an embedded wire mesh) for the inner barrier layer faced
toward the cable tray.  The stress skin for the outer layer faced away from
the cable tray.  All joints and seams were offset.  The edges of the
individual panel sections were buttered with trowel-grade Thermo-Lag 330-1
material before they were joined and secured.  This assembly technique, as
opposed to the dry-fit method, ensured that each joint and seam was filled to
its full thickness with Thermo-Lag material.  The individual barrier pieces
for Test Articles 1, 2, and 4 were banded with stainless steel tie wire.  The
individual pieces for Test Article 3 were not banded.  Instead, each seam and
joint was reinforced with stainless steel wire stitches and laces.  In
addition, flanges were formed along the edges and butt joints of the outer
layer.  The flanges were bolted together with nominal �-inch-20 by 2-inch
machine bolts and hex-nuts.  After the barriers were installed, the test
articles were cured for at least 30 days in a secure temperature-controlled
environment before the tests were conducted.

The instrumentation used to record test data, including the SNL data logging
equipment and the UL furnace-monitoring and control systems, was calibrated
using equipment traceable to National Institute of Standards and Technology
standards.  NRC, SNL, and UL participated in and observed all four tests.
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Fire Endurance Tests

The following performance capabilities were evaluated:  (1) the ability of the
Thermo-Lag barrier to keep the average temperature of the unexposed side of
the barrier (as measured on the exterior surface of the cable trays) from
rising more than 139 �C [250 �F] above the ambient temperature at the start of
the test, (2) the ability to keep the temperature of any single thermocouple
from rising more than 30 percent above the allowable average temperature rise
(181 �C [325 �F]), (3) the ability to maintain circuit integrity during the
fire exposure and hose stream test, (4) the ability to maintain the cables
free of visible fire damage, and (5) the ability to remain intact during the
fire and hose stream tests.  

Temperatures were measured by Teflon-insulated Type K thermocouples installed
on certain cables (as documented in the vendor test reports).  In addition,
thermocouples were installed on the cable tray side rails, on the unexposed
side of the Thermo-Lag panels, and in the air space between the cables and the
unexposed side of the Thermo-Lag panels.  In keeping with the objective of
evaluating thermal performance against test results previously reported by the
vendor, the temperature results reported below were those measured by the
thermocouples installed on the cables and the cable tray side rails.  Four
cables in each of the fire tests were connected to a separate low-voltage
power supply (28-VDC, 1 Amp) which was configured to conduct circuit-to-
circuit (conductor-to-conductor), circuit-to-ground (conductor-to-ground), and
circuit-to-system (conductor continuity) integrity tests as documented in the
vendor test reports.

The three fire endurance tests were performed in the UL column furnace.  To
facilitate duplication of the original TSI test configurations, UL modified
the nominal 10-foot by 10-foot by 10-foot furnace to allow the test to be
inserted into the furnace through one of the furnace walls.  The standard
time-temperature fire from American Society for Testing of Materials (ASTM)
Standard E-119-75, "Standard Methods of Fire Tests of Building Construction
and Materials," was followed.  UL technicians operated the test furnace and
recorded the furnace temperature data.  SNL provided the instrumentation and
data acquisition system for obtaining and recording the test temperature and
circuit integrity data.  During the fire exposure, visual observations were
made through viewing ports located in three of the furnace walls.  The
following test results are summarized in Table 2.

Article 1 was tested on December 8, 1993.  The ambient temperature at the
start of the test was 19 �C [66 �F].  Therefore, the average temperature rise
criterion for this test was 158 �C [316 �F] and the single-point temperature
rise criterion was 200 �C [392 �F].  The single-point temperature criterion
was exceeded about 1 hour and 5 minutes after the start of the test (1:05).  A
conductor-to-ground fault was detected at about 1:16 and the average
temperature rise criterion was exceeded at about 1:20.  The test was
terminated at 2:30.

Article 2 was tested on December 7, 1993.  The ambient temperature at the
start of the test was 19 �C [66 �F].  Therefore, the average temperature rise
criterion for this test was 158 �C [316 �F] and the single-point temperature .                                                            IN 94-22
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rise criterion was 200 �C [392 �F].  The single-point temperature criterion
was exceeded at about 0:55, a conductor-to-ground fault was detected at
about 0:59, and the average temperature criterion was exceeded at about 1:03. 
The test was terminated at 2:00.  

Article 3 was tested on December 6, 1993.  The ambient temperature at the
start of the test was 20 �C [68 �F].  Therefore, the average temperature rise
criterion for this test was 159 �C [318 �F] and the single-point temperature
rise criterion was 201 �C [394 �F].  The single-point temperature criterion
was exceeded at about 1:50, the average temperature rise criterion was
exceeded at about 1:58, and a conductor-to-ground fault was detected at
about 1:59.  The test was terminated at 3:00.

For all three fire tests, when the tests were terminated, most of the
individual thermocouples exceeded the single point temperature criterion.  In
addition, Thermo-Lag panels had fallen off the test articles exposing the
cable trays and cables to the fire.  Most of the remaining Thermo-Lag had been
reduced to char.  Post-test inspections revealed that all of the cable jacket
and conductor insulation had been consumed during the fire exposures.  Only
bare copper conductors remained in the cable trays.  Detailed test results,
including temperature data, observations and photographs will be provided in
SNL Report SAND94-0146.

The test plan specified that a standard ASTM solid hose stream test would be
performed at the end of the fire test.  However, because of the early
termination of two of the three tests and the poor condition of all three
articles when the tests were terminated, the hose stream tests were not
conducted.  Less severe hose streams were used, however, to extinguish the
burning Thermo-Lag material and to cool the test articles.  These hose streams
washed away most of the Thermo-Lag that had not fallen from the articles
during the fire exposure.

Ampacity Derating Test

Test Article 4 was an ampacity derating test article constructed in accordance
with TSI Report 82-5-355F, "Ampacity Derating Test for 1000V Power Cables in a
Ladder Cable Tray Protected with a Three Hour Rated Design of the
Thermo-Lag 330-1 Subliming Coating Envelope System," July 13, 1982.  The cable
tray was loaded to about 60 percent of the full tray depth with 20 lengths of
1/C, 2/0 AWG, 600-V cable; 58 lengths of 1/C, 4 AWG, 600-V cable; and 99
lengths of 1/C, 8 AWG, 600-V cable.  One length represented one pass through
the cable tray.  All of the cables of a given cable size were joined together
into a single electrical loop.  Each loop was instrumented with six 24-gauge
bare-bead Type K thermocouples with welded junctions.  In each case, the
insulation on the cable was slit so that the thermocouple junction could be
installed below the insulation in contact with the conductor.  Thermocouples
were also installed on the cable tray side rails, on the inner surface of the
fire barrier, and on the outer surface of the fire barrier.  Three
thermocouples were installed to measure the ambient temperature in the test
chamber discussed below.
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Cable ampacity and temperature data was obtained for Test Article 4 before the
Thermo-Lag fire barrier was installed (baseline or unprotected cable tray
data).  On October 14, 1993, Article 4 was placed in a high-ambient
temperature environmental test chamber set at 40 �C [104 �F] and allowed to
soak for about four hours.  A separate power supply was connected to each of
the three cable loops and power was applied according to an initial estimate
of the ampacity of each cable.  The amperage was adjusted over a period of
about six hours until it appeared that a steady state conductor temperature
near 90 �C [194 �F] at the hot spot for each cable size would be reached.  The
test article was left to settle overnight (about 16 hours).  The next day,
final ampacity adjustments were made, and the test article was again allowed
to settle (typically two to three hours after each adjustment).  Stable
conditions were achieved after the final adjustments when the cable
temperatures did not fluctuate more than �1 �C [1.8 �F] between repeated
10-minute interval data scans.  After stable conditions were reached, the
baseline temperatures were logged at 10-minute intervals for a final 1-hour
period.  Cable amperage readings were also taken at the beginning and end of
the final hour to verify the presence of stable source currents.  Following
the baseline test, the 3-hour Thermo-Lag fire barrier described above was
installed on Article 4 and allowed to cure.  On December 9 and 10, 1993, the
protected cable tray ampacity and temperature data were obtained in accordance
with the process used to obtain the baseline data.

Baseline and protected cable ampacity adjustment factors (AF) were calculated
for each cable size according to the following formula from Insulated Cable
Engineers Association (ICEA) Standard P-46-426, "Power Cable Ampacities:"

where the values with primes indicate the desired conditions and the values
without primes indicate the experimental data.  Temperature units are degrees
Celsius.  For both the baseline and the protected cases, the desired cable
temperature (T�c) was 90 �C [194 �F] and the desired ambient temperature (T�a)
was 40 �C [104 �F].  The measured baseline temperatures and ampacities and the
calculated baseline ampacity adjustment factors are provided in Table 3.  The
measured temperatures and ampacities and the calculated ampacity adjustment
factors for the protected cables are provided in Table 4.  For both the
baseline and protected cases, the average of the hot-spot cable temperatures
recorded at 10-minute intervals during the final hour were used to calculate
the ampacity adjustment factor for that cable.

The ampacity derating factor (ADF) for each cable type is the ratio of the
reduction in current carrying capacity (protected ampacities) to the original

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current carrying capacity (baseline ampacities).  The ADF for each cable type
was calculated using the following formula:

In this format, the ADF is expressed as a percentage drop in current-carrying
capacity.  The calculated ampacity derating factors were 46.4 percent,
36.0 percent, and 35.3 percent for the 8 AWG, 4 AWG, and 2/0 cables,
respectively.  Table 5 provides a comparative summary of the ampacity data and
ampacity derating factors from the SNL/UL test and the results reported by the
vendor in TSI Report 82-5-355F.  Table 5 also shows the results of
recalculations performed by SNL of the test data reported in TSI
Report 82-5-355F.  Detailed explanations of the two-step recalculations, which
were needed to allow comparisons of the SNL/UL test results with the reported
vendor test results, will be documented in SNL Report SAND94-0146.

This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear
Reactor Regulation (NRR) project manager.


                                    /s/'d by BKGrimes

                                    Brian K. Grimes, Director 
                                    Division of Operating Reactor Support
                                    Office of Nuclear Reactor Regulation   


Technical contact:  Steven West, NRR
                    (301) 504-1220

Attachments:
1.  Table 1, "Summary of Test Article
      Characteristics," and Table 2, "Summary 
      of Fire Endurance Test Results."
2.  Table 3, "Baseline (Unprotected Cable 
      Tray) Ampacity Test Data and Calculations,"
      and Table 4, "Protected Cable Tray Ampacity 
      Test Data and Calculations." 
3.  Table 5, "Comparative Summary of Ampacity
      Test Data and Derating Factors."
4.  List of Generic Communications Concerning
      Fire Barriers
5.  List of Recently Issued NRC Information Notices.                                                            Attachment 1
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               Table 1.  Summary of Test Article Characteristics

Article.Test Type.Description.Barrier Design .1.3-Hour
Fire
Endurance.6-inch-wide by 6-inch-high,
solid-bottom, steel cable tray
based on Test Article 2 of TSI
Report 82-5-355B, "Three-Hour
Fire Endurance Test on
Thermo-Lag 330-1 Subliming
Coating Envelope System for
Washington Public Power Supply
System Nuclear Projects,"
July 1982. .Based on TSI
Technical
Note 20684,
Revision V,
November 1985..2.3-Hour
Fire
Endurance.12-inch-wide by 4-inch-high,
ladder-back, steel cable tray
based on Test Article 4 of TSI
Report 82-11-81, November 1982..Same as Article 1..3.3-Hour
Fire
Endurance.Same as Test Article 2..Methods documented
in TSI Report
82-11-81,
November 1982..4.Ampacity
Derating.12-inch-wide by 4-inch-high,
ladder-back, steel cable tray
based on TSI Report 82-5-355F,
July 13, 1982..Same as Test
Article 1.

               Table 2.  Summary of Fire Endurance Test Results
            (All times in Hours:Minutes from the start of the test)

Article.Single Point
Temperature
Criterion and Time
to Exceed .Average
Temperature
Criterion and Time
to Exceed.Time to
Circuit
Fault.Test
Duration.1.200 �C [392 �F].158 �C [316 �F].

1:16.

2:30..1:05.1:20...2.200 �C [392 �F].158 �C [316 �F].

0:59.

2:00..0:55.1:03...3.201 �C [394 �F].159 �C [318 �F]....1:50.1:58.1:59.3:00.                                                            Attachment 2
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                  Table 3.  Baseline (Unprotected Cable Tray)
Ampacity Test Data and Calculations

Cable
Size.Tc (�C).Ta (�C).Ic (Amps).AFc.I�c (Amps).8 AWG.91.1.40.5.23.8.0.996.23.7.4 AWG.91.2.40.5.38.0.0.995.37.8.2/0.92.0.40.5.115.0.0.988.113.6


                        Table 4.  Protected Cable Tray
Ampacity Test Data and Calculations

Cable
Size.Tc (�C).Ta (�C).Ic (Amps).AFc.I�c (Amps).8 AWG.92.9.40.1.13.0.0.977.12.7.4 AWG.93.2.40.1.24.8.0.975.24.2.2/0.91.6.40.1.74.4.0.988.73.5


          Key for Tables 3 and 4:

                  Tc = Average of cable temperatures recorded at 10-minute
                         intervals during the final hour.
                  Ta = Average of ambient (test chamber) temperatures 
                         recorded at 10-minute intervals during the final
                         hour after reaching desired stable conditions.
                  Ic = Measured cable ampacity at the end of the
                         final hour.
                  AFc = Cable ampacity adjustment factor.
                  I�c = Adjusted cable ampacity.
.                                                            Attachment 3
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      Table 5.  Comparative Summary of Ampacity Data and Derating Factors

Cable Size.Data Source.Baseline
Ampacity
(Amps).Protected
Ampacity
(Amps).Derating
Factor
(Percent).8 AWG.SNL. 23.7.12.7.46.4..TSI�. 17.46.14.64.16.15..TSI�. 20.38.13.89.31.84..TSI�. 23.96.14.83.38.11.4 AWG.SNL. 37.8.24.2.36.0..TSI�. 35.77.29.74.16.86..TSI�. 41.75.28.21.32.43..TSI�. 41.75.28.21.32.43.2/0.SNL.113.6.73.5.35.3..TSI�.105.91.87.18.17.68..TSI�.123.60.82.69.33.10..TSI�.131.60.84.82.35.55.�  Data reported in TSI Report 82-5-355F, July 13, 1982.
�  Inverted term in ampacity adjustment factor (AF) equation corrected.
�  Measured individual conductor temperatures used to calculate ampacity
adjustment factors for each cable size.
.                                                            Attachment 4
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            List of Generic Communications Concerning Fire Barriers



Information Notice 91-47, "Failure of Thermo-Lag Fire Barrier Material
to Pass Fire Endurance Test," August 6, 1991

Information Notice 91-79, "Deficiencies in the Procedures for
Installing Thermo-Lag Fire Barrier Materials," December 6, 1991

Information Notice 92-46, "Thermo-Lag Fire Barrier Material Special
Review Team Final Report Findings, Current Fire Endurance Tests, and
Ampacity Calculation Errors," June 23, 1992

Bulletin 92-01, "Failure of Thermo-Lag 330 Fire Barrier System to
Maintain Cabling in Wide Cable Trays and Small Conduits Free from Fire
Damage," June 24, 1992

Information Notice 92-55, "Current Fire Endurance Test Results for
Thermo-Lag Fire Barrier Material," July 27, 1992

Bulletin 92-01 Supplement 1, "Failure of Thermo-Lag 330 Fire Barrier
System to Perform Its Specified Fire Endurance Function,"
August 28, 1992

Information Notice 92-82, "Results of Thermo-Lag 330-1 Combustibility
Testing," December 15, 1992

Generic Letter 92-08, "Thermo-Lag 330-1 Fire Barriers,"
December 17, 1992

Information Notice 93-40, "Fire Endurance Test Results for Thermal
Ceramics FP-60 Fire Barrier Material," May 26, 1993

Information Notice 93-41, "One Hour Fire Endurance Test Results for
Thermal Ceramics Kaowool, 3M Company FS-195 and 3M Company
Interam E-50 Fire Barrier Systems," May 28, 1993


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