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HomeNRC LibraryDocument CollectionsGeneral CommunicationsInformation Notices1993

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                                UNITED STATES 
                         NUCLEAR REGULATORY COMMISSION
                     OFFICE OF NUCLEAR REACTOR REGULATION
                            WASHINGTON, D.C. 20555

                                 May 26, 1993


NRC INFORMATION NOTICE 93-40:  FIRE ENDURANCE TEST RESULTS FOR THERMAL
                               CERAMICS FP-60 FIRE BARRIER MATERIAL


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 alert addressees to results of fire endurance and ampacity derating
test reports submitted by Thermal Ceramics on the FireMaster FP-60 fire
barrier system and the results of NRC staff reviews.  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

In Generic Letter (GL) 92-08, "Thermo-Lag 330-1 Fire Barriers," the staff
stated it would evaluate other known fire barrier materials and systems that
are used by licensees to fulfill NRC fire protection requirements.  The staff
is now evaluating fire barriers manufactured by other vendors to verify the
ability of the barriers to adequately perform their 1-hour or 3-hour fire
resistive functions and to meet stated ampacity derating values.  Thermal
Ceramics, Inc., formerly the Insulating Products Division of Babcock and
Wilcox, Inc., of Augusta, Georgia, manufactures the FP-60 fire barrier system
and submitted reports on two fire endurance tests and one ampacity derating
test to the NRC in a letter of February 23, 1993.  

Discussion

In its review of the Thermal Ceramics reports, the staff identified the
following information.  

In its product literature, Thermal Ceramics states that the FP-60 product is
manufactured for use on cable trays, conduits, junction boxes, and other cable
raceways.  The primary component, the FireMaster FP-60 blanket, is a ceramic
fiber blanket with thicknesses varying from 2.5 cm [1 inch] to 7.6 cm
[3 inches].  Optional aluminum or stainless steel foil, Kao-Tex (woven cloth),
or other cloth facings are provided for physical protection of the blanket. 
The vendor claims that the material, when installed according to the
instructions, is qualified for up to a 1�-hour fire rating using the American 

9305260385.

                                                            IN 93-40
                                                            May 26, 1993
                                                            Page 2 of 4


Society for Testing and Materials (ASTM) Standard E-119, "Standard Test
Methods for Fire Tests of Building Construction and Materials." 

FIRE ENDURANCE TESTS

According to one report submitted by Thermal Ceramics, a 1-hour fire endurance
test of the FP-60 fire barrier in various configurations was performed at
Underwriters Laboratories, Inc. (UL File R11044-1, Project 84NK8356,
March 22, 1985).  The test followed UL Subject 1724, "Outline of
Investigation, Fire Tests for Electrical Circuit Protective Systems," 
May 1984.  According to the report, the furnace temperatures followed the 
ASTM E-119 standard time-temperature curve for fire exposure, and the barriers
were subjected to a solid hose stream test.  The report also states that
circuit integrity was monitored.  

Documented test configurations included 91.4 cm [36 inch] wide open-ladder and
solid-back steel cable trays, an air drop assembly, 12.7 cm [5 inch] diameter
steel conduits, and a 30.5x15.2 cm [12x6 inch] steel junction box.  All
configurations contained cables.  Two hundred fifty thermocouples were
reportedly used to measure temperatures of cables, cable trays, junction
boxes, conduits and electrical circuit protective systems on the unexposed
side of the assembly.

According to the report, within 30 seconds of the start of the test, the
filament tape around the blanket wrap ignited.  At 5 minutes, flames
reportedly issued from seams and butt joints.  The report also states that at
20 minutes, some of the wrap slipped out of position resulting in an opening
in the barrier, and at 60 minutes, there was a 8.9 cm [3� inch] opening in the
barrier.  Some thermocouple measurements reportedly ranged from 204 �C
[400 �F] to 260 �C [500 �F] at the end of the fire test.

After the test, some cables were documented to be fused together, and cable
jackets were melted and blistered.  The hose stream eroded the bottom surface
of the cable tray barrier so that the tray was exposed.

The UL report concluded that the tested fire barrier had a 1-hour fire rating
because circuit integrity was maintained during the fire exposure and hose
stream test.  However, it appears that the UL approval is limited to minimum
91.4 cm [36 inch] wide cable trays and 12.7 cm [5 inch] or larger-diameter
conduits with minimum No. 16 AWG jacketed multi-conductor cables or minimum
No. 300 MCM jacketed copper single conductor power cables with polyvinyl
chloride jackets.

The second fire endurance test report submitted by Thermal Ceramics documented
a Southwest Research Institute small-scale test, "One Hour Fire Qualification
Test of a Protective Envelope for Class 1E Electrical Conduit Circuits," (SwRI
Project 01-8305-053, February 1986).  According to this report, the test
employed the ASTM E-119 standard time-temperature curve for fire exposure and
a subsequent solid hose stream test.  The report also states that circuit
integrity was monitored.  SwRI documented the use of a small-scale furnace
(maximum test specimen of 425.8 square cm [66 square inches]) to test a  
2.5 cm [1 inch] diameter conduit with a pull box, a 5.1 cm [2 inch] diameter
conduit with a junction box, and an air drop.  According to the report, these.

                                                            IN 93-40
                                                            May 26, 1993
                                                            Page 3 of 4


test assemblies each contained a single-conductor power cable and two control
cables, all with PVC jackets.

Recorded cable temperatures (measured at the cable jackets) at the end of the
fire exposure ranged from 146.5 �C [296 �F] to 164 �C [327 �F].  According to
the report, circuit integrity was maintained during the fire exposure and hose
stream tests.

The barrier and cable conditions after the fire exposure were not reported. 
The test report suggests that the hose stream test caused some barrier damage,
although the test report did not clearly report the extent of damage.  SwRI
did not report a conclusion as to the acceptability of the fire barrier
system.

In a letter of April 27, 1993 to Thermal Ceramics, Inc., the staff expressed
concerns regarding the ability of the FP-60 system to meet existing NRC fire
barrier acceptance criteria.

AMPACITY DERATING TEST

The ampacity derating test report submitted by Thermal Ceramics was SwRI
Project 01-8818-210, "Ampacity Derating of Fire-Protected Cables in Conduit
and Cable Trays Using Babcock & Wilcox, Incorporated's Passive Fire Protection
System," issued by SwRI on July 8, 1986.  According to the report, a 1-hour
fire barrier was used in the test.  Three-conductor XLPE-insulated 6 AWG
cables with Hypalon protective wraps were reportedly installed in a 
61 cm  [24 inch] wide by 10.2 cm [4 inch] deep cable tray, and 3-conductor
XLPE-insulated 3 AWG cables with Hypalon protective wraps were installed in a
10.2 cm [4 inch] diameter conduit.  Both assemblies were reported to be 
3.7 m [12 feet] long and completely filled.  The report stated that
thermocouples were installed in slits in the cable insulation.

According to the report, a steady-state temperature of 90 �C (194 �F) at the
hottest single thermocouple was monitored.  Equilibrium temperature was
reportedly established when a steady-state condition (+/-1�C per hour 
[+/-1.8�F per hour]) was achieved for 3 hours without any perturbation to the
system.

The ampacity derating for the cable tray and conduit was estimated to be 62.4
and 41.4 percent, respectively, based on the test results.  

Some licensees use the FP-60 fire barrier system to achieve physical
independence of electrical systems in accordance with Regulatory Guide 1.75,
"Physical Independence of Electrical Systems."  Ampacity derating in fire
barrier systems installed to achieve physical independence of electric systems
is a consideration in the design of such systems as well as in those installed
to protect safe shutdown capability from a fire. 

Cables enclosed in electrical raceways protected with fire barrier materials
are derated to ensure that systems have sufficient capacity and capability to
perform their intended safety functions.  These cables are derated because of
the insulating effect of the fire barrier material.  Other factors that affect
ampacity derating include cable fill, cable loading, cable type, raceway
construction, and ambient temperature.  
.

                                                            IN 93-40
                                                            May 26, 1993
                                                            Page 4 of 4


Cable derating calculations that are based on inaccurate or nonconservative
derating factors could result in installation of undersized cables or raceway
overfilling.  This could cause operating temperatures to exceed design limits
within the raceways thereby reducing the expected design life of the cables.  

In the letter to Thermal Ceramics, Inc., of April 27, 1993, the staff
requested additional information on ampacity derating.

The National Electrical Code, Insulated Cable Engineers Association (ICEA)
publications, and other industry standards provide general ampacity derating
factors for open-air installations but do not include derating factors for
fire barrier systems.  The Insulated Conductors Committee of the IEEE Power
Engineering Society, Task Force 12-45, has been developing IEEE Standard
Procedure P848, "Procedure for the Determination of the Ampacity Derating of
Fire Protected Cables," for use as an industry standard.  The industry
consensus standard development process may formulate an appropriate technical
approach to the determination of ampacity derating factors for cables enclosed
by fire barrier systems.

The staff is continuing to review this product for its ability to perform its
fire resistive function and will evaluate whether further generic
communications are needed to address the issues discussed above.

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.


                                 ORIGINAL SIGNED BY


                              Brian K. Grimes, Director 
                              Division of Operating Reactor Support
                              Office of Nuclear Reactor Regulation   

Technical contact:  Isabel M. Miller, NRR
                    (301) 504-2852

Attachment:
List of Recently Issued Information Notices


.ENDEND
```

*Page Last Reviewed/Updated Thursday, March 29, 2012*

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