Information Notice No. 95-52: Fire Endurance Test Results for Electrical Raceway Fire Barrier Systems Constructed from 3M Company Interam Fire Barrier Materials
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
November 14, 1995
NRC INFORMATION NOTICE 95-52: FIRE ENDURANCE TEST RESULTS FOR
ELECTRICAL RACEWAY FIRE BARRIER SYSTEMS
CONSTRUCTED FROM 3M COMPANY INTERAM FIRE
BARRIER MATERIALS
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 addressees of the results of recent
fire endurance tests for electrical raceway fire barrier systems
constructed from 3M Company Interam fire barrier materials. It
is expected that recipients will review the information for
applicability to their facilities and consider this information,
as appropriate, in their review of Interam fire barriers.
Background
On April 20, May 17, and July 7, 1995, the NRC staff visited
Omega Point Laboratories (OPL), San Antonio, Texas, to witness
full-scale fire endurance tests for electrical raceway fire
barrier systems constructed from 3M Company Interam fire barrier
materials. These tests were sponsored by Peak Seals Corporation
(Peak Seals). Peak Seals informed the NRC staff that the test
specimens included in this test program were intended to
represent generic Interam fire barrier systems and that these
test programs were conducted in accordance with Generic Letter
(GL) 86-10, Supplement 1, "Fire Endurance Test Acceptance
Criteria for Fire Barrier Systems Used To Separate Redundant Safe
Shutdown Trains Within the Same Fire Area." The following
information is based on observations made by the NRC staff who
witnessed these fire tests. The NRC staff has not reviewed the
test reports.
Description of Circumstances
1-Hour Fire Endurance Tests
The first test assembly included nominal 24-inch and 6-inch-wide
steel cable trays; 1-inch, 2-inch, 3-inch, and 5-inch-diameter
steel conduits; a 2-inch diameter air drop; each was arranged in
a U-shaped configuration; and a 12-inch by 12-inch by 8-inch
steel junction box. With regard to the 2-inch-diameter steel
conduit, the junction box was installed in one of its vertical
runs and the 2-inch diameter air drop was installed in the other.
These test specimens did not include cable fill and were
supported by a common trapeze
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support. They were protected with three layers of Interam E53A
fire barrier mat material. Each layer was 7.6 mm [0.3 inch]
thick.
On April 20, 1995, OPL subjected the test assembly to the test
fire specified in American Society for Testing and Materials
(ASTM) Standard E-119, "Fire Test of Building Construction and
Materials," for 1 hour. After the fire exposure, the test
specimens were subjected to a fog-nozzle hose stream test. The
24-inch-wide cable tray; the 3-inch-, 2-inch-, and 1-inch-
diameter conduits; and the air drop exceeded the temperature rise
acceptance criteria of GL 86-10, Supplement 1, near the end of
the 1-hour fire exposure. None of the barriers burned through
during the fire exposure nor were they breached by the hose
stream. Table 1 (see Attachment 1) summarizes the test specimen
and fire barrier configurations and the results of the
April 20, 1995, test.
The second test assembly included a 24-inch-wide steel cable
tray, 1-inch- and 5-inch-diameter steel conduits, and a 2-inch-
diameter air drop. These test specimens did not contain cables
and were protected with three layers of Interam E54A fire barrier
mat material. Each layer was 10 mm [0.4 inch] thick.
On May 17, 1995, OPL subjected the test assembly to the test fire
specified in ASTM Standard E-119 for 1 hour. After the fire
exposure, it subjected the test specimens to a fog-nozzle hose
stream test. These 1-hour test specimens met the acceptance
criteria of Supplement 1 to GL 86-10. Table 2 (see Attachment 1)
summarizes the test specimen and fire barrier configurations and
the results of the May 17, 1995, test.
3-Hour Fire Endurance Test
The third test assembly included nominal 24-inch- and 6-inch-wide
steel cable trays; nominal 1-inch-, 3-inch-, and 5-inch-diameter
steel conduits; a 2-inch-diameter air drop; each was arranged in
a U-shaped configuration; and a nominal 12-inch by 12-inch by
8-inch steel junction box. The cable trays were filled with a
single layer of mix cables. The cable trays, the 1-inch- and
3-inch-diameter steel conduits, and the air drop were protected
with five layers of Interam E54A fire barrier mat material. The
5-inch-diameter conduit and the junction box were protected with
six layers of Interam E54A fire barrier mat material. Each layer
was 10 mm [0.4 inch] thick.
On July 7, 1995, OPL subjected the test assembly to the test fire
specified in ASTM Standard E-119 for 3 hours. After the fire
exposure, it subjected the test specimens to a fog-nozzle hose
stream test. The barriers did not burn through during the fire
exposure, nor were they breached by the hose stream. There was
no visible damage to the test specimen cables. However, all of
the test specimens exceeded the temperature rise acceptance
criteria of GL 86-10, Supplement 1. Table 3 (see Attachment 1)
summarizes the test specimen and fire barrier configurations and
the results of the July 7, 1995 test.
Discussion
Section 50.48 of Title 10 of the Code of Federal Regulations
requires that each operating nuclear power plant must have a fire
protection plan that
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satisfies General Design Criterion (GDC) 3 of Appendix A to 10
CFR Part 50. Fire protection features required to satisfy GDC 3
include features to ensure that one train of systems necessary to
achieve and maintain shutdown conditions is free of fire damage.
One means of satisfying this requirement is to separate one safe
shutdown train from its redundant train with a fire-rated
barrier. The level of fire resistance required of the barrier, 1
hour or 3 hours, depends on the other fire protection features in
the fire area.
The NRC issued guidance on acceptable methods of satisfying the
regulatory requirements of GDC 3 in Branch Technical Position
(BTP) Auxiliary and Power Conversion Systems Branch (APCSB)
9.5-1, "Guidelines for Fire Protection for Nuclear Power Plants";
Appendix A to BTP APCSB 9.5-1; BTP Chemical Engineering Branch
(CMEB) 9.5-1, "Fire Protection for Nuclear Power Plants"; and
GL 86-10, "Implementation of Fire Protection Requirements."
These guidance documents state that the fire resistance ratings
of fire barriers should be established in accordance with
National Fire Protection Association (NFPA) Standard 251,
"Standard Methods of Fire Tests of Building Construction and
Materials" (1975), by subjecting a representative test specimen
to a standard fire exposure.
On March 25, 1994, the NRC issued Supplement 1 to GL 86-10 to
(1) clarify the applicability of the test acceptance criteria in
GL 86-10 to raceway fire barrier systems, (2) specify a set of
fire endurance test acceptance criteria that are acceptable for
demonstrating that fire barrier systems can perform the required
fire-resistive function and maintain the protected safe shutdown
train free of fire damage, (3) specify acceptable options for
hose stream testing, and (4) specify criteria for cable
functionality testing when a deviation is necessary, such as when
the fire barrier temperature rise criteria are exceeded or the
test specimen cables sustain visible damage. These positions are
incorporated by the NRC staff in its review and evaluation of the
adequacy of fire endurance tests and fire barrier systems
proposed by licensees or applicants to satisfy existing NRC fire
protection rules and regulations.
Some temperatures observed during the tests exceeded the maximum
allowable temperature acceptance criteria of Supplement 1 to GL
86-10. In accordance with this supplement, an engineering
evaluation could be performed to determine the acceptability of
an in-plant Interam fire barrier that was bounded by a deviating
test specimen configuration. Information about such evaluations
can be found in Enclosure 2 of Supplement 1 to GL 86-10. By
letter dated August 7, 1995 [accession number 9509050173 ], Peak
Seals submitted to the NRC staff additional documentation
relating to the thermal performance of the 3-hour fire barrier
test specimens for information.
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This information notice requires no specific action or written
response. If you have any questions about the information in
this notice, please contact one of the technical contacts listed
below or the appropriate Office of Nuclear Regulation (NRR)
project manager.
/s/'d by DMCrutchfield
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Patrick M. Madden, NRR
(301) 415-2854
Amarjit Singh, NRR
(301) 415-1237
Attachments:
1. Tables 1, 2, and 3, Summaries of Endurance Tests [see WordPerfect file ]
2. List of Recently Issued NRC Information Notices
Page Last Reviewed/Updated Tuesday, March 09, 2021