ML20056D853
| ML20056D853 | |
| Person / Time | |
|---|---|
| Issue date: | 05/27/1993 |
| From: | Marcus G Office of Nuclear Reactor Regulation |
| To: | Larkins J Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-GENERAL, GL-92-08, GL-92-8, NUDOCS 9308180161 | |
| Download: ML20056D853 (26) | |
Text
r3 a...
MTf 27, 1993'
- ac l
I MEMORANDUM FOR: John T. Larkins, Executive Director Advisory Committee on Reactor Safeguards FROM:
Gail H. Marcus, Chief Generic Communications Branch Division of Operating Reactor Support Office of Nuclear Reactor Regulation
'i
.i
SUBJECT:
FORWARDING OF PROPOSED NRC SUPPLEMENT I TO GENERIC LETTEP 92-08, " FIRE ENDURANCE TEST ACCEPTANCE CRITERIA FOR FIRE BARRIER SYSTEMS USED TO SEPARATE REDUNDANT SAFE SHUTDOWN TRAINS WITHIN THE SAME FIRE AREA" i
Enclosed is the proposed NRC generic letter supplement for your information.
The NRR staff has transmitted it to the Committee for Review of Generic i
Requirements for its review and comment, We intend to notice this proposed generic letter supplement for public comment in the Federal Reaister following the completion of this review.
Ashok C. Thadani, Director, Division of System Safety and Analysis is the sponsoring division director.
/S/
Gail H. Marcus, Chief Generic Communications Branch Division of Operating Reactor Support i
Office of Nuclear' Reactor Regulation
Enclosure:
As stated CONTACT:
Richard J. Kiessel, NRR 504-2840 l
-t DISTRIBUTION w/o enclosure DISTRIBUTION w/ enclosure l
FJMiraglia,NRR MFlee, ACBS JGPartlow,NRR RPSavio,- ACBS BKGrimes,NRR WMDean, NRR-AEChaffee,NRR HNPastis, NRR CIGrimes,NRR RJKiessel,NRR-GHMarcus,NRR Central Files.
..DDRS r/f' 0GCB r/f l
RJKiessel-r/f
.]
'l l
1 OGCB, DORS,NRR.
C/0GCB,00RS,NRR PJKiessel /
GHMarcusg4ff 5/ff/93: //
S/a /93 DOCUMENT NAME:
MEMO.355 d Qf,f 5 6Ene m W.
~ i
(.
'T)QQ
)( l')l146 Q18 ys y g g _ f C - G ;
lyihqp gg py :
,w.,mJ
.().qnnnn a i a a w--
geig2
. g,&g,(, e j gcg
-a ec vaos27 GENERAL PDR'-
~
,j
~.
>. 1
ff
- r UNITED STATES NUCLEAR REGULATORY COMMISSION n
5 y
W ASHINGTON, D. C. 20$55
\\...../
May 27,1993 HEMORANDUM FOR:
John T. Larkins, Executive Director Advisory Committee on Reactor Safeguards FROM:
Gail H. Marcus, Chief Generic Communications Branch Division cf Operating Reactor Support Office of Nuclear Reactor Regulation
SUBJECT:
FORWARDING OF PROPOSED NRC SUPPLEMENT 1 TO GENERIC LETTER 92-08, " FIRE ENDURANCE TEST ACCEPTANCE CRITERIA FOR FIRE i
BARRIER SYSTEMS USED TO SEPARATE REDUNDANT SAFE SHUTDOWN TRAINS WITHIN THE SAME FIRE AREA" Enclosed is the proposed NRC generic letter supplement for your information.
The NRR staff has transmitteo it to the Committee for Review of Generic Requirements for its review and comment. We intend to notice this proposed generic letter supplement for public comment in the Federal Reaist.er following the completion of this review.
Ashok C. Thadani, Director, Division of System Safety and Analysis is the sponsoring division director.
u Gail H. Marcus, Chief Generic Communications Branch Division of Operating Reactor Support Office of Nuclear Reactor Regulation
Enclosure:
As stated CONTACT: Richard J. Kiessel, NRR 504-2840 d
..4
F ps no..
UNITED STATES f
A f j >m ' i NUCLEAR REGULATORY COMMISSION
~b W ASHINGTON. D. C. 20555 n
TO:
ALL HOLDERS OF OPERATING LICENSES OR CONSTRUCTION PERMITS FOR NUCLEAR POWER REACTORS
[
SUBJECT:
FIRE ENDURANCE TEST ACCEPTANCE CRITERIA FOR FIRE BARRIER SYSTEMS USED TO SEPARATE REDUNDANT SAFE SHUTDOWN TRAINS WITHIN THE SAME FIRE AREA (SUPPLEMENT 1 TO GENERIC LETTER 92-08," THERM 0-LAG 330-1 FIRE EARRIER SYSTEMS")
PURPOSE The U.S. Nuclear Regulatory Commission (NRC) is issuing this supplement to Generic Letter (GL) 92-08 in order to disseminate to licensees the NRC position en fire endurance test acceptance criteria for fire barrier systems useo to separate redundant safe snutdown trains within the same fire area.
This position will be used by the NRC to evaluate licensee fire endurance testing programs.
?
BACMGROUND The W stiff began a review of Thermo-Lag 330-1 fire barrier system fire endurance and ampacity derating test reports, installation procedures, and as-built configurations af ter receiving reports from Gulf States Utilities about' f ailed qualification fire tests and installation problems.
The staff issued the results of its initial review in NRC Information Notice (IN) 92-46, "Thermo-Lag Fire Barrier Material Special Review Team Findings, Current Fire U1 durance Tests, and Ampacity Calculation Errors," June 23, 1992.
The special review team report enclosed with IN 92-46 included the technical bases for this generic letter supplement. The staff found the following regarding 1 barriers: incomplete or indeterminate fire test results, Thermo-Lag
'ity derating test results and a wide range of documented questionabi
. actors. some barrier installatiuns that are not constructed ampacity dei n' o
in accordance wdh vendor-recommendeo installation procedures, incomplete installation procedures, and as-built' fire barrier configurations-that may not i
be qualified by a valid fire endurance test or evaluated in accordance with the guidance previously provided by the staff in'GL 86-10 " Implementation of Fire Protection Requirements." April 24, 19BC.
As a result of the snecial review team report findings, the staff issued GL 92-03. Thermo-Lag 330-1 Fire Barriers, on December 17, 1992.
Licensees were requested to confirm (1) that the Thermo-Lag 330-1 barrier systems have been qualified by representative fire endurance tests, (2). that the ampacity derating factors have'been derived by. valid tests, and (3) that these qualified barrio.7 have been installed with appropriate procedures and quality controls to " -
e that they comply with the NRC's requirements.
GL 92-08 Reporting Ru -
T 't 2(a) recuired licensees te state whether or not they had qualified tLa 1 7.-Lag 330-1 fire barriers by. condccting fire endurance tests in accor n with the NRC's requirements and guidance or licensing i
J commitments.
T'
..applement to GL 92-08 clarifies the NRC's requirements and guidance applicaola to this reporting recuirement.
- =. -
Generic Letter 92-08 SUPPLEMENT 1 May
, 1993
.. v AREAS OF CONCERN The NRC's areas of concern are:
(1)
The fire endurance test acceptance criteria used by the industry and l
licensees did not fully demonstrate the fire barrier performance required by NRC regulations.
i Cable functionality testing did not fully demonstrate the capability of (2) the protected circuit to function during and after a postulated fire.
r The NRC is concerned that qualification tests for fire barrier systems used to separate redundant safa shutdown trains within the same fire area may not demonstrate that these fire barrier systems provide the level of fire endurance intended by licensees. Therefore, licensees that use fire barth s systems that have not had their fire-resistive performance evaluated against NRC fire barrier acceotance criteria may not be meeting the requirements of y
Section 50.48. " Fire Protection," and General Design Criterion (GDC) 3, " Fire Protection," of Appenoix A, " General Design Criteria for Nuclear Power Plants." of Part 50 of Title 10 of the Code of Federal Reaulations (10 CFR Part 50).
i r
FIRE ENDURANCE CAPABILITY NRC Dealifica+ ion Reouirements and Guidance for Fire Barriers j
Section 50.48 of 10 CFR requires that each operating nuclear power plant have a fire protection plan that satisfies GDC 3.-
GDC 3 requires that structures,
- i systems, and ccmponents important to safety be designed and located to minimize, in a manner consistent with other safety requirements, the-probability and effects of fires.
Fire protection features-required to r
satisfy GDC 3 include features to ensure that one train of those systems a
neces:ary to achieve and maintain shutdown conditions be maintained free of fire damage. One means of complying with this requirement is to separate'one r'
The safe shutdown train frem its reoundant train with fire-rated barriers.
level of fire resistance required of the barriers, I hour. or 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. depends -
on the other fire protection features in the-fire area.
dance.on acceptable methods of satisfying the regulatory..
t The NRC issued.-
requirements of uDC 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 APCSS 9.5-1; BTP Chemical Engineering Branch (CMEB) 9.5-1, " Fire Protection for Nuclear Power Plants," July 1981;-
In the BTPs and in GL 86-10, the staff stated that the fire and GL B6-10.
resistance ratings of fire barriers should be established in-accordance with Nationai_ Fire Protection Association (NFPA)- Standard 251, " Standard Methods of Fire Tests of Building Construction and Materials," by subjecting a test specimen that represents.the materials, workmanship, method of assembly, i
'I f
F i
.i
Generic Letter 92-08 SUPPLEMENT I May
, 1993 dimensions, and conficuration for wnich a fire rating is desired to a 1
"standara fire exposure."'
The industry and licensees have used the acceptance criteria of American Nuclear Insurers (ANI) Information Bulletin No. 5 (79) "ANI/MAERP Standard Fire Endurance Test Method To Qualify a Protective Envelope or Class IE Electrical Circuits," July 1979, to evaluate the performance of their fire carrier systems.
The ANI test methodology requires the cables within the protective fire barrier test specimen to be monitored for circuit integrity wnile the test specimen is subjected to a fire +.est that follows the American Society of Testing and Materials (ASTM) Standard E119, " Standard Methoas of i
Fire Tests of Building Construction and Materials," standard-time-temperature curve ana to a hose stream test. Under this criterion, the fire barrier system is evaluated by monitoring the capability of the cables inside the fire barrier to pass a low voltage circuit integrity tt.st.
During the fire nnd hose stream tests,* if cable circuit integrity is nit lost the tests are considered successful. The ANI test methodology das not establish acceptance criteria for temperature rise during the fire test 1.n the unexposed side of the barrier nor does it establish cable thermal der;radation criteria.
This test methodology does not prohibit the barrier from being breached by either the fire or the nose stream and would allow the cables to be thermally cegraceo as long as circuit integrity was not lost during the test.
The NRC in GL 86-10 identified NFPA Standard 251, Chapter 7, fire testing acceptance criteria for Non-Load Bearing Partitions, as being applicable to cable wrap systems.
Under the acceptance criteria established by NFPA Standard 251, Chapter 7, the fire-resistive performance of the barrier system is evaluated by reviewing the test results against the following criteria:
(1)
The fire barrier design has withstood the fire endurance test without the passage of flame or the ignition of cotton waste on the unexposed side for a period of time equivalent to the fire-resistance rating required of the barrier.
(2)
The temperature levels recorded on the unexposed side of the fire barrier when analyzed demonstrate that the maximum ten.;te sture rise does not exceed 139 *C
[250 'F] above amoient.
(3)
The fire barrier remains intact and does not allow projection of water beyonc the unexposed surface during the hose stream test. " Interpretations of Appendix 1," to GL 85-10, provided additional-guidance with respect to the term " free from fire damage."
Interpretation 3,_
" Fire Damage," states, "In promulgating Appendix R, the Commission has provided methods acceptable for assuring that necessary structures, systems, 3
and components are free from fire damage (see Section III.G.2a, b, and c),
that is, the structure, system or component under consideration is capable of performing its intended function during and af ter the postulated fire, as neeaed."
American Society for Testing and Materials (ASTM) Standard E119 was adopted by NFPA as NFPA Standard 251.
Generic Letter 92-08 SUPPLEMENT 1 May
, 1993 Since experience has demonstrated that fire endurance testing of these fire barrler systems may not have yielded results that meet the acceptance criteria established by NRC guidance and that the acceptance criteria identified in are not specifically applicable to raceway fire barrier systems, the GL 86J NRC %s oeveloped a staff position on fire endurance test acceptance criteria for fire barrier systems used to separate redundant safe shutdown trains l
within the same fire area.
This NRC staff position clarifies the use of NFPA 251, " Fire Test Acceptance Criteria for Non-Bearing Partitions," identified by GL 86-10 as being applicable to raceway fire barrier systems, by providing an interpretation of-this criteria as they apply to raceway fire barrier systems and fire barrier systems used to separate redundant safe shutdown functions within the same This staff position is one method that specifies acceptable fire fire area.
endurance test acceptance criteria which demonstrate that these fire barrier systems can perform the required fire-resistive function and maintain the In addition, this staff protected safe shutdown train free of fire damage.
position provides acceptab b options for hose stream testing and establishes criteria for functionality testing of cabling if the fire barrier temperature rise criteria is exceeded and cable damage is visible. The staff position is being used as review guidance by the staff.
Other methods and approaches that will demonstrate an equivaient level of protection can be proposed to the NRC and will be reviewed and considered by the staff on a case-by-case basis.
Any i
future fire barrier fire endurance testing by licensees to demonstrate compliance with existing NRC rules and regulations should follow the staff position or an NRC approved alternative. is the NRC position on' fire endurance test acceptance criteria for tire barrier systems used to separate redundant safe shutdown trains within the same fire area.
Fire Endurance and Funct onality Testino - Evaluation and Acolication of Test t
Results 2.ccording to the staff position, the fire endurance qualification test is successful if the following conditions are met.
The internal temperature of the fire barrier system, as measured on the (1) exterior surface of the raceway or component, does not rise more than-139 *C [250 *F) above its initial temperature.
(2)
If the above thermal limits are exceeded, a visual inspection of the cables is made and the cables when inspected do not show. signs of 3
[325 "F) temperature condition addressed in The 163 "C GL 36-10 was established by allowing the internal temperature to rise 13 9.. *C [250 F] above ambient laboratory air temperature, assumed to be 24 *C [75-F], during the fire test.
an assessment'
~
When the temperoture. criterion'is exceeded, 3
of component operability at the temperature conditions that would-be experienced-by the' component during the fire test is required; '
fire endurance test results that are judged acceptable j
that is, c
Generic Letter 92-08 SUPPLEMENT 1 May
, 1993 degraded conditions' resulting from the thermai effects of the fire exposure.
The raceway fire carrier system remains intact during the fire exposure (3) and water hose stream test without developing any openings through which the electrical conductor or raceway is visible.
For the raceway fire barrier system, the staff adopts the hose stream testing methocology established by NUREG-0800, Standard Review Plan (SRP) for the Review of Safety Analysis Reports for Nuclear Power Plants," Section 9.5.1,
" Guidelines for Fire Protection for Nuclear Power Plants," Revision 2.
July 1981, Position 5.a.
This SRP position establishes the acceptability of using the fog nozzle method for hose stream testing of fire barrier penetration seals.
The staff position is tha', if cables show signs of thermal degradation during the fire test, the fire barrier did not perform its required fire-resistive function. Under these conditions, the licensee can submit a deviation based on demonstrating the functionality of thermally degraded cables to the staff for review.
The staff position provides testing guidance for demonstrating cable functionality.
Functionality testing includes subjecting the cables to The results of these tests can be used to megger and high potential tests.
determine the insulation resistance characteristics of the thermally damaged cable and to determine if the cable insulation would have been sufficient to maintain circuit functionality during and after _the fire exposure.
ACTIONS RE0 VESTED None REPORTING REOUIREMENTS None on the basis of a visual inspection may not be applied to other components without a specific evaluation.
' Examples of cable thernal degradatien are the following:
swollen, split, cracked, blistered, nelted, or discolored jacket; exposed shield;. exposed, degraded, or discolored conductor insulation; exposed copper conductor.
j
Generic Letter 92-08 SUPPLEMENT 1 May
, 1993 BACKFIT DISCUSSION The types of barriers addressed in this supplement are installed at many operating power reactor sites and are requireo to meet either a condition of a
[
plant's operating license or NRC requirements such asSection III.G of Appendix R to 10 CFR Part 50.
The NRC staff has determined that fire endurance test acceptance criteria specified by GL 86-10 and those specified i'
by ANI Bulletin No. 5 (79) do not ensure that these fire barrier systems will adequately perform their required fire resistive function.
This Supplement 1
.i' to GL 92-08: 1) modifies existing NRC guidance for fire endurance test i
acceptance criteria to clarify its applicability to fire barrier systems used to separate safe shutdown functions within the same fire area, 2) provides additional guidance on options for hose stream testing and, 3) establishes criteria for the placement of thermocouples and functionality testing of cabling if the fire barrier temperature rise criteria is exceeded and cable damage is visible.
Although this supplement contains a change in staff position with respect to the application of existing fire endurance testing acceptance criteria, it does not change the fire resistive performance goals of the fire barrier system.
This staff position is one method that specifies i
acceptable criteria wnich demonstrate that these fire carrier systems can perform the required fire-resistive function and maintain the protected safe shutdown train free of fire damage.
The staff position is being used as
.i review guidance by the staff.
Any future fire barrier fire endurance testing by licensees to demonst ate compliance with existing NRC rules and regulations should follow the staff pcsition or an NRC approved alternative.
The staff has concluded that this change in staff position is a backfit which is necessary in order to ensure compliance with GDC 3, 10 CFR Section 50.48, and Appendix R to 10 CFR Part 50. This position clarifies existing fire endurance testing acceptance criteria established by GL 86-10 and does not reject past tests of raceway fire barrier systems that may have been performed to this previous criteria. This position incorporates the fire hose stream testing criteria for fire barrier penetration seals specified in SRP Section 9,5.1 and applies this criteria to raceway fire barrier systems.
In addition, it provides guidance, which was not previously specified by GL E6-l
- 10. on the placement of thermocopies on the test specimen and identifies the type of tests needed to verify cable functionality when the fire barrier does~
not meet the specified acceptance criteria. Accordingly, this generic letter is being issued as a compliance backfit under the terms of 10 CFR 50.109(a)(4)(i) and a backfit analysis is not required.
i e
PAPER REDUCTION ACT STATEMENT This generic letter contains no information collection requirements and, therefore, is not: subject to the requirements of the Paperwork Reduction Act of 1980 (44U.S.C. 3501 el g n).
I
g-.
3'...
r Generic Letter 92-08 SUPPLEMENT 3 May, 1993 if you have any questions about this matter, please contact the technical
-j contact or the lead project manager listed below.
.i Sincerely, r
James G. Partlow i
Associate Director for Projects' Office of Nuclear Reactor Regulation
Enclosures:
1.
NRC Staff Position on Fire Endurance Test Acceptance Criteria for Fire Barrier Systems Used To Separate f
Redundant Safe Shutdown Trains Within the Same Fire Area 2.
List of Recently Issued Generic Letters l
TECHNICAL CONTACT:
Patrick M. Madden, NRR (301) 504-2854 LEAD PROJECT MANAGER:
William H. Dean, NRR-(301) 504-1054.
9
+-'
4 i
l b
h I
r 1
a q
DRAFT a
FIRE ENDURANCE TEST ACCEPTANCE CRITERIA FOR FIRE BARRIER SYSTEMS USED TO SEPARATE REDUNDANT SAFE SHUTDOWN TRAINS WITHIN THE SAME FIRE AREA I.
BACKGROUND In 1975, the Browns Ferry' Nuclear power plant experienced a serious electrical l
cable tray fire.
This fire had a significant impact on operator respcase to the event from a safety perspective. The fire caused spurious instrumentation indications and affected the control of several safety systems.
As a result of this fire, the NRC issued the following fire protection guidelines and-regulations concerning fire protection programs at nuclear power plants.
May 1, 1976 Branch Technical Position (APCSB) 9.5-1, " Fire Protection Program."
l February 24, 1977 Appendix A to Branch Technical Position APCSB 9.5-1, " Guidelines for Fire Protection for Nuclear Power Plants Docketed Prior to July 1, 1976."
February 19, 1981 10 CFR 50.48,." Fire Protection."
l February 19, 1981 Appendix R to 10 CFR 50, " Fire Protection Program for Nuclear Power Facilities Operating Prior to. January 1979."
l July 1981 NUREG-0800, Standard Review Plan (SRP), 9.5.1,.
" Fire Protection for Nuclear Power Plants."
l In addition to the above fire protection guidance and regulations, the NRC, in an effort to clarlfy its fire protection requirements to the industry, issued i
Generic Letter (GL) 81-12. " Fire Protection Rule (45 FR 76602.
November 19, 1980)," February 20, 1981; GL 83-33,."NRC Position on Certain Requirements of Appendix R to 10 CFR 50," October 19, 1983; and GL 86-10
" Implementation of Fire Protection Requirements," April 24, 1986.
GL Ei 10, which took precedence over previous staff guidance, provided staff interpretations to Appendix R and answers-to industry questions relating to-the-implementation of Appendix R.
The NRC, in an effort to give-the licensees more flexibility to make changes to their plant specific. fire protection-
-program. issued GL 88-12, " Removal of Fire Protection Requirements From Through the implementation and the adoption of a'
~ Technical Specifications."
standard license condition, a licensee can make changes which do not adversely affect plant ability ~to achieve and maintain post-fire safe' shutdown to their r
fire protection program in accordance with 10 CFR 50.59.
[
The aforementioned NRC documents provided the industry'with NRC staff guidance concerning fire barriers separating plant fire areas, including the fire resistance (endurante) ratings for these barriers and the qualification testing'that establishes their fire resistance ratinos.
In addition,:these I
'l I
1
~
documents provided guidance on comDustibility of structural materials and the 4
testing required to demonstrate low flame spread properties.
The following sections of this document provide the objective for providing safe snutdown related fire barriers in nuclear power plants, definition of a
fire protection terms related to fire barriers, and the NRC fire endurance
.i testing acceptance criteria for fire barriers used to separate safe shutdown functions within the same fire area.
II.
OBJECTIVE OF FIRE BARRIERS USED TO SEPAP. ATE SAFE SHUTDOWN FUNCTI:
WITHIN THE SAME FIRE AREA Fire rated barriers are used in nuclear power plants to provide fire area separation between redundant safety related components and safe shutdown functions.
They provide fire resistance protection, as required by Appenaix R', to one safe shutdown train in those fire areas which contain
.t both trains.
The objective of the safe shutdown related Appendix R fire barrier is to ensure that a safe shutdown train is conservatively protected from fire-related thermal damage. The necessity for these fire barriers has These PRAs been verified by multiple probabalistic risk assessments (PRAs).
indicate, even with these fire barriers installed, fires provide a major I
contribution to core melt probabilities.
It is the position of the Plant Systems Branch that fire endurance ratings of-building construction and materials are demonstrated by testing fire barrier assemblies in accordance with the provisions of the applicable sections of NFPA 251, " Standard Methods of Fire Tests of Building Construction and-Materials " and ASTM E-119, " Fire Test of Building Construction and Materials." Assemblies which pass specified acceptance criteria-(e.g.,-
standard time-temperature fire endurance exposure, unexposed side temperature rise, and hose stream impingement) are considered to have'a specific fire-resistance rating. to GL-86-10, Interpretations of Appendix R, provided additional guidance with respect to the term " free from fire damage."
Interpretation 3, i
" Fire Damage," states, "In promulgating Appendix R, the Commission has provided metho6 acceptable for assuring that necessary structures, systems,-
and components are free from fire damage (see Section III.G.2a, b, and c),
that is, the structure, system or component under consideration is-capable of performing its intended function during and after the postulated fire,'as-needed."
GL 85-10,' Response 3.2.1, also stated that, "The resulting 325 "F' cold side temperature criterion is used for cable tray wraps because they perform a fire It is clear barrier function to preserve the cables free from fire damago.
that cable that beains to dearade at 450 *F is free from fire damage-at 325'"F."
(Emphasis added.)
In addition, the. staff's response stated ~that, "for newly identified conduit and cable trays requiring such wrapping new For advanced reactor designs,, redundant safe shutdown functions;are -
required to be located in separate 3-hour fire areas.
,T r
?
i which meet the 325 *F criterion should be used, or justification materia snould be provided for the use of material which does not meet the 325 *F criterion. This may be based on an analysis demonstrating that the maximum recoroed temperature is sufficientiv below the cable insulation ignition temperature."
(Empnasis added.)
The basic premise of the NRC fire resistance criteria is that fire barriers wnich oo not exceeo 163 *C [325 *F] cold side temperature and pass the hose stream test provide ~ adequate assurance that the shutdown capability is protected without further analyses.
If the temperature criteria is exceeded, sufficient additional information is needed to perform an engineering evaluation to demonstrate that the shutdown capability is protected.
III.
DEFINITIONS In order to support the understanding of the technical terms used throughout this document, the following definitions are provided.
Combustible Material - Material that does not meet the definition of non-combustible.
Fire Barrier - Those components of construction (walls, floors and their supports), including beams, joists, columns, penetration seals.or closures, fire doors, and fire dampers that are rated by approving laboratories in hours of resistance to fire and are used to prevent the spread of fire.
i Raceway Fire Barrier - Non-load bearing partition typa envelope system installed around electrical components and cabling that are rated by approving laboratories in hours of-resistance to fire and are used to maintain safe.
shutdown functions free from fire damage.
Fire Resistance Ratina - The time that materials of a test assembly'have withstood a standard ASTM E-119 fire exposure and have sucessfully met the' established test acceptance criteria (Fire-Barrier Testing Acceptance Criteria refer to Sections IV, V and VI).
L Noncombustible Material - (a) Material which in the form in which it is used and unoer the conditions anticipated, will not ignite, burn, support combustion, or release flammable. vapors when subjected to fire' or heat: (b)
Material having a structural base of noncombustible material, with a surfacing -
l not over 1/8-inch thick that has a' flame spread rating of.not higher than 50 wnen measured using ASTM E-84 Test " Surface Burning Characteristics of-
~
Building-Materials."
(Note - There is an exception to this definition as-defined by BTP Appendix A, Position D. 1. d.
This position allows the use of 3
combustible interior finishes when listed by a nationally recognized testing j
i 11aboratory, such as Factory Mutual or Underwriters Laboratories, Inc. for a flame spread, smoke and fuel contribution of 25 or less in its use configuration.)-.;
j
FIRE ENDURANCE TESTING ACCEPTANCE CRITERIA FOR FIRE BARRIER WALLS, IV.
FLOORS, AND CEILINGS USED TO SEPARATE SAFE SHUTDOWN FUNCTIONS WITHIN THE SAME FIRE AREA To demonstrate the adequacy of fire barrier walls, floors, ceilings, and NRC enclosures, barrier designs should be verified by fire endurance testing.
fire protection guidance refers to the guidance of NFPA 251 and ASTM E-Il9 as acceptable test methods for cemonstrating fire endurance performance.
The following are the fire endurance testing acceptance criteria for the subject fire barriers:
The fire barrier design has withstood the fire endurance test without the passage of flame or the ignition of cotton waste on the unexposed side for a period of time equivalent to the fire resistance rating required of the barrier; The temperature levels recorded on the unexposed side of the fire barrier are analyzed ano demonstrable that the maximum temperature does not exceeo 250 *F above ambient; and 1
The fire barrier remains intact and does not allow projection of water beyond the unexposed surface during the hose stream test. (For acceptable hose stream test methods and time of application - See Section VII.)
If the above criteria are met for fire barrier walls, floors, and ceilings separating' safe shutdown functions within the same fire area, the. barrier is considered to be acceptable.
NRC fire protection guidance also ensures that door and ventilation openings _
and penetrations are properly protected. The guidance requires that these openings be protected with fire doors and fire dampers which have been fire tested and listed by a nationally recognized testing laboratory (e.g.,
Underwriters Laboratories or Factory Mutual).
In addition, the construction and installation techniques for door and ventilation openings and other penetrations through these fire barriers should be appropriately qualified by fire resistive testing.
The guidance of NFPA 251 and ASTN E-119 should be consulted with regard to-construction, materials, workmanship, and details such as dimensions of parts, and the size of the specimen (s) to be tested.
In addition, NFPA 251 and ASTM-should be consulted with regard to the placement of thermocouples on the specimen.
ELECTRICAL-RACEWAY AND COMPONENT FIRE BARRIER SYSTEMS FOR SEPARATING V.
SAFE SHUTDOWN FUNCTIONS WITHIN THE SAME FIRE AREA The NRC provided guidance in Appendix A to Branch Technical Position 9.5-1, Position D.3.(d), for cable tray fire barriers.
This' fire-protection guidance.
-m.
I states that the design of fire barriers for horizontal and vertical cable trays should, as a minimum, meet the requirements of ASTM E-119, " Fire Test of On Building Construction and Materials," includino hose stream test.
Novemoer 19, 1980, the NRC issued Appendix R to 10 CFR 50.
The tecnnical I
basis for Section III.M, " Fire Barrier Penetration Seal Qualification." states that " Fire barriers are ' rated' for fire resistance by being exposed to a
'stancard test fire.'
This standard test fire is defined by the American Society of Testing and Materials in ASTM E-119."
In addition, this technical basis stated that "If specific plant conditions preclude the installation of a r
3-hour fire barrier to separate the redundant trains, a 1-hour fire barrier i
and automatic fire suppression and detection system for each redundant train Will be considered the equivalent of a 3-hour barrier."
In 1984 Appendix R workshops held with industry, and later in GL 86-10, the l
In i
staff provided guidance related to fire barrier designs for raceways.
', Question and Answers, to this GL, Question 3.2.1.,
" Acceptance Criteria." the staff provided guidance on the cold side temperature for fire barrier cable tray wraps.
In response to this question the staff stated that t
the acceptance criteria contained in Chapter 7 of NFPA 251, " Standard Methods of Fire Tests of Building Construction and Materials," pertaining to non-Dearing fire barriers was applicable to cable tray fire barrier wraps.
Chapter 5 of NFPA 251 explains the conduct of the fire test.
The following is the NFPA 251 acceptance criteria:
i The wall or partition shall have withstood the fire endurance test-without the passage of flame or gases hot enough to ignite cotton waste, for a period equal to that for which classification is.
desired:
The wall or partition shall have withstood the fire and hose. stream-.
l test as specified in Chapter 5, without passage of flame, or gases hot enough to ignite cotton waste, or of.the hose stream.
The assembly shall be considered to have f ailed the hose stream test.if i
an opening cevelops and permits projection of water from the stream and beyond the unexposeo surface during the hose stream test:
Transmission of heat through the wall or partition during the fire endurance test shall not have been such as to raise the temperature.
on its unexposed surface more than 139 "C [250 'F] above its initial temperature.
The staff considers the fire endurance qualification test to be successful if
.f the following conditions are met:
i ;
t s
t The internal temperature of the fire barrier system, as measured on the exterior surface of the raceway or comoonent, did not exceed f
139 *C [250 *F] above its initial temperature ; or i
(Staff Guidance: NFPA 251/ ASTM-E119 allows this temperature to be determined by averaging thermocouple temperature readings.
For the l
purposes of this criterion, thermocouple averaging can be used provided similar series of thermocouples (e.g., cable tray side rail) are averaged together to determine temperature performance of In addition, the conditions of l
the raceway fire barrier system.
acceptance are also placed on the temperatures measured by a single thermocouple. Under the conditions of acceptance, if any single thermocouple exceeds 30 percent of the maximum allowable temperature rise (i.e.,139 *C + 42 *C - 181 *K [250 *F + 75 *F - 325 '*F] the test is considered to have exceeded the criteria temperature limit.);
Where the above thermal limits are exceeded, a visual inspection of is required.
Cables when inspected shall not show 3
the cables signs of degraded conditions' resulting from the thermal affects of' the fire exposure; and (Staff Guidance: For those cases where signs of thermal degradation to the cables is present, it is considered that the fire barrier did not perform its intended fire resistive function.
For those i
barriers which are not capable of performing their intended
[
function, a deviation based on demonstrating that the functionality T
of thermally degraded cables was maintained and that these cables would have adequately performed their intended function during and j
after a postulated fire exposure may be granted.
The attachment to i
this proposed position provides a suggested methodology for j
demonstrating the functionality of. safe shutdown cabling during and after a' fire test exposure.)
ll The 163 C [325 *F] temperature condition was established by allowing 2
F).above ambient the internal temperature on the raceway to rise 139 *C (250 laboratory air temperature, assumed to be 24 *C (75 F), during the fire test.
l For components, when the temperature criteria is exceeded, an 3
assessment of component operability' at the temperature conditions which would
[
be experienced by the component during the fire test is required that is, raceway fire endurance tests which are judged acceptable on the basis of a visual inspection may not be applied to other components without a specific evaluation.
I
' Examples of thermal cable degradation are: -jacket swelling, splitting, conductor cracking, blistered, melted, or discoloration; snield exposed:
insulation exposed, degraded, or discolored; bare copper conductor exposed.
-s-
C The raceway fire carrier system shall have remaineo intact during the fire exposure and water nose stream test without developing any openings througn which the electrical conductor or raceway is visible.
Sectich VII identifies acceptable hose stream test methods and the time of application.
The test specimen shall be representative of the construction for which the fire rating is desireo, as to materials, workmanship, and details such as dimensions of parts, and shall be built under representative conditions.
Raceway fire barrier systems being subjected to qualification fire endurance testing should be representative of the end use.
For example, if it-is intended to install a cable tray fire carrier system in the plant without protecting the cable tray supports, then the test program should duplicate these field conditions.
In addition, the fire testing program should encompass the raceway sizes and the various configurations for those fire barrier systems installed in the plant. It should be noted that several test specimens will be required in order to qualify various sizes of horizontal and vertical runs of cable trays and conduits, junction boxes and pull boxes, etc.
i The raceway design used for testina should be constructed with materials and configurations representative of ii1 plant conditions (e.g., mas's associated with typical steel conduit, steel cable trays).
Measuring cable temperatures is not considered a reliable means for determining excessive temperature conditions which may occur at any point along the length of the cable during the fire test.
In lieu of measuring the unexposed surface temperature of the fire barrier test specimen, methods which j
will adequately measure the surface temperature of the raceway-(e.g., exterior
~
of the conduit, side rails-of cable trays, bottom and top of cable tray surfaces, junction box external surfaces) can be considered as equivalent if-i the raceway components used to construct the fire test specimen represent
~
plant specific components and configurations.
The metal surfaces of the -
raceway, under fire test conditions, exhibit good thermal conductivity properties.
Temperatures measured on these surfaces provide a conservative indication of the actual temperature rise within the fire' barrier system.
l ANI criteria for testing fire Darriers recommends the cable temperatures be monitored by thermocouDies.
Industry considers this the_ proper location for determining the temperature rise within the raceway fire barrier system.
j Since cable jackets have a low thermal conductivity, the actual local temperatures of the cable jackets indications-of. barrier failure, and internal fire barrier temperature rise conditions _during the. fire exposure are masked.
Monitoring cable temperatures can give indications of low internal fire barrier temperature conditions during the fire endurance _ test.
Using this temperature monitoring approach, cable damage can occur without-intiication of.
excessive temperatures cn the cables.
This linked with no loss of circuit integrity would give indications of a successful test.
The staff considers; monitoring the cable temoe-ature as the primary means of determining barrier.
performance to be nonconservative.
As discussed _above, temperatures monitored on the exterior surface of the raceway provide a more representative i
indication of fire barrier performance.
c 7.-
f I
l e
The following are acceptable placements of thermocouples on raceway fire l
barrier enclosures:
Conduits - measure the temperature of the conduit by placing the thermocouples every 6-inches on the conduit surface underneath the fire i
barrier material.
Cable Trays - measure temperature rise of cable tray by placing the thermocouples on the exterior surface of the tray side rails underneath the fire barrier material.
In addition to placing thermocouples on the side rails, thermocouples shall be attached to two 14 gage bare copper conductors. The first copper conductor will be installed on the bottom of the cable tray rungs along the entire length of the cable tray run.
The second conductor shall be installed along the outer top surface of the cables closest to the top and towards the center of the fire barrier.
The bare copper wire is more responsive, than cable jackets, to temperature rise within the fire barrier enclosure.
The temperature changes measured along the bare copper conductors provide indication of joint failure or material burn through conditions. Thermocouples shall be placed every 6-inches along the cable tray side rails and along the bare copper conductors.
In addition, thermocouples shall be placed every 12-inches on the surface of the outer cables nearest to the raceway and on the surface of the cables nearest to the underside of_ the top of the fire barrier.
Temperature condition's on the raceway during the fire-test will be determined by averaging the temperatures measured by the thermocouples.
In determining the raceway temperature conditions, the thermocouples measuring similar fire barrier areas of performance shall be averaged together and the basis of acceptance will be based on these individual averages. The following method of averaging shall be followed:
Conduits - The thermocouples applied to the outside metal surface of the conduit will be averaged together.
Cable Travs - The thermocouples on each cable tray side rail shall.be.
averaged separately.
For example, thermocouples placed on one side rail will be averaged separately from the other side rail.
In addition, the temperature conditions measured by thermocouples on th= bra copper conductors shall be averaged separately.
Cables - The thermocouples used to measure individual cable temperatures will be used for engineering purposes and shall not be used for evaluating the performance of the fire barrier system.
For each thermocouple group, the averages shall not exceed 139 *C [250 *F]
above the initial temperature at the' onset of the fire endurance test.
In addition, the temperature of each individual thermocouple will be evaluated.
~
Individual thermocouple conditions shall not exceed the 139 'C [250 'F]
temperature rise by more than 30 percent.
1 VI.
HOSE STREAM TESTING l
NFPA 251 and ASTM E-119 allow some flexibility in hose stream testing.
The standards allow the hose stream test to be performed on a duplicate test specimen subjected to a fire endurance test for a period equal to one-half of that indicated as the fire resistance rating, but not for more than I hour (e.g., 30 minute fire exposure to qualify a 1-hour fire rated barrier).
For safe shutdown related fire barrier systems, the staff finds the hose stream application specified by the NFPA 251 acceptable.
NFPA 251 reouires the stream of water to be delivered through a 6.4 cm [2\\-inch] hose discharging through a standard 2.9 cm [1%-inch] playpipe nozzle onto the test specimen after the fire exposura test.
The stream is applied with the nozzle orifice positioned 6.1 meters [20 feet) away from the center of the test specimen at a pressure of 207 kPa [30 psi gauge).
The application of the stream is to all exposed parts of the specimen for a minimum duration of 1 minute for a 1-hour barrier and 2i minutes for a 3-hour barrier.
As an alternate, the application of the hose stream test on the test specimen can ce performeo immeciately after tne completion of the full fire encurance test period.
If this method is used to satisfy the hore stream testing criteria, the following hose stream applications are considered acceptable:
The stream applied at random to all exposed surfaces of the test specimen through a 6.4 cm [2\\-inch] national standard playpipe with e
a 2.9 cm [1%-inch] orifice.at a pressure of 207 kPa [30 psi) at a distance of-6.1 meters [20 feet) from the specimen. (Duration of the hose stream application - 1 minute for a-1-hour barrier.and'2\\
minutes for a 3-hour barrier); or 5
The stream applied at random to all exposed surfaces of the test specimen through a 8.3 cm [li-inch] fog nozzle set at a discharge angle of 30 degrees with a nozzle pressure of 517 kPa [75 psi] and a minimum discharge of 284 1pm [75 gpm] with the tip of the nozzle at a maximum of 1.5 meters [5 feet] from the test specimen. -(Duration of the hose ~ stream application - 5 minutes for both 1-hour and'3-hour barriers); or The stream applied at random to all exposed surfaces of the test specimen through 8.3 cm [1\\-inch] fog nozzle set at a discharge angle of 15 degrees with a nozzle pressure of 517 kPa [75 psi] and a-minimum discharge of 284.1pm [75 gpm] with the tip of the nozzle at a maximum of 3 meters [10 feet) from the. test-specimen.
(Duration of'the hose stream application - 5 minutes for both 1-hour and 3-hour barriers.)
VII.
FIRE BARRIER COMBUSTIBILITY The NRC's fire protection guidelines-and requirements establish-the need for
~
. each nuclear power plant to perform a plant-specific fire hazard analysis.
The fire hazard analysis shall consider the potential for-in-situ and transient fire hazards and comoustibles. With respect to building materials
_g_
i M.
(e.g., cable insulation and jackets, plastics, thermal insulation, fire barrier materials), the combustibility, ease of ignition, and flame spread over the surface of a material shall be considered by the fire nazards analysis.
One method of determining ccmbustibility is by subjecting a sample of the fire barrier material to a small scale vertical tube furnace as described by ASTM E-136.
The flasnover ignition temperature, as determined by ASTM-01929, and the flame spread characteristics, as determined by ASTM E-84, of the fire barrier material shall be evaluated.
The potential heat release of the material shall also be determined and factored into the fire nazards analysis.
The heat release of the material can be determined by testing to the provisions of ASTM 0-3286 or NFPA 259.
Fire barrier materials used as radiant energy heat shields inside containment and used to achieve a combustible free zone are required to be noncomDustible as defined in Section III.
VIII. REFERENCES Nuclear Reculatorv rommission 1.
May 1. 1976 Brancn Technical Position (APCSB) 9.5-1, " Fire Protection Program."
2.
February 24, 1977 Appendix A to the Branch Technical Position APCSB 9.5-1, " Guidelines for Fire Protection for Nuclear Power Plants' Docketed Prior to July 1, 1976."
3.
February 19. 1981 10 CFR 50.48, " Fire protection.
4 February 19, 1981 Appendix R to 10 CFR 50, " Fire Protection for.
Nuclear Power Plants."
5.
February 20, 1981
" Staff Position - Safe Shutdown Capability,"
6.
July 1981 NUREG - 0800, Standard Review Plan (SRP), 9.5.l',
" Fire Protection for Nuclear Power Plants."
7.
October 19,,1983 "NRC Positions on Certain Requirements of.
Appendix R to 10 CFR 50," (Generic Letter 83-33).
8.
April 24, 1986
" Implementation of Fire Protection Requirements," (Generic Letter 86-10).
American Society for Testino and Materials (ASTM) 1.
ASTM E-84 Test " Surface Burning Characteristics of Building. Materials."
2.
ASTM E-119. " Fire Test of Building Construct' ion and Materials."
3.
ASTM E-136, " Behavior of Materials in a Vertical Tube furnace at 750*C." _ -_
f~
j
.. L
_]
]
4.
ASTM D-1929, " Test Method for Ignition Properties of Plastics."
5.
ASTM D-3286, " Test Method for Gross Calorific Value of Solid Fuel by the Isothermal-Jacket Bomb Calorimeter."
American Nuclear insurers (ANI) i 1.
July 1979, ANI Information Bulletin No. 5 (79) test criteria for " Fire-Endurance Protective Envelope Systems for Class IE Electrical Circuits."
National Fire Protection Association (NFPA) l 1.
NFPA 251, " Standard' Methods of Fire Tests of Building Construction and Materials."
i 2.
NFPA 259, " Standard Test Method for Potential Heat of Building.
I Materi al s. "
l i
a k
I I
t
'i 1
i.
E
.c ATTACHMENT ACCEPTABLE METHODS FOR DEMONSTRATING FUNCTIONALITY OF CABLES PROTECTED BY RACEWAY FIRE BARRIER SYSTEMS DURING AND AFTER FIRE ENDURANCE TEST EXPOSURE a.
INTRODUCTION The NRC considers fire barrier systems, which meet the acceptance-criteria, adequate under NRC fire protection regulations.
The licensee, where the criteria are not met, can submit an engineering analysis to the staff that clearly demonstrates the functionality of the protected cables. This engineering analysis should consider the cable insulation type, actual voltage and current conditions, cable function, and thermal affects on the cable and its ability to function. This evaluation shall also consider cable operating temperatures within the fire barrier at the onset of the fire exposure.
b.
CABLE CIRCUIT INTEGRITY TESTING ANI Criteria In 1981 American Nuclear Insurers (ANI) developed a fire endurance test criteria for raceway fire barrier systems. This criteria, " Fire Endurance Protective Envelope Systems for Class IE Electrical Circuits,"
specifies a circuit. integrity test.
The intent of this test was to identify the onset of fire damage to the cables.within the. raceway fire barrier test specimen during the fire. endurance' test period.
The circuit integrity test voltage is 8~ to 10' volts DC; therefore the loss of circuit integrity under these voltage conditions may only. occur ~as a
~
result of a dead short or open circuit.
During actual fire testing conditions of raceway fire barrier systems thermal damage to the cables has resulted. ~This thermai-damage has led to cable jacket--and insulation degradation'without the loss of circuit ~
integrity as monitored using ANI criteria.
Since cable voltages used for ANI circuit integrity testing do not replicate cable operating voltages, loss of cable insulation conditions can-exist during the fire test without a dead short occurring.
It is expected that if the cables-were at rated power and current a fault would propagate.
Therefore, the use of ANI circuit integrity monitoring during the fire endurance test is not considered a valid method for' demonstrating that the protected shutoown circuits are capable of performing their required function -
during and after the test fire exposure.
c.
CABLE INSULATION TESTING-The two principal materials used as cable insulation and cable jackets by the nuclear industry are thermoplastics and thermosetting polymeric-materials. A thermoplastic material can be softened and resoftened by-heating and reheating. : Conversely,' thermosetting cable insulation materials cure by chemical reaction and do not soften when heated.
3 Under excessive heating thermosetting insulation becomes stiff and Electrical f aults may be caused by softening and flowing of brittle.
thermoplastic insulating materials at temperatures as low as 149 *C
[300 'F).
Thermosetting electrical conductor insulation materials i
usually retain their electrical properties under short-term exposures to temperatures as high as 260 *C [500 'F].
Insulation resistance (Megger) i testing provides an indication of the condition of the cable insulation
{
resistance, wnereas the high potential (Hi-Pot) test provides assurance that the cable has sufficient dielectric strenoth to withstand the A cable insulation failure usually results from i
applied rated voltage.
)
one failure mode is excessive dielectric loss two breakdown modes:
which is due to low insulation resistance, and the other failure mode is overpotential stress which is due to loss of dielectric strength of the insulation material.
If megger tests are not performed at frequent intervals during the fire exposure, indications of insulation damage in insulation may go q
Insulation, when removed from elevated temperatures will undetected.
Megger testing of insulated cables after the fire endurance test reset.
ana after the caole has sufficiently cooled may not detect degradation in the insulation resistance.
Therefore, wet or dry megger of cables after a fire exposure does not provide reasonable assurance that the l
caoles would have functioned as intended during the fire exposure.
i To provide reasonable assurance that the cables would have functioned I
during and after the fire exposure, megger tests need to be performed before the fire test, at multiple time intervals during the fire exposure (i.e. every 20 minutes during the 1-hour fire test and every-i hour during the 3-hour fire test) for instrumentation cables only, and after fire endurance test to assess the cable insulation resistance i
This testing will assure that the cables will maintain levels.
sufficient insulation resistance levels necessary for proper operation t
of instruments.
I The megger tests (pre-fire, during the fire [if performed],.and l
immediately after the fire test conditions) should be done conductor-to-i conductor for multi-conductor and conductor-to-ground for all cables, The minimum acceptable insulation resistance (IR) value, using the test voltage values as shown in the table below, is determined by using the following expression:
+
IR (Mega-ohms) >
(T(1 Meca-ohm per KV) + 1 1
- 1000 (fti 1 Length (ft) i Additionally, in determining the insulation resistance levels required for nuclear instrumentation cables, an assessment of the minimum insulation resistance value (e.g., one mega-ohm) and its potential impact on the functionality of these cables shall be ' evaluated.
In addition, an AC or.DC high potential (Hi-Pot) test for power cables -
i greater than 1000 volts shall.be performed after the post-fire megger t
tests to assess the dielectric strength.
This test provides assurance l
that the cable will withstand the applied voltage during and after a fire.
The high potential test shall be performed for a 5 minute duration at 60 percent of either 80 volts / mil ac or 240 volts / mil dc 8bb0 1
dc The table below summarizes the megger and Hi-Pot test voltages which, l
when applied to power, control and instrumentation cables, would l
constitute an acceptable cable functionality test.
OPERATING MEGGER TEST HIGH POTENTIAL i
TYPE VOLTAGES V0LTAGE TEST VOLTAGE ~
POWER
> 1000 vac 2500 vdc 60% x 80 V/ mil (ac) 60% x 240 V/ mil (de) i POWER
< '000 vac 1500 vde #
NONE INSTRUMENT 1 250 vac 500 vdc NONE l
~< 120 vac f
CONTROL
- A megger test voltage of 1000 vdc will be acceptable provided a Hi-Pot test is performed after the megger test for power cables rated at less than 1000 vac.
d.
CABLE THERMAL EXPOSURE THRESH 0 Q The following is an acceptable analysis _ method for evaluating the cable-functionality.
This analysis is based on determining whether a specific insulation material will maintain the electrical integrity and operability within a raceway fire barrier system during and after an external fire-exposure.
In order to determine cable functionality, it is necessary to consider the operating cable temperatures within the fire barrier system at the:
onset of the fire exposure and the thermal exposure threshold (TET) temperature of the cable. - For example, if the TET of a specific thermoplastic cable insulation (Brand X) is 149 *C [300 *F] and the normal operating temperature within the fire barrier' system is 66 *C _
[150 *F], then the maximum temperature rise within the fire barrier-system shall not exceed 83 *C [150 *F] during ' exposure to an external' fire of a duration equal to the required fire resistance rating of the barrier.
For this examole the TET limit for Brand X cable is 83 *C
[150 *F] above the cable operating temperatures within the fire barrier The cable TET limits system at the onset of the external fire exposure.
in conjunction with a post test visual ' cable inspection and the Hi-Pot test described above should readily demonstrate the functionality of the
.:able circuit during and after a fire.
r-
_T%\\
- c The cable normal operating temperature' can be determined by loading cable specimens installed within a thermal barrier system in the test The TET temperature configuration with rated voltage ind current.
limits for most cable insulation may be obtained from the manufacturer's With-published data which is given as the short-circuit rating limit.
the known TET and normal operating temperature for each thermal barrier' system configuration, the maximum temperature rise limit within a fire barrier system may then be determined.
,.