Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609 MAY 1 0 1993 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Gentlemen: In the Matter of Tennessee Valley Authority ) ) Docket Nos. 50-259 50-260 50-296 LETTER (GL) 92-08 - BROWNS FERRY NUCLEAR PLANT (BFN) - GENERIC THERMO-LAG 330-1 FIRE BARRIERS, REVISION 1 References: 1. TVA letter to NRC dated April 14, 1993, "Response to Generic Letter 92-08, Thermo-Lag 330-1 Fire Barriers" 2. TVA letter to NRC dated September 30, 1992, "Response to NRC Bulletin 92-01, Supplement 1, Failure of Thermo-Lag Fire Barrier System to Perform Its Specified Fire Endurance Function, Sequoyah Nuclear Plant (SQN) and Browns Ferry Nuclear Plant (BFN)" 3. TVA letter to NRC dated July 31, 1992, "Response to NRC 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 - Sequoyah Nuclear Plant (SQN) and Browns Ferry Nuclear Plant (BFN)" On April 14, 1993, TVA provided its initial response to GL 92-08 for BFN (Reference 1). Due to administrative errors in that submittal, TVA is resubmitting as Enclosure 1 to this letter the information requested by NRC in GL 92-08 concerning qualification of the Thermo-Lag fire barrier material, ampacity derating factors used by BFN, and the qualification of the Thermo-Lag installations at BFN. I U' (I 9305140180 930510 PDR ADOCK 05000259 a PDR
Transcript
Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609
MAY 1 0 1993
U.S. Nuclear Regulatory CommissionATTN: Document Control DeskWashington, DC 20555
Gentlemen:
In the Matter ofTennessee Valley Authority
)) Docket Nos. 50-25950-26050-296
LETTER (GL) 92-08 -BROWNS FERRY NUCLEAR PLANT (BFN) - GENERICTHERMO-LAG 330-1 FIRE BARRIERS, REVISION 1
References: 1. TVA letter to NRC dated April 14,1993, "Response to Generic Letter92-08, Thermo-Lag 330-1 FireBarriers"
2. TVA letter to NRC datedSeptember 30, 1992, "Response to NRCBulletin 92-01, Supplement 1,Failure of Thermo-Lag Fire BarrierSystem to Perform Its Specified FireEndurance Function, Sequoyah NuclearPlant (SQN) and Browns Ferry NuclearPlant (BFN)"
3. TVA letter to NRC dated July 31,1992, "Response to NRC Bulletin92-01, "Failure of Thermo-Lag 330Fire Barrier System to MaintainCabling in Wide Cable Trays andSmall Conduits Free From Fire Damage- Sequoyah Nuclear Plant (SQN) andBrowns Ferry Nuclear Plant (BFN)"
On April 14, 1993, TVA provided its initial response toGL 92-08 for BFN (Reference 1). Due to administrative errorsin that submittal, TVA is resubmitting as Enclosure 1 to thisletter the information requested by NRC in GL 92-08 concerningqualification of the Thermo-Lag fire barrier material, ampacityderating factors used by BFN, and the qualification of theThermo-Lag installations at BFN. I
U' (I9305140180 930510PDR ADOCK 05000259a PDR
2
U.S. Nuclear Regulatory Commission
MAY 1 0 1993
Additionally, TVA requests in accordance with 10 CFR 50.12 anexemption from 10 CFR Part 50, Appendix R requirements for theResidual Heat Removal Service Water (RHRSW) system power cablesin the Intake Pump Station (Enclosure 2).
Finally, Enclosure 3 provides an engineering evaluation asdescribed by Generic Letter 86-10, Fire ProtectionRequirements, for separation of redundant RHRSW pump powercables in the Turbine Building in accordance with 10 CFR 50,Appendix R requirements.
As a result of Staff concerns over the qualification of theThermo-Lag fire barrier systems, CBFNhas--fntiat7td)tmodý----_1n ah-•t-w-•i•l---ar.low•-BFN--t-o--comp-ly-wit-h-Sec-t-i-on-Lmod-f 3:ati ons tht-Se4-onCilII-.G. b. 2-of-10-CFR-5.0_,Appendlx-Rt-ofhuitheuse (of '
Theii6~ ag ~01fI eb rir-yst ems-.- T-VA-i ~trorppteteci•eis-e-,mo'd-i-f-i-ca-t-i-ens-p-r-i-e-r--to-Uni-t-2-2-Cycle 7_--oper-at-ion-.---•',
Enclosure 4 provides the commitment made by this letter.
Please direct questions concerning this issue to me at(205) 729-2636.
Sincerely,
Pedro SalasManager of Site Licensing
Enclosurescc (Enclosures):
Mr. Thierry Ross, Senior Project ManagerU.S. Nuclear Regulatory CommissionOne White Flint, North11555 Rockville PikeRockville, Maryland 20852
U.S. Nuclear Regulatory CommissionRegion II101 Marietta Street, NW, Suite 2900Atlanta, Georgia 30323
ENCLOSURE 1
Tennessee Valley Authority
Browns Ferry Nuclear Plant (BFN)
Response to NRC Generic Letter (CL) 92-08,
Thermo-Lag 330-1 Fire Barriers
The following is in response to NRC requests for information specified inGL 92-08.
Each information request item from GL 92-08 is provided below withcorresponding responses.
1. State whether Thermo-Lag 330-1 barriers are relied upon (a) to meet 10 CFR50.48, to achieve physical independence of electrical systems, (b) to meeta condition of a plant's operating license, or (c) to satisfy a licensingcommitment. If applicable, state that Thermo-Lag 330-1 is not used at thefacility. This GL applies to all 1-hour and all 3-hour Thermo-Lag 330-1materials and barrier systems assembled by any assembly method such as byassembling preformed panels and conduit shapes, as well as spray, troweland brush-on applications.
Item 1 Response:
(a) Thermo-Lag 330-1 barriers have been installed at BFN and are reliedupon to meet nuclear power plant fire protection requirements forelectrical systems as specified in 10 CFR 50.48. The material hasbeen used to achieve compliance with 10 CFR 50 Appendix R, SectionIII.G requirements for BFN Unit 2. As described in item 3a (below),limited amounts of Thermo-Lag 330-1 barriers are installed on Units 1and 3, to support Unit 2 Appendix R requirements.
(b) Thermo-Lag 330-1 barriers are not relied upon to meet a condition of aplant's operating license, nor do they satisfy a licensing commitment.
(c) Thermo-Lag 330-1 barriers are not installed to satisfy a licensingcommitment.
2. If Thermo-Lag 330-1 barriers are used at the facility,
(a) State whether or not the licensee has qualified the Thermo-Lag 330-1fire barriers by conducting fire endurance tests in accordance withthe NRC's requirements and guidance or licensing commitments.
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Item 2.(a) Response:
Prior to installation at BFN, TVA did not qualify the Thermo-Lag 330-1fire barriers by conducting independent fire endurance tests in accordancewith the NRC's requirements and guidance or licensing commitments. TVAprocured the vendors acceptance test as part of the Thermo-Lag firebarrier system contract. At the time of installation, TVA believed thatthe barriers had been qualified to existing NRC requirements andguidance. The NRC requirements for test performance, acceptance, andcomparison of tested to installed configurations has evolved over time.Recently provided Nuclear Management and Resource Council (NUMARC)information indicates that many early fire endurance test results werebased on cable temperature rather than cold side barrier temperature, asdiscussed in GL 86-10. Depending on the time the test was used to qualifya particular barrier, this may have been acceptable. There was norequirement for the licensees to "conduct" qualification testing of thefire barriers.
2. (b) State (1) whether or not the fire barrier configurations installed inthe plant represent the materials, workmanship, methods of assembly,dimensions, and configurations of the qualification test assemblyconfigurations; and (2) whether or not the licensee has evaluated anydeviations from the tested configurations.
Item 2.(b) Response:
As stated in response to Item 2.(a), TVA did not conduct fire endurancetesting of the Thermo-Lag 330-1 fire barrier configurations, but reliedupon furnished Thermal Science Incorporated (TSI) test report data for thequalification of the Thermo-Lag 330-1 fire barrier systems that wereinstalled at BFN. Therefore, the qualification of the fire barriersystems installed at BFN, to achieve 10 CFR 50 Appendix R compliance, isbased on TSI performed fire endurance tests. To our knowledge, thepre-shaped Thermo-Lag 330-1 fire barrier systems for individual conduitsinstalled in the plant do represent the materials, workmanship, methods ofassembly, dimensions, and configurations of the qualification testassembly. However, Thermo-Lag fire barriers installed on some junctionboxes may not represent the dimensional configuration of testedassemblies. Also, Thermo-Lag fire barriers for multiple conduitassemblies (i.e., conduits collectively wrapped or boxed in) may notrepresent the configuration of tested assemblies. BFN has not evaluatedany deviations from tested configurations.
2. (c) State (1) whether or not the as-built Thermo-Lag 330-1 barrierconfigurations are consistent with the barrier configurations usedduring the ampacity derating tests relied upon by the licensee for theampacity derating factors used for all raceways protected byThermo-Lag 330-1 (for fire protection of safe shutdown capability orto achieve physical independence of electrical systems) and (2)whether or not the ampacity derating test results relied upon by thelicensee are correct and applicable to the plant design.
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BFN Item 2.(c) Response:
TVA did not conduct ampacity derating testing of the Thermo-Lag 330-1 firebarrier configurations, but relied upon furnished TSI test report data forthe qualification of the Thermo-Lag 330-1 fire barrier systems that wereinstalled at BFN. Therefore, the qualification of the fire barriersystems installed at BFN to achieve 10 CFR 50 Appendix R compliance, isbased on TSI performed ampacity derating tests. However, the correctiveactions identified in response to question 3a below will eliminate theneed to use Thermo-Lag 330-1 as a fire barrier system to achieve physicalindependence of electrical systems as required by 10 CFR 50 Appendix R;thus, eliminating the need for ampacity analysis on these circuits.
3. With respect to any answer to items 2(a), 2(b), or 2(c) above in thenegative, (a) describe all corrective actions needed and include aschedule by which such actions shall be completed and (b) describe allcompensatory measures taken in accordance with the technicalspecifications or administrative controls. When corrective actions havebeen completed, confirm in writing their completion.
BFN Item 3(a) Response:
The following is a list of conduits/junction boxes (JBs) and compartmentationfeatures where Thermo-Lag protection is provided. Corresponding to each item,the proposed corrective action has been listed.
I. CONDUITS
CONDUIT
2ES3033-II
2ES3045-II
2ES3047-II
LOCATION
U2 ReactorBuildingEL565
U2 ReactorBuildingEL565
U2 ReactorBuildingEL565
CONDUIT SIZE
1 Inch
1 Inch
1 Inch
CORRECTIVE ACTION
Circuit modification to-replace existing emergencyopen switch to avoid relianceon the seal-incircuit eliminated the needfor Thermo-Lag. (DesignChange Notice (DCN) W20653).
Conduits were wrapped tomeet the 18" rule inassociation with 2ES3033-II.Need for fire wrap has beeneliminated.
Conduits were wrapped tomeet the 18" rule inassociation with 2ES3033-II.Need for fire wrap has beeneliminated.
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I. CONDUITS (continued)
CONDUIT LOCATION CONDUIT SIZE CORRECTIVE ACTION
2ES3034-II
2B290-IID
2ES173-I
U2 ReactorBuildingEL565
U2 ReactorBuildingEL593 and EL593
U2 ReactorBuildingEL593 and EL593Board Room
1 Inch
1.5 Inch
1.5 Inch
2PC931-I
2ES3906-II
1B284-IIC
2PC2450-I
U2 ReactorBuildingEL593
U2 ReactorBuildingEL593
U2 ReactorBuildingEL621
U2 ReactorBuildingEL593
1.5 Inch
1.5 Inch
2 Inch
2 Inch
Conduits were wrapped tomeet the 18" rule inassociation with 2ES3033-II.Need for fire wrap has beeneliminated.
Circuit modification toinstall isolation fuses inthe 250V DC Electrical BoardRoom control power normalremote indicating lightcircuit on 480V ShutdownBoard 2B to eliminate theneed for Thermo-Lag.(DCN W20660)
Based on analysis containedin associated circuit lowimpedance calculationED-Q2999-880675, this conduitis acceptable without therequirement of Thermo-Lag.(DCN S20656)
Conduit is being reroutedoutside the fire zone to meetAppendix R III.G.2.bseparation requirements.(DCN W20655)
Conduit is being reroutedoutside the fire zone to meetAppendix R III.G.2.bseparation requirements.(DCN W20653)
Conduit located in Unit 1Reactor Building and is notrequired to be wrapped forUnit 2 Appendix Rcompliance. Therefore, nocorrective measures arewarranted.
Conduit is being reroutedoutside the fire zone to meetAppendix R III.G.2.bseparation requirements.(DCN W20661)
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I. CONDUITS (continued)
CONDUIT LOCATION CONDUIT SIZE CORRECTIVE ACTION
2ES3907-II
2B284-IB
2PC918-I
2ES3046-II
U2 ReactorBuildingEL565
U2 ReactorBuildingEL621Board Room 2A
U2 ReactorBuildingEL593
Ul & 2 ReactorBuildingEL565
U2 ShutdownBoard RoomEL593
U2 ShutdownBoard RoomEL593
2 Inch
2 Inch
2 Inch
2.5 Inch
Circuit modificationeliminates the emergencyopen function as required bythis cable/conduit. Newcable/conduit 2ES5691-II nowhas this function and isrouted outside fire zone tomeet Appendix R III.G.2.bseparation requirements.(DCN W20653)
Conduit is being reroutedoutside and Shutdown the firezone to meet Appendix RIII.G.2.b separationrequirements. (DCN W20654)
Cable 2PC945-I is routed inconduits 2PC931-I and2PC918-I. 2PC931-I wasrerouted out of fire zone.(DCN W20655). 2PC918-I wasinadvertently included onlyby association. Hence, nofurther corrective actionsare required.
Conduit was wrapped to meet18" rule in association with2ES3033. Need for fire wraphas been eliminated.
Based on analysis containedin calculationED-Q2999-920327, this conduitis acceptable without therequirement of Thermo-Lag(DCN S20656). Hence, nofurther corrective actionsare required.
Based on analysiscontained in calculationED-Q2999-880675, this conduitis acceptable without therequirements of Thermo-Lag(DCN S20656). Hence, nofurther corrective actionsare required.
2PL5 250-II
2ES141-I
2.5 Inch
3 Inch
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I. CONDUITS (continued)
CONDUIT LOCATION CONDUIT SIZE CORRECTIVE ACTION
2ES215-I
2PL451-II
2PL453-II
2ES3235-II
3ES225-I
U2 ShutdownBoard RoomEL593
U2 ShutdownBoard RoomEL621
U2 ShutdownBoard RoomEL621
U2 ReactorBuildingEL565
U3 ShutdownBoard RoomEL593
3 Inch
3 Inch
3 Inch
3 Inch
3 Inch
Based on analysis containedin associated circuit lowimpedance calculationED-Q2999-880675, this conduitis acceptable without therequirement of Thermo-Lag.(DCN S20656)
Conduit is being reroutedoutside the fire zone to meetAppendix R III.G.2.bseparation requirements.(DCN W20657)
Conduit is being reroutedoutside the fire zone to meetAppendix R III.G.2.bseparation requirements.(DCN W20657)
Based on analysis containedin associated circuit lowimpedance calculationED-Q2999-880675, this conduitis acceptable without therequirement of Thermo-Lag.(DCN S20656)
Based on analysis containedin associated circuit lowimpedance calculationED-Q2999-880675, this conduitis acceptable without therequirement of Thermo-Lag.
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I. CONDUITS (continued)
CONDUIT LOCATION CONDUIT SIZE CORRECTIVE ACTION
ES75-IES88-IES100-IES113-I3ES1580-I3ES1590-I
2B76-B2S
2B80-B3S
Intake PumpStationEL550
U2 ReactorBuildingEL565
U2 ReactorBuildingEL565
3 Inch
4 Inch
4 Inch
A 10 CFR 50.12 ExemptionRequest for lack of 20'separation between redundanttrains is being submitted aspart of this letter(reference Enclosure 2). Itwas concluded a fireaffecting one division of theshutdown circuits will notcause damage to its redundantdivision. This conclusionwas reached by utilizing amulti-compartment computerfire model (HAZARD I). Itwas also demonstrated thatsprinkler heads in the areawill actuate prior to targetdamage. Therefore,Thermo-Lag fire wrap is notrequired in this area.
Conduit being reroutedoutside the fire zone to meetAppendix R III.G.2.bseparation requirements.(DCN W20658)
Conduit being rerouted outsidethe fire zone to meetAppendix R III.G.2.bseparation requirements.(DCN W20659)
Ul Reactor Building EL593 andShutdown Board Room B
Ul Reactor Building EL621 and
Shutdown Board Room A (NoThermo-Lag in this area)
U2 Reactor Building EL593 andShutdown Board Room D
U2 Reactor Building EL621 andShutdown Board Room C
U3 Reactor Building EL593 andShutdown Board Room F
U3 Reactor Building EL621 andShutdown Board Room E
Required cables being reroutedoutside the fire zone. JB nolonger needed to be wrapped.
Required cables being reroutedoutside the fire zone. JB nolonger needed to be wrapped.
Required cables being reroutedoutside the fire zone. JB nolonger needed to be wrapped.
Required cables being reroutedoutside the fire zone. JB nolonger needed to be wrapped.
Background:The above listed conduits andJBs were protected by Thermo-Lagto meet Appendix R III.G.2.bseparation requirements, i.e.,these conduits (cables) arerequired to remain operable for afire in the area. In addition tothe above described Thermo-Laginstallations, in some cases smalllengths (2 to 5 feet) of flexibleconduits have also been protectedwith Thermo-Lag; however, theseconduits are not required to remainoperable for a fire in the area.The fire wrapping was done tomaintain the integrity of theflex conduit such that theinternal conduit seal willsatisfactorily withstand exposureto a fire event.
Corrective Action:Calculation MD-N0026-920544evaluated the necessity ofThermo-Lag fire wrapprotection for small lengths offlexible conduits. It wasconcluded that Thermo-Lag wasnot required to maintain theintegrity of the flexible conduitand that the internal conduitseals were adequate to prevent thepassage of fire, smoke, or hotgases. Therefore, Thermo-Lag firewrap is no longer required.
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II. JUNCTION BOXES AND COMPARTNENTATION (continued)
(c) Conduit Pull Box Cover(Radwaste Pipe Tunnel)
Background:Conduit pull box covers were firewrapped with 3-hour Thermo-Lag toprovide separation betweenredundant trains in accordancewith Appendix R III.G.2(a)requirements. However, the firewould have to travel approximately400 feet to damage redundant safeshutdown circuit.
Corrective Action:An engineering evaluation perGL 86-10 has been performed. Itconcluded that lack of complete3-hour fire barrier betweenredundant circuits is adequatelycompensated by the substantialseparation (400 feet) and numerousfire travel path obstacles.Therefore, fire wrap for conduitpull box covers is not required.
All corrective actions will beUnit 2 Cycle 7 operation.
completed prior to
See Enclosure 2
See Enclosure 3
BFR Item M,(b) Response:
Fire watches were posted in all areas where Thermo-Lag fire barriersystems were installed (Reference 2).
4. List all Thermo-Lag 330-1 barriers for which answers to item 2 cannot beprovided in the response due within 120 days from the date of this genericletter, and include a schedule by which such answers shall be provided.
4. Response:
None.
ENCLOSURE 2
Tennessee Valley Authority
Browns Ferry Nuclear Plant (BFN)
10 CFR 50.12 Request for Exemption
From 10 CFR 50. AppendIx R
Exemption Request
10 CFR Part 50, Appendix R, Section III.G.2.b requires that cables andequipment of redundant safe shutdown trains be separated from each other by 20or more feet of space with no intervening combustibles. It also requires thatautomatic suppression and detection be provided in the area. Contrary to thisrequirement the Residual Heat Removal Service Water (RHRSW) system safeshutdown circuits located in the Intake Pump Station are not separated by 20or more feet. Automatic suppression and detection is provided in the area.Pursuant to 10 CFR 50.12 an exemption is requested from 10 CFR Part 50,Appendix R, section III.G.2.b requirement for separation of redundant divisionof RHRSW circuits by 20 or more feet with no intervening combustible in theIntake Pump Station.
Description of Intake Pump Station
The Intake Pumping Station is constructed of reinforced concrete. Elevation550 of the Intake Pump Station contains redundant RHRSW safe shutdowncircuits. Figures 1 and 2 of the attached appendix depict the layout ofelevation 550 of the Intake Pump Station. The redundant RHRSW circuits arelocated in Area 1 of Figure 1. RHRSW Division I circuits enter the IntakePump Station through the north wall from an underground conduit and are routedin conduits are located on the south wall approximately 9 feet from theDivision II cables except for a small portion located on west wall where theseparation is approximately 6 feet. The cables then penetrate the ceilinginto the pump room above. The Division II circuits enter the Intake PumpStation from the cable tunnel (Area 2) and are routed in cable trays runningalong the north wall. The cables exit the trays and pass through conduits,and cross over the ceiling into the ceiling penetrations. Either division ofRHRSW can satisfy the safe shutdown requirements. RHRSW cables in cable traysare coated with "Flamastic" or they are of fire retardant material (i.e.,satisfy IEEE requirements). The conduits are fire wrapped with "Thermo-Lag".In addition, air supervised preaction sprinkler system is provided in thisarea (Area 1). Photoelectric smoke detectors are provided on EL 550 (Areas 1& 3) and linear beam detectors are provided in the cable tunnel (Area 2). Thedetection system is a microprocessor based addressable Class A system withlocal and main control room annunciation. Hose stations and portableextinguishers are also available in the area.
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The cable trays are the only significant source of combustibles in the areawhere redundant RHRSW circuits are located. Another combustible source is thelube oil associated with the CCW pump discharge valves which are fully sealedand, therefore, are not be considered to be an exposed combustible.Administrative controls are in place to limit the risk of transientcombustible fire. Therefore, a cable tray fire is the only fire that needs tobe considered. The fixed combustible load for EL 550 of the Intake PumpStation is 42,000 Btu/ft 2 or an equivalent fire severity of 32 min.Furthermore, in the theoretical analysis to follow, no credit is being takenfor the current Thermo-Lag fire wrap protection of Division I RHRSW conduits.
Theoretical Analysis
For a postulated fire in the Intake Pump Station, an analysis has beenperformed to show that the environmental conditions (temperature and heatflux) in the area will not cause damage to the redundant safe shutdowncircuits. The detailed analysis is provided by an appendix to this request.
The initial screening using a conservative methodology (i.e., FIVE Methodologyin EPRI TR-100370) has demonstrated that area temperatures remain well belowcable damage threshold. However, the heat flux was slightly above criticalconditions. Subsequently, a detailed multi-compartment analysis (HAZARD 1fire model) was performed taking into account the fire growth rate of thecable trays. No credit was taken for the Thermo-Lag fire wrap or automaticsprinklers. The analysis demonstrated that the temperature and heat flux wasbelow the damage threshold.
Additional analysis (i.e., FPETOOL) was performed to take credit for theautomatic sprinklers. That' analysis demonstrated that the sprinklers willactivate well before the redundant cables reach their damage threshold.
Evaluation
TVA has evaluated the existing fire protection features for the Intake PumpStation and has determined that adequate measures exist to provide a level ofprotection equivalent to Section III.G.2.b of 10 CFR 50, Appendix R. Thesemeasures are:
1. The only significant combustible in the Intake Pump Station is cableinsulation in cable trays. Generally, these cables are coated withFlamastic or IEEE-383 qualified. Out of a total combustible loading of42,000 Btu/ft 2 , 32,000 Btu/ft 2 consist of cable insulation/jacketing.Other combustibles are scattered through the intake structure and will notsustain continuity of combustion. In Area 1, where the RHRSW circuits arelocated, local control stations are spaced equal distance and are not asignificant combustible source. Area 1 is separated from othercombustible sources, such as electrical cabinets, transformers, and pumpswhich are located in Area 3. Area 2 is a cable tunnel with cableinsulation as the only combustible loading. Thus the RHRSW divisions areseparated with no intervening exposed combustible material or ignitionsources.
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2. The cable insulation is covered with Flamastic or it satisfies thecriteria of IEEE-383 or equivalent and would not sustain combustion unlessan external heat source is present. An internal fire in exposed cables isnot postulated due adequate circuit/fused/breaker coordination. Thecables in the conduits are not considered a source of combustion.
3. The grease in the CCW pump discharge valves is completely enclosed and isnot considered a hazard.
4. Administrative controls are in place to limit the risk of a transient,combustible fire.
5. An air supervised preaction sprinkler system provides area wide coveragein Area 1. Class A supervised area wide detection is provided byaddressable photoelectric smoke detectors in Areas 1 and 3 of Intake PumpStation. Linear beam type smoke detectors are provided in the cabletunnel (Area 2). These systems will provide early warning detection bothlocally and in the main control room. Hose stations and portableextinguishers are available in the area.
Consequently, TVA has determined that the existing fire protection featuresprovided for the BFN Intake Pump Station would ensure one division of theRHRSW necessary to achieve and maintain hot standby would remain free of firedamage and, thereby, provide an equivalent level of fire protection asrequired by Section III.G.2.b of 10 CFR 50, Appendix R. Additionally, theimposition of modifications to satisfy the methods specified by Appendix R of10 CFR 50 for the Intake Pump Station would not significantly enhance thelevel of fire protection currently provided.
Applicable Special Circumstances
TVA has determined that the requested exemption conforms to the applicableexemption criteria of 10 CFR 50.12(a). There are no prohibitions of law topreclude the activities that would be authorized by the requested exemption,and the requested exemption, if granted, would have no impact the commondefense and security. Additionally, the requested exemption does not presentan-undue risk to the public health and safety since an equivalent level offire protection as required by Section III.G.2.b of 10 CFR 50, Appendix R isprovided.
Special circumstances are applicable to the requested exemption in accordancewith 10 CFR 50.12(a)(2)(ii) in that application of the regulation for theseparticular circumstances is not necessary to achieve the underlying purpose ofthe rule. Section III.G.2.b of 10 CFR 50, Appendix R specifies a method toensure one train of systems necessary to achieve and maintain hot standby isfree of fire damage. The underlying purpose of the rule is satisfied byBrowns Ferry since the existing fire protection features described aboveprovide an equivalent level of fire protection to meet required by SectionIII.G.2.b of 10 CFR 50, Appendix R. Thus, implementing modifications simplyto satisfy the methods specified by Appendix R is not necessary.
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Additional special circumstance are applicable to the requested exemption inaccordance with 10 CFR 50.12(a)(2)(iii) in that the application of theregulation would represent an unwarranted burden on TVA resources and thecosts may be in excess of those incurred by another utility similarlysituated. The modification of the Intake Pump Station fire protectionfeatures would result in considerable expenditures of engineering,construction and plant staff resources for its installation, maintenance andoperation. The associated cost would include:
" Engineering the design and installation of fire protection features suchas erecting a fire rated barrier between the two divisions of RHRSWcircuits or routing one division of RHRSW circuitry underground.
* Implementation of increased surveillance and maintenance requirements forthe fire protection features.
" Impracticality of design and installation associated with a three-hourfire rated enclosure around one division or a three-hour fire rated wallseparating the two divisions.
" Impracticality of design and installation associated with a reroute ofone division of RHRSW circuitry outside the Intake Pump Station.
The cost associated with modifications to the Intake Pump Station fireprotection features would represent an unwarranted burden to TVA resource,considering the resulting negligible increase in safety benefit and thealternative means of fire protection described above.
In conclusion, TVA considers that special circumstances in accordance with10 CFR 50.12(a)(2)(ii) and 50.12(a)(2)(iii) justify the requested exemption.The completion of additional modifications to satisfy the methods specified byAppendix R of 10 CFR 50 are not necessary to satisfy the underlying purpose ofthe rule. The existing fire protection features provided for the BFN IntakePump Station will ensure one train of systems necessary to achieve andmaintain hot standby is free of fire damage and, thereby, provide anequivalent level of fire protection as required by Section III.G.2.b ofAppendix R.
APPENDIX
Tennessee Valley Authority
Browns Ferry Nuclear Plant (BFN)
Response to NRC Generic Letter (CL) 92-08,
Thermo-Lag 330-1 Fire Barriers
Impact of Fire in the Intake Pump Stationon
Redundant Safe Shutdown Capability of RHRSW System
2
PROBLEM:
10CFR50 Appendix R, Section III.G.2.b requires that cables andequipment of redundant safe shutdown trains be separated fromeach other by 20 or more feet of space with no interveningcombustibles. It also requires that automatic suppression anddetection be provided in the area. Contrary to this requirementRHRSW safe shutdown circuits located in the Intake Pump Stationare not separated by 20 or more feet. Automatic suppression anddetection is however provided in the area.
OBJECTIVE:
The purpose of this analysis is to show the impact of a fire inthe Intake Pump Station (IPS) on RHRSW pumps safe shutdowncircuits. The analysis will show that a fire affecting onedivision of the RHRSW pump circuits will not cause damage to itsredundant division.
REFERENCES:
1. EPRI TR-100370, Fire Induced Vulnerability Evaluation (FIVE)Methodology, April 1992.
2. EPRI NP-7332, Design Guide for Fire Protection of GroupedCables, May 1991.
3. EPRI TR-100443, Methods for Quantitative Fire HazardsAnalysis, May 1992.
4. NUREG/CR-3192, SAND83-0306- Investigation of 20 footSeparation Distance as a Fire Protection method as Specifiedin 10CFR50, Appendix R, October 1983.
5. NUREG/CR-5384, SAND89-1359, A Summary Of Nuclear Power PlantFire Research at Sandia National Laboratories, 1975-1987
6. SFPE Handbook of Fire Protection Engineering. First Ed.
7. "HAZARD I" Fire Assessment Method, Version 1.1 NationalInstitute of Standards and Technology.
8. Generic Letter 86-10, Implementation of Fire ProtectionRequirements, April 1986.
10. "FPETOOL", Computerized package of fire hazard evaluation,National Institute of Standards and Technology.
11. Tewarson and Khan, Electrical cables- Evaluation of FirePropagation Behavior, FM Research Corp, 1989.
3
ASSUMPTIONS:
1. Cable trays are the only significant combustibles in thearea where redundant RHRSW circuits are located. Anothercombustible source is the lube oil associated with the CCWpump discharge valves which is fully sealed and will not beconsidered as an exposed combustible. Administrativecontrols are in place to remove the risk of transientcombustibles fire. Therefore cable tray fire is the onlyfire that needs to be considered.
2. No credit is being taken for the current THERMOLAG fire wrapprotection of division. I RHRSW conduits. THERMOLAG will beleft in place or removed pending completion of ongoing testsregarding its combustibility and cable derating factors.
ANALYSIS:
The analysis for a fire in the Intake Pump Station is organized
as follows:
1. Description of the area
2. Cable damage criteria
3. Type of fire
4. Consequences of a fire
(A) Fire screening methodology (FIVE-Conservative, neglectsfire growth).
(B) HAZARD I, Multi compartment fire growth model.
(C) Response of smoke detector and sprinkler headactivation.C.1 - Sprinkler head and smoke detector response
using FPETOOL.
5. Conclusion.
Attachment 1 - HAZARD I Fire Model OutputAttachment 2 - FPETOOL, Sprinkler Head Actuation OutputAttachment 3 - FPETOOL, Smoke Detector Actuation Output
4
Description of the Area:
The following sketch shows the layout of elevation 550 of theIPS. RHRSW Division II circuits are located in cable trays,running along the north wall. Division I circuits are inconduits and are located approximately 9' from the cable trayswith the exception of small section of conduit located 6' away.Generally cables in cable trays are coated with "Flamastic" orare IEEE-383 qualified and conduits are fire wrapped with"Thermolag". Air supervised preaction sprinkler system isprovided in this area (Shown as Area 1). Photoelectric smokedetectors are provided on EL 550 (Areas 1 & 3) and linear beamdetectors are provided in the cable tunnel (Area 2). Thedetection system is a microprocessor based addressable Class Asupervised system with local and main control room annunciation.
INTAKE PUMP STATIONELEVATION 550'-PLAN
PIGRE 1
cable tunnel
(335') Height = 1.8 m
Cable trays (RH:
Cond. -41Ibelow ceil/ Fire
0%,'W I LocationFirelwrapped conduits (RHRSW Div. 1)j2
outside vent0.91m x 0.6mi
Div. II)RSW
- 9' 4.OmIM 3. m
3.66m (12 j
(Figure 2)
~--3 .66m
0I
Non-Safety Components Area 7.3m(24') I•j 1 l.22m door opening
I70.0 m (230') L
4 INote: All dimensions are approximate. Figure is not to scale
e-
INTAKE PUMP STATIONELEVATION SSO* BECTION
FZGME1 a
13'
0
Division IIcables
LB I
6 LM9,
D W.alkway
Wall opening(Height varieS)
Assumed floor elevation
I
T
-7
13'14'
Note: All dimensions are approximateFigure not to scale
6
2. CABLE DAMAGE CRITERIA:
The power cables for the RHRSW pumps in the IPS are cross-linkedpolyethylene insulation (XLPE), polyvinyl-chloride jacket (PVC).The conductor size is 2/0 awg (3-1/c). These cables arequalified for vertical flame test in accordance with IPCEA S-19-81, section 6.19.6.
Appendix R states that the redundant safety system shall be "freeof fire damage". Therefore the temperatures and heat fluxes atwhich cable damage occurs need to be identified. The exposurefire can then be analysed and resulting heat flux andtemperatures can be compared to the cable damage criteria.
Several small scale cable burn tests were done by Factory Mutual(Reference 11) which determined the critical heat flux forcables. The results have also been summarized in Reference 2,Table 3.2. The critical heat flux for various cables ranges from10 to 30 kW/sq. m. However, the predominant values are between15 to 25 kW/sq. m. UL tests performed in a radiant heat facility(Reference 4) indicates the critical heat flux to be -8 kW/sq. mfor non-qualified cable (piloted ignition) and -22 kW/sq. m fornon-qualified cable (non-piloted ignition). Reference 11 alsoconcluded that for most insulation and jacketing materials, thefire propagation index decreases with increase in overall cablediameters. The cables being analysed are classified as largecables. Based on the above review a conservative critical heatflux value can be selected as 10 kW/sq. m or 0.9 BTU/sec/sq ft.
Research conducted by FMRC and sponsored by EPRI addressedquantifying cable ignitability in terms of auto ignitiontemperatures. This is summarized in Table 3.1 of Reference 2.The worst auto ignition temperature for the non-qualified PE/PVCcable was 789 OK or 960 OF. A conservative critical temperatureof 700 OF will be selected to account for circuit failures priorto auto ignition.
Critical flux = 0.9 BTU/sec/sq ft (10 kW/sq m)Critical Temperature = 700 deg OF (371 C)
7
3. TYPE OF FIRE:
For purposes of this analysis the fire is assumed to occur in thecable trays (area 1, figure 1). Since the cables in cable traysare generally coated with Flamastic or are IEEE qualified, themost likely type of fire will be small and self extinguishing.However, a much worse fire will be considered which would be mostlikely initiated by an external source.
The type of fire was determined using an equation developed byB.T. Lee in a study conducted in 1985. This research indicatesthat the peak full scale heat release rate (qfs) can be predictedaccording to bench scale measurements
=fs = 0.45 . Z" . A (Reference 6Section 2-1)
where the bench scale heat release value (1") is the peakmeasured under irradiance conditions of 60 kW/sq m, and A is theexposed tray area actively pyrolyzing. The active pyrolysis areais estimated based on the type of cable and its bench scale heatrelease rate which can be obtained from Figure 2-1.18 (Reference6), which gives dA/dt as a function of 4". Thus at any giventime t,
A(t) = A + dA/dt . t
Using a conservative number 350 kW/sq m for the bench scale heatrelease rate and 0.75 sq m/min rate of flame coverage (Obtainedfrom Ref. 6 Figure 2-1.18), the following fire growth wasgenerated:
TIME (sec)060
120180240300360420480540600660720780840900960
10201800
AREA (sq m)0.000.751.502.253.003.754.505.256.006.757.508.259.009.75
10.5011.2512.0012.7522.50
HEAT RELEASE (kW)0
118236354472590708827945
1063118112991417153516531772189020083540
8
The above fire growth information will be used as input data inthe "HAZARD I" fire model. For a constant heat release rateevaluation, select 1181 kW or 1125 Btu/sec as the representativeheat release rate. This heat release rate corresponds toapproximately 7.5 sq m (81 sq ft) or approximately 54' length ofa 18" wide cable tray burning.
4. CONSEQUENCES OF A FIRE:
A) Fire Screening Methodology
This screening methodology will permit the preliminaryevaluation of the IPS with respect to its fire potential.It is intended to permit conservative estimates to be madeof the environmental conditions that could develop at thetarget as a result of a specified fire scenario. Theseestimated environmental conditions are then compared withtarget damage threshold criteria. For screening purposestemperature and heat flux criteria are used. If theestimated maximum environmental condition does not exceedthe damage threshold criteria, it can be concluded that theredundant RHRSW circuits will remain free of fire damage.The methodology is extracted from "Fire InducedVulnerability Evaluation" (Reference 1).
See Figures 1 and 2 for location of the potential firesource (cable trays) and the target (Division I conduits).This fire scenario corresponds to the target being outsideplume and subjected to the effects of a ceiling jetsublayer.
Following is an evaluation of target outside plume scenario:
Area Geometry: (See Figures 1 and 2)
Height of target above fire source Z = 6'(value selected represents target being closerto ceiling, thus is conservative)
Height from fire source to ceiling H = 7'Longitudinal distance from the source to target L = 9'Ratio of Z & H, Z/H = 6/7 = 0.85(Ratio is > 0.85. Hence target would be subjected to ceilingjet sublayer effects which will yield higher ceilingtemperatures.)
Note that Figure 1 shows a small section of a conduit isapproximately 6' from the redundant cables. However it islocated well below the ceiling and will not be affected bythe ceiling jet temperature affects.
Plume temperature rise at ceiling: (Equation 9, Ref. 1)
A7 0F) =340Qeff(Btu/sec) lHc$l (ft)
= 340 (2250)2/37:
= 2324 OF or 1600 OF maximumMax. temp rise is set at 1600 OF (Table 5E, Ref. 1)(Also see Reference 3, Section 7.1.1)
Ceiling jet temperature rise factor:(unconfined ceiling) (Equation 10, Ref. 1)
A T,,/ A T.ceil =O. 3/(L/B92/3
= 0.31(917)JV
= 0.25
(Confined ceiling jet factors are approximately thesame as unconfined ceiling jet factors. Table 6BReference 1)
Ceiling jet temperature rise at target:
Tcj,Target = 1600 x 0.25- 400 OF
Therefore ceiling jet temperature at the target- 400 + 90 = 490 OF
Hence the temperature at the target (conduits) will bebelow its damage threshold.
10
b) Critical radial distance determination:
Critical flux for cable = 0.9 Btu/sec/sq. ftHeat release rate q = 1125 Btu/secRadiant fraction - 0.4(Typically 20 to 40% of total heat release rate infires is radiative, with the remainder beingconvective. 40% will be selected as a conservativevalue.)Radiant heat release rate R = Peak heat release rate
Actual distance between source and target is 9'(Note that one conduit located 6' from the cable trayswill not be subjected to the full impact of the radiantheat. For approximately 1/4th heat release rate, thecritical distance is 3').
Where R is radial distance from exposure fire to target= 450/47(9)2= 0.44 Btu/sec/ft 2
Convective heat flux 4"0 0.3 I~ffXO. 13 /(RI/Z)1
Where Z is target heightabove fire source (Equation 18 & 19 Reference 1)
4" = 0.3 x 2250/62 x 0.13/(9/6)1/3= 9(Max value) x 0.11
(per Table A-4E, Ref 1)= 0.99 Btu/sec/ft 2
Total heat flux at the target = 4R " + h," = 0.44 + 0.99= 1.4 Btu/sec/sq ft
Critical heat flux at cable = 0.9 Btu/sec/sq ft
The calculated heat flux values based on conservativeapproach are higher than the critical heat flux.Detailed analysis using "HAZARD 1" fire model willhowever show that the resulting heat fluxes at thetarget are substantially lower.
11
B) HAZARD I. multi compartment fire growth model:
The Intake Pump Station (IPS) has been modeled as athree compartment configuration. See Figure 1 fordetails. Compartment # 1 is "where redundant circuitsare located. Compartment # 2 is the cable tunnelhaving single train of safe shutdown circuits.Compartment # 3 houses the fire pumps and other non-safety equipment. Vertical vents in compartment # 1have been modeled as horizontal slits near the ceiling.Openings between compartment 1 & 3 have been combinedinto two openings. Outside vents from compartment 2 &3 have been modeled as closed doors with undercuts.Sills and soffits have been taken into account.
The fire source is the cable trays. Fire growth (heatrelease rate) has been calculated as described in "Typeof Fire". This information will be used as input tothe program. Heat of combustion is 12000 Btu/lb(Reference 9). Oxygen limiting index has been chosenas 12% (HAZARD I guide).
Three separate computer runs have been made by varyingthe length of the fire compartment and/or fuel height.Since.the fire compartment is long and narrow (230'long and 13' wide), the possibility of non-uniformconditions may exist in an actual fire situation (notethat the program considers uniform flux andtemperatures throughout the upper hot gas layer andlower colder layer). A reduced length (using 100'instead of 230') will yield more conservative results.The fuel height was also varied to account for variouslevel of cable trays.
The results are tabulated on the following sheet. ForCase 1 and Case 2 the heat flux and temperatureconditions in the upper hot gas layer remain well belowthe damage threshold of the cables. For Case 3, thetemperature and heat flux conditions momentarily reachdamage threshold but quickly decline due to lack ofoxygen to sustain combustion. Therefore, a fire in theIPS is not likely to cause damage to redundant RHRSWcircuits.
Attachment 1 include the computer runs for the 3analysed cases.
TIME TEMP HEAT TEMP HEAT TEMP HEAT(SEC) FLUX FLUX FLUX
oK kW/me 0K kW/m OK kW/m.
0 305 0 305 0 305 0
240 376 0.6 426 1.4 439 1.6
480 421 1.3 502 3.1 519 3.6
720 461 2.1 540 4.3 581 5.9
960 494 2.9 535 4.1 631 8.5
1200 509 3.3 551 4.7 661 11.0
1440 507 3.2 475 2.4 606 7.1
1680 509 3.3 477 2.4 517 3.6
1800 511 3.4 - - 482 2.6
OF = (°K-273)9/5 + 32
Btu/sec/sq. ft = kW/m 2
Critical Temperature =Critical Heat Flux =
x 0.088055
700 OF (644 'K)0.9 Btu/sec/ft 2 (10 kW/m 2)
13
C) Potential for critical damage of cables(target) and responsetime of smoke detector and sprinkler head
The IPS EL 550 is protected with an area wide photo-electricsmoke detection system. The detection system is a Class A(Style 6 and Z per NFPA 72), microprocessor basedaddressable system. Upon detection of smoke in the vicinityof RHRSW power cables, the preaction system is automaticallyactivated.
The following transient response method permits conservativeestimates of the time to critical damage of targets exposedto supercritical environmental conditions. It also permitsestimation of actuation of thermally responsive firedetection devices, such as automatic sprinklers. Theestimated target damage time can then be compared with theexpected response time of suppression systems to evaluatethe potential for critical damage of target.
Time for target damage:Evaluation of the targets thermal response requires dataregarding the thermal properties exposed to the imposed heatflux conditions. For semi-infinite solids, a parameter forthe thermal response of the surface is needed. This iscalled the thermal response parameter (TRP) and is expressedas:
TRP=V/ pc,( Td- TO)
Thermal Response Parameter (TRP) for the cables beingevaluated is chosen from Table A-7E (Reference 1) to be 30(Btu/sec/ft 2 ) s112 which is the value for the largest PVC/PVCcable (.51"). (Note that the TRP for RHRSW cables will bemuch higher since its cable diameter is 1.2").Time to target damage (td): (Reference 3, Eq. 9, Appendix A)
( td) =" (rRP/qtotaj) 24
7 i/4(30/.9) 2 = 872 secondsResponse time for sprinkler head:Sprinkler head temperature rating (Tspr) = 212 OF
dTdet = 212 - 90 122 OFGas temperature rise at ceiling = 1600 OF (see page 9)Gas temperature rise factor at sprinkler head
(dTgas) factor = 0.3/(r/H) 2/13= 0.3/(6/7)2/3
= 0.33
14
Where r =Radial distance from fire source to sprinkler head.Sprinkler heads are spaced -6' apart and arelocated -3' from the cable trays. Select 6 ft asa conservative radial distance.
H = Distance from source to'ceiling (ft)
dTGAs (at sprinkler head) = dTGAsCEILING X (dTGAS) FACTOR
= 1600 X 0.33= 528 OF
dTDET / dTGAs = 122/528= 0.23
Dimensionless actuation time of sprinkler (t/r)(Eq. 21, Reference 1)
t -n(-1 dTdet/dTga,)
= -ln(l-0.23)= 0.26
Time constant for solder type of sprinkler headT = -100 sec (Table A-6E, Reference 1)
Estimated time for sprinkler actuation (TACT)TACT = t/r x Time constant
= .26 x 100 = 26 seconds
Therefore, target damage will occur in 872 sec. however,sprinkler head will activate prior to target damage.
15
C.1 Calculation of sprinkler head response time using FPETOOL(Reference 10) and comparison with calculated values
The sprinkler head activation calculation performed above isnot conservative, because it assumes a fully developed fireacting instantaneously. A more realistic activation timecan be based on the growth rate of fire. Using the DETACTportion of FPETOOL, which calculates sprinkler head responsetime based on defining the sprinkler location with respectto the fire source, its thermal parameters and fire growth.Response Time Index (RTI) for the sprinkler was chosen to bea conservative 700 (English Units). The RTI of a standardsprinkler head varies from 200 to 700.
The response time of the sprinkler (Detector) was calculatedto be 394 seconds (Attachment 2). The increased durationover earlier calculation (26 seconds) can be attributed tothe slow fire growth considerations as opposed to a largerconstant heat release rate fire.
Smoke detector response time using FPETOOL:
Smoke detector actuation can also be predicted based onpostulated temperature rise due to a fire. For PVC cablesfire source, a temperature rise of 13 OF (7 °C) isconsidered to cause detector activation (Reference NBS-GCR-77-95). Per reference 3, section A.2.1.1, a temperaturerise of 20 OF will cause smoke detector actuation. Using atemperature rise of 20 OF and defining additional parametersi.e. room dimensions, vents etc. the smoke detector responsetime is calculated to be 42 seconds by the Fire Simulatorportion of FPETOOL (Reference 10), Attachment 3. Note thatthe sprinkler head actuated at 350 seconds which is notsignificantly different from that calculated by DETACTprogram (394 seconds).
16
5.0 Conclusion:
For a postulated fire in the IPS, analysis has beenperformed to show that the environmental conditions(temperature and heat flux) in the area will not besignificant enough to cause damage to the redundant safeshutdown circuits.
The initial screening using a conservative methodologydemonstrated that area temperatures remain well below cabledamage threshold, whereas the heat flux was slightly abovecritical conditions. Subsequently, a detailed multi-compartment analysis (HAZARD 1 fire model) was performedtaking into account the fire growth rate of the cable trays.No credit was taken for the Thermo-Lag fire wrap orautomatic sprinklers. Temperature and heat flux conditionswere demonstrated to be below the damage threshold.
Additional analysis was performed to take credit for theautomatic sprinklers. It was demonstrated that thesprinklers will activate well before the redundant cablesreach their damage threshold.
A, -r A c, -VYrA -,i T - 'LL.A
FAST version 18.5.2 - creat.d May 1, 1990 INTAKE _.MP STATION(se6 -•CUýL " pO A(2EA I IFoe-
Name Conductivity Specific heat Density Thickness Emissivity
CONCRETE 1.75 1.000E+03 2( .000 3 0
Compartment of origin isPrint interval (seconds)Number of fire specification intervals isTotal time (seconds)Fire positionLimiting oxygen index (%)Initial relative humidity (%) =Fire type is a SPECIFIED (CONSTRAINED)
Pyrolysis temperature (K) =Ambient air temperature (K)Ambient reference pressure (Pa) =Reference elevation (m) =External ambient temperature (K) =External reference pressure (Pa) =Reference elevation (m) =
Name Conductivity Specific heat Density Thickness Emissivity
CONCRETE 1.75 1. OOOE+03 2. 200E+03 0. 150 0.940
Compartment of origin isPrint interval (seconds)Number of fire specification intervalsTotal time (seconds)Fire positionLimiting oxygen index (%) =Initial relative humidity (%) =Fire type is a SPECIFIED (CONSTRAINED)
Pyrolysis temperature (K)Ambient air temperature (K)Ambient reference pressure (Pa) =Reference elevation (m) =External ambient temperature (K) =External reference pressure (Pa) =Reference elevation (m) =
Compartment of origin isPrint interval (seconds)Number of fire specification intervals isTotal time (seconds)Fire positionLimiting oxygen index (%)Initial relative humidity (%) =Fire type is a SPECIFIED (CONSTRAINED)
Pyrolysis temperature (K) =Ambient air temperature (K)Ambient reference pressure (Pa) -
Run title: Intake Pump Station Smoke and Sprinkler Head Actuation
ASCII file name: TOOL.PRN
Heat of combustion:Specific extinction coefficient:Flashover temperature:Oxygen starvation threshold:Radiant energy fraction (from flame):Maximum pre flashover energy loss:
12000.00 BTU/lb 27883.20 KJ/Kg.10
1112.00 F 600.00 C12.00 % by volume
.35
.80
Sprinkler/Heat detector description:Radial distance 6.00 ft 1.83 mRTI: 700.00 (Ft-Sec)A.5 386.46 (m-Sec)A.5Sprinkler rating: 212.00 F 100.00 CSprinkler is not sidewall mounted
Smoke detector description:Radial distance 15.00 ft 4.57 mSmoke temperature at detection: 110 F 43.33334 CSmoke detector is not sidewall mounted
Description of initial outsideHeight of opening:Width of opening:Height of sill above floor:
opening:12.00 ft12.00 ft0.00 ft
3.66 m3.66 m0.00 m
Spacial dimensions of room:Room height: 14.00 ftRoom floor area: 1300.00 ftA2Room wall perimeter: 226.00 ftRoom is rectangular: 100.00 ft
Description of ceiling materials:100% CONCRETE
Description of wall materials:100% CONCRETE
4.27 m120.77 mA268.88 m
by 13.00 ft 30.48 m by 3.96 m
18.000 in
18.000 in
457.200 mm
457.200 mm
There is no HVAC defined
Fire height: 7.00 ft 2.13 m
cable tray fireFire description was manually entered as follows:
TIME (Sec) FIRE (kW)0.1 0.010
60.0 118.000120.0 236.000180.0 354.000
1020.0 2008.0001800.0 3540.000
Data file is TOOL.PRN 03-17-1993 11:06:06
TIME ----- TEMP -----sec F C0.0 70.0 21.1
Smoke at Smoke detector =
------ LAYER---- ----- FIRE -----ft m kW BTU/sec
14.0 4.3 0.1 0.10 % of detectable concentration.
Link temperature - 70.0 F 21.1 CCeiling Jet Temperature (at link) 70.8 F 21.5 CCeiling Jet Velocity (at link) = 0.25 ft/sec 0.08 m/secVision distance (smoke layer) = 3000.00 m 9842.52 ftSmoke gases : oxygen = 21.0 % : CO = 0.0000 : C02 = 0.0000 %Smoke vent rate is 0 cfm 0.00 cmsEnthalpy (Heat content) 0 btu/sec 0 kWInside flow of unburned fuel potential 0 BTU/SEC 0 kW
Smoke detector activated at 42 seconds.I
42.0 94.2 34.6 13.3 4.1Link temperature - 73.2 F 22.9 CCeiling Jet Temperature (at link) = 136.2 FCeiling Jet Velocity (at link) = 2.43 ft/secVision distance (smoke layer) = 12.30 mSmoke gases : Oxygen = 20.6 % : CO = 0.0000 :Smoke vent rate is 0 cfm 0.00 cmsEnthalpy (Heat content) 0 btu/secInside flow of unburned fuel potential
SEPARATION OF REDUNDANT RHRSW PUMP POWER CABLES IN TURBINEBUILDING IN ACCORDANCE WITH 10CFR50 APPENDIX R REQUIREMENTS
1
PROBLEM:
10CFR50 Appendix R, Section III.G.2(a) requires that cables andequipment of redundant safe shutdown trains be separated by 3-hour fire rated barriers. Contrary to this requirement RHRSWsafe shutdown circuits located in the Turbine Building cabletunnel are not completely separated by 3-hour barriers from theredundant circuits located in the pipe tunnel and are not inliteral compliance with section III.G.2(a).
EVALUATION:
Division I of the safe shutdown circuits for the RHRSW system(pumps Al, A2, Cl and C2) are routed in embedded conduits in theceiling of the pipe tunnel under Elevation 565 of the TurbineBuilding. There are two recessed cable pull boxes located in theceiling of the pipe tunnel. The redundant division II circuitsof the RHRSW system (pumps B2 and D2) are routed in the adjacentcable tray tunnel (see Figures 1 and 2).
The cable and pipe tunnels are separated by a 15" reinforcedconcrete wall that exceeds 3-hour fire rated construction. Thesetunnels are provided with entrances which can be accessed fromelevation 565 of the Turbine Building. However, access for cableand pipe tunnel may also be a potential path of fire spread tothese areas. A fire spread from the cable tunnel access to thepipe tunnel entrance and through the pipe tunnel into the non-fire rated cable pull box has the potential of damaging redundantsafe shutdown circuits.
There are two paths between the access to the cable tunnel andthe recessed pull boxes. Figure 1 shows the layout of the pipeand cable tunnel. The shortest path is from the cable tunnelaccess (point 1) to stair #12; down the stairs to backwashreceiving room 533.0-T-1; through door 211 and then up the ladderto the entrance to the pipe tunnel (point 2); through the pipetunnel to the pull box at column T8 (point 4). The totalcumulative horizontal separation between the cable trays and thepull boxes is approximately 380 feet. The other path is from thecable tunnel access (point 1) to stair #19; down the stairs tobackwash receiving room 533.0-T-3; up a ladder and into the pipetunnel access (point 3); through the pipe tunnel to the pull boxat column 8 (point 4). The total cumulative horizontalseparation between the cable trays and the pull boxes isapproximately 500 feet. Both paths involve passing through the565 floor elevation.
2
There are negligible combustibles in the pipe tunnel. Smokedetectors are provided in the cable tunnel. A fire originatingin the cable tunnel will have to be of such a magnitude to engulfthe Turbine Building, travel down the stairs and through the doorto the pipe tunnel entrance and travel another 200 feet throughthe pipe tunnel which is void of any combustibles and reach thecable pull box. This is considered incredible. A fire in thereverse direction is even more incredible.
Based on the above evaluation, the lack of complete 3-hour firebarrier between cable and pipe tunnels is adequately compensatedby the substantial separation (at least 380 feet) between thenearest openings in the pipe and cable tunnels and numerous firetravel path obstacles.
Therefore, the power circuits for RHRSW pumps Al, A2, Cl and C2are adequately separated from the power circuits of RHRSW pumpsB2 and D2 and meets the intent of the Appendix R separationrequirements.
-5
PKY5ZCL~L EPARKTIOk4 BETWZEN REDUNDANT RKRSW CIRCUITSIN TURINEU BUILDING
BFN has initiated modifications that will allow BFN to comply withSection III.b.2 of 10 CFR 50, Appendix R without the use of Thermo-Lag firebarrier systems. TVA intends to have these modifications complete prior toUnit 2, Cycle 7 operation.
