ML20198T455
| ML20198T455 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 08/14/1997 |
| From: | Sorensen J NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20198T458 | List: |
| References | |
| GL-86-10, NUDOCS 9801270061 | |
| Download: ML20198T455 (11) | |
Text
Northern States Power Company Prairie Island Nuclear Generating Pbnt t 717 Wakonade Dr. East Welch. Mmnesota 65089 August 14,1997 10 CFR Part 50 Appendix R U S Nuclear Regulatory Commission Attn.: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50 300 DPR-60 Request for Exemption from 10 CFR Part 50, Appendix R, Section Ill.G,
" Fire Protection of Safe Shutdown capability" In accordance with the provisions of 10 CFR Part 50.12, Prairie Island hereby requests an exemption from the provisions of 10 CFR Port 50, Appendix R, Section Ill.G, " Fire protection of safe shutdown capability."
Dhtussiom 10 CFR Part 50, Appendix R, section Ill.G," Fire Protection of safe shutdown capability," paragraph Ill.G.2.c requires:
" Enclosure of cable and equipment and associated non safety circuits of one redundant train in a fire barrier having a 1-hour fire rating. In addition, fire detectors and an automatic fire suppression system shall be installed in the fire area."
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For non inerted containments, paragraph Ill.G.2.f requires: / VO,t <~.
Separation of cables and equipment and associated non-safety circuits of redundant trains by a non-combustible radiant energy shield.
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USNRC NORTHERN STATES POWER COMPANY !
August 14,1997 l Page 2 ;
Prairie Island utilizes the above separation criteria, in conjunction with NRC granted exemptions relieving Prairie Island of the requirement for an installed automatic fire :
suppression system, as part of the overall compliance strategy for a fire that occurs in ;
the Auxillary Building (Fire Areas 58,59,60,73,74 and 75) and in selected areas of the ;
Twbine Building (Fire Areas 31 and 32). Specifically, Pralrie Island desires to use !
Rockbestos Firerone'R Appendix R fireproof cable in the control circuitry of 11,12,21 and 22 Power Operated Relief Valves (PORVS) and 12 and 22 Charging Pumps as part of a compliance strategy for a fire that occurs in the Auxiliary Building Fire Areas '
58,59,73 and 74. An exemption is considered necessary because the Firezone*R cable does not meet the strict dcfinition of a fine barrier as listed in Generic Letter 86- ,
10, Supplement 1, based on standard fire barrier test criteria. ;
in addition to the specific applications listed above, since the concept remains the f same, we are requesting approval to use Rockbestos Firezone'R Appendix R fireproof !
cable for Installation of new or re-routing of existing safe shut down cables. These ,
applications include cable runs in the Auxillary Building (Fire Areas 58,59,60,73,74, and 75) and in selected areas of the Turbine Building (Fire Areas 31 and 32), with fire severity less than i hour on the ASTM E 119 standard time temperature curve, either with or without automatic fire suppression systems, in lieu of the required 1-hour fire barrier. Also for areas such as containment (Fire Areas 1 and 71) where separation by a non combustible radiant energy shield is acceptable under 10 CFR Part 50, Appendix R section Ill.G.2.f and in Firo Areas 31 and 32 where separation by a non-combustible radiant energy shield is acceptable under an NRC grar,ted exemption, that Rockbestos Firezone'R Appendix R fireproof cable will provide equivalent protectic; when installed per manufacturers requirements, dualification A fire barrier is an assembly that has been assigned an hourly fire rating by testing laboratories based on meeting the acceptance criteria of standard fire barrier fire test methodologies. Such fire barriers are typically walls and floor / celling assemblies.
Electrical raceways (conduits, cable trays, Junction taxes, etc.) contain!rg fire safe shutdown circuits required to demonstrate compliance with Appendix R are also often enclosed with fire barrier assemblies.
This exemption is based on demonstrating that the Rockbestos Firezone'R Append!x R fireproof cable provides protection equivalent to that provided by enclosure of cables in a 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> rated fire barrier when tested in accordance with the standard time-
- temperature curve outlined in the Standard for Fire Tests of Building Construction and Materials, ASTM E-119 (UL 263, NFPA 251) and that the application at Prairie Island is bounded by the testing provided by the manufacturer, R RWEMg h00 i
USNRC NORTHERN STATES POWER COMPANY August 14,1997 Page 3 For radiant energy shields, the guidelines in BTP CMEB 9.5-1, Section C.7.a(l)b.
Indicate that these shields should have a fire rating of 1/2 hour, therefore any material should be capable of performing the required function.
with a 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Rockbestos Firezone fire rating'R Appendix R fireproof cable is a 1-hour rated barrie meets or exceeds the requirements for non-combustible radiant energy shields.
The Rockbestos Firezone*R Appendix R fireproof cable has been tested by Underwriters Laboratories Inc. In order to provide data on the electrical characteristics of the fire resistant cable under controlled fire exposure conditions and during an extended cool-down period. The testing program investigated fire resistant electrical cables installed in trays, conduits and air drops beneath a floor / celling assembly. The trays also contained non fire resistant cables to simulate fuel loading in actual installations. The complete test report is included as Attachment 1.
For specific application at Prairie Island both the cable type and installation details have been compared to the tested configurations of the Underwriters Laboratories report it should be noted that the Underwriters Laboratories test was a " type test' in that it tested various representative samples of cables of various configurations. The specific cable type to be installed at Prairie Island (7/C-12AWG) is enveloped by the test report by the 3/C-14AWG because they both use the same materials (type, thickness, etc.), however the 7/C 12AWG has more conductor (non combustible thermal mass) which acts as a heat sink and a greater radiating surface area, both of which yield conservative results compared to the 3/C-14AWG cable as tested. For general application at Prairie Island any Rockbestos Firezone*R Appendix R fireproof cable that is equal to or exceeds the conductor cross sectional area and is equal to or exceeds the over-all diameter (i.e.
radiating surface area) as that tested in the Rockbestos type test will be enveloped by the UL fire test and will be acceptable for use in applications requiring a 1-hour rated fire barrier or radiant energy shield, provided they are installed per the manufacturers requirements.
During certification testing, the fire exposure in the furnace was controlled in accordance with the standard time-temperature curve per ASTM E-119, Standard for Fire Tests of Building Construction Materials, for a one hour duration in both the large scale and the small scale testing. The fire resistant cables were energized with predetermined steady-state low voltage AC electrical currents (for personnel safety concerns)'to verify and record continuity prior to and throughout the duration of the fire exposure.. The cables were tested as close to continuous rated current as the testing
- facility could achieve during the large scale testing and open circuit at a nominal 480/277 volts 3-phase AC during the small scale testing. Each cable in the large scale testing was also energized with a DC voltage and monitored continuously from o maxa.. =
s
I USNRC NORTHERN STATES POWER COMPANY !
August 14,1997 !
Page 4 conductor to conductor, conductor to sheath / ground, conductor to shield and conductor to shield / ground to verify and record any electrica! Insulation faults. The cables were de-energized for 10 seconds immediately prior to an inrush current test performed on each fire resistant cable during the last 15 minutes of the fire exposure. Both tests confirmed that both conductor continuity and insulation Integrity were acceptable. For the specific application discussed abos 1, the installed cables will be part of 120 volt AC and 125 volt DC control circuits and would therefore be bounded by the Rockbestos test results. In future applications at Pralrie Island the cables could be installed in any 3 phase or alngle phase application that is equal to or less than a nominal 480/277 volt AC or nominal 250 voit DC systems.
Following the fire exposure, the installation was subjected to the impact, erosion and cooling effect of a water hose stream test. A second hose stream test was conducted after an extended (93 hour0.00108 days <br />0.0258 hours <br />1.537698e-4 weeks <br />3.53865e-5 months <br />) cooldown period. The cables were de-energized during each hose stream test. The cables were energized throughout the extended cooldown period with steady-state low voltage ao electrical currents, except for 10 seconds immediately prior to the inrush current tests. Four inrush current tests were performed on each cable during the first 79 hours9.143519e-4 days <br />0.0219 hours <br />1.306217e-4 weeks <br />3.00595e-5 months <br /> of the extended cooldown period, with a final inrush test conducted following the second hose stream test at the end of the extended cooldown period.
The results of the fire, hose stream, steady state and inrush current tests revealed the following:
- 1. Other than discoloration of the fire resistant cable ends, no changes were noted in the appearance of the fire resistant cables following the one hour fire exposure test.
- 2. No electrical faults occurred in any of the fire resistant cable configurations during the fire endurance test.
- 3. Following the first hose stream test, each conductor of each fire resistant cable carried its steady-state current.
- 4. Each fire resistant cable remained electrically functional during the fire endurance test and during the extended cool-down period.
Standard fire barrier test acceptance criteria consist of three distinct elements. One of the acceptance criteria is to prevent passage of flame or gases hot enough to ignite cotton waste on the opposite side of the barrier. Another criterion is to withstand hose stream application without creating openings in the assembly through which fire, hot
USNRC NORTHERN STATES POWER COMPANY August 14,1997 Page6 gases, or water from the hose stream could pass to the opposite side of the barrier.
The third criterion is to limit heat transmission through the barrier so as not to raise the temperature on the cold side of the barrier more than 250'F above its initial temperature.
Based on these results, the Rockbestos Firezone*R Appendix R fireproof cables to be installed will directiv meet the acceptance criteria to (1) prevent passage of flame or gases to the opposite side of the barrier and (2) withstand hose stream application without creating openings in the assembly through which fire, hot gases, or water from the hose stream could pass to the opposite side of the barrier.
The acceptance criteria to limit heat transmission through the barrier 90 as not to raise the temperature on the cold side of the barrier more than 250*F above its initial temperature is not directly met because, in a practical sense, this has no meaning for this application, therefore it was not directly included in the Rockbestos test program.
However, the intent of the acceptance criteria is met since no electrical faults occurred in the fire resistant cable during the fire exposure test and because each cable (and each conductor of each cable) remained electrically functional during and after the fire exposure and hose stream tests.
In the tested installation at Underwriters Laboratories, the cables wers: Installed in galvanized steel trays with no other trays above or in rigid steel conduits. Duri .g the course of the testing,'the test fixture tray system essentially failed leaving the Rockbestos Firezone R Appendix R fireproof cable as the solo intact cable running' between the cable supports. To provide assurance that the Rockbestos Firozone Appendix R fireproof cable will not be damaged by a tray structure falling down on top of it, the cables will be restricted to top tier installations only. This tested configuration at UL is due to space limitations within the UL test facility, however as a conservative installation practice for both the specific applications and the general applications at Prairie Island, the use of Rockbestos Firezone*R Appendix R fireproof cable will be restricted to installation in rigid steel conduit or trays on the top tier of the tray system.
The trays and conduits in the tested installation at Underwriters Laboratories were supported by L4x3x1/2" angle,1/2" threaded steel rods and steel nuts. Thn supports were wrapped with an unspecified protective material and were not considerad as part of the materials under test by Rockbestos. Therefore, also as a conservative installation practice for both the specific applications and the general applications at Pralrlo Island, all raceway supports will be fabricated from Unistrut* (or equivalent) channelin accordance with existing Prairie Island engineering and electrical coristruction guidelines, The supports will not be required to be wrapped which is supported in fire test report FCTR/04/0060 from Darchem Industries (included as u_m=..me
USNRC NORTHERN STATES POWER COMPANY August 14,1997 Page 6 ), which used Unistrut' P1001 channel to support trays and conduit for a 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> fire test in accordance with ASTM E-110 testing requirements for qualification of Darmatt' KM 1 fire barrier material. As is noted in the test by inference due to the successful outcome of the test, the supports did not fail and are only wrapped for a short distance (less than 10 inches) as a thermal short. The remaining portion of the support remained unwrapped ano exposed to the fire.
As was mentioned previously, per the provisions of 10CFR50.12, Northern States Power requested and received exemption from the requirements of Appendix R, Section Ill.G.2 to the extent that for Fire Areas 58,59,60,73,74 and 75 of the Auxiliary Building an automatic fire suppression is lacking. These exemptions are based essentially on the following:
- 1. There are negligible in-situ combustibles in these areas, any postulated fire would be limited to transient combustible material. Hazardous quantitles of transient combustibles would not be expected in these fire areas for several reasons. First, the areas are not adjacent to or near any major plant traffic route. Second, maintenance and operations in these areas do not involve the use of combustible materials. Third, accessibility to these areas is restricted to personnel performing essential duties in the areas because of potential radiation hazards.
- 2. The combustible load is mainly cable insulation with a light fuel load which, if totally consumed, would result in a fire severity of approximately less than i hour on the ASTM E-119 standard time temperature curve.
- 3. Because detectors are installed in the fire areas and because of the availability of adoquate manual fire fighting equipment, the fire brigade would be expected to extinguish a postulated fire before significant damage occurred. During the time a fire is being detected and extinguished as a result of fire brigade intervention, the one-hour fire rated barriers anclosing safe shutdown cable trays and spatial separation between safe shutdown equipment will provide reasonable assurance that one safe shutdown division will remain free of fire damage.
- 4. On this basis, it was concluded that any fires in these areas resulting from transient combustibles would be of limited severity and duration. Aii cables are qualified to IEEE-383. The installed early waming detection system would be able to promptly detect incipient fire conditions, and the separation between redundant trains in each area will maintain the integrity of the cables and equipment until the fire brigade should be capable of reaching each of these areas within a few minutes after an alarm is received in the control room. This AP,8tEI( .110C
USNRC NORTHERN STATES POWER COMPANY August 14,1997 Page 7 combination of protective features provides reasonable assurance that one train of equipment necessary for safe shutdown will be maintained free of fire damage.
Also, per the provisions of 10CFR50.12, Northern States Power requested and received exemption from the requirements of Appendix R, Section Ill.G.2 to the extent that for Fire Areas 31 and 32 of the Turbine Building twenty foot separation free of intervening combustibles between components of redundant trains needed for safe shutdown or one hour fire rated enclosure of one of the redundant trains is lacking. These exemptions are based essentially on the following:
- 1. The safe shutdown evaluation identified the coexistence of redundant power, and control cables required for safe shutdown with less than twenty feet horizontal separation. The redundant cables are installed and within 3 feet of the ceiling. The redundant cables cross over one another and are separated by approximately one foot at the crossover. The Train B conduits containing safe shutdown cables have been wrapped in one-hour fire rated barriers.
- 2. The exemption request as approved by the NRC allowed the use of thermal barriers on the tops and bottoms of the Train B cable trays. The existing automatic splinkler systems installed at the ceiling were modified to also provide partial area sprinkler coverage in accordance with NFPA 13 below the cable trays and components in the areas.
- 3. The combustibles are lubricating oil and cable insulation. The combustibles comprise a light fuel load which, if totally consumed, would correspond to a fire severity of less than 15 minutes on the ASTM E-119 standard time temperature curve.
- 4. The fire protection in these areas consists of automatic sprinklers, thermal and ionization detectors, and portable fire extinguishers. Nearby standpipe hose stations and extinguishers will serve both fire areas.
For Containments, Fire Areas 1 and 71, per the provisions of 10CFR50.12, Northem States Power requested and received exemption from the specific requirements of Appendix R, Section Ill.G.2, to the extent that these areas have intervening combustibles between components of redundant trains needed for safe shutdown, less than 20 feet of separation between redundant cabling associsted with the pressurizer level transmitters for Unit 2 (Fire Area 71), and no automatic suppression systems. This area contains light combustible loading consisting of lubricating oil and cable insulation corresponding to a fire severity of less than 15 minutes on the ASTM E-119 standard temperature curve.
Fire protection consists of smeka detectors with control room alarms and stand pipe hose AP,R EXM, , [OC
i USNRC NORTHERN STATES POWER COMPANY !
August 14,1997 Page 8 stations. These areas are not normally occupied during normal operation. Transient combustibles are not normally allowed inside containment; in that event, a fire watch )
would be set, One train of pressurizer level cables for Unit 2 was protected.
As such, the Rockbestos Firezone*R Appendix R fireproof cables meet the intent of Appendix R Section Ill G.2.c criteria for an 1-hour fire barrier and by extension also meet the intent of Appendix R Section Ill.G.2.f criteria for a non-combustible radiant energy shield, which is to ensule that one train of systems necessary to achieve and ;
maintain hot shutdown conditions is free of fire damage.
Conclualon Based on the technicaljustification detailed above, Pralrie Island believes the use of the Rockbestos Firezone*R Appendix R fireproof cables achieves the underlying purpose of 10 CFR Part 50, Appendix R, Section Ill.G.2.c and 10 CFR Part 50, Appendix R, Section Ill.G.2.f. Prairie Island requests an exemption from the requirements of 10 CFR Part 50, Appendix R, Section ill.G," Fire protection of safe shutdown capability "
E paragraph G.2.c. The exemption is requested for use of Rockbestos Firezone R Appendix R fireproof cables in Fire Area 58,59,73 and 74 specifically in lieu of a rated 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> barrier and for Fire Areas 31,32,60, and 75 in general, in addition based on .
the technical Justification detailed above, Prairie Island requests an exemption from the requirements of 10 CFR Part 50, Appendix R, Section Ill.G," Fire protection of safe shutdown capability," paragraph G.2.f in Fire Areas 1,31,32 and 71 to use Rockbestos Firezone'R Appendix R fireproof cables in lieu of a radiant energy shield. ,
in this letter we have made the following new Nuclear Regulatory Commission commitments:
- 1. All Rockbestos Firezone'R Appendix R fireproof cables will be insta' led in either trays (on the top tier) or in rigid steel conduit in accordance with manufacturers recommendations.
- 2. Raceway supports for Rockbestos Firezone'R Appen6x R fireproof cables will be constructed from Unistrut* (or equivalent) channel ir accordance with existing
- Psalrie Island engineering and electrical construct'an guidelines.
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, . AP.REEN . DOC i
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USNRC NORTHERN STATE 3 POWER COMPANY August 14,1997 Page 9 Please contact Jack Leveille (612 3801121. Ext. 4662) if you have any questions related to this letter.
f.&L / .
Ct/
.) e y Joel P Sorensen Plant Manager Prairie Island Nuclear Generating Plant c: Regional Aoministrator - Regle' 111, NRC Senior Resident inspector, NF '
NRR Project Manager, NRC J E Silberg State of Minnesota, Attn: Kris Sanda Attachments:
- 1. Underwriters Laboratories Inc. File R10925-1, Reoort on Fire Resistant Cables, dated April 10,1984.
7
- 2. Letter from Robert Konick, Rockbestos Cable Corporation to Marcia Thompson, dated March 3,1997.
- 3. Faverdale Technology Centre Lst Report FTCR/94/00SO, Test Reoort for a 1 Hour Fire Hose Stream Tests on Darmatt KM1 Fire Protection System for Electrical Circuit Systems to ASTM E119 NRC GL 86/10 Sucolement 1. lasue B, dated September 1,1994 I
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Attachment 1.
Underwriter's Laboratory Report on Fire Resistant Cab,44 !
File R10925-1
dated April 10,1984 1
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@ UfHierwriters Labotstories loc.e .
Wo MsINo. 2M-SM3 7.i.* **ceMaus september 15,1997 D Mr. Wayne Gembin FAX 612-3304247 g pg er est Het Northom States Power Prairie Island Nucsear Generating Station 171 Wakonede Drive East .
Welch, MN 56089 Re: Walvor of Copyright Restrictions -UL file R10925-1, Rp: Deted April 10,1964 for Project 84NK2320
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, Dont Mr. Gambirr frit' Underwriters Laboratories Inc. ('UL") authorizes the Nuoiser Regulatory Commission to reproduce the referenced report, regarding Rockbestos Firarone A pmvided it is reproduced in its entirety and for internal use only.
In no event shell Underwiters Laboratories Inc. be responsble to anyone for wtistever uso or nonuse is mede of the information contened in the reforgmed .W and in no event shall Underwriters Laboratorlos Inc., its employees, or its ar, ants locur any l
obilgat!on or liability for damag*s of any kind, ariping out o(or in connection Wth the use, or inability to use, the Information contained in the referenoeci report.
This conditional Walver of Copyright Restrktiona is granted with the understanding that any copies of the referenced report will continue to beer the copyright notlee, which will be reproduced along with the referenced report. .
D is Waiver of Copyright Restrictions shall be in sfFoot until December 31,1999, and a nsite at that time, unless notification la made in wetting to the NRC by UL. )
. dinoerely, ,
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STEVEN R. MICKELSON "
Assistant to the Corporate Secretary P Eadenelon 42082 '
Fax: 647-272-9562 E Mail: raickelsonagul.com '
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