ML20127F658

Informs Commission of Staff Action Re Fire Endurance Testing Acceptance Criteria for thermo-lag Fire Barrier Sys for CPSES Unit 2

ML20127F658
Person / Time
Site:	Comanche Peak
Issue date:	11/06/1992
From:	Taylor J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO)
To:
References
SECY-92-378, NUDOCS 9211120283
Download: ML20127F658 (11)

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November 6, 1992 SECY-92-378 (Information)

[or: The Commissioners from: James M. Taylor Executive Director for Operations

. hlb.itc_t: FIRE ENDURANCE TES11NG ACCEPTANCE CRITERIA TOR COMANCHE PEAK STEAM ELECTRIC STATION UNIT 2

Purpose:

To inform the Commission of the staff's action relating to fire endurance testing acceptance criteria for Thermo-Lag fire barrier systems for Comanche Peak Steam Electric Statica Unit 2.

Q11rM 11AD: In June 1991, the NRC began a comprehensive review of Thermo-Lag 330-1 fire barriers after receiving reports about installation problems and qualification fire tests that failed. The staff found that Thermo-Lag 330-1 fire barriers may not provide the level of fire resistance required.

The staff has developed an Action Plan to resolve technical issues associated with Thermo-Lag 330-1 fire barriers. An important part of the action plan to re wive fire endurance testing and qualification concerns is te work with industry in a public forum to reach a common understanding on fire -

endurance testing acceptance criteria for fire barrier systems used to separate safe shutdown functions within the same fire area.

Currently, Thermo-Lag 330-1 fire barrier qualification tests are being conducted by TV Electric for its Comanche Peak Steam Electric Station. Tennessee Valley Authority (TVA) is planning fire tests for its Watts Bar Nuclear plant. The Nuclear Management and Resources Council (NUMARC) is also developing an industry-wide fire test program for Thermo-lag 330-1 fire barriers. The staff has been

4~107 interacting with TV Electric, TVA, and NUMARC in an effort to establish acceptance criteria to be used for the various tests. TV Electric is in the lead with respect to the need to establish criteria. A series of TV Electric qualification tests started on November 3,1992.

CCNTACT: NOTE: TO BE MADE PUBLICLY AVAILABLE P. Madden, SPLB/DSSA/NRR IN 10 WORKING DAYS FROM Tile 504-2854 -

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The enclosed letter to 10 Electric reflects the staff's comments and final agreement on its proposed acceptance criteria. We have agreed to an approach that can be used to acceptably demonstrate cable functionality in the event there are deviations from the fire barrier acceptance criteria. All such deviations will be submitted for IRC review and approval.

The staff will continue to work with industry, including NUMARC and TVA, on propos,d fire barrier acceptance criteria. The staff is also developing generic NRC fire barrier acceptance criteria. Consistent with the Comnissior, guidance on issuing generic staff positions (SECY-92-224),

the staff will review its proposed staff position with the Committee to Review Generic Requirements (CRGR) and the Advisory Committee for Reactor Safety (ACRS), and will request public comments.

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1. xecutive irector for Operations

Enclosure:

Letter from S. Black to W. Cahill dated October 29, 1992, "Thermo-Lag Acceptance Methodology for Comanche Peak Steam Electric Station - Unit 2" DISTRIBUTION:

Commissioners OGC OCAA OIG OPA OPP REGIONAL OFFICES EDO ACRS SECY

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/I NUCLEAR REGULATORY COMMISSION o,  ! W ASHINGToN. D.C. 202 s' *-...* J October 29, 1992 Docket No. 50-446 Mr. William J. Cahill, Jr.

Group Vice Priisident, Nuclear TV Electric 400 North Olive Street, L.B. 81 Dallas, Texas 7520

SUBJECT:

THERMO-LAG ACCEPTANCE HETHODOLOGY FOR COMANCHE PEAK STEM ELECTRIC STATION - UNIT 2 The NRC staff has completed a review of TV Electric's submittal dated September 24,1992, " Confirmatory Te$ttrg of Thermo-Lag Fire Barrier System at CPSES." A meeting was held on October 27, 1992 between HRC and TU Electric, where you updated your fire barrier testing acceptance criteria. The enclosure to this letter provides the revised acceptance criteria you proposed at that meethg.

This letter informs you o=' the results of the staff review of your criteria.

Fir.al NRC staff review of your fire barrier acceptance testing will be documented in a future safety evaluation.

Your acceptance criteria, including the use of a fog hose stream test in accordance with NUREG-0800, is acceptable based on the following conditions:

1. The NRC maintains that the temperature measured on the externa'i surface of the raceway should not exceed 325'F. Your criteria, submitted in your September 24, 1992 let,ter, states that cable temperatu.es are to be maintained below 325'F as measured by thermocouples installed at six-inch intervals on cables close to the inside of the protective envelope.

In your previous tests, the raceway, in addition to the cables, was instrumented with thermocouples. These thermocouples provide a better indication of barrier unexposed side thermal performance during the fire test. You have stated that you will be monitoring various raceway locations in these upcoming tests; hoeever, in reviewing your criteria as submitted in your September 24, 1992 letter, we could not determine how you propose to evaluate the barrier's thermal performance using the raceway thermocouples.

' The 325'F temperature condition was established by allowing the internal temperature on the raceway surface to rise 250*F above ambient laboratory air temperature, assumed to be 75*F. during the fire test.

Mr. William J. Cahill, Jr. In the October 27, 1952 meeting, we discussed this concern and your staff indicated that the cable tray side rail and the external conduit temperatures would be used to determine the temperature acce)tance of the fire barrier system. In addition, your staff agreed, for ca)1e trays, to also use the cable thermocouple temperature readings to supplement the raceway thermocouples in assessing the thermal performance of the fire barrier system.

With respect to determining the temperature acceptance criteria, the NRC staff considers thermocouple averaging acceptable, provided similar series of thermocouples (e.g., cable tray side rai') are averaged together. It was determined that the temperature performance of the cable tray fire barrier would be based on temperature averages (i.e., the thermocouples on each side rati, and the thermocouples on each of the three instrumented cables) and would be independently evaluated gainst the temperature acceptance criteria. in addition it was agread that averaging the thermocouples on the external conduit surface would bt used to evaluate the thermal performance of the conduit fire barrier system. It is or understanding tnat your temperatere acceptance criteria wot.id find the test results in deviation if the average temperature of any thermocouple series exceeds the 250'F plus ambient condition or if any single thermocouple exceeds 30 percent above the maximum allowable temper:ture rise (i.e., 250*F + 75'F - 325'F, above ambient) during the test. If this occurs, under your criteria a visual inspection of the cables for signs of thermal damage is required. Any sign of thermal cable dam:ge would be a deviation to the fire barrier requirements which would require the functionality of the cabling to be demonstrated by tes.ing.

2. Your barrier inspection criteria, submitted in your September 24, 1992 letter, allows burnthrough no greater than one-half square inch, in the October 27, 1992 meeting, your staff revised its position on burnthrough.

In this meeting your staff indicated that any burnthrough is now a deviation requiring cable functionality testing. If burnthrough occur;,

based upon visual examination and notwithstanding the size of the defect, the NRC views the fire barrier as deviating from the fire barrier requirements and would require that cable functionality be demoretrated.

3. Your visual cable acceptance criteria, submitted in your Se)tember 24, 1992 letter, statad that none of the following attributcs s1ould be identified: jacket swelling, splitting, or discoloration; shield exposed; or jacket hardening. The NRC staff has determined that the following attributes also indicate thermal degradation: Jacket blistering, cracking or melting; conductor insulation exposed, degraded, or discolored; and bare copper conductor exposed. It is our understanding that your criteria for visual cable acceptance will include all of the ab;ve attributes.

Mr. William J. Caliill, Jr. 4. Your acceptance methodoltagy calls for a megger test after the cable has been installed in the rv;eway, continuity measurements during the test, and a subsequent megger test immediately following the test. At the October 27, 1992 meeting, ycu provided additional details and clarification regarding your proposed testing to 6mnstrate cable functionality. Additirmally, you stcted that you ma, use loss-of-coolant-accident (LOCA) cable qualification test results in evaluating cable functionality at elevated temperatures.

At the October 27, Ifi92 meeting, the NRC staff described the following tests which can bis ut.ed to demonstrate functional performance of cables where there arc sigt,s of thermal damage to cables or where barrier burnthrough or openings occur:

The megger tests (pre-fire, during the fire [if performed], and immediately after the fire test conditions) should be done conductor-to-conductor for multiconductor and conductor-to-grounJ for all cables.

The minimun acceptable insulation resistance (IR) value, using the 't.est voltage values for various system voltages is determined by using the following expression:

IR (Mega-ohms) 2 !T(1 Heoa-ohm.p.er KV) + 11

• 1000(ft))

Length (ft)

In addition, an AC or DC high potential (Hi-Pot) test for power cables greater tr 'no volts should be performea after the post fire meg; sts to assess the dielectric strength. This test pr - ; assurance that the cable will withstand the applied voltage during and after a fire. The high potential test shculd be performed for :

five minute duration at 60 percent of either 80 volts / mil AC or 240 volts / mil DC (e.g.,125 mil conductor insulation thickness X 240 volts DC X 60% - 18,000 vde).

The table below summarizes the megger and Hi-Pot test voltages which, when applied to power, control and instrumcntation cables, would constitute an acceptable cab'le fur.ctionality test.

OPERATING HEGGER TEST HIGH POTENTIAL

]H1 VOLTAGES VOLTAGE TEST V01.TAGE 2 1000 volts 2500 VDC 60% x a V/ mil (AC)

POWER 60% x 240 V/ mil (DC)_

< 1000 volts 1500 VDC NONE INSTRUMENT s 250 vde 500 VDC NONE AND CONTROL s 120 vac

Mr. William J. Cahill, Jr. In addition, at time intervals (at least once) during your one-hour fire exposure test, a megger test should be performed for instrumentation cables in order to assure that the cable will maintain sufficient insulation resistance levels necessary for proper .geration of instruments. LOCA temperature profiles may be used to evaluate cable functionality instead of megger testing duting the fire test. If this approach is taken, you should ensure that the LOCA temperatures bound the fire temperature prof 9e, by including cable operating temperatures. Ade .ionally, in determining the insulation resists.nce 1e e1+ .auired for nuclear instrumentation

e. ables, an as. , snient of the minimum insulation resistance velue (e.g., one mega-ohm) and its potential impact on the functionality of these cables should be evaluated.

The NRC concludes that performance of your proposed testing, with the additional megger and Hi-he testing described above, would constitute an acceptable set of tests tc demonstrate t' at any fire barrier test deviations, should they occur, will not affect the capability of the protected cable to perform its safety function. Other tests or combination of tests for cable functionality, different from those describad above, would require NRC review and approval.

5. Discussions with your staff indicate that CPSES power and instrument cable meets IEEE-383 and is all thermoset insulation type. Additionally, you have stated that installation procedures prohibit cabling to extend above cable tray side rails. When you submit your next test summary, confirm these facts in writing.

In summary, your criteria, as supplemented with the above conditions, ensures that adequate cable and barrier tests will be performed. Satisfactory results froa these tests (raceway / cable temperattn <325*F and no barrier burnthrough) constitutes a satisfactory basis for _ rated fire barrier qualification. Where the temperature criteria is not met aM cable inspection criteria results in deviation (s), and/or barriar inspectic esults in deviation (s), your criteria calls for subsequent cable functionality testing. Also, as discussed at the October 27, 1992 meeting, since no cabling greater than 1000 volts is being subjected to the fire tests, additional testing would be required on this voltage class to demonstrate functionality should test deviations warrant cable functionality verifications. NRC review of your test deviation (s),

should they occur, will be included in the staff's safety evaluation of your fire barrier acceptance testing.

Mr.-William J. Cahill,-Jr. The NRC staff plans on observing your upcoming: testing. Further, we request that you meet with the NRC following completion of this next set of testing to-review test results.

Sincerely, Original Signed By Suzanne C. Black, Director Project Directorate IV -

Division of Reactor Projects III/IV/V Office of Nuclear Reactor Regulation

Enclosure:

TU Revised Acceptance Criteria cc w/ enclosure:

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Senior Resident Inspector - Jack R. Newman, Esq.. .

. U.S. Nuclear Regulatory Comission Newman & Holtzinger '

P. O. Box 1029 1615 L-Street,'N.W.

Granbury, Texas 76048 Suite 1000 Washington, D. C. 20036-Regional Administrator, Region IV U.S. Nuclear Regulatory Comission Chief, Texas Bureau of Radiation Control 611 Ryan Plaza Drive, Suite 1000 Texas Department of Health Arlington, Texas 76011 1100 West 49th-Street Austin, Texas 78756 Mrs. Juanita Ellis, President

-Citizens Association for Sound Energy Honorable' Dale McPherson 1426 South Polk County Judge Dallas, Texas 75224 P. O. Box 851 Glen Rose Texas 76043 Owen L. Thero, President Quality Technology Company Lakaview Mobile Home Park, Lot 35

'4793 East Loop-820 South Fort Worth, Texas 76119 Mr. Roger'D. Walker, Manager Regulatory Affairs. for Nuclear Engineering Organization

Texas Utilities Electric Company 400 North Olive Street, L.B. 81 Dallas, Texas 75201 Texas Utilities. Electric Company c/o-Bethesda Licensing .

'3 Metro Center, Suite 610.

Bethesda, Maryland 20814 William _A.'Burchette, Esq.

Counsel; for Tex-La Electric

-Cooperative of Texas-Jorden,:Schulte,-& Burchette 1025 Thomas Jefferson Street, N.W.

Washington, D.C. 20007 GDS Associates,-Inc.

' Suite 720 1850 Parkway P1 ace.

-Marietta,. Georgia' 30067-8237

Mr. William J. Cahill, Jr. DISTRIBVUDE:

Docket File NRC PDR Loc:1 PDR PDIV-2 Reading PDIV-2 Plant File TMurley/FHiraglia JGPartlow WTRussell JRoe MVirgilio --

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PGill RJenkins CMcCracken RArchitzel PMadden SWest 4 AMasciantonio OGC ACRS (10)

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Test Sequence Build Sample Megger Temperature FimTm Acceptance

- Measure Sat Conduit / Cable Tray Continuity < Amb + 250 F avg Temocrature < Amb + 325 F peak i

Fog NonelTest -

Hot Megger Fire BarrierInspection Potentini Deviation Functionality Tests * """^

Visual Cable Inspection

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- a Enclosure CABLE FUNCTIONALITY TESTING TU ELECTRIC PROPOSAL JUSTIFICATION TEST SEQUENCE DURING FIRE CONTINUITY TEST AT 12VDC -

UL 1724 RECOMMENDS Tlf AT LOW VOLTAGE TEST SIIOULD BE USED ON CIRCUIT DURING FIRE TESTING LABORATORY PERSONNEL SAFETY REQUIREMENTS

- LOGISTICS OF MEGGFMING ALL CONDUCTORS DURING TIIE ONE IIOU'A FIRE TEST RESTRICTS INTERMITTENT TESTING 4 FUNCTIONALITY OF CABLE AT ELEVATED

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TEMPERATURE MAY BE CONFIRMED BY LOCA TEST RESULTS PROVIDED CABLE JACKET TEMPERATURES DID NOT EXCEED LOCA QUALIFICATION TEMPER ATURES AFTER IIOST IIOT MEGGE't TEST -

ACCEPTANCE CRITERIA B ASED ON MOST LIMITING STREAM TEST INSTALLATION (5 M )

- INSTRUMENTATION CABLF ACCEPTANCE CRITERI A FOR CONTROL / LOW 500VDC VOLTAGE CABLE BASED ON DC EQUIVAISNT TEST VOLTAGES OF RATED AC VOLTAGE (1500VDC)

CONTROL / LOW VOLTAGE C'BLE AT 1500VDC O