ML18153B422

Rev 11 to Engineering Evaluation 25, Evaluation of Existing Fire Enclosure Around Ventilation Duct,North Anna Power Station.

ML18153B422
Person / Time
Site:	Surry, North Anna
Issue date:	07/31/1993
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18153B420	List: ML18153B419 ML18153B421 ML18153B422 ML18153B423
References
25, 25-R11, NUDOCS 9401030370
Download: ML18153B422 (12)

Text

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e 25.

EVALUATION OF EXISTING FIRE ENCLOSURE AROUND VENTILATION DUCT NORTH ANNA POWER STATION Description of Evaluation One inch thick Thermo-Lag 330-1 material was originally installed to satisfy a three hour fire resistance rating per Section III.G.2.a of 10CFR50 Appendix R for protection of a ventilation duct located on el. 259 ft. 6 in. of the Auxiliary Building. The ventilation duct enclosure is located in an area provided with detection and suppression. Since detection and suppression are installed, the one inch thick Thermo-Lag material is only required to meet an one hour fire resistance rating per 10CFR50 Appendix R Section III.G.2.c.

This evaluation assesses the ability of the Thermo-Lag installed around the duct to meet the intent of Section III.G.2.c.

Area Description Fire Area 11 consists of the Auxiliary Building, Fuel, and Decontamination Buildings. The buildings are located side by side in a north-south ori en tat ion, with the Auxiliary Building to the North, the Decontamination Building to the south and the Fuel Building in the center. The Auxiliary Building is a four story structure consisting of the 244 ft. 6 in., 259 ft. 6 in., 274 ft., and 291 ft. 10 in. elevations. The main access point into the Auxiliary Building is through its north wall on the 274 ft. elevation via a three hour rated fire door. Access is provided to the Auxiliary Building roof from ladders on the building exterior.

The combustible loading for each fl oar of the Auxiliary Building is low.

Cable insulation and miscellaneous class A combustibles contribute to the majority of the combustible loading.

25-1 Revision 11 7/93

V Fire Protection Features An automatic detection system that alarms in the continuously manned Control Room is provided in the Auxiliary Building. Ionization smoke detectors are located on each elevation of the Auxiliary Building, consisting of ceiling mounted smoke detectors located primarily in the vicinity of the cable trays, duct enclosure, and duct detectors 1ocated in the HVAC exhaust ducts. One cei 1i ng mounted detector and one duct detector is provided in each charging pump cubicle.

A low pressure CO2 fire suppression system is provided at the ventilation system charcoal filters located on the 291 ft. 6 in. elevation. An automatic wet pipe sprinkler system is provided over the component cooling water (CCW) pumps and their associated power feeds on the 244 ft. 6 in. elevation. Automatic sprinkler coverage is also provided on the 259 ft. 6 in. elevation which protects the CCW and charging pumps power feeds. The ventilation duct enclosure located on the 259 ft. 6 in. elevation is also located within the area protected by automatic sprinklers. Portable extinguishers and manual hose stations are provided on all levels of the Auxiliary Building for manual fire fighting purposes.

Safe Shutdown Eguipment The Auxiliary Building contains six charging pumps, four CCW pumps, and associated cabling and valves for safe shutdown purposes. The CCW and charging pumps are located on the 244 ft. 6 in. elevation, with the component cooling water pumps located in the main open floor area of this elevation. The charging pumps are located in separate cubicles on the 244 ft. 6 in. elevation that are accessed from the 259 ft. 6 in. elevation. Ventilation fans located in the Auxiliary Building provide cooling to the charging pumps and the CCW pumps.

Evaluation The 291 ft. 6 in. elevation contains the normal Auxiliary Building exhaust fans, Containment purge supply fans, miscellaneous supply and exhaust fans, and the ventilation system charcoal filters. Sheet metal ducting from each roof mounted fan is cross-connected and backdraft dampers are installed. Once inside the CHl0-25 25-2 Revision 11 7/93

e Auxiliary building, hard and flexible ducts are routed down to 259 ft. 6 in. and 274 ft. elevations.

An enclosure exists around the ventilation duct at the 259 ft. 6 in. elevation.

The enclosure is constructed of 1 inch thick panels of Thermo-Lag 330-1 attached to a steel frame. The enclosure is approximately 7 ft. high with sides 4 ft.

wide and is provided with a three hour rated fire door. The enclosure contains flexible ducting that will be used to provide forced ventilation to individual charging pump cubicles in an emergency. Ventilation is needed for the charging pump cubicles to assure continued operation of the pumps during the shutdown

• . process.

The Thermo-Lag installed around the ventilation duct is 1 inch thick and normally associated with a 3 Hr. fire resistance rating.Section III.G.2.c of Appendix R requires only a 1 Hr. fire resistance rating when detection and automatic suppression is installed in the area. The NRC has indicated in Supplement 1 to Bulletin 92-01 (see pages 4 - 6 of Attached) that 1 inch thick Thermo-Lag will not provide a 3 Hr. fire resistance rating. The test information contained in the NRC documents indicate that 1 in. thick Thermo-Lag did not fail within 1 Hr.

into the test. Therefore the 1 in. thick Thermo-Lag would be expected to provide at least a 1 Hr. fire resistance rating.

Conclusion Based on the above analysis, it has been determined that the 1 in. thick Thermo-Lag 330-1 provides the level of protection required by Section III.G.2.c of Appendix R. The technical bases that justify this conclusion are summarized as follows:

1. A fire barrier having a 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> rating and not a 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> rating is required for Appendix R compliance since the enclosure is located in an area provided with detection and an automatic fire suppression system.

2. The enclosure constructed of 1 in. thick Thermo-Lag panels is expected to provide at least a 1 Hr. fire resistance rating as required by Section III.G.2.c of Appendix R.

3. The combustibility of the Thermo-Lag material is not a factor since intervening combustibles are acceptable when suppression and detection are present. Even though Thermo-Lag is combustible, 1 inch thick Thermo-Lag is expected to provide at least 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of fire resistance.

CHl0-25 25-3 Revision 11 7/93

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.. . e 0MB No.: 3150-0012 NRCB 92-01, SUPP. 1 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 August 28, 1992 NRC BULLETIN NO. 92-01, SUPPLEMENT 1: FAILURE OF THERMO-LAG 330 FIRE BARRIER SYSTEM TO PERFORM ITS SPECIFIED FIRE ENDURANCE FUNCTION Addressees For Action:

All holders of operat;ng licenses for nuclear power reactors For Information:

All holders of construction permits for nuclear power reactors Purpose The U.S. Nuclear Regulatory Conmission (NRC) ;s issuing this bulletin supplement to not;fy licensees and construction permit holders of additional apparent failures in fire endurance testing associated with the Thermo-Lag 330 fire barrier system which many plants have installed to protect safe shutdown capability. to request all operating reactor licensees that have Thermo-Lag fire barriers to take the reconnended actions, and to require that these licensees submit a written response to the NRC describing the actions taken associated with this bulletin supplement.

aJckgroynd On August 6, 1991, the NRC 1_s~ued. Information* Notice ( IN) 91-,7, ~-F~_iJ_11re,-*of __ _

Thermo-Lag Fire Barrier Mater1a1 To:Pass Fire Endurance Test," which contained 0

information on the fire*endurance tests perfoffledby the Gulf States Ut1-11ties Company on Thermo-Lag 330. fire-barrier systems'. installed on wide aluminum1,.,

cable trays and the associated failures. On December 6, 1991, the NRC issued IN 91-79. "Deficiencies In The Procedures For Installing -Thermo-Lag Fire-Barrier Materials," which contained-information on deficiencies in procedures that the vendor (Thermal Science, Inc.) supplied for installing Thenno-Lag 330 fire barrier material. Recognizing the concerns stated in INs 91-47 and 91-79 regarding the Thermo-Lag 330 fire barrier system, Texas Utilities (TU)

Electric instituted a fire endurance testing program to qualify its Thermo-Lag 330 electrical raceway fire barrier systems for its Comanche Peak Steam Electric Station. On June 17-23, 1992, TU Electric conducted the first- series of these "full scale fire endurance tests at Omega Point Laboratories in San 6

Antonio, Texas.

e e NRCB 92-01, SUPP. 1 August 28, 1992 Page 2 of 9 The results of these tests have raised questions regarding the ability of the Thermo-Lag 330 fire barrier system to perform it~ specified funct~on as a 1-hour fire barrier. On June 23, 1992, the NRC issued IN 92-46, Thermo-Lag Fire Barrier Material Special Review Team Final Report Findings, Current Fire Endurance Testing, and Ampacity Calculation Errors," in which it di~cussed the safety implications of these questions. On ~une 24, _1992, the NRC 1~sue~ NRC Bulletin 92-01 "Fai1ure of Thermo-Lag 330 Fire Barrier System to Ma1nta1n Cabling in Wid; Cable Trays and Small Conduits Free From Fire Damage."

Description of Circumstances TU Electric and the NRC recently sponsored additional testing of Thermo-Lag 330 material.

TESTS SPONSORED BY TU ELECTRIC ..'....i -.

On August 19-21, 1992, TU Electric sponsored a second series of tests at.the Omega Point Laboratory to aid in Qualifying its Thermo-Lag 330 electrical_

raceway fire barrier systems for its Comanche Peak Steam Electric Station.

This series of tests consisted of 1-hour fire endurance tests (using.the ASTM*

E-119 Standard Time Temperature Curve) on a variety of cable tray and,canduit 11 mock-ups." TU Electric designed these *mock-ups* or test articles, to*.c:

• duplicate existing installed plant configurations. Plant personnel used,,stock material to construct the test articles. The Thermo-Lag fire barriers* wera-installed on the test articles in accordance with TU Electric 1 s The""'iLagt*:'.";

installation procedures .. TU Electric wrote these procedures based oni,VeiKlor**

recommended installation procedures. *, *-;-:-,?:;:**,.~.--,

The Thermo-Lag fire barrier systems for the TU Electric test articles;wer*"""***.

constructed using pre-formed 1-hour* Thermo-Lag 330 panels and condu1t,shapes.

The joints and seams were constructed by pre-buttering seams and jo1ntstwtth* ..

trowel grade Thermo-Lag 330-1 and holding the usembly together with ,:stainless*

steel banding as required by TU procedures and as the system* is 1nstaJ,:ljd:dn,:o--<.

th, phn\. C * * ' --~ ~- ')?ff~1:;:::*::i~r!t::';::

The articles tesfed during this series of tests consisted of a condui,tf~(\., <-:-* .

configuration, which exposed five*-conduits of various sizes (3-inch~*-)2;;.lnch*r"*

.1-1/2-inch and two 3/4-inch) to the same test fire, a 24-inch wide cable.tray with a T-section and a 30-inch wide cable tray. * {t'* "**

On August 19, 1992. TU Electric performed a- 1-hour fire endurance test-on the conduit conf;guration. The fire barrier systems installed on the 3-tnch,.

2-inch and 1-1/2-inch conduits and their associated cable pull bcxes:..-were~,,.* *.

constructed using I-hour Thermo-Lag 330 conduit pre-shapes and panels,.

respectively. The 3/4-inch conduits were constructed using a Thermo-Lag-,330 conduit pre-shape as a base material. The two 3/4-inch conduits were"dtvtded:::

at the middle of the test specimen, and four different enhanced barrier.-* *

) systems were tested. Th, first of these-consisted of a 3/4-inch condqtt/run,;\{ ,_

one half of which was protected by a 3/4-inch Thermo-Lag 330* fire- barrt*er_,;., ,.-:, ..

conduit pre-shape, and the other half protected w;th a 1/2-inch thick conduit

• • _1

e e NRCB 92-01, SUPP. 1 August 28, 1992 Page 3 of 9 pre-shape ~ith a wire mesh "stress skin" applied on th~ exterior and 1/4-inch of trowe) grade Thermo-Lag_ applied to the st~ess sk~n. One ~ilf of the se~ond 3/4-inch conduit run was protected by a 1/2-,nch thick condu1t pre-shape w1th a 1/4-inch thick Thermo-Lag flexi-blank~t ~rap. ~he oth~r half was protected by a 1/2-inch thick conduit pre-shape with a l/4-1nch thick pre-shape overlay.

TU Electric did not conduct a hose stream test after the fire endurance test.

The post-fire visual inspection of- the test specimen revealed that the interface joints between the vertical conduit runs and the cable pull boxes hid opened and exposed conduit metal surfaces to the fire. In addition, the cables exhibited visjble* fire dam~ge to cable jackets in all conduits, except for the 3/4-inch conduit protected by the 1/2-inch thick conduit pre-shape with the 1/4-inch ~re-shape overlay. Throughout the fire endurance test, the thermocouple temperatures on the cables inside the 3/4-tnch conduit protected by the overlay never reached 163 *c (325 °F). All other conduit configurations exceeded- 163* -(325 "f) on the cables during the test.

On August 20, 1992,. TU Electric sponsored a test of a 24-inch wide ladde*r back -

tray with a T-tray configuration. Post-fire inspection of this specimen revealed that five joint and seam type openings had occurred. These openings were both in horizontal and vertical runs of the cable tray. Fire damage to the cables was also identified during the post~fire inspection, raising questions whether the cables would have functioned properly during a fire.

The thermocouples indicated that internal temperatures in certain areas. of the test article exceeded 163 *c (325 "F) at 47 minutes. The maximum monitored cable temperature during the test was 194 *c (381 "F).

On August 21, 1992, TU Electric sponsored a test of a 30-inch wide ladder back tray configuration. During the post-fire inspection of this specimen, ftv1 joint and seam type openings were identified 1n horizontal and vertical runs of the cable tray. The Thermo-Lag barrier also experienced areas of loss of its material, leaving spots of bare stress skin covering the tray. Firt damage to the cables wis identified during the post-fire inspection.

• Thermocouples indicated that intimal t1mper1tures 1n certain areas of the,-

test article *exceeded 163 *c (3ZS *F) at 30 minutes. The maximum monitored:

cable temperature during the, test was,,approximately 371 *c (700 *F). ,.. -*

• Although prevfous tests conducted by TU Electric (s~t Bulletin 92-01) resulted:.

in the apparent successful perfonnance of l 1rge diameter condu;ts and .n-~raw['.{/

trays, new inrormation provided by these recent tests has led the NRC to,:*' "* ** **

believe that potential early failures of Thermo-Lag barriers are not limited*:~ -

• to specific sizes. The NRC considers the. openings at the joints and seaasrof: *.

the Thermo-Lag material to be of high significance. The characterist1cs*of-the configurations of the*material protecting the trays or cond~its in quest ion seemed to impact the effectiveness of the barrier materhl more"' than-

• their specific sizes. The tests *sponsored by TU Electric revealed that the Thermo-Lag material lost its structural integrity primarily at the seams,.and:o*

joints and that cable damage was most significant at these seam and joint separations.

Fol lowing the tests conducted 1n June 1992, the test assemblies were- subjected"*'

to hose streams which altered the conditions of the barriers. Due to the hose stream, post-fire inspection of these assemblies for joint failures and burn

..:. *- - . .: =*:- .,....,r- -

e NRCB 92-01, SUPP.

August ~8, 1992 Page 4 of 9 through was orevente:. The assemblies test~d in August 19~2 were cooled with water. essentially leaving the test assemb11es 1n the cond1t1on they wer~ in at the completion of the fire test. Areas of burn through and seam and Joint failures were observed during post-fire inspection.

Further. the TU Electric assemblies tested in June 1992 were constructed using supports that were covered with two layers of Thermo-Lag material. The assemblies tested in August 1992 had supports which were insulated to only 9 inches, corresponding to the TU Electric actual plant installations. Thus, the June 1992 tests did not model the installed plant configuration, as was the case in the August 1992 tests.

TESTS SPONSORED BY THE NRC On July 15 and 17, 1992, the NRC sponsored a series of "small scale" fire endurance tests on 1- and 3-hour Thermo-Lag 330 pre-formed fire barrier panels at the National Inst;tute of Standards and Technology (NIST). On July 27, 1992, the NRC issued the results of the first series of small scale tests in IN 92-55, "Current F;re Endurance Test Results for Thermo-Lag Ftre Barrier Material." On August 6-7 and 14, 1992, the NRC sponsored a second series of 1- and 3-hour small scale fire endurance tests on Thermo-Lag 330 fire barrier pre-formed panels.

On July IS, 1992, the NRC sponsored a I-hour fire endurance test. The I-hour panel stress skin was oriented away from the fire exposure, according to vendor reconvnendation. The average thermocouple reading on the unexposed surface exceeded 162.7 *c (325 °F) in approximately 22 minutes, and the unexposed surface of the material reached an average temperature of 652 *c (1206 °F) at 45 minutes. The unexposed surface of the material exhibited visible browning in 35 minutes. During the test, the thermocouple on the unexposed surface reached a peak reading of 935 °C (1716 °F), exceeding the corresponding furnace temperature.of 923 *c (1694 °F}, u the material burned and added heat to the baseline furnace temperature. The panels burned through at two locations in 46 minutes, resulting in a corresponding drop in surface thermocouple readings as the cold air entered the furnace. After l hour, apprax-imate1y- es -percent of the unexposed- surface was--blackened.

On July 17, 1992. the NRC sponsored a 3-hour test. The 3-hour panels had stress skin installed on both sides of the Thermo-Lag material. To prepare for the test, the techn;cians installed the ribbed side of the specimen on the unexpos*ed side with the non-ribbed side of the material towards the furnace side. :The stress skin on the furnace side of the specimen was restrained by the furnace specimen support li~ during the test. The average thermocouple reading exceeded 162.7 *c (325 F) in 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 20 minutes, the average temperature at the end of 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> was 206 *c (403 °F), and the peak of thermocouple reading was 222 *c (432 °F). After the test, the material was soft and exhibited plastic deformation. and the fire-exposed stress skin crumbl~d upon contact. Nevertheless, visible signs of damage on the unexposed side were limited to off-gassing. slight browning, and crystallization at the surface.

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e e

NRCB 92-01, SUPP.

August 28, 1992 Page 5 of 9 On Auoust 5, 1992, the NRC sponsored a fire endurance test on a 3-hour Thermo-Lag fire barrier pane1, which had stress skin on both sides. The e~ges of the stress skin of the 3-hour material ~ere cut away from the exposed s1de of the panel so that the outer edges of the stress sk~n contact~d the support l~p of the furnace. The stress skin was kept from being restra1ned in compression at the edges of the panel around the lip of the furnace. The average thermocouple temperature of the unexposed surface exceeded the ASTM E-119 temperature acceptance criterion of 163 *c (325 *F) in 45 minutes. After l hour, the unexposed surface temperature reading was 75~ *c (1392 "F). At 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 20 minutes, the panel was burned through. Th,s 3-hour configuration performed Quite differently during this test than did the Thermo-Lag 330 fire barrier panel in the July 17, 1992, 3-hour fire test in which the stress skin was restrained on the side exposed to the fire. In this previous test, the average unexposed surface temperature of the restrained specimen did not exceed 163 *c (325 *F) until 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 20 minutes into the test, and the max,mum temperature at the end of the 3-hour test was 194 *c (381 *F). The specimen tested on July 17, 1992 did not burn through.

On August 6. 1992. the NRC sponsored a second I-hour fire endurance test on a Thermo-Lag 330 1-hour panel, which had stress skin on one side only. This panel was placed an the furnace with the stress skin towards the fire, although the vendor reconvnends that the 1-hour panel be installed with the stress skin away from the fire exposure. The deviation from the vendor recommendation aided in the deterndnation of the material's sensitivity to installation variations. The stress skin was restrained by the furnace specimen support lip. The average unexposed surface temperature of the specimen exceeded 163 *c (325 *F) in 34 minutes, and at 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, the maxi1n111 temperature of the unexposed surface was 237 *c (458 *F). However, the specimen was not burned through. The performance of the specimen in this test was superior to the specimen tested on July 15, 1992, at which the stress skin faced the unexposed side, as reco11111end1d by the vendor. The specimen tested an July 15, 1992, exceeded the 161 *c (325 *F) acceptance criterion in 20 minutes and the unexposed surface reached 649 *c (1200 *F) in 37 minutes.

Burn through was observed in 46 minutes.

On August 7,- 1992,. the NRC sponsored. a- third 3-hour fire endurance test-~::*,:~.,:_,

1-hour fire barriers were dry fitted together wifh their stress skins on the*

outer sides of the test specimen. As in the test conducted an Augusts. the exposed side stress skin was tr;nmed away to prevent the material from-being"'"

restrained. One hour into the test, the specimen abruptly began releas;ng gases, and the thermocouple readings inside the furnace indicated that the thermocouple had come into contact with burning material. The average*

thermocouple reading exceeded 163 *c {325 *F) in l hour and 26 minutes. After 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, burn holes were observed in several locations. After the burn holes formed, unexposed surface thermocouple readings oscillated dramatically. with a peak reading of 947 *c (1737 *F) at the end of the test. Nonetheless, thts test specimen performed better than did the prefabricated 3-hour panel wtth its stress skin trimmed away.

On August 14, 1992, the NRC sponsored a flnal 3-hour test, again using two,., .*.

1-hour panels dry fitted together with their stress skins on the outer sides of the test specimen. The stress sk1n was not trimmed away from the specimen

.. e NRCB 92-01. SUPP. 1 August 28. 1992 Page 6 of 9 for th1s test; it was restrained in _Jmpression at the edges of the panel.

The averaqe thermocouple reading exceeded 163 *c (325 "F) in 2 ho~r~ and .

40 m1nutes and reached 176 °C (349 "F) at the end of the ~est: V1s1ble signs of damage ~ere limited to off-gassing and slight crystall1zat1on at the surface of the unexposed side, and no browning w~s observed.

The following table summarizes the data collected during these smal1 scale tests.

Test Date Barrier Stress Sic.in Stress S1c1n Time to Burn Rating Restraint Orientation Exceed Through 163 *c*

(hrs:min) (hrs:min) 7/15/92 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> N/A unexposed 0:22 0:46 8/06/92 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> restrained exposed 0:34 none 7/17/92 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> restrained both sides 2:20 none 8/05/92 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> unrestrained both sides 0:45 1:20 8/07/92 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />

... unrestrained both sides 1:26 2:03 8/14/92 3 hour** restrained both sides 2:40 none .

• _ Average unexposed s~rface thermocouple temperature Two 1-hour panels fitted face to face In IN 92-55, the staff listed specific furnace spec;f;cations and test assembly parameters used in both ser;es of tests conducted by NIST.

The NRC views the results of the NIST tests as indicative of an inability of the Thermo-Lag material itself to provide protection according to its specified fire resistive rating, depending on its configuration. The tests conducted at NIST were not considered definitive in that the tests were not*>,

0 full scale and only panels were*tested-;* However, the- infonna.tion:**gleantdLlfraait the tests provided enough evidence* to the NRC to confirm doubts raised during,:

the TU Electric tests, such as the bare stress skin observed following; the*"TU' 30-inch wide cable tray test on August 21, 1992, discussed above, leading;:;;toia; conclusion that Thermo-Lag fire barriers should be treated as inoperable in the absence of successful, applicable plant specific tests~

Discussion Section 50.48(a) of Title 10 of the Code of Federal Regulations (10 CFR 50.48(a)) requires that each operating nuclear power plant have a f;re protection plan that satisfies Appendix A to 10 CFR Part 50, General Oas;gn-Criteria (GDC) 3, "Fire Protection." GOC 3 requires that structures, systems, and components important to safety be designed and located to minimize, in a manner consistent w;th other safety requirements, the probabi 1i ty and. effects..

of fires and explosions. 10 CFR 50.48{b) states that Appendix R to

• 10 CFR Part SO establishes fire protection features required to satisfy

• - - . ~*- -

e e NRCB 92-01, SUPP. l August 2S, 1992 Page 7 of 9 Criterion 3 of Appendix A to 10 CFR Part 50 for certain generic issues for nuclear power plants licensed to operat~ before January 1, 1979.

Sections III.G, III.J, and. III.a of Appendix R apply to nuclear power plants licensed to operate before January l, 1979. In 10 CFR 50.48(e), the NRC requires that all licensees for plants licensed to ope~ate a~ter January l, 1979 shall complete all fire protection m~d1ficat1ons ne~ded to satisfy Criterion 3 of Appendix A to 10 CFR Part 50 in accordance w1th the provisions of their operating l"icenses.

NRC-approved plant fire protection programs as referenced by the Plant Operating License Conditions and Appendix R to 10 CFR Part 50, Section III G.l.a, ttFire Protection of Safe Shutdown Capability," require one train of systems necessary to achieve and maintain hot shutdown conditions from either the control room or emergency control stations to be free from fire damage.

To ensure that electrt~al cables and components are free from fire damager Section III G.2 of Appendix R requires the separation of safe shutdown trains by separation of cables and equipment and ~ssociated circuits of redundant trains by a fire barrier having a 3-hour rating or enclosure of cable and equipment and associated rton-safety circuits of one redundant train in a fire barrier having a I-hour rating. In addition to providing the 1-hour barr;er, a fire detection and an automatic fire suppression system shall be installed in the fire area.

Under fire conditions. the thermal degradation of fire barrier systems (e.g.,

walls, floors, equipment vaults. and electrical raceway enclosures), such as the Thermo-Lag system, could lead to both trains of safe shutdown systems:

being damaged by fire. This may significantly affect the plant's ability to achieve and maintain hot standby or shutdown conditions.

The NRC con-sidered the apparent failures of the recent Thermo-Lag fire barrier fire endurance-tests and determined that the 1- and 3-hour pre-formed assemblies installed_ on conduits, cable trays (of all sizes and configurations), and used to construct fire barrier walls and ceilings, and-equipment enclosures do not provide the level of safety as required by NRC.

requirements.- The tests sponsorad,.by TU Electric raised concerns rela~tng~t~J,,:<;i, jo;nt and seam separation leading to cable damage. *1n addition, tfiey ri1'se=,-.**-*--

• concerns about the potential for burn through of the Thermo-Lag material * . _

itself. The. tests sponsored by the NRC appear to con fl nn concerns re 1attngi~o':-

burn through of the Th~rmo-Lag material in certain configurations in the',* * ,*:*, *-'*

absence of joints and seams ..

Reouested Actions All holders of operating license$ for nuclear power reactors. i11111ediately upon rece;ving this bulletin supplement, ~re requested to take the following actions. These actions are essentially the same as those listed in Bulletin-"

92-01, but the scope has been ~xpanded to include all size$ of conduits and~

trays and to include walls, ceilings, and equipment enclosures.

1. For those plants that use either 1- or 3-hour pre-formed Thermo-tag<330.":-'"*

panels and conduit shapes, identify the areas of the plant which have

e --- -- ---

e August NRCB 92-01, SUPP. 1 28, 1992 Page 8 of 9 Thermo-Lag 330 fire barrier material installed and determine the plant areas which use this material for the protect1on and separation of the safe shutdown capability.

2. In those plant areas in which Thermo-Lag fire barriers are used in raceways, walls. ceilings, equipment enclosures, or other areas to protect cable trays, conduits, or separate redundant safe shutdown functions, the licensee should implement, in accordance with.plant procedures, the appropriate compensatory measures, s~ch as fire watches, consistent with those that would be implemented by either the plant technical specifications or the operating license for an inoperable fire barrier. These compensatory measures should remain in place until the licensee can declare the fire barriers operable on the basis of applicable tests which demonstrate successful 1- or 3-hour barrier performance.

Although the specific details of this supplement to Bulletin 92-01 may not apply to holders of construction permits for nuclear power reactors, it is requested that the general concerns of this bulletin supplement be reviewed for current or future applicability.

Reay ired Re poet Each licensee who has installed Thermo-Lag 330 fire barriers must inform the NRC in writing within 30 days of receiving this bulletin supplement, whether or not it has taken the above actions. Where fire barriers are declared inoperable, the licensee is required to describe the measures being taken to ensure or restore fire barrier operability. These measures should be consistent with actions taken in response to Bulletin 92-01 *.

Backfit Discussion These types of fire barriers are installed at operating power reactor sites and are required to meet either a condition of a plant's operating license or the requirements of Section III.G of Appendix R to 10 CFR Part 50. The actio~s requested by this bulletin supplement--do not -represent a new staff.

position but are considered necessary to bring licensees into compliance with existing NRC rules and regulations where these test results are relevant.

Therefore, the NRC 1s issuing this bulletin supplement as a compliance backfit under 10 CFR 50.l09(a)(4).

Address the required written reports to the U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk,- Washington, O.C. 20555, under oath or affirmation under the provisions of Section 182a, Atomic Energy Act of 1954, as amended and 10 CFR S0.54(f). In addition, submit a copy to the appropriate regional administrator.

This request is covered by Office of Management and Budget Clearance Number 3150-0012, which expires June 30, 1994. The estimated average number of burden hours is 120 person hours for each licensee response, including those needed to assess the new recommendations, search data sources, gather and

e e NRCB 92-01, SUPP. l August 28. 1992 Page 9 of 9 analyze the data, and prepare the reQuired letters. This estimate of the averaqe numoer of buraen hours pertains only to the identified response-related matters and does not inc1ude the time needed to implement the requested action. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to the Information and Records Management Branch, Division of Information Support Services, Office of Information Resources Management, U.

S. Nuclear Regulatory Commission, Washington, O.C. 20555, and to the Paperwork Reduction Project (3150-0012), Office of Information and Regulatory Affairs, NEOB-3019, Office of Management and Budget, Washington, D.C. 20503.

Although no specific response is required for the following information, the following information would assist the NRC in evaluiting the cost of complying with this bulletin supplement:

{l) the licensee staff's time and costs to perform requested inspections, corrective actions, and associated testing; (2) the licensee stiff's time and costs to prepare the requested reports and documentation;

{3) the additional short-term costs incurred to address the inspection findings such as the costs of the corrective actions or the costs of down time; and (4) an estimate of the additional long-term costs that will be incurred as a result of implementing canmitments such as the estimated costs of conducting future inspections or increased maintenance.

If you should have any questions about this matter, please contact one of the technical contacts listed below or the appropriate NRR project manager.

ek--&~ z:. Jl-,~'

Charles E. Rossi, Director Division of- Operational Events Assessment .... ****- . .

Office of Nuclear Reactor Regulat1on Technical contacts: Ralph Architzel, NRR (301) 504-2804 Patrick Madden, NRR-(301) 504-2854

Attachment:

List of Recently Issued NRC Bulletins