ML20058D539

Describes Actions Taken to Resolve Facility Cable Test Program

ML20058D539
Person / Time
Site:	Sequoyah
Issue date:	10/23/1990
From:	Medford M TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-77129, TAC-77130, NUDOCS 9011060152
Download: ML20058D539 (33)

Text

I

[:

1. a. ;

TENNESSEE VALLEY AUTHORITY:

CH ATTANOOGA. TENNESSEE 374ol' 6N 38A-Lookout Place-l L

00T 231990T j

l l

U.S. Muclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.

20555 Gentlemen:

=6 In the Matter of

).

- Docket'Nos. 50-327-Tennessee Valley Authority

):

50-328-g.

1 SEQUOYAH NUCLEAR PLANT (SQN)1-UNITSil and 2'- CABLE ~ TEST PROCRAM (CTP)-

-1 RESOLUTION PLAN (TAC NO. 77129/77130) l

References:

1.

TVA letter'to NRC= dated _ August;17,g1990,i"Sequoyah Nuclearl Plant (SQN) Units 1 and 2 - Cable' Test'Piogram (CTP) r Resolution Tian (TAC No. 77129/77130)"-

2.

TVA letter.to NRC dated July 27,:1990,'"Sequoyah Nuclear Plant (SQN)

Condition Adverse to Quality Report (CAQR) i SQP900305 - Operability Determination" e

The purpose of this letter is to describe the actions taken'and~ define the' actions remaining to resolve the SQN CTP. These efforts are intended tol allow final closure of CTP concerns at SQN.

TVA and NRC met on October 5,1990, in Rockville,. Maryland, to discuss the; results of the CTP resolution-plan submitted'in Reference 1.. Enclosure 1-

.contains the meeting presentation material that provided the results'of'TVA's efforts and our proposal to achieve final resolution.of SQN CTP issues.

The-1 presentation included background information-thct necessitatedLTVA's.

development and implementation,of a new ranking process'for SQN.t_The activities performed by TVA'were described and details =of the screening t

tormula ana ranning cuiculas.iGia viarc proviriad. 2 The results ef the' pullby,-

TVA provided a plan for final resolution of'these~issuas.

1 januning,'and vertical' supported cable calculation ef f orts kare presented and The results of the pullby calculation indicated that two SQN cLnduits were not bounded reasonably by previous.SQN or Browne Ferry Nucis:.r Plant'(BFN) testing-and one conduit was marginally bounded.

The other byN conduits;were adequately bounded by previous test'ag and M.;e'significantly lower in1 percent I

allowable sidewall bearing-pressure (SWBP)Lauch that no additio4 & actions.

would be required. 'In general, the results'showed_a small population of

j conduits with high SWBP and a range of values similar.to those seen'at BFN..

j

~

l' This supports a conclusion that,SQN conduits have configurations:with limited susceptibility for'pullby damage.

9011060152 901023 0

PDR ADOCK 05000327 (0

P PDC

~

g' LAn'Equ'ai Opportunity Employer s

l

)

s.

( U.S. Nuclear Regulatory Commission 00T 23198R In addition, seven of the top 32 SQN_ conduits had been previously tested, which provides confidence that cable damage would have been discovered.

With the highest Unit 2 conduit falling well below the top three, TVA proposed--and it was agreed that no additional' testing would be needed for' Unit _2 conduits.

For' Unit 1, TVA agreed to test the top three ranked conduits at. the Unit 1 Cycle 5 refueling outage-or earlier if-a forced Unit 1 outage provided.

anticipated sufficient. duration. A forced outage of at.least 14 days in Mode 5_would be required to provide sufficient duration for this testing effort. The testing for the first and third highest ranked conduits, itM21361 and IPM1192II,,will be performed dry because they include shielded cable and the test for the second highest ranked conduit,-ISC266S, will-be performed-wet, in accordance with previous agreements.

NRC's concern regarding the-potential-for use of parachute cords during cable installation, similar to the practice'at Watts Bar Nuclear Plant (WBN),

j resulted in an additional commitment., To provide further assurance that this

<I practice has not been employed -at SQN, TVA inspected the SQN conduits = that I

exceeded 100 percentLallowable SWBP for presence of parachute cords.

On-

~

October 14, 1990 TVA completed this inspection of the 18 affected conduits and verified no parachute. cords present. However. three anomalies not related j

to parachute cord were found and will'be dispositioned through the condition adverse to quality (CAQ) process. A description of the anomalies is provided in Enclosure 3.

For the jamming and vertical supported cable calculations, TVA indicated _that-the corrected results have not invalidated the original test program and that the same.or equivalent conduits we're-tested.

TVA considers theijamming and 1

. vertical supported cable issues at SQN resolved with no furthec actions required.

A revised operability determination. based on the results of the new pullby ranking calculation, which supersedes' the deterraination submitted by g

Reference 2, is included as Enclosure 2.

d W

A summary statement of :the commitment contained in this submittal'is provided ~

i in Enclosure 4.

m i

Please direct questions concerning this issue to Marcia A. Cooper at I

(615) 843-6422.

3

\\l Very truly yours, ja TENNESSEE VALLEY AUTHORITY

]

f

'f E

Mark,0. Medford, Vice President j

. Nuclear Assurance, Licensing l]

& Fuels 1

. Enclosures

'ec:

See page-'3

)

d

i El s.

3-U.S. Nuclear Regulatory Commission 00T 231990 i

cc (Enclosures):-

'f Ms.-S. C.-Black, Deputy Director

[

Project Directorate 11-4

(

U.S. Nuclear Regulatory Commission i

One White Flint.. North 11555-Rockville Pike-t Rockville, Maryland 20852 i

Mr. J. N. Donohew.

ProjectiManager-U.S. Nuclear Regulatory Commission.

i One White Flint, North-11555 Rockville' Pike r

Rockville,' Maryland, 20852 -

)

NRC Resident. Inspector Sequoyah Nuclear Plant 2600'Igou. Ferry Road Soddy: Daisy.. Tennessee 37379 Mr.

B.'A. Wilson, Project Chief U.S. Nuclear Regulatory Commission Region II.

101 Marietta Street, NW,' Suite 2900 Atlanta,, Georgia 30323 f

f

.i A

l-s 1

)

{

.f t

,m

,r w)

1 ENCLOSURE 1 TVA/NRCMEETING SEQU0YAHNUCLEARPLANI CAB 12 TEST PROGRAM RESOLUTION-1 OCTOBER 5,1990 i

f 1.

i h

u

. c SEQU0YAHNUCLEARPLANT' CABLETESTPROGRAMRESOLUTION-1.

INTRODUCTION

.J.R.BMM II BACKGROUND AND RECENT ACTIVITIES PERF0 M D BY P. G. TREEL TVA 1

III.

IDENTIFICATION 0F WORST CASE PULLBY;P0PULATION,. K. W. BROWN SCREENINGF0NLAANDSCREENING/RANKINGRESULTS-1 IV. RESOLUTION OF PULLBY CONCERNS P.G.TRUDEL l

l V. VERTICAL CABLE AND J M ING CALCULATIONS P. 0. TREEL L

VI CONCLUSIONS J.R..BYM

.?

'1 1

1 o

i

+.

CABLETESTPROGRAMRESOLUTION-I.

INTRODUCTION PURPOSEOFMEETINGISTOOBTAINNR0CONOURRENCEWITHSQNCABLETEST.

PROGRAM (CTP) RESOLUTION TVACOMMITTEDTOIMPLEMENTTHECABLETESTPROGRAMRESOLUTIONPLANTO FURTHERVERIFYTHEINTEGRITYOFSAFETYRELATEDCABLESATSQN OPERABILITYDETERMINATION00N0LUDEDTHATTHEPROBABILITY0FDAMAGEIS LOW,PROBABILITYTHATDAMAGEWOULDHAVEBEENIDENTIFIEDISHIGH,AND SAFETYCONSEQUENCESOFP0TENTIALDAMAGEARELOW' t

PROGRAMIMPLEMENTATIONHASREINFORCEDEARLIER00N0LUSIONS 1

TESTINGOfUNIT2CONDUITSWOULD~NOTADDITIONALLYINCREASECONFIDENCE-LEVEL CONFIRMATORYTESTINGONUNIT1DURING; UNIT 1 CYCLE 500TAGEISPROPOSED IOTOTALLYOLOSEOUTISSUE l

l L

1 1

1 CABLETESTPROGRAMRESOLUTION:

II.

BACKGROUND CONCERN SQN AFFECTED BY WATTS BAR PROBLEMS UNISSUEDCALCULATIONS ERRORSINCALOULATIONSQNCSS009 JULY 23MEETINGWITHRESOLUTIONS

- SCREEN CONDUITS BY R M ING

- NEW RANK BY SWBP

- ISSUE J M ING AND VERTICAL SUPPORTED CABLE-CALOULATIONS

- EVALUATE APPROPRIATE ACTIONS

-QAINVOLVER l

MULTIPHASEAPPROACH OPERABILITYDETERMINATIONINPLACEANDACCEPTED s-

CABLETESTPROGRAMRES0LilTION II. ACTIVITIES PERFORMED BY TVA

.l I

i BASECALC009DATASAMPLED-NEEDFORDATAVERIFICATION PHASEIANDPHASEIICOMPLETED RANKEDPERTHECRITERIA f

DEVELOPEDIS0 SAND?ERFORMEDSWBPCALO l

1 EXTENSIVEQAC0VERAGE j

o

j 1

-.i

CABLETESTPROGRAMRESOLUTION

III, IDENTIFICATION OF WORST CASE PULLBY POPUIATION (AUGUSTSUBMITTAL)

IDENTIFY TOTAL POPULATION 0F IE 00EUITS (APPR0XIMATELY 9500 IDENTIFY 00EUIIS CONTAINING SEVEN OR MORE CABLES (803)

USING FIELD SECHES OR DESIGN DRAWING IDENTIFYLC0 FEETLONG(269)

OBTAIN FIELD Sm0HES FOR THOSE CONDUIIS TO DETEMINE LEETH AND TOTAL BEES BETWEEN PULL POINTS INPUT CABLE AND 00EUIT CONFIGURATION DATA INTO DATABASE:

L PERF0ESCREENINGOALCULATIONS.-

L o

L WALE 0WN TOP 30 00EUITS TO 0BTAIN DETAILED IS0 METRIC-PERF0ESWBPCALOULATIONS U

00NFIM ADEQUATE CORRELATION OR EXPAND FAMILY TO BE WAIJ(E D0WNFOR:DETAILEDIS0METRIO g

L

CABLETESTPROGRAMRESOLUTION III.

SCREENING CALCULATION F0 M LA L*K*We*F*p*exp(K*A*We*n)=SCREENINGFACTOR R

WHERE:

L = 00EUIT SEGMENT LENGTH (FEET)

K = C0 EFFICIENT OF FRIOTION We=WEIGHTCORRECTIONFACTOR-i F = 00 EUIT FILL PER0ENTAGE P = PULLBY FRACTION R = 00EUIT BEE RADIUS (FEET).

A = TOTAL BEES IN A SECENT (RADIANS) n = CONFIGURATION COMERSION FACTOR' i

t i

e

.i

t CABLETESTPROGRAMRESOLUTION III.

SCREENING /RAEINGRESULTS 269 CONDUITS EVALUATED BY SCREENIE FORMULA IS0METRIOS DEVELOPED FOR TOP 30 00EUITS AE SEPs i

CALOULATED/CORRELATIONNOTADEQUATE l

l 1

WAIDOWNS AND CALOULATIONS FIFAEED-TOTAL 0F 93 IS0ETRICS OBTAINED INCLUDING TOP 60 AND 00EUITS WITHGREATERTHAN330DEGREESBETWEENPULLPOINTSEX0EPTONE.

t (8% FILL) 4

- SEP CALOULATIONS PERF0 RED FOR 93 a

1 I

i(

)

'f r

CABLEIESIPROGRAMRESOLUIION

III, SCREENING /RANKINGRESULTS(CONTINUED)

MAXEXP SEP %

V-LEVEL REMARKS 1.

IPM2136 I 3816 V2 2.

180266 8 3255-V3 3.

IPM1192 II 1563 V2 4,

2PM2140 I 655 V2 U2(6OVER1)

.5, M02796 A 381 V4 l

6.M01728B(TESTED) 349 V3 U2 7.-LPM 2080I 275 V2

8. M02606 A-185 V3 U2 9,

IV6636 A 182 V3 U1/U2 1

10, IPL4342 A 158 V3 I

~

ll IPM2132 I 134 V2 12, 2PM2084 I 131 V2 U2 13.

IPM2087 II 131 V2.

14, IV801 A 112 V3-l 15, IPM2107 II 108 V2 a

16, IPS359 IV 106 V2 l

17, 2PM2087 II 104-V2 U2(21/1) l I

18.

IPL311T A 103 V4:

l 19, 1PM4704 A 99 V2 l

20, 1PM2111 II 98 V2:

l 21.M01751A(IESTED) 84 V3 U2 1

[

f SEVEN 0F-THE TOP 32 ERE TESTED IN THE ORIGINAL PROGRAM FIVE OF THE TOP ELEVEN CONDUITS CONTAINING U2 0 ABLES ERE TESTED INTHELORIGINALPROGRAM(#2,#7AND19i11)

Q ONE BLE OUT OF-24 DESIGNATED U2 INSTALLED SUBSEQUENT TO WORST

CABLETESTPROGRAMRESOLUTION IV. RESOLUTION 0F PULLBY CONCERNS BROWNSFERRYANDSEQU0YAHPER0ENTALLOWABLESWBPINTEGRATEDLI

% ALLOWABLE SWBP l

"" "'."".....L...25^".."!!.1.....L...':25^".51.2 1

24810 T 2

3816 3

3255

-4 2250 T l'

j 5

1563 l

6 828 T l

7 745 T 8

655 9

643 T 10 612 T 11 -

381

_12 364 T l

13 349 T 14

-275

• 15 206 16 185-17 182 182 18 160 T 19 158-134 20'

~'

21

-131 22 131

• 23 129 T 24 112 25 110 26 109 27 108-28 106 29 104 30 103 31 99 i

32 98 T l

33 98 l

34 84 T l

• 0ne cable out of 24 designated'U2 installed subsequent to worst case pullby T is equivalent to the word'" TESTED."

.l

~

CABLETESTPROGPE. RESOLUTION IV. RESOLUTION OF PULLBY CONCERNS GENERAL LIMITEDNUMBEROFSEPCALCSHIGH

.BROWSFERRYANDSEQU0YAHRESULTSIhiERSPERSED-SEQU0YAH UNIT 2 GENERALLY L0ER SEP THAN WII 1 00NFIRMS SEQU0YAH CONFIGURATION HAS LIMITED SUSCEPTIBILITY FOR D.3 AGE 7 0F 32 IN TOP SEP RAEING PREVIOUSLY TESTED

(#6,21,24,26,28,31,and32)

AllBUT2SEQU0YAHCONDUITSB0EDEDBYBROWSFERRYTESTING l

HIGHCONFIDENCEANYDAMAGEDISCOVERED 1

I CABLETESTPROCRAMRESOLUTION I

IV RESOLUTION 0F PULLBY CONCERNS UNIT 2 UNIT 2 SEPS SIGNIFICANTLY L0ER THAN UNIT 1 50FTOP11 UNIT 2CONDUITSPREVIOUSLYTESTED N0PRACTICALPURPOSETOTESTTHEHIGHESTUNIT2 CONDUIT

- 6 OVER 1 PULLBY

- NOT THE HIGHEST

- B0UNDED BY SEVERAL BROWNS FERRY TESTS

- SIMIIAR TO A TESTED SEQU0YAH UNIT 2 CONDUIT N0ADDITIONALACTIONSREQUIRED i

I

0ABLETESTPROGRAMRESOLUTION IV.

RESOLUTION 0F PULLBY CONCERNS UNIT 1 SEQU0YAHUNIT1B00EEDBYBROWSFERRYIESTINGWITHTWO F10EPTIONS(00EUIT1PM2136IAE1S0266S) 00EUIT IPM 2136 I

- 00NIAINS 18 CABLES THAT ARE PART OF INSTRUMENTATION LOOPS THATTIEPRIMARYSYSTEMTEMPERATURE,PRESSUREANDFLOW INDICATIONTOTHEREACIORPROTECTIONSYSTEM 00EUITIS0266S

- 00NIAINS 7 CABLES ASSOCIATED WITH CONTROL AE INDICATION 0FDEVICESAFFECTINGOPERATIONOFTHESTEAM-DRIVEN AUXILIARYFEEDWATERPUMP SAFETYSIGNIFICANCEOFPOIENTIALDAMAGE

- 1PM21361

- N0 POST LOCA HARSH PIPE BREAK EW IR0 M NTS

-REQUIREDPROTECTIVEFUNCTIONSOCCURQUICKLY

- 180266S

~

- N0 POST LOCA HARSH PIPE BREAK ENVIRONMENT

-INEVENTOFHARSHENVIR0MNTDEVICENOTREQUIRED OPERABILITYDETERMINATIONhSBESNUPDATED SEQU0YAH WILL TEST TWO UNIT 100EUITS IN U105 0UTAGE TO CLOSEISSUE

- IPM2136 I - DRY TEST--CONTAINS SHIELDED SIGNAL CABLE.

- 180266S.

- ET TEST

CABLETESTPROGRAMRESOLUTION V

VERTICAL CABLE AND J H ING CALOULATIONS VERTICALCABLECALCULATION TVA HAS REGENERATED THE UE&C W0 E AND REACHED THE S M 00N0tUSIONS JMINGCALCETION TVA HAS REGENERATED THE ORIGINAL W0E THAT NARR0VED THE POPULATION TO 48 00NDUIIS AND REACHED THE SM GENERAL CONCLUSION TVAHASREGENERATEDIBEWORK10REDUCETHEP0PETIONT015 TESTEDCONDUITSBYAPPLYINGTHEFIVEINDICATEDCRITERIA THEPOPULATIONAVAILABLEFORTESTSLIGHILYDIFFERENT i

00N0LUSIONISTHATTHEMATCHISADEQUATE ISSUESCONSIDEREDCLOSED J

l l.

0ABLETESTFR00RAMRESOLUTION VI CONCLUSIONS MilLTIPLEREEVALUATIONSHAVEBEENPERFORMED EXTENSIVEQAOVERVIEWDURINGTHEREEVALUATIONS N0PROGRAMMATICCABLEINSTALLATIONPROBLEMSIDENTIFIED i

ISSUEOLOSEDFORUNIT2 CONFIRMtTORY TESTS FOR UNIT 1 OLOSURE WILL BE MADE t-i r

r

-+

+

n w

o 5 ENCLOSURE 2 SEQUOYAH NUCLEAR PLANT (SON)

CONDITION ADVERSE TO QUALITY REPORT (CAQR) SQP900305 R0 OPERABILITY DETERMINATION Discussion Deficiencies were identified with the application of the criteria used in ranking conduits that were tested to address pullby concerns during restart at SQN.

These problems were documented in CAQR SQP900305 R0. Continued operation of SQN in light of the deficiencies is justified by the following.

1.

Probability of Occurrence at SQN Watts Bar Nuclear Plant (WBN) had specific employee concerns related to cable installation.

SQN did not have any substantiated cable installation employee concerns. Subsequently, SQN-conducted extensive reviews of the cable raceway systems and the attributes that contribute to the possibility that undetected cable damage during installation could-occur. These prerestart reviews, involving cable pull data retrieval and conduit walkdowns, were undertaken as a part of the SQN cable test program (CTP) and included the issues of pullbys, jamming, and silicone-rubber cables supported in vertical conduits by conduit bodies at the top of the run.

In addition, as a postrestart comitment, other 10 CFR 50.49 cables in vertical conduits were evaluated for compliance with the National Electrical Code requirements and provided support as required.

As a prelude to the SQN ef forts to address the WBN concerns, NRC consultants visited SQN, conducted interviews, and walked down areas of the plant.

While they concluded that there were deficiencies in the instructions for cable pulling activities from 1973 to 1979, they did not find that the conduit configurations dif fered significantly from other nuclear plants of SQN's vintage. Recent comparisons of conduit configurations have shown that SQN's installations closely resemble those at Browns Ferry Nuclear Plant (BFN).

The short runs with many pull points translate into ' easy pulls".

To provide additional information about the similarity between SQN and i

BFN, calculation SQN-CSS-033, " Calculation for Analysis of Cable Pullby i

Concerns" (CACPC) was prepared and issued.

In order to produce CACPC, SQN conducted additional walkdowns of more than 250 conduits for physical configuration.

October 18, 1990' 2901E

1 l

As expected, the CACPC results have proven that the SQN calculated sidewall bearing pressure (SWBP) values (percent allowable) are bounded by those resulting from the BFN pullby analysis. However, because the SWBP value for the worst-case conduit at BFN appears to be extremely conservative, it is concluded that the top two SQN conduits may not be bounded by the BFN tests. This is discussed further in Section 2.

Both TVA and the industry have recognized that the potential for cable i

i damage during a pullby operation increases with conduit fill. During reviews conducted at WBN for the issue of pullbys, the presence of a large quantity of overfilled conduits resulted in the identification of this as a significant factor.

In contrast, review of SQN data during the pullby analysis effort has shown that relatively few conduits are overfilled and, therefore, the potential for undetected pullby damage is correspondingly reduced.

{

l Two other significant differences were noted between SQN and WBN which can be expected to have resulted in less potential for cable damage during pullbys at SQN.

First, conduit' configurations at SQN are regarded i

as being of lesser complexity than comparable conduits at WBN.

This observation is consistent with those reported in the Technical Evaluation Reports prepared for the two plants.

Since forces encountered within a conduit-during a pullby are a direct function of configuration. SQN pullbys can, therefore, be expected to have been of lesser severity.

Second, in contrast to WBN, previous SQN reviews have indicated that nylon " parachute" cords have not been used in performing pullbys. The y

use of this cord was determined to be one of. the primary causes of pullby i

damage at WBN. The absence of this cord at SQN was recently furt:ler i

confirmed by inspection of the top 18 conduits as determined by the CACPC.

i TVA concludes that there was not then nor is there now, any evidence that SQN hab any safety-related. cables installed that were damaged by the pulling practices.

2.

Probability of Damage Discovery at SQN Even though there was no evidence of damaged cables at SQN, a population of conduits and cables was identified to conduct high-voltage tests for l

the purpose of detecting damage caused by pullbys, jamming, and silicone rubber insulated vertical cables supported by conduit bodies near the top of the condvit run. Over 900 conductors were successfully tested at voltages ranging from 4.8 kilovolt (kV) to 10.8 kV dc. The SQN CTP represents one of the most comprehensive in-situ test programs ever i

undertaken in the industry.

l

-~

October 18, 1990 2901E I

1

i a ?

SQN's CTP selection criteria cas' biased toaard material damage susceptibility.

However, even though discrepancies have been discovered in the unissued calculation to document the application of the selection criteria, TVA has confirmed by reapplication of the selection criteria that seven of the original 15 tested pullby conduits remain in the i

worst-case or higher-risk category.

The remaining eight conduits could, i

therefore, be considered to be randomly selected.

The successful testing of these conduits still provides a high degree of confidence that if a programmatic problem with the installation practices at SQN existed it would likely have been found.

The CACPC performed a screening of the SQN conduits in order to determine the worst-case population.

This process was based on a method that approximates the SWBP formulas.

SWBP calculations were performed for the i

top 60 conduits from this screening process.

In addition, conduits from l

existing SWBP calculations were merged with the 60 conduits from this screening, resulting in a total of 93 conduits ranked in order of percent allowable SWBP.

The results of the ranking show that all conduits except for the top five are bounded by conduits previously tested at SQN.

The remaining five conduits are bounded by the SWBP values from the BFN cable test program.

However, as previously mentioned, it appears that the SWBP value for the worst-case conduit at BFN is overly conservative.

Therefore, the top two SQN conduits may not actually be bounded by the BFN tests.

The top two conduits (IPM21361 and ISG2665) contain cables associated with the Reactor Protection System and the-Turbine Driven Auxiliary Feedwater Pump (TDAFWP) controls, respectivel).

They are both located in the Auxiliary Building. With regard to IPM2136I, the environment was classified as " harsh", only for the scenario of an RHR suction line break while in Mode 4 (hot shutdown).

A review of the environmental conditions j

for that conduit has shown that a maximum temperature peak of 198 degrees (F) occurs 800 seconds after an RHR line break and decreases linearly to 104 degrees at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

In this situation, the plant is already shutdown and the consequences of the potential failure of associated RPS cables is considered minimal.

There is no_significant pressure increase in the area around this conduit, so the only possible moisture intrusion into the condult.would be a result of condensation.

Thus, there is little likelthead of cable failure during the' postulated event and if a failure did occur, the consequences would be minimal.

For ISG266S, the environment is considered harsh with a maximum temperature of 110 degrees only in the event of a steam supply line break to the TDAFWP.

In this event, the affected end device is already inoperable.

n L I October 18, 1990' 2901E i

l l

I

.}

In January 1989, SQN implemented a Cable Monitoring Program to document and trend problems.

These problems include age-related failures that would surface if the cable was installed improperly.

To date, no cables have been identified as incapable of performing their safety-related function by this program.

Additionally, many maintenance and modification i

activities and Quality Control inspections have been performed since the initial concern and no installation damage to cables or operational failures of cables attributed to installation practices have been identified.

TVA's overall confidence in the integrity of SQN cables has increased.

The large number of review and test activities have not found cable installation problems.

The overall favorable information about the SON conduit configurations, and results of both the SQN and BFN CTPs are the i

basis for this increased confidence.

3.

Consequences of Undiscovered Cable Damage In the unlikely event that a SQN safety-related cable was damaged during installation, the consequences of that damage can be evaluated by the two types of failure mechanisms that might occur.

The first type is the random failure.

For the purposes of this discussion, and based on the operating experience at SQN, this type of failure is limited to age-related damage due to improperly installed cables. This failure is mitigated by,the fact that the redundant circuit for the failed cable is expected to perform the safety-related function that might be lost by the cable failure.

The effects of a-random failure are inconsequential because of the redundancy, diversity, and defense in depth af forded by the standard design requirements.

For example, the' i

ef fects of a faulted cable inside containment are mitigated-by the diverse and redund.nt penetration overcurrent protection design (fuse and breaker combination). The effects on emergency safeguards actuation are mitigated by the redundant and diverse design of the reactor protection system (e.g 2/3 and 2/4 logic combinations in conjunction with diverse parameters sensing containment pressure and pressurizer pressure).

l The second type of failure is the common mode failure. This type of cable failure is primarily related to environmental conditions (water, steam, and humidity) created by an accident.

For the purposes of this discussion, the environmental conditions will be-separated into those inside containment and those outside containment.

l

~4~

- October :18.1990 -

2901E

o For the cables inside containment, there are several factors that support the adequacy of the installed sa:ety-related cables.

Because the containment equipment is typically a termination point for conduits and i

cables (as opposed to a distribution point), there are relatively fewer pullbys in the conduit systems there.

The straight line space limitations i

inside containment result in shorter conduit runs and more cable pull points than in more spacious areas.

Redundant safety-related equipment is physically separated and compartmented by concrete walls and barriers inside containment to provide protection against events that create dynamic environmental ef fects.

The conduits and cables that supply this equipment derive some benefits f rom this line of protection.

As a result, the common mode failure from undetected cable damage is unlikely.

Other Category I areas outside containment include the auxiliary building (AB) and the control building (CB). The harsh areas of the AB are primarily. transition areas for safety-related cables (and the vast majority of them are in cable trays).

However, the harsh environments e.re less severe and not as prolonged as those inside containment.

The primary safety function required for events that produce these-environments is-the ability to achieve and maintain safe shutdown conditions.

This function is also the focus of Appendix R evaluations.

As such, separation, compartmentalization, and fire wrap all provide a measure of protection from environmental effects.

Conduits are also sealed to prevent water intrusion from flooding and flood propagation between rooms and floors.

The sealing also provides a measure of protection against water or moisture intrusion. As a result, the common mode failure from undetected cable damage is unlikely.

In the power, control, and signal cable distribution areas of the CB, as well as the AB, where a large number of pullbys occur, the environment is considered mild or of less severity and is, therefore, not impacted by.

adverse effects of an accident that would create a potential common mode failure: mechanism from undetected cable damage.

l t

i

. October 18, 1990

-2901E

j p

conclusion The probability of cable damage during installation is low.

Substantial evidence f rom a variety of sources establishes that the SQN conduits are typical of its vintage of nuclear plant and that there are no progranrnatic cable installation problems.

Inspections performed on the top 18 conduits that have the highest potential for dif ficult pullbys (Reference SQN-CSS-033) f urther confirmed that parachute cord type pull ropes were not used at SQN during pullby activities.

Also, no installation damage resulting from pullbys j

has been detected.

The SQN CTP results provide a high degree of confidence that cable damage in material susceptible cable would have been detected.

The BFN and SQN CTP test results in conjunction with the SWBP calculations performed for SQN give a high degree of assurance that the forces developed during pullbys were not large enough to cause cable damage.

The physical nature of the SQN conduit configurations also support this conclusion.

The potential consequences due to the random failure from undetected cable

. damage is inconsequential because of the redundance, diversity, and defense in depth af forded by standard design requirements.

Common mode failures from undetected cable damage are highly unlikely. The most severe environments (inside containment) that might trigger the common mode failures are in locations where pullbys (and hence damage from pullbys) were least likely to occur. On the other hand, pullbys were most likely to occur in areas outside primary containment that are mild or of greatly reduced severity and unlikely to initiate common mode failures.

In addition, the separation and protection features incorporated for other programs (e.g., fire protection, moderate energy line break flooding, and high energy like break protection) provide additional protection from environmental effects. These features further lessen the likelihood of common mode failure.

As a result, there is a high degree of confidence that the SQN safety-related cables will perform their intended functions.

O k.

lo/te /qo Prepared by A N vmu --

Date lo//8/?o

/

/

Reviewed by

,At i -

Date /0/n/90 i <

4~

October 18, 1990 2901E

]

5 ENCLOSURE 2 i

SEQUOYAH NUCLEAR PLANT (SQN)

CONDITION ADVERSE TO QUALITY REPORT (CAQR) SQP900305 R0

)

OPERABILITY DETERMINATION i

Discussion Deficiencies were identified with the application of_ the criteria used in ranking conduits that were tested to address pullby concerns during restart at SON. These problems were documented in CAQR SQP900305 RO.

Continued l

operation of SQN in light of the deficiencies is justified by.he following.

1.

Probability of Occurrence at SQN Watts Bar Nuclear Plant (WBN) had specific employee concerns related to cable installation. SON did not have any substantiated cable installation employee concerns.

Subsequently, SQN conducted extensive reviews of the cable raceway systems and the attributes that contribute.

to the possibility that undetected cable damage during installation could occur. These prerestart reviews, involving cable pull data retrieval and conduit walkdowns, were undertaken as a part of the SQN cable test program (CTP) and included the issues of pullbys, jamming, and silicone-rubber cables supported in vertical conduits by conduit bodies at the top of the run.

In addition, as a postrestart commitment, other 10 CFR 50.49 cables in vertical conduits were evaluated for compliance with the National Electrical Code requirements.and provided support as required.

As a prelude to the SQN efforts to address the WBN concerns, NRC consultants visited SQN, conducted interviews, and _ walked down areas of.

the plant. While they concluded that there were deficiencies in the instructions for cable pulling activities f rom 1973 to 1979, they did not find that the conduit configurations differed significantly from other nuclear plants of SON's vintage.

Recent comparisons of conduit 4

configurations have shown that SQN's installations closely. resemble those at Browns Ferry Nuclear Plant (BFN).

The short runs with many pull points translate-into " easy pulls".

To provide additional information about the similarity between SQN and BFN, calculation SQN-CSS-033, " Calculation for Analysis of Cable Pullby-Concerns" (CACPC) was prepared and issued.

In order to produce CACPC, SQN conducted additional walkdowns of more than 250 conduits for' physical configuration.

1 i

~

October 18, 1990 2901E l

,r As expected, the CACPC results have proven that the SQN calculated sidewall bearing pressure (SWBP) values (percent allowable) are bounded by those resulting from the BFN pullby analysis. However, because the SWBP value for the worst-case conduit at BFN appears to be extremely conservative, it is concluded that the top two SQN conduits may not be bounded by the BFN tests.

This is discussed further in Section 2.

Both TVA and the industry have recognized that the potential for cable damage during a pullby operation increases with conduit fill. During reviews conducted at WBN for the issue of pullbys, the presence of a large quantity of overfilled conduits resulted in the identification of this as a significant factor.

In contrast, review of SQN data during the pullby analysis effort has shown that relatively few conduits are overfilled and, therefore, the potential for undetected pullby damage is correspondingly reduced.

Two other significant dif ferences were noted between SQN and WBN which can be expected to have resulted in less potential for cable damage during pullbys at SQN.

First. conduit configurations at SQN are regarded as being of lesser complexity than comparable conduits at WBN. This observation is consistent with those reported in the Technical Evaluation Reports prepared for the two plants.

Since forces encountered within a conduit during a pullby are a direct function of configuration, SQN pullbys can, therefore, be expected to have been of lesser. severity.

Second, in contrast to WBN, previous SQN reviews have indicated that nylon ' parachute" cords have not been used in performing pullbys.

The use of this cord was determined to be one of the primary causes of pullby damage at WBN.

The absence of this cord at SQN was recently further confirmed by inspection of the top 18 conduits as determined by the.CACPC.

TVA concludes that there was not then, nor is there now, any evidence that SQN has any safety-related cables installed that were damaged by the pulling practices.

2.

Probability of Damage Discovery at SQN Even though there was no evidence of damaged cables at SQN, a population of conduits and cables was identified to conduct high-voltage tests for the purpose of detecting damage caused by pullbys, jamming, and silicone rubber insulated vertical cables supported by conduit bodies near the top of the conduit run.

Over 900 conductors were successfully tested at voltages ranging f rom 4.8 kilovolt (kV) to 10.8 kV dc. The SQN CTP represents one of the most comprehensive in-situ test programs ever undertaken in the industry.

! October 18, 1990 2901E-

SQN's CTP selection criteria tas biased totard material damage susceptibility.

However, even though discrepancies have been discovered in the unissued calculation to document the application of the selection criteria, TVA has confiroed by reapplication of the selection criteria that seven of the origl'ial 15 tested pullby conduits remain in the worst-case or higher-r'.sk category.

The remaining eight conduits could, therefore, be conside"ed to be randomly selected.

The successful testing of these conduits st'11 provides a high degree of confidence that if a programmatic problem with the installation practices at SQN existed it would likely have been found.

The CACPC performed a screening of the SQN condutts in order to determine the worst-case population.

This process was based on a method that approximates the SWBP formulas.

SWBP calculations were performed for the top 60 conduits from this screening process.

In addition, condutts from existing SWBP calculations were merged with the 60 conduits from this screening, resulting in a total of 93 conduits ranked in order of percent allowable SWBP.

The results of the ranking show that all conduits except for the top five are bounded by conduits previously tested at SQN.

The remaining five conduits are bounded by the SWBP values from the.BFN cable test program.

However, as previously mentioned, it appears that the SWBP value for the worst-case conduit at BFN is overly conservative. Therefore, the top two SQN conduits may not actually be bounded by the BFN tests.

The top two conduits (IPM2136I. and ISG2665) contain cables associated with the Reactor Protection System and the Turbine Driven Auxiliary Feedwater Pump (TDAFWP) controls, respectively.

They are both located in the Auxiliary Bu11 ding. With regard to IPM2136I, the environment was classified as " harsh", only for the scenario of an RHR suction line break while in Mode 4 (hot shutdown).

A review of the environmental conditions for that conduit has shown that a maximum temperature peak of 198 degrees (F) occurs 800 seconds after an RHR line break and decreases linearly to 104 degrees at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

In this situation, the plant is already. shutdown and the consequences of the potential failure of associated RPS cables is considered minimal.

There is no significant pressure' increase in the area around this conduit, so the only possible moisture intrusion into the condult.would be a result of condensation.

Thus, there is little likelihood of cable failure during the postulated event and if a failure did occur, the consequences would be minimal.

For ISG2665, the environment is considered harsh with a maximum temperature of 110 degrees only in the event of a steam supply line break to the TOAFWP.

In this event, the affected end device is already_ inoperable.

i l October 18, 1990 290lf

l e

.s In January 1989, SQN implemented a Cable Monitoring Program to document and trend problems.

These problems include age-related failures that would surf ace if the cable was installed improperly.

To date, no cables have been identified as incapable of performing their safety-related function by this program.

Additionally, many maintenance and modification activities and Quality Control inspections have been performed since the initial concern and no installation damage to cables or operational failures of cables attributed to installation practices have been identified.

TVA's overall confidence in the integrity of SQN cables has increased.

The large number of review and test activities have not found cable installation problems.. The overall favorable information about the SQN conduit configurations, and results of both the SQN and BFN CTPs are the basis for this increased ccnfidence.

3.

Consequences of Undiscovered Cable Damage in the unlikely event that a SQN safety-related cable was damageo during installation, the consequences of that damage can be evaluated by the two types of failure mechanisms that might occur.

The first type is the random failure.

For the purposes of this discussion, and based on the operating experience at SQN this type of-failure is limited to age-related damage due to improperly installed cables. This failure is mitigated by the fact that the redundant circuit for the failed cable is expected to perform the safety-related function that might be lost by the cable failure.

The effects of a random failure are inconsequential because of the redundancy, diversity, and defense in depth af forded by the standard design requirements' For example, the ef fects of a faulted cable inside containment are mitigated by the diverse and redundant penetration overcurrent protection design (fuse and breaker combination).

The ef fects on emergency safeguards actuation are niitigated

'1 by the redundant and diverse design of the reactor protection system (e.g 2/3 and 2/4 logic combinations in conjunction with diverse parameters sensing containment pressure and pressurizer pressure),

ihe second type of failure is the common mode failure.

This type of cable failure is primarily related to environmental conditions (water, steam, and humidity) created by an accident.

For the purposes of this discussion, the environmental conditions will be separated into those inside containment and those outside containment.

I 1

October 18, 1990

'4-2901E

e For the cables inside containment there are several factors that support the adequacy of the instelled safety-related cables.

Because the I

containment equipment is typically a termination point for conduits and cables (as opposed to a distribution point), there are relatively fewer pullbys in the conduit systems there. The straight line space limitations inside containment result in shorter conduit runs and more cable pull points than in more spacious areas.

Redundant safety-related equipment is physically separated and compartmented by concrete walls and barriers inside containnent to provide protection against events that create dynamic environmental effects. The conduits and cables that supply this equipment derive some benefits from this line of protection. As.a result, the common mode failure from undetected cable damage is unlikely.

Other Category I areas outside containment include the auxiliary building (AB) and the control building (CB). The harsh areas of the A6 are primarily transition areas for safety-related cables (and the vast majority of them are in cable trays). However, the harsh environments are less severe and not as prolonged as those inside containment. The primary safety function required for events that produce these environments is the ability to achieve and maintain safe shutdown conditions.

This function is also'the focus of Appendix R evaluations.

As such, separation, compartmentalization, and fire wrap all provide a measure.of protection from environmental effects. Conduits are also sealed to prevent water intrusion from floodirig and flood propagation between rooms and floors.

The sealing also provides a measure of protection against water or moisture intrusion.

As a result, the connen mode failure from undetected cable damsge is unlikely.

In the power, control,'and signal cable distribution areas of the CB, as well as the AB, where a large number of pullbys-occur, the environment is considered mild or of less severity and is, therefore, not impacted by adverse effects of an accident that would create c potential common mode

- f ailure mechanism f rom undetected cable damage.

l l October 18, 1990 2901E a

. _., ~,

I Conclusion The probability of cable damage during installation is low.

Substantial evidence f rom a variety of sources establishes that the SQN conduits are typical of its vintage of nuclear plant and that there are no programatic cable installation problems.

Inspections performed on the top 18 conduits that have the highest potential for difficult pullbys (Reference SQN-CSS-033) further confirmed that parachute cord type pull ropes were not used at SQN l

during pullby activities. Also, no installation damage resulting f rom pullbys has been detected.

The SQN CTP results provide a high degree of confidence that cable damage in material susceptible cable would have been detected. The BFN and SQN CTP test results in conjunction with the SWBP calculations performed for SQN give a high degree of assurance that the forces developed during pullbys were not large enough to cause cable damage.

The physical nature of the SQN conduit configurations also support this conclusion.

The potential consequences due to the random failure f rom undetected cable damage is inconsequential because of the redundance, diversity, and defense in depth af forded by standard design requirements.

Comon mode failures f rom undetected cable damage are highly unlikely.

The most severe environments (inside containment) that might trigger the comon mode failures are in locations where pullbys (and hence damage from pullbys) were least likely to occur. On the other hand, pullbys were most likely to occur in areas outside primary containment that are mild or of greatly reduced severity and unlikely to initiate comon mode failures.

In addition, the separation and protection features incorporated for other programs (e.g., fire protection, moderate energy line break flooding, and high energy like break protection) provide additional protection from environmental effects.

These features further lessen the likelihood of common mode failure.

I As a result, there is a high degree of confidence that the SQN safety-related cables will perform their intended functions.

0am G.

Iolt 8lQu Prepareo by AN h

Date lo//8/90

/

Reviewed by b

d Date

/0/i3 0

/9 October 18, 1990 2901E i

l o

ENCLOSURE 3 l

During the walkdown of the 18 top ranked pullby conduits as defined by SQN-CSS-033, three anomalies were discovered. A description of these anomalies is as follows:

Condutt Number Description of Condition MC1728B A two-conductor (#14 AWG) cable was found abandoned and not tagged.

Disposition for this condition.will be documented under CAQR SQP900410.

l MC2796A Upon inspection of Junction Box (JB) 2352, it was verified that only four cables were routed through-this condutt.

This was the number f1ve ranked conduit per SQN-CSS-033.

The Conduit and Cable Routing System (CCRS) showed that this conduit contained nine-cables.

A field inspection of JB 2352 was performed which determined the number of cables in each conduit, cable type, and number of conductors.

Five of the t

seventy-four cable types contained in JB 2352 were obtained by comparison to similar known cables since markings on the outer jacket could not be read. As a result of this inspection it was determined that conduit number MC2798A contained 13 cables. CCRS information revealed that this conduit was scheduled L

to contain eight cables.

By evaluation of cable types Engineering concluded that the five cables routed in MC2798A were those actually scheduled to be installed in MC2796A. A sensitivity analysis was performed and docuniented on an engineering judgement paper on t

MC2798A to evaluate the impact of SWBP ranking of the top four conduits.. By using the existing QA pull records, new pull groups were established.

These pull

{

groups were then evaluated and the values obtained were found to be significantly lower than those conduits proposed for teJting.

In addition, this evaluation also revealed that MC2798A contains no parachute chord, fill =was less than 40 percent, and that ampacity considerations were not of concern since i

these cables supply motor-operated valves which have short operating times. CAQR SQP900423 will document these findings.

2PM2087II During the inspection at an "LB" condulet, there were some cables that exceeded the minimum bend radius, t October 18. 1990 2901E l

i w.-

v

ep*.

ENCLOSURE 3 g

)

- However.this will be d'ispositioned in accordance with TVA's submlttal-to NRC dated January 23, 1989 (L44

- 890123 803),- regarding rework'of existing bend radius violations.

t

(

-2-s '

October 18.-1990-2901E 1

'lis '

F.NCLOSURG 4 LIST OF-COP 9tITMENTS TVA will'high potential test the top three ranked Unit 2 pullby conduits:

IPM21361 (dry), ISG266S (wet), and IPM11921I (dry) during the' Unit.1 Cycle 5 refueling outage, or earlier, in the event of a forced outage in Mode 5-or lower of sufficient duration.

e 4

9 f

l D

u n >

o