ML20059L577

Rev 2 to Browns Ferry Nuclear Plant Cable Issues Supplemental Rept Corrective Actions

ML20059L577
Person / Time
Site:	Browns Ferry
Issue date:	09/30/1990
From:	TENNESSEE VALLEY AUTHORITY
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.n_, "'**rw 5 022 '90 0917 024 TENNESSEE VALLEY AUTHORITY '

DMelon of Nuclear Engineer 6ng BROWSTERRYNUCLEARPl#T CABLEISSUESSUPPLEMENTALREPORT "

CORRECTIVEACTIONS

. September 1990 -

Revision 2 Prepared by _,. <c Date /M(C Reviewed by Ek/ Bass wJ B d .c Date V-/7 '/R App oved by ,r.mntsu eA/ Date 9-lbT Q V

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TABLE OF CONTENTS Page 1.0 Introduction . . . . . . . .................. I p.

2.0 Cable Bend Radius . . . . . .................. 1 2.1 Walkdown Inspection Results .......-........ 1 2.2 Testing Results . . . .................. '

1 2.3 Disposition of Existing Bend Radius Conditions . ..... 4-3.0 Support of Vertical Cables .................. 5 3.1 Walkdown Results . .. .................. 5 3.2 Testing Results .. .. ................. 5 3.3 Disposition of Existing Vertical Support Conditions ... 5 4.0 Use of Condulets for Pull Points for Large 600V Cables .... 6 4.1 Corrective Actions . . . . . . . . . . . . . . . . . ... 6 5.0 Further Review of Cable Jamming . ............... 6 6.0 Cable Pullby . . . . . . . .................. 7 6.1 Introduction . . . . . .................. 7 6.2 Selection of Test Conduits . ............... 7 6.3 Testing . . . . . . . . . . . . . . ...~. .=. . . . . . . 9-6.4 Test Results . . . . .. ................. 9 6.5 Resolution of Damage Caused by Conduits with l Missing Bushings . . . . ................. 10 6.6 Conclusion of Pullby Issue . ............... 12 7.0 Conclusions . . . . . . . . .................. 12 8.0 References . . . . . . . .. ................. 12 l

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1.0 INTRODUCTION

In June 1988 TVA began an evaluation to determine if past practices were adequate to ensure that damage did not occur during cable installation at  ;

Browns Ferry Nuclear Plant (BFN). The Evaluation of Browns Ferry Nuclear l Plant Cable Installation Concerns Summary Report, (Reference 1) was ]

issued documenting this evaluation including conclusions and I recommendations for resolution of each of the concerns. The Summary )

Report made recommendations for the resolution of four of the issues; ,

Vertical cable Supports, Cable Bend Radli Pu11bys, and Use of Condulets I for Pull Points for Large 600V Cables. I This report provides an overview of the work performed to satisfy the recommendations made in the Summary Report for these issues. Details of the walkdowns and analysis are contained in the documents referenced in this report.

2.0 CABLE BEND RADIUS 2.1 Walkdown Inspection Results The action recommended in the Summary Report. Section 5.5 (Reference

1) for closure of the bend radius issue was the performance of a walkdown and inspection of Class 1E medium voltage cables, using IVA's General Construction Specification G-38 as acceptance criteria. Cables not meeting the acceptance criteria would be technically justified or replaced.

An inspection was performed and documented in Reference 2 and the results are summarized in Table 1.

Upon evaluation of the walkdown data, it was noted that 52 of 54 class lE cables violated the allowable bend radius requirements.

Fifteen of the worst case cables were-tested as described in'Section 2.2.

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. 2. 2 . Testing Results To determine the acceptability of these cables. TVA proposed and the .

NRC concurred that High Potential (Hi-Fat) testing should verify 8 that the cables were capable of performing their intended safety function.

The methodology for-selection of the 15 worst case cables to be tested was discussed in a letter to the NRC on December 9. 1988 (Reference 3), and requires rankie- them by using the following ratio.

Actual Bend Radius = Bend Radius Ratio l' Allowable Bend Radius t

2.2 T: sting R:sults (Conticued)

The bend radius ratio is then indexed from lowest to highest values. Certain categories were excluded from the test sample.

These categories are identified'below and the Category 1 and 2 cables excluded from the test sample are noted in the last column of Table 1.

1. Cables which were identified by other programs for replacement before U206 restart.

2. Cables which are in diesel generator neutral ground circuits and are not' subjected to rated voltage and current on a normal operating basis.

3. Cables which are nonsafety related. l The conduit bend radii were measured for exposed conduits.

Inspection of the actual bend radii conditions of cables in embedded conduit (Table 1) was not possible. These conduits are short embedded runs (less than 30 feet). The embedded runs are assumed to ,

have standard or greater bend radii commensurate with the conduit '

f.ize.. Conduit configurations with standard be.sd radii have bend radius values well above the worst 15.

The test and acceptance criteria are in accordance with Reference 3. The wore'. 15 esbles were Hi-Pot tested at 20,000 volts DC for a duration of 15 minutes. The voltage level was the maintenance test voltage recommended by IEEE 400-1980. The acceptance criteria for the test was a polarization index of one or greater. This test was performed following Special Electrical Maintenance Instruction SEMI-65 (Reference 4). Test results are tabulated in Table 1. '

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Table 1

. WALKDDWN IN1PECTION OF CLA$$ 1E 5kV CABLES - CABLF BEND _ RADIUS RESui?S

' Max. Leakage During Polarization Reason for Cable Number Band Egj1ga_Atuo 20 kV Hi-Pot Test Inder Not Testino Ltaup I ---

ES113-1 2.95 3 microamp 1 Tested E$2550-11 3.37 1 microanip 1 Tested E550-1

• 3.37 1 microamp 1 Tested PP453-IID 3.b6 1 microamp 1 Tested E54379-IIC 3.80 - -- Osl Nebtral Gr E$13-1 3.90 ----- -- Replaced PP633-1 4.01 --- --- -- Replaced 3ES4102-IIC 4.08 1 micreamp 1 Tested 3E54101-IIC 4.49 1 microamp 1 Tested E52089-11

• 4.81 1 microamp 1 Tested ES2588-!! *.06 ---------- -- Replaced 3E54 *. 34-IIC 5.59 ----- -- Osl Neutral Gr E575-1 5.64 2 microamp 1 Tested E52575-11 5.75 ---------- -- Replaced ES88-1 5.88 2 microamp i Testeu Groun 2 -= --

PP493-Il 6.41 1 microamp 1 Tested E$4404-110 E.89 ---------- -- Ds) Neutral Gr 3[54090-11 7.08 - ----- -- Replaced 3E14080-II 7.12 ---------- -- Replaced PP637-Il 7.36 1 microamp 1 Tested PP625-1 7.44 1 microamp 1 Tested PP456-1E 7.57 1 microamp 1 Tested PP462-IE 7.04 1 microamp 1 Tested PP463-!E 7.64 1 microamp 1 Tested 3PP734 7.67 - - - - -

PP454-IID 7.96 - -- ---

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PP451-lE 8.44 -- ---- -- ---

PP457-!E 8.44 ------- -- --

E54375-!!C 8.60 ------ -- ---

ES141-1 8.63 - - - - - - - - - - -- Replaced ES1900-18 8.65 - - - - - - -

PP629-!! 8.75 ---------- -- ---

ES1875-IA 8.99 -- -- -

ES100-1 9.37 --- -- -- ---

PP4F" IB 9.47 ---------- -- ---

PP4 9.47 -- - - --

PP4L.... 9.92 ---- -- ---

PP469-!E 9.92- ---- - -- ---

PP450-lE 10.03 -- ---

PP491 11.39 ---- -- ---

ES189-1 11.89 -- Reglaced E52513-11 18.96 -- -- ---

ES2641-Il 14.52 --

E$18?6-IA Embedded Conduit - - - - - - - -- ---

E$1877 IA Embedded Conduit --- -- ---

ES1879-1A Embedded Conduit --- - -- Ds1 Neutral Gr E51901-IB Embedded Conduit -- ---

E51902-1B Imbedded Conduit -- -- ---

ES1904-1B Embedded Conduit - --

Osl N6utral Gr ES4376-IIC Embedded Conduit ---- -- ---

ES4377-IIC- Embedded Conduit ---- -- ---

E$4400-110 Embedded Conduit -- ---

ES4401-IID tmbedded Conduit - - - - - - - - - - -- ---

____ES44Q1-110 Embedded Conduit =-- -- ---

Nonsafety related cables are not tecluded in Table 1.

• These cables were selected for replacement by the environmental qualification program af ter this test was complete.

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" -. J2.31 Disposidon of Existing Bend Radius Conditions

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The. cables having a bend raalus less than t'ae allowable (twelve- times the' cable'0D) were classified in three groups as-shown below.:

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,. Group (2.95' -

5'.88) x Cable OD

. Group 2 (6.50:- 7.95) x Cable OD Group 3- -(8.43 - 11'.42) x cabl- OD basedLon the-satisfactory results of the tests, the existing bend:

,' 1 radii of the cables listed ~in Table.1 are acceptable.as installed for.

Unit 2 restart.= Five cables (ES113-I, ES2550-II, PP453-IID, ES75-I, and ES88-1)'in Group 1 operate at full system voltage. These cables are approximately 15 years old. Since the Hi-Pot tests produced-satisfactory results for these cables, engineeringzjudgment supports =

continued operation for at least another: fuel cycle. -However, in view of.the: severity of the bend radius conditions and the ageof taa

-cable, these cables will be replaced during the next scheduled U2l rafueling outage. The renuaing four cables (ES4379-IIC, 3ES4102-IIC. 3ES4104-IIC, and 3ES4101-IIC) in Group 1 are diesel Generator Neutrals which carry a reduced voltage or near zero voltage except~for small voltage caused by phase imbalance or short duration voltages. caused oy Mult conditions. These cables are also located in a mild environment. Therefor ( i. heir installed condition is acceptable

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without modification or further testing.

V Group 2 cables are in tb bend radius range of.6.5 to 4 times the-cable OD. This radius is significantly less than the. allowable 12-

. times. Fnwevar,. separation of the shield tape would not. occur at these radii. The test results support these cables. remaining in

-service. Reference.5 requires all cables in Group-2 to be tes Dd to

. the requirements ofjSEMI-65 during the next scheduled U2. outage er subsequentLoutages to-facilitate a trend analysis. hFN plans to

-evaluateLthe trend ~analysisiat the end of the third refueling cutage.

T" 'following restart of unit 2 to assess the need for continued trending of these cables.

TVA will further support its conclusions for the Group 2 cables by

. application of data to be obtained through HBN's long-tern bend radius program. 'In the WBN tests, medium voltage cables will be bent to a radius of.4 times the cable OD and then retrained to 8'.tices. The

. specimens will then be subjected to a period of load-cycli.og followed-by a. corona test =to' assess the effects of 'he' excessive b ed. .TVA j . considers!that this testing will encompass the less severe Group 2 i(. bends. = Per NRC's request, TVA will also review the est prcgram with '

its major suppliers.

The cables in Group 3 have installed bend radii ranging from 8 t.imes the OD to near 12 times. None of the cables are locau d inalde of the edrywell. The environmen'.a1 transients in the remainder of the plant are.less: severe.. While the Insulated Cable Engineers Association (ICEA) recommends a "12 t 'imes factor for training this type of cable, theLworst Group 3' bend can be shewn to produce only about a 7 percent elongating stress which is negligible when contrasted with the b' l-> materials' capabilities. Therefore, those cables will remain _n

@. service:without retra!ning and will be subjected only to the normal 4, naintenance 'esting; i k'y' 3" %Ns , m4E

y 3.0 SUPPORT OF VERTICAL CABLES 3.1 Walkdown Results The action recommended in the Summary Report sReference 1) for closure of the Vertical Cable Support issue was the performance of a walkdown of class lE medium voltage cables, using G-38 as acceptance criteria. Any vertical sections of cable not properly supported would be Hi-Pot tested at the maintenance voltage levels specified in IEEE Standard 400-1980 and supports added if the cable passed the test.

An inspection was performed as recommended. Thirteen class lE cables had an unsupported vertical length greater than allowed by G-38. Since there were only 13 class LE cables which did not meet the vertical drop criteria, the methodology identified in Reference 3 for selecting the worst 15 conditions, was not utilized.

3.2 Testing Results Five of the 13 cables (ES2689-II, ES189-1, ES141-I, ES13-I, and ES2641-II) are being replaced by other issues prior to Unit 2 restart and therefore were excluded from the testing program. The remaining eight were HVDC tested as previously discussed. All eight cables met the acceptance criteria of SEMI-65 (Reference 4).

3.3 Disposition of Existing Vertical Support Conditiona Evaluations were performed on those eight c ses to determine if the static sidewall bearing pressures resulting am the vertical drops in excess of that recommenced by the National Electrical Code were within the acceptable range as defined by available vendor guidance (Reference 6 and 7). This r. .hodology is consistent with that successfully applied in resolution of these issues at SQN. The recommendations provided by these references are generic rather than restricted to certain materials. These vendors have offered a wide range of insulating materials of differing durabilities with respect to static sidewall bearing ptessures (crosslinked polyetbylene, ethylene prcpylene rubt ir, silicone rubber, chlorosulf onated polyethylene, fluoro.olymers, etc.) for Class lE service. These crosslinked polyethylene insulated cables, applied at loading stresses well below the recommended maximums, will perforo equal to or bester than many of the referenced polymers. Utilizing this approach seven cables were technically justified (Reference 8) and are shown in Table 2. A support has been added to the final cable (ES2513-II) to bring it in compliance with the requiremor is of G-38.

A program for evaluating the support of low voltage cable verticel drops wi.1 be implemented with ccheduled completion by Cycle 7 startup.

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- Table 2 0 -

STATIC SIDEWALL BEARING PRESSURE VALUES FOR' EVALUATION OF-VERTICAL CABLE DROP MARK OD (Inches) CABLE- VERT DROP COND SIZE / KERITE OKONITE u

CABLE NO. DS E12.1.13 LB/FT FT.- BEND RAD IN. P- SWP-w

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PP453-IID' WNC 1.136 1.215 28.08 3"/12.07 14.9- 101.76 3PP734-IIJ WNB- 1.04~ .899 30.42 3"/12.75 12.4 77.42 ES50-I WNB 1.04 .899 28.58 3"/13.27- 11.27 69.70 ES2550-II- WNB 1.04 .899 23.83 3"/11.47 10.78 67.24 PP451-IE WNC 1.136 1.215 25.17 3"/15.76 10.25 69.86 PP450-IE WNC 1.136 1.215 25.17 3"/15.76 10.25 69.86 PP497-I' WNB m 1.04 .899 26.00- 3"/15.76 8.56 53.39 Okonite maximum recommended SWP8 (1b/ft) = 120 lbs/ft Kerite maximum recommended P (1b/in ) = 50 lbs/in' r

l '4.0 USE OF CONDULETS FOR PULL PQiNTS FOR LARGE 600V CABLES 4.1 Corrective Actions As recommended 3r the Summary Report (Reference 1), all eight of the circuits identified as 3-400 MCM cables which see installed in three inch' conduit and utilizing standard format condulets as pull points will be-replaced prior to Unit 2 restart. Tnese raceways are being reworked to: increase the conduit size to four inch and incorporate junction boxes or'large format, mogul-type condulets as pull points.

Additionally, TVA Electrical Design Standard E13.6.2 R2 (Reference 9),

Construction Specifications and EFN Site:Proceoures were revised to prohibit the use of standard condulet-bodies as pull points for 300-MCM and. larger low voltage power cables.

5.0 FURTHER REVIEW OF CABLE JAMMING BFN's program (as described in Reference 1) for evaluationm and inspection for-the potential of damage due to jamming has-been implemented. No evidence'of damage was observed. Subsequent to this evaluation, numerous circuits'were replaced as a part of'on-going modifications to address other electrical issues (ampacity, Appendix R,'EQ, large 600V cablis in condulets, etc). In accordance wi4 h an NRC request in'a telucon on

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August 8, 1990, a review was performed of those circuits s ich wet initially identified as being in the critical jam ratio'ra..ge in order to assess their current status. This review, the results of which were e ' discussed in a September 5, 1990, telecon,' identified that only one such conduit remains with cables in the critical jam ratio range; conduit ES1400-I. The three 600V, 400 MCM cables in this conduit feed the control

^ bay water chiller A. It was noted that the cables feeding control bay

. water chiller- B (the redundant chiller) have been replaced during this outage. It was agreed in the latter telecon that no further action was required by BFN-for this issue.

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660.' CABLE PULLBY

!6.1. IntroductionL '

m 'The walkdowns'of potential pullby conduits identified in Reference 1 P' established a high degree of-confidence'that the installed rafety-related systems at BFN will perto a their required function and  ;

that cable pullby damage was not present. Subsequent to the

-completion of the reviews and to the submittal'of the above referenced  ;

documentation, damage to cables was discovered at Watts Bar Nuclear i  : Plant (WBN).. Analysis indicated that the damage was attributed to- "

e pullbys . --

Even though no pullby damage was identifled at BFN, the findings at. l WBN warrant additional evaluations. This ef fort includer.' further analysis of install adults and cables at BFN and a program of high-potential tet ..of cables which may have experienced.high sidewall bearing pressures during the pullby. process, n

TVA met with the NRC on December 18, 1989, January 18, 1990, and. '[i February 13, 1990, to discuss the plan for resolution of cable-pullby 5 concerns at BFN. This plan (Reference 10. Enclosure 1) included the selection criteria to define and identify a group 'of ten " worst"-

conduits.and the test program criteria. The NRC staff concurmd with .

TVA's test program after the February 13, 1990 meeting (Refe s ll). L' 6.2 Selection of Test Conduits. ,J Since the ini,tial cereeni*ig process did not include direct +

consideration for raceway configuration (this.could-only be known as ,

the' result of f!. eld 'welsdowns). TVA's plan was to compare those ';

results with th 5W8P ranking process-to confirm adequate-correlation between the two nethodologies. This comparison was made and it was noted that several conduits; were ranked much higher using the SWBP values thai with the initial screening process. 3 o The select 10n cr.teria submitted to the dRC stated that if ranking' of .

the top 30 conduits produced-by these two methods did not adequately correlate, the remaining conduits would be walked down to obtain~

values for SWBP calculations. Upon application of the.above process, "

a. review of the remaining 64 conduits ~ identified that 35 were 50 feet or less A n . length.- These short conduits 'e re not considered likely to .

contain auf ficlent complexity- r.o L.a considered worst case when

. compared to the longer,thighly-filled conduits identified by the.

screening parameters. This observation lead to a decision to expand: s the walkdown-and SWBP calculation process to include conduits which q: are greater than 50 feet long. This expanulon provided walkdown data  !>

, lon a total of 59 conduits. This methodology was discussed with the

's ',  ; NRC during their inapection in' April 1990. ,

'These 59 con .Its w(re ranked according to the percent of their allowable SWBP. Ten conduits were selected for testing. These conduits consist of the top-senn V3, the top two V4, and the top V2.

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6.2 Selection of Test Conduits (Continued)

As was discussed in a September 13, 1990, telecon with the NRC, several differences exist between the final rankings (and the associated forces) and the preliminary rankings (and forces). This latter data had been shared with the NRC during the course of its development and during the test program. As the cable test program has neared a close, two efforts have been undertaken which have resulted in the above changes.

First, BFN's QC organization parformed an independent review of the walkdown sketches of conduits LS4508-IIC, 3ES1676-IB, and ES1539-1 used to obtain the configuration data necessary to perform sidewall bearing pressure calculations. This review found errors in bend angles and conduit lengths. The QC data was reverified and entered into the SWBP calculation. The revised data lowered the SWBP and swapped the sixth and seventh ranked conduits (3ES1676-IB and ES1540-1). Four additional walkdown sketches were reviewed (ES4035-II, 2ES3106-II, ES.028-II, and ES2835-II) and the changes enterec into the SWBP calculation. Although, differences were found in three of the conaults, most of the changes were within the tolerance of the walkdown procedure and the changes to the SWBP calculation were not significant. To ensure that the calculated SWBP were correct for the tested conduits, TVA decided to verify the sketches for the remainder of these conduits (3ES4177-IID, ES2052-IB, ES337-I, 3ES3677-II, ES1540, ES2051 ES335-I, ES359-I, and 2ES904-I).

The revised SWBP calculation based on this data made no other changes to the ranking order for this group. Walkdown sketches for two additional conduits (ES223-1 and 3ES4538-IIC) were verified as requested by the NRC on September 5, 1990, to confirm that any discrepancies would not in rease SWBP and nove these conduits into the population requiring testing. The revised calculation based on this data resulted in lower SWBP for these two conduits.

Based on the results of the walkdowns of these 18 conduits, it was concluded that although discrepancies were found, they would not significantly impact the SWBP conduit rankings and that no further action was required. The above was discussed with the NRC on-September 3, 1990.

The second effort was the normal process of checking and review of the test-conduit selection calculatic In the course of thic review, it was determined that the computer p.ogram which evaluated pullslip data to establish pull-groupings did not properly consider multiple

= pullslips having the same cable number. Multiple pullslips may exist as the result of cable replacement for any of a variety or programs.

The initial version of the program recognized only the first pull-date associated with a given cable number. Following the discovery of this oversight, the ccmputer code was modified so as to include the additional pullslips in its conduit's database prior to establishing the individual pull groups. Approximately 140 records were added to the existing database of 34,000 pullslips. Using the same 30 day window for establishing pull groups (Reference 12), conduits 3ES3677-II, ES4508-IIC, ES1676-IB, and ES2051-IB were unaffected by the above changes. The calculated SWBPs for conduits ES335-I, ES359-I, 3ES4177-IID, and ES337-I increased since the consideration of the addtional records resulted in significan*1y heavier worst case pull groups.

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. cablesiin the worst case pull group also. increased 1(from 6 to 9)'..

LInl general,the expression for.SWBP is T/R, where 'T' is the1 tension _

is th'e radius cf the conduit.

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However, for pulls of 4 or more. cables the expression becomes' (x

• T)/R, where 'x' 'is used to E-  : account: for the distribution of the SWBP across: the various cables.- 1

[ LTVA's G-38,-using methodology developed by T. A. Kommers of the Okonite j

. Company,: requires the use of an 'x' of .7 and .44 for pulls of 6 and 9. ,

. cables, respectively.- In this case, tk.e increased tension resulting~

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from the slightly heavier pull was more than offset by the: change-in the' distribution factor 'x', and resulted inca small decrease in.the

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calculated SWBr. ,

. The forces and rankings shown in the test conduit selection calculation.

, (Reference 12) include consideration for both ofLthe above efforts.

-In addition to the worst segment of the ten conduits selected for testing (top _seven V3, top 2 V4,_and top V2) all additional-segments in

, those conduits'which had expected SWBPs greater than the maximum b  : allowed by G-38 were tested. The applied test voltage was 240V de per g mil of insulation. thickness (minimum required insulation thickness for b qualified cables or nominal thickness for nonqualified cables) with a 1; maximum test voltage of 7200V de and not exceeding 80% of industry l'

standard' test ~ values.

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The voltage was. applied for a duration of five minutes. A polarization 7 , index of 'one 'or greater at the applied voltage was the acceptance - [

criteria for the test. Testing was performed with V3 and V4 conduits-  ;

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~ filled with water. All V2 cables involved in this program are constructed with an overall shield. This shield provided the required =

ground: plane for testing, therefore water was not used for conduits which contained,only V2 cables. These ten conduits contained ~137 j cables _which were comprised of 520 conductors. 1 6.4 Test Results-- 4 s

The ten conduits were tested in accordance with Special_ Test,90 O' (ST:90-01) (Reference 13). The cables tested passed'the acceptance.

requirements'except for the following anomalies:

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1. Cable ES327-I in conduit ES337-I had a high leakage current during '

the Hi-Pot' test.- Additional meggering was performed and a cut was L observed in the jacket and insulation of this multi-conductor cable  ;

p at a conduit pressure boundary seal. The NRC s'.uf f inspected this . i

,e N cable and concurred with TVA that the. damage was not caused by g ,

pullbys and probablyLoccurred during a previous removal of the  ;

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seal. A large number of conduit seals are being replaced-during  ;

E" the current outage for Appendix R and additional seals are replaced "

, during' modifications for other electrical issues. BFN procedures thc.t control the installation of the fire seals require y ,

M inspection of the cables prior to the installation of t% aew seal. '

s Mindful of this high level of activity in seal reple' m .t with no .!

.e evidence of a negative trend and of the presence ci seals t a other tested conduits, TVA determined and the NRC concusted th.. this p j damage was an isolated case. The damaged area wan re N .ed and the g cable was successfully re-tested. -

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2. Six. conductors routed in' conduit ES2051-I'and'ES2052-1 exhibited" o* .high leakage currents and the-test-.was stopped.L Additional testing wan performed.to locate the anomalies. It was noted that

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1. . .the segret ' in which the anomaly had been isolated had:a-disconnectedLeonduit bushing at a mid-point pull box. Cables.were removed from that segment and carefully inspected by TVA engineers.

and NRC resident inspectors. Small tears were found in the1 jacket-and insulation.- The cables 'he1 remaining segments of these conduit' rer.. were successfut., .ested.

6.5 Resolution of Damage Caused by Missing Conduit Bushings The damage found in conduits ES2051-1 and ES2052-1 was postulated to have'been the result of pulling the cables over a conduit with a missing bushing. In an effort to confirm.this hypothesis, simulated.

pulls were performed across a conduit without a bushing. The-resulting damage was similar to the damage found cn the test cables..

This simulation was witnessed by the NRC. It was agreed that the-damage to the test cables closely resembled that created by the-simulated pull and that it was-not: caused by a pullby. The-damaged cables were single conductor TVA type PN which have 30 mils of.

.po_yethylene insulation covered by a 4 mil nylon jacket. Other cable

-types in.use>at TVA have substantially. thicker jackets.

A'ptogram was established for identifying conduits with missing bushings. Boxes containing Unit 2 10CFR50.49 circuits were inspected, either by reviewing. existing photos taken during previous inspections or by plant ,walkdown inspections. Those boxes. covered with fire barrier material for Appendix R were excluded from the inspection progran since removal of the fire barrier material-is costly and the conduits entering these boxes do not contain PN type cables. N1'ne conduits'were identified-with missing-bushings by reviewing 627-

-photos. Nine additional missing bushings.were identified during the plant walkdown inspection of 313 boxes. Of these 17 missing' bushings, ten were-located at end device enclosures and it.was evident that the=

cable was not' pulled over the' exposed' conduit edge.. On conduit 2ES922-I the bushing was missing from a part of.the conduit segment-which was less than two feet in length-to the next pull point (a f '

condulet). . Three to four feet ofoflex conduit is. installed between that fitting and the panel. Given the short length of straight conduit involved it is likely that the cable was pushed or hand-fed

'through this segmant. Therefore, testing was not warranted. This was discussed and agreed upon with the NRC on August 2, 1990 and August'6, a 1990.

On conduit ES4070-II the bushing was missing from a condrit sleeve which penetrates the wall between Units 1 and 2 and terminates in a box on each side of the wall. As above the cables would likely have been hand-fed through the sleeve and testing was not warranted. This-conduit was discussed in the above telecon. The rema aing five conduits with missing bushings were Hi-Pot tested following ST 90-01.

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6l.5 L . Rssolution 'of = D: mage 'Causet by Missing Conduit Bushings, (Continusd) 1.q,"'

5 Consistent with-the' testing performed for-the pullby' program, sh1 Sided-

"A' cables were' tested dry,-whereas unshielded cables were-tested wet in

, order tol obtain an acceptable ground plane. - A non-bushing relatedE failure occurred' in- 2RP1917-IB,- as described below. All other tests;

, were' successful.

Conduit Junction Box- Remarks.

'2ES1313-1 2474 -Wet O 2ES905-I 6541 Dry '

n 2R.81919-IB . 6541 Dry ESit26-1B- 3301 Wet 2RP1917-IB -2476 Dry As noted above, during testing of conduit 2RP1917-IB a. f ailure occurred. Atlapproximately 2-1/2 minutes into the test at: 4.0 kVDC:

. the leakage current on the black conductor of cable 2RP1945- ros c to

-approximately 1 mA.- When the problem could not-be cleared by

additional cleaning and taping of the terminal ends the. cable wta cut at varinus intermediate pull points. By this process;the:failura-was1 isolated to'a. segment approximately4 22 feet in length. The cable 011n the suspect segment were carefully removed and inspected. No damage

-was observed. It was decided to send this cable, a TVA' mark letter WVA, type MS, manufactured by Brand Rex on contract 80K6-825419 to the University-of; Connecticut's (UCONN) Electrical Insulation

-Research Center for further analysis. This approach was discussed

.with the NRC on August 2 and August 6, 1990..

Analysis of the failed cable concluded that no damage had been-inflicted at'the box with the missing bushing and that-the test failure resulted from the presence of a large number of atypically large contaminant- particles concentrated in the region of the- f ault'.

In-order to: determine whether or not the- contaminant in the

-insulation was isolated, it was decided-to subject additional segments of othe same cable to a dielectric breakdown test. Both

segments, one f rom each end of the faulted section, broke down at 12kVAC (approximateiy 36 kVDC). UCONN therefore concluded'that the contamination was isolated in nature.

Further review by TV.. determined that at least 17 cables of the same mark number and contract had been successfully tested as a part oft the pullby program. This i her supports the conclusions drawn by UCONN.

Existing procedures requir 'he installation of conduit bushings at each conduit end.

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,, 'h. L6.6: Conclusion'of Pullby Issue-.

Approximately"1330Leonduits were identified as possible candidates

'for pullby during cable' installation.' 'Using the screening' process of-

~

this programi..the' population was reduced to 94. 0fithis number, 59-were walked downland 10 were tested..

Although anomalies were identified by the testing. no pullby damage

.was identified at BFN by this extensive review ~and testing' program.

Th'erefore, the program serves to confirm that the cable installation'

. practices at BFN were adequate to ensure that pullby damage does not exist.

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7.0 CONCLUSION

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-For the issues above, TV?." hee completed an aggressive program of walkdowns, inspections, testing,-and recurrence control to ensure that

. safety related cables will perform their required function.-

8.0 REFERENCES

1. . Browns Ferry Nuclear Plant'- Evaluation of Browns Ferry Nuclear. Plant

>: Cable 1 Installation Concerns Summary Report (B22 890322 012)

2. TSD E180 Cable: Pulling Issues, Cable Bend Radius and Vertical Drop Analysis'(B22'881111 243)

3. ' Letter to.U. S. Nuclear Regulatory Commission - Browns Ferry Nuclear Plant'- Response to, Request for Additional Information on Electrical Issues (TAC 62260) (L44 881'09 806) v c

4. Special Electrical Maintenance Instruction SEMI-65 R3

5. General-Construction Specification G-38 SRN-83 (B22.900607 012) 7, " Variance Number.16-SkV Bend Radius Violations"

16. Installation Practices for Cable Raceway Systema, The Okonite m/ '. , Company, May 1982 (B43 880617 708)=

Kerite Installation Data, The Kerite Company, March 1979 7.

(B43 880617 709)

S;k . ' 8.- G-38 SLN 32 (B22890112002) " Variance Number 5-SkV Vertical Support-K Violations"

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-9. TVA Electrical-Design Standard E13.6.2 R2 " Raceways - Use of; Conduit

!di g Bodies in Conduit Systems" (B43 890725 908)

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10. Letter to U.S. Nuclear Regulatory Commission from Tennessee Valley

i. '

Authority dated February 5, 1990 (L44 900205 801) - Resolution of Cable Installation Concerns (TAC No. 62260) i

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.7 8.0' REFERENCES (Coatinued)

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11. ' Letter.to' Tennessee Valley Authority from the U.S. Nuclear Regulatory-Consnissica dated February. 16,_1990'- Summary of heeting_with

- Tennessee _ Valley Authority held on February _ 13,'1993 to discuss-the

' Browns Ferry Nuclear Plant Unit 2 Cable Installation Program (TAC No. 00421) ci ,

12. Calculation for Analysis of Cable Pullby Concerns at BFN (B22 90 0917 113);

1.

3 Special Test Procedure for High Potential Testing of- Low Voltage Cables ST-90-01 p 1 h.

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1- ENC 1.0SURE 2--

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1 -COMMITMENT

SUMMARY

, .c New Commitment l@ ,

,h l ['IVA will? review the results of WBN's' long-term bend' radius program- to BFN.

Commitments Made in TVA's September 10. 1990 Submittal,

'1.0- The five cables that operate at full system voltage in Group l'of the

. bend radius evaluation will be-replaced to correct.the ben.. radius,

_corditions during the next unit 2 refueling outage.

2.0 . Group'2 cables will be tested toLthe-requirements of SEMI-65 during the next-scheduled unit 2 outage and subsequent outages to facilitate a tiend' analysis. BFN plans to evaluate the trend analysis at the end of three outages to' determine the need for' continuing this analysis.

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3.0 A post unit 2 restart program for evaluating the support of low voltage cable vertical drops will-be implemented with a-scheduled completion by cycle.7 startup.

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