ML18033B425

Forwards Cable Installation Supplemental Rept,In Response to NRC Request During 900506 Telcon.Rept Contains Results of Walkdowns & Testing Except Work on Ongoing Cable Pullby Issue

ML18033B425
Person / Time
Site:	Browns Ferry
Issue date:	07/10/1990
From:	Wallace E TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-62260, NUDOCS 9007130362
Download: ML18033B425 (24)

Text

..ACCELERATED DI MBUTION DEMONST ATION SYSTEM t

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REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9007130362 DOC.DATE: 90/07/10 NOTARIZED: NO DOCKET FACIL:50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 AUTH.NAME AUTHOR AFFILIATION WALLACE,E.G.

Tennessee Valley Authority RECIP.NAME, RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Forwards cable installation supplemental rept, in response to NRC request during 900506 telcon.

DISTRIBUTION CODE:

A001D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: OR Submittal:

General Distribution NOTES:1 Copy each to: S.Black,B.WILSON 05000260 RECIPIENT ID CODE/NAME KREBS,M.

ROSS,T.

INTERNAL: ACRS NRR/DOEA/OTSB11 NRR/DST/SELB 8D NRR/DST/SRXB 8E OC/LFMB

.REG FIL~E02.

EXTERNAL:

LPDR NSIC NOTES:

COPIES LTTR ENCL 1

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RECIPIENT ID CODE/NAME PD NRR/DET/ECMB 9H NRR/DST 8E2 NRR/DST/SICB 7E NUDOCS-ABSTRACT OGC/HDS2 RES/DSIR/EIB NRC PDR COPIES LTTR ENCL 1

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1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED:

LTTR 32 ENCL 30

TENNESSEE VALLEYAUTHORITY CHATTANOOGA. TENNESSEE 37401 5N 157B Lookout Place JUL I 0 1980 U.S. Nuclear Regulatory Commission ATTN:

Document Control Desk Washington, D.C.

20555 Gentlemen:

In the Matter of Tennessee Valley Authority Docket No. 50-260 BROWNS FERRY NUCLEAR PLANT (BFN) UNIT 2 CABLE INSTALLATION ISSUES SUPPLEMENTAL REPORT CORRECTIVE ACTIONS

Reference:

TVA letter to NRC dated June 19, 1989, Electrical Cable Installation Revised Walkdown and Summary Reports (TAC No. 62260)

This.letter transmits BFN's report 'titled "Cable Installation Issues Supplemental Report Corrective Actions".

This report is in response to NRC's request made during a May 6, 1990 telecon and augments the reports transmitted by the referenced letter.

The referenced letter transmitted a summary report (dated March 1989) on the evaluation of BFN cable installation concerns.

Actions recommended in the March 1989 report to resolve the cable concerns are in progress and are discussed in Enclosure l.

Additionally, the enclosed report contains a

summary of the required actions for closure of the BFN cable installation concerns.

The results of all walkdowns and testing are contained herein, except for work relating to the ongoing cable pullby issue.

This report will be revised to add the information on the cable pullby issue and transmitted to NRC when the cable pullby program is complete.

Enclosure 2 contains a summary list of commitments made in this submittal.

If you have any questions, please telephone Patrick P. Carier, BFN, Site Licensing, (205) 729-3570.

Very truly yours, TENNESSEE VALLEY AUTHORITY E.

G. Wallace, Manager Nuclear Licensing and Regulatory Affairs Enclosures cc:

See page 2

9007130362 900710 PDR ADOCK 05000260 PDC An Equal Opportunity Employer

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U.S. Nuclear Regulatory Commission cc (Enclosures):

Ms. S.

C. Black, Deputy Director Project Directorate 11-4 U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike, Rockville, Maryland 20852 NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637

Athens, Alabama 35609-2000 Thierry M. Ross U. S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Chief of TVA Projects U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323

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ENCLOSURE 1

CABLE INSTALLATION SUPPLEMENTAL REPORT

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TABLE OF CONTENTS

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1.0 Introduction 2.0 Cable Bend Radius Issue Disposition.

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2 2.1 Walkdown Inspection Results 2.2 Testing Results 2.3 Disposition of Bend Radius Conditions

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3.0 Support of Vertical Cables

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7 3.1 3.2 3.3 Walkdown Inspection'esults Testing Results

.Disposition of Existing Vertical Suppo Conditions

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7 4.0 Use of Condulets for Pull Points for Large 600V Cables.

8 4.1 Corrective Actions.

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5.0 Conclusions......................

8 6.0 References 9

Page 1 of 9

1.0 INTRODUCTION

In June

1988, TVA began an evaluation to determine if significant cable abuse had occurred during installation at Browns Ferry Nuclear Plant (BFN).

A report, Evaluation of Browns Ferry Nuclear Plant Cable Installation Concerns Summary Report, (Reference

1) was issued documenting this evaluation including conclusions and recommendations for resolution of each of the BFN specific cable installation concerns.

The Summary Report made recommendations for the resolution of four of the issues; Vertical Cable Supports, Cable Bend Radii, Pullbys, and Use of Condulets for Pull Points for Large 600V Cables.

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 justification methodology are contained in the documents referenced in this report.

The ongoing corrective actions identified will resolve all of the cable installation concerns except for pullbys.

(,1

Page 2 of 9 2.0 RESOLUTION OF CABLE BEND RADIUS 2.1 Walkdown Inspection Results The action recommended in the Summary Report, Section 5.5 (Reference

1) for closure of the cable bend radius issue was the performance of a walkdown and inspection of Class 1E medium voltage cables, using TVA's General Construction Specification G-38 as acceptance criteria.

Cables not meeting the acceptance criteria would be technically justified or replaced to ensure compliance with G-38 requirements.

A walkdown inspection was performed and documented in Reference 2 and the results are summarized in Table l.

Upon evaluation of the walkdown'ata, it was noted that 52 of 54 class 1E cables violated the allowable bend xadius requirements.

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

2.2 Testing Results To determine the acceptability of these

cables, TVA conducted High Potential (Hi-Pot) testing to verify that the cables were capable of performing their intended safety function.

The methodology for selection of the 15 worst test cables was discussed in a letter to the NRC, on December 9,

1988 (Reference 3),

and requires ranking them by using the following ratio.

Actual Bend Radius

= Ranking Position Allowable Bend Radius The ranking position number 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 were identified by other programs for replacement before unit 2 restart.

2:

The cables are diesel generator neutral ground cables and are not subjected to a rated voltage and current on a normal operating basis.

3:

The cables are non-safety related.

The conduit bend radii were measured for exposed conduits.

Ipspection 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 size.

Conduit configurations with standard bend radii have bend radius values well above the worst 15.

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Page 3 of 9 Table 1

WALKDOWN INSPECTION OF CLASS 1E 4160V CABLES CABLE BEND RADIUS RESULTS'<

Cable Number Allowable Worst Bend Radius in Cable Bend Radius Pass/Fail Reason for Excluding From Worst 15 14.40 14.40 14.40 14.58 14.40 14.40 13.62 14.52 16.08 16.20 14.40 14.40 14.40 14.40 14.40 14.40 14.40 14.40 14.40 11.64 11.64 14.52 14.52 14.52 11.64 14.58 14.58 14.58 14.40 16.20 14.40 11.64 14.52 14.40 14.58 14.58 14.52 14.52 14.58 11.64 16.20 11.64 15.36 14.52 14.40 14.40 14.52 14.52 14.40 14.52 14.52 11.64 14.52 14.52 ES113-I ES2550-II ES50-I PP453-IID ES4379-IIC ES13-I PP633-I 3ES4102-IIC 3ES4101-IIC ES2689-II ES2588-II 3ES4104-IIC ES75-I ES2575-II ES88-I PP493-II ES4404-IID 3ES4090-II 3ES4080-II PP637-II PP625-I PP456-IE PP462-IE PP463-IE 3PP734 PP454-IID PP451-IE PP457-IE ES4375-IIC ES141-I ES1900-IB PP629-II ES1875-IA ES100-I PP465-IB PP466-IB PP468-IE PP469-IE PP450-IE PP497-I ES189-I ES2513-II ES2641-II ES1876-IA ES1877-IA ES1879-IA ES1901-IB ES1902-IB ES1904-IB ES4376-IIC ES4377-IIC ES4400-IID ES4401-IID ES4402-IID 3.54 4.05 4.05 4.45 4.56 4.68 4.55 4.93 6.01 6.50 5.83 6.71 6.77 6.89 7.06 7.69 8.27 8.50 8.54 7.,13

7. 22

9. 16

9. 25

9. 25 7.44 9.66 10.25 10.25 10.32 11.65 10.38 8.48 10.88 11.25 11.51 11.51 12.01 12.01 12.19 11.04 16.06 18.37 18.54 Embedded Conduit Embedded Conduit Embedded Conduit Embedded Conduit Embedded Conduit Embedded Conduit Embedded Conduit Embedded Conduit Embedded Conduit Embedded Conduit Embedded Conduit Non-safety related cables are not included in Table 1

Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail" Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Fail Pass Pass Indeterminate Indeterminate Indeterminate Indeterminate Indeterminate Indeterminate Indeterminate Indeterminate Indeterminate Indeterminate I~determinate

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\\ I'l Dsl Neutral Gr Replaced Replaced Replaced Dsl Neutral Gr Replaced Dsl Neutral Gr Replaced Replaced Replaced Replaced Dsl Neutral Gr Dsl Neutral Gr

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The, test and acceptance criteria are in accordance with Reference 3.

= The worst 15 cables 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).

The tested cables passed the acceptance criteria and the data is tabulated in Table 2.

Table 2

TEST RESULTS OF 15 WORST BEND RADIUS CABLES Cable:

ES113-I ES2550-II ES50-I

• PP453-IID 3ES4102-IIC 3ES4101-IIC ES2689-II

• ES75-I ES88-I PP493-II PP637-II PP625-II PP456-IE PP462-IE PP463-IE Semi-65 Test MR

=, A-,898053 A-898061 A-898054 A-898160 A-898074 A-898075 A-898062 A-898056 A-898057 A-898065 A-898162 A-898058 A-898156 A-898178 A-898179 Minimum Value 2500V Megger 15 sec 5 min.

45K MEG OHMS

>150K NEG OHMS

>250K MEG OHMS

>250K MEG OHMS

>250K MEG OHMS 200K MEG OHMS 50K MEG OHMS lOOK NEG OHMS 150K MEG OHMS 250K MEG OHMS 100K MEG OHMS

>250K MEG OHNS 150K MEG OHMS

>250K NEG OHMS

>250K MEG OHMS Maximum Leakage Current During 20 kV Hi-Pot Test 3 microamp 1 microamp 1 microamp 1 microamp 1 microamp 1 microamp 1 microamp 2 microamp 2 microamp 1 microamp 1 microamp 1 microamp 1 microamp 1 microamp 1 microam Minimum Polarization Index

<<These cables were selected for replacement by the environmental qualification program after this test was complete.

2.3 Disposition of Existing Bend Radius Conditions The cables having a bend radius less than the allowable (twelve times the cable's outside diameter (OD) were classified in three groups as shown below.

Group 1

Group 2

Group 3

2.95 5.88 x Cable OD 6.50 7.95 x Cable OD 8.43 11.42 x Cable OD

Page 5 of 9

Based on the satisfactory results of the tests, the existing. bend radii of the cables listed in Table 3 are acceptable as installed for Unit 2 restart.

Five cables 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, engineering judgement supports continued operation for at least another fuel cycle.

However, in view of the severity of the bend radius conditions and the age of the cable, these cables will be reworked to correct the bend radius conditions during the next scheduled unit 2 refueling outage.

The remaining four cables in Group 1 are diesel generator neutrals which carry a reduced voltage or near zero voltage except for small voltage caused by phase inbalance or short duration voltages caused by fault conditions.

These cables are also located in a mild environment.

Therefore, since these cables operate at a significantly reduced stress, their

,installed condition is acceptable without modification or further testing.

Group 2'cables are.in the "bend radius

.range of 6 to 8 times the

. cable OD.

This radius is significantly less than the allowable 12 times.

However, 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 tested to the requirements of SEMI-65 during the next scheduled unit 2 outage and subsequent outages to establish a trend analysis.

BFN plans to evaluate the trend analysis at the end of three reviewing outages following startup of Unit 2 to determine the need for continuing this analysis.

The cables in Group 3 have bend radius conditions from 8 times the OD to near 12 times the OD.

These cable bend radii are not as severe as Groups 1 and 2 and based on the test results it is reasonable to allow these cables to remain in service without modification and only normal maintenance testing.

Browns Ferry's past testing practices and the results of these tests are documented in Reference 6.

TABLE 3 Page 6 of 9

5KV CABLES WITH BEND RADIUS LESS THAN 12 TIMES THEIR OUTSIDE DIAMETER Cable:

Allowable Worst Case Bend Bend Radius Radius Cable:

Allowable Worst Case Bend Bend Radius Radius Group 1

ES113-I 8 ES2550-II 8 PP453-IID 8 ES4379-IIC

• 'ES4102-IIC 0 3ES4101-IIC 0

3ES4104-IIC vc'S75-I 8

ES88-I 8 14.40" 14.40" 14.58" 14.40" 14.52" 16.08" 14 40 14.40" 14.40" 3 54t ~

4 05 lt 4.45" 4.56" 4 93 II 6.01" 6.71" 6.77" 6 77" Group 3

PP451-IE PP457-IE ES4375-IIC ES1900-IB PP629-II ES1875-IA ES100-I PP465-IB vc PP466-IB Yc PP468-IE PP469-IE PP450-IE PP497-I 14.58" 14 58" 40><

14 40ss 11.64" 14.52".

14 40"

] 4 58II

] 4 58lt

] 4 52lt

14. 52" 14.58" 11.64"

10. 25ss 10.25" 10.32" 10.38" 8.48" 10.88" 11.25" 11.51" 11.51" 12.01" 12.01" 12.19" 11.04" Group 2

PP493-II ES4404-IID

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PP637-II PP625-I PP456-IE PP462-IE PP463-IE 3PP734-II PP454-IID 14.40" 14.40" 11.64" 11 64" 14.52" 14.52" 14.52" 11 64" 14 58" 7.69" 8.27" 7.13" 7.22" 9 ]6ll 9.25 9.25" 7 44II 9.66"

• = These cables were not tested per SEMI-65 because they are diesel generator neutral ground cables and therefore do not appear in Table 2.

8 = These five cables, in Group 1, operate at full system voltage.

These four cables, in Group 1, operate at a reduced voltage or near zero voltage.

3.0 Su ort of Vertical Cables Page 7 of 9 3.1 Walkdown Inspection Results The action recommended in the Summary Report (Reference

1) for closure of the Vertical Cable Support issue was the performance of a walkdown of class 1E medium voltage cables, using TVA's General Construction Specification 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.

A walkdown inspection was performed as recommended.

Thirteen class 1E 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-I, ES141-I, ES13-I, and ES2641-II) are, being replaced to resolve other issues prior to Unit 2.restart and therefore were excluded from the testing program.

The remaining eight-were Hi-Pot'ested as previously discussed.

All eight cables met the acceptance criteria of'EMI-65 (Reference 4).

3.3 Disposition of Existing Vertical Support Conditions Seven class 1E cables were technically justi'fied in Reference 7 to remain installed with unsupported vertical drops greater than recommended by Article 300-19 of the National Electrical Code 1987.

The justification is based on the same method used for the unsupported vertical cable concern identified in the Technical Evaluation Report for TVA's Sequoyah Nuclear Plant (Reference 8).

This method calculated static sidewall bearing pressure values using equations recommended by the Kerite Company and the Okonite Company.

The sidewall pressures are less than the maximum recommended by Kerite and Okonite.

These seven cables are shown in Table 4.

One remaining cable (ES2513-II) has been modified to add a support, in accordance with the requirements of General Construction Specification G-38.

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

Table 4

STATIC SIDEWALL BEARING PRESSURE VALUES FOR JUSTIFICATION OF VERTICAL CABLE DROP Page 8 of 9

CABLE MARK NO.

OD (Inches)

DS E12.1.13 CABLE LB/FT VERT DROP FT.

COND SIZE/

BEND RAD IN.

KERITE OKONITE P

SWP PP453-IID 3PP734-II ES50-I ES2550-II PP451-IE PP450-IE PP497-I WNC WNB WNB WNB WNC WNC WNB 1.136 1.04 1.04 1.04 1.136 1.136 1.04 1.215

.899

.899

.899 1.215 1.215

.899 28.08 30.42 28.58 23.83

25. 17

25. 17 26.00 3"/12.07 3"/12.75 3s'/13.27 3"/11.47 3"/15.76 3"/15.76 3"/15.76 14.9 12.4 11.27 10.78 10.25 10.25 8.56 101.76 77.42 69.70 67.24 69.86 69.86 53.39 Okonite maximum recommended SWP (lb/ft) for medium voltage cables

= 120 lbs/ft Kerite maximum recommended P (lb/in ) for medium voltage cables

= 50 lbs/in 4.0 USE OF CONDULETS FOR PULL POINTS FOR LARGE 600V CABLES 4.1 Corrective Actions As, recommended in the Summary. Report, (Reference 1), all eight of the circuits identified as 3-400 MCM cables which are installed in three inch conduit and utilizing standard format condulets as pull points will be replaced prior to Unit 2 restart.

These raceways are being reworked to increase the conduit size to four inches 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 BFN Site Procedures were issued to prohibit the use of standard condulet bodies as pull points for 300-MCM and larger low voltage power cables.

5.0 CONCLUSION

S For the issues

above, TVA has completed an aggressive program of walkdowns, inspections,

testing, and recurrence control to ensure that safety related cables will perform their required function.

A

Page 9 of 9

6.0 REFERENCES

1. Browns Ferry Nuclear Plant Evaluation of Browns Ferry Nuclear Plant Cable Installation Concerns Summary Report (B22890322012) 2.

TSD E180 Cable Pulling Issues, Cable Bend Radius and Vertical Drop Analysis (B22881111243)

3. Letter to U. S. Nuclear Regulatory Commission Browns iFerry Nuclear Plant

Response

to Request for Additional Information on Electrical Issues (TAC62260)

(L44881209806)

4. Special Electrical Maintenance Instruction SEMI-65 R3

5. General Construction Specification G-38 SRN-83 (B22900607012)

"Variance Number 16-5kV Bend Radius Violations"

6. Cable Issues Supplemental Report Cable Testing (B22880923005

)

7. G-38 SRN 32 (B22890112002)

"Variance Number 5-5kV Vertical Support Violations"

8. Technical Evaluation Report "Evaluation of Sequoyah Units 1 and 2

Cable Pulling and Bend Radii Concerns" dated March 9, 1987 9.

TVA Electrical Design Standard.E13.6.2 R2 "Raceways Use of Conduit Bodies in Conduit Systems" (B43890725908)

ENCLOSURE 2

SUMMARY

LIST OF COMMITMENTS 1.0 The five cables that operate at full system voltage in Group 1 of the bend radius evaluation will be reworked to correct the bend radius conditions during the next unit 2 refueling outage.

2.0 Group 2 cables will be tested to the requirements of SEMI-65 during the next scheduled unit 2 outage and subsequent outages to establish a trend analysis.

BFN plans to evaluate the trend analysis at the end of three outages to determine the need for continuing this analysis.

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 startup from the next scheduled unit 2 refueling outage.