ML18038A913

Responds to NRC Ltr Re RAI on Medium Voltage Cable Bend Radius Issues

ML18038A913
Person / Time
Site:	Browns Ferry
Issue date:	09/15/1994
From:	Salas P TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-M86253, TAC-M86254, TAC-M86255, NUDOCS 9409260160
Download: ML18038A913 (15)

Text

R.IC3 R.I MY'CCELERATED RIDS PROCESSING)

REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9409260160 DOC.DATE: 94/09/15 NOTARIZED: NO DOCKET FACIL:50-259 Browns Ferry Nuclear Power Station, Unit 1, Tennessee 05000259 50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 50-296 Browns Ferry Nuclear Power Station, Unit 3, Tennessee 05000296 AUTH.NAME AUTHOR AFFILIATION SALAS,P.

Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION R

Document Control Branch (Document Control Desk)

SUBJECT:

Responds to NRC ltr dtd 940701 re RAI on medium voltage cable bend radius issues.

DISTRIBUTION CODE:

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TITLE: TVA Facilities Routine Correspondence NOTES:

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1 RECIPIENT ID CODE/NAME WILLIAMS,J.

FILE CENTER 09, OC'FDCB'ES/DE/SSEB/SES NRC PDR COPIES LTTR ENCL 1

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N NOTE TO ALL"RlDS" RECIPIENTS:

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Tonnossoo Valley Authority. Post Offico Box 2000, Decatur, Afabama 35609 September 15, 1994 U.S. Nuclear Regulatory Commission ATTN:

Document Control Desk Washington, D.C.

20555 Gentlemen:

In the Matter Of Tennessee Valley Authority Docket Nos.

50-259 50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN)

UNITS 1~

2q AND 3 REPLY TO NRC REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING MEDIUM VOLTAGE CABLE BEND RADIUS ISSUES (TAC NOS ~ M86253q M86254~

AND M86255)

The purpose of this letter is to respond to NRC's letter dated July 1,

1994, RAI regarding medium voltage cable bend radius issues.

Specifically, NRC requested TVA to:

(1) justify why the Appendix R function for cable PP453-II will be fulfilled, given the potentially degraded condition of this cable because of excessively tight bend radius; and (2) provide information on medium voltage cables that are classified as non-safety related, but relied upon to fulfill regulatory requirements.

The regulatory requirements addressed in the RAI are:

Appendix R, Station Blackout, (SBO) and Anticipated Transient Without Scram (ATWS).

TVA conforms to the appropriate regulatory and Quality Assurance requirements for non-safety related equipment, required to support an Appendix R,

SBO, and ATWS event.

The enclosure to this letter contains specific details concerning the NRC requested information.

There are no commitments contained in this letter. If you have any questions please contact me at extension (205) 729-2636.

Since Pedro Sa s

Manager of Site Licensing Enclosure 94092b01b0 940915 PDR ADOCK 05000259 p

.PDR

@DE

U.S. Nuclear Regulatory Commission Page 2

September 15, 1994 Enclosure cc (Enclosure):

Mr. Mark S. Lesser, Section Chief U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637

Athens, Alabama 35611 Mr. J.

F. Williams, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852

ENCLOSURE TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

UNITS iq 2g AND 3

RESPONSE

TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING MEDIUM VOLTAGE CABLE ISSUES (TAC NOS M86253q M86254q Am M86255)

PURPOSE AND BACKGROUND This enclosure provides TVA's reply to NRC's July 1,

1994, request for additional information regarding medium voltage cable issues.

NRC requested TVA to provide justification for why the Appendix R function for cable PP453-II will be fulfilled.

Further, NRC requested information on medium voltage cables that are classified as non-safety related, but relied upon to fulfill regulatory requirements.

Examples of regulatory requirements are Appendix R, Station Blackout, and Anticipated Transient Without Scram.

In order to address the cable installation issues at. BFN, TVA performed extensive reviews and walkdowns with the assistance of independent industry consultants.

The evaluations and conclusions of these reviews are documented in Reference 1.

Items 1 and 2 below are a restatement of NRC's July 1,

1994, request for additional information followed by TVA's response.

ITEM 1 ~

NRC REQUEST "Provide justification for why the Appendix R function for cable PP453-II will be fulfilled, given the potentially degraded condition of this cable because of excessively tight bend radius."

TVA RESPONSE I

Cable PP453-II was included in safety-related walkdowns for Unit 2 restart.

The tight bend of 4.45" (3.7 X OD) for this cable is located in a pullbox in Unit 2 Reactor Building, El.

593 which is a harsh environment area during a design basis accident (DBA).

The area normal'verage temperature is 80 degrees (F).

TVA has performed Load Cycle and Corona testing on this vintage cable with bend radius of six times the OD imposed.

This testing was patterned after an Association of Edison Illuminating Company CS5-87 design qualification protocol used to establish the integrity of the shield/insulation interfaces.

The test exposed the cable to multiple cycles of high current while under an elevated voltage stress.

TVA modified the protocol by performing the tests on cable bent to six times rather than on straight, lengths as permitted by the specification.

The conclusions of the test showed favorable results.

Interfacial disruption and material degradation did not exist when the cable bends were inspected.

TVA performed this testing on old cable that had been in storage, rather than new cable that is tested by the manufacturer.

Cable PP453-II also received a High Potential (Hi-Pot) test during BFN Unit 2 restart activities.

At the time of this

test, the cable had been installed approximately 15 years.

The Hi-Pot test results were satisfactory.

Cable PP453-II met the acceptance criteria of 1.0 polarization index for leakage current.

The cable configuration has not changed since it was installed during construction approximately 20 years ago.

The cable bend is located where conditions that could possibly cause elongation of insulation material or separation of tape shielding will not occur.

While the bend for cable PP453-II is tighter than the parameter

tested, the Load Cycle and Corona test demonstrated a high degree of margin since the old cable sample tested met new cable requirements even when bent.

Additionally, this circuit is not normally energized thus heat degradation due to loading is not a concern.

TVA considers that cable PP453-II, with its slightly tighter bend is capable of performing its Appendix R function for the following reasons.

First, the Load Cycle and Corona testing was successful.

Second, Hi-Pot testing was satisfactory.

Third, cable PP453-II is in a location where it will be undisturbed.

Fourth, it will'operate for relatively short duration during an Appendix R event.

ITEM 2 ~

NRC REQUEST "Discuss the effect of cable installation deficiencies on other cables which are classified as non-safety-related, but are relied upon to fulfillregulatory requirements such as Appendix R, station blackout, or anticipated transients without scram.

Note that this request is not limited to the bend radius issue.

Provide a justification which demonstrates the fulfillment of regulatory requirements."

E-2

TVA RESPONSE Zn general, BFN cables were installed using standard industry practices applicable during the time frame of installation.

Walkdown inspections identified good craftmanship as compared with other nuclear stations of BFN vintage.

These observations were made based on inspections which were not restricted to Class XE raceways.

TVA investigated five potential cable issues for the restart of BFN Unit 2.

The issues are described

below, along with TVA response.

2-l.

Sidewall Bearing Pressure TVA addressed the excessive cable sidewall bearing pressures during the resolution of cable installation issues for BFN Unit 2.

Physical tests were conducted to establish the acceptable sidewall pressure limits.

These limits were used as acceptance criteria when calculating expected sidewall bearing pressures of selected conduits.

The conduits were selected during the walkdown documented in Reference 2, Section 5.

These conduits were selected because they contained more degrees of bend than allowed by TVA's criteria.

Based on acceptable results from these sidewall bearing pressure calculations, TVA determined that excessive sidewall bearing pressures did not occur due to TVA's past conduit and cable installation practices.

Basically, conduits were installed in

straight, short runs with minimal bends.

Cable installation practices and materials for safety-related and non-safety related cables were the same.

2-2 Cable Jamming TVA determined that cable damage due to jamming was not evident.

This determination was based on inspections performed during the walkdowns documented in Reference 2, Section 5.3.

The walkdown team members had total access to plant areas.

This was possible since all three units were shutdown.

Although the walkdown was primarily focused on Class 1E cables, general observations were made of all raceway conditions.

The conditions which would have permitted damage by cable jamming did exist.

Those conditions which would have permitted undetected jamming did not occur.

BFN's compact design enabled

raceways, or conduits, to be installed in straight, short runs with minimal bends and an abundance of pull boxes permitted easy cable installation.

E-3

2-3 Cable Pullbys The issue of pullbys was initially addressed by, the walkdown team in Reference 1, Section 5.2.

Reference 1 concluded that pullby damage was not evident.

This was credited to the abundance of cable pulling lubricant, the absence of braided ropes in the

raceways, and lack of cable jacket damage observed during the walkdowns.

Also, plant layout and short runs of conduits contributed to the absence of damage.

After the discovery of pullby damage at Watts Bar, TVA expanded the scope of the pullby program to identify the cables judged to have the highest credible chance of having sustained pullby damage.

To insure that the testing included specimens which were representative of various cable constructions utilized at BFN, various voltage levels were selected.

Testin'g was performed on these selected specimens and it was concluded that pullby damage did not occur at BFN.

The expanded program involved loading numerous pull records into a data-base for analysis.

Since the occurrence of pullby damage is not affected by the classification of the cable, the records that were entered were not selected or biased due to their safety classification.

Considering past cable installation was performed to the same installation procedures, regardless of safety classification, the results and conclusion of this effort apply generically to BFN cables regardless of unit or safety classification.

2-4 Cable Bend Radii The same walkdowns that evaluated and inspected the other cable issues also encompassed medium voltage cable bend radius.

Some medium voltage cable bend radius violations were discovered.

These were addressed and evaluated by programs in place to support Unit 2 restart.

In addition, Load Cycle and Corona testing technically justified that cables with bend radius down to 6 times their OD could remain in their installed configuration.

The results of these walkdowns indicated that 5KV circuits were installed with relatively few violations of bend radius.

This was due to good cable installation practices associated with craftsmanship during construction.

Safety-related and non-safety related cables were manufactured from the same materials and were installed in the same manner.

For those bends that required further analysis and evaluations, technical justification was required for the cable to continue in service.

2-5 Vertical Supports The walkdowns performed to evaluate various cable issues for Unit 2 restart also encompassed vertical drop of medium voltage safety-related cables.

Cables that did not meet the vertical drop criteria were documented and technically justified in accordance with BFN procedures.

Overall, BFN cables were adequately supported even though they did not meet support spacing requirements.

2-6 CONCLUSION The walkdowns and evaluations provided TVA with assurance that the non-safety related conduits and cables were installed to the same requirements as the safety-related cables.

Again, this was attributed to good craftsmanship during construction of BFN and the relatively short runs of conduit associated with these cables.

The above cable installation issues were reviewed and accepted by NRC for BFN Unit 2 restart.

Refer to Section 3.11.5 of NUREG-1232, Volume 3, Supplement 2.

3 '

REV1EW OF MEDIUM VOLTAGE CABLES ASSOCIATED WITH REGULATORY ISSUES TVA reviewed the medium voltage cables associated with the regulatory issues.

These cables are in a harsh environment in the event of DBA.

None of the following regulatory issues result in a DBA nor is a DBA required to be postulated to occur concurrently.

3-1 APPENDIX R TVA performed a review of BFN's Appendix R medium voltage cables.

TVA concluded that Appendix R cables are safety-related with the exception of cable PP453-II.

This cable is an intertie cable which is used to parallel diesel generators D and 3D or to power Shutdown Board D during a Unit 2 Appendix R event.

BFN does not take credit for this cable for shutdown of the units from any design basis accident, therefore, it is classified as non-safety related.

Cable PP453-II is discussed in Item 1.

3-2 STATION BLACKOUT (SBO)

TVA performed a review of walkdown data for BFN units 1, 2, and 3 medium voltage cables available for SBO.

TVA concluded that two cables were not inspected.

However, the two SBO medium voltage cables were routed in the same cable tray raceway as cables which were walked down.

The results documented during the E-5

walkdowns confirm that all bends were bounded by the Load Cycle and Corona test performed for bend radius conditions of the safety-related cables.

This same walkdown confirmed that the medium voltage SBO cables have vertical drop conditions less severe than those justified for the population of class IE, safety-related cables.

Since these cables are routed in cable trays, sidewall bearing pressure, cable

jamming, and pullby's are not a concern.

3-3 ANTICIPATED TRANSIENTS WITHOUT SCRAM (ATWS)

There are no medium voltage cables associated with ATWS.

However, there are non-safety related low voltage cables associated with the ATWS system.

The non-safety related cables are installed in system 85 (Control Rod Drive) associated with alternate rod injection (ARI) valves, system 63 (Standby Liquid Control) and system 68 (Reactor Water Recirculation).

The system 85 ARI valves and system 68 components were added by new design prior to BFN Unit 2 restart, thus the cables were installed per General Engineering Specification G-38, which contains improved installation requirements to prevent cable installation damage.

TVA researched the As-Constructed drawings and concluded that the ATWS non-safety cables for system 63 are those associated with SLC pumps 2A and 2B.

These cables are fed from the 480V Shutdown Boards located on Elevation 621 of the Unit 2 Reactor Building.

The pumps are located on Elevation 639 of Unit 2 reactor building.

Since the difference in floor elevation is only 18 feet, the allowable vertical drop of 25 feet without support is not exceeded.

Based on the raceway size, the cables feeding the SLC pumps are in cradle formation without a jam condition and the standard bend radius for a 1.5" conduit provided an adeguate pulling radius for installation.

Based on the limited length of the raceway, it is highly unlikely that the maximum allowable pulling tension of 784 pounds (based on sidewall pressure limits) was exceeded.

Further, it is highly unlikely that damage due to sidewall bearing pressure exists in the cables associated with the SLC pumps.

TVA performs periodic system operability verification for ATWS-Recirculation Pump Trip and SLC system in accordance with BFN technical specifications.

Also, TVA performs functional tests of ARI solenoid valves which provide positive indication of valve operation.

This testing is performed in accordance with site surveillance instructions once per refueling cycle.

E-6

4 0

REGULATORY REQUIREMENTS 4-1 APPENDIX R TVA maintains an Appendix R program in accordance with the applicable sections of 10 CFR 50 Appendix R.

BFN Appendix R program ensures that the required safe shutdown equipment is available to ensure safe shutdown during an Appendix R event.

This program ensures that if equipment is not available, appropriate actions and/or compensatory measures are established in order to ensure safe shutdown.

In addition, this includes appropriate QA requirements.

STATION BLACKOUT (SBO)

The regulatory requirements for SBO are described in 10 CFR 50.63.

NRC issued Regulatory Guide (RG) 1.155, Station Blackout which describes means acceptable to the NRC Staff for meeting the requirements of 10 CFR 50.63.

RG 1.155 provides the SBO regulatory requirements and quality assurance guidance for non-safety systems and equipment.

BFN Unit 2 is in compliance with the SBO rule as stated in Reference 3.

BFN Units 1 and 3 will comply with the SBO rule prior to restart of each unit as stated in Reference 3.

4-3 ATWS 10 CFR 50.62 provides the regulatory requirements for ATWS.

10 CFR 50.62 does not require ATWS equipment to be safety related.

Therefore, systems and equipment required by 10 CFR 50.62 do not have to meet all the stringent requirements normally applied to safety-related equipment.

This position is consistent with Generic Letter 85-06, Quality Assurance Guidance for ATWS Equipment that is not safety related.

However, equipment installed in accordance with the ATWS rule is required to be diverse from the existing reactor trip system.

TVA conforms with the ATWS diversity rule for BFN Unit 2 as stated in Reference 4.

TVA will install diversity designs similar to BFN Unit 2 on BFN Unit 1 and 3

prior to restart of the respected units as stated in TVA response Reference 5.

5 '

CONCLUSION TVA concludes that non-safety related cables required to support Appendix R, Station Blackout, and ATWS are installed in a manner which will allow them to perform their design function.

TVA considers that E-7

the non-safety related cables for BFN were installed in the same manner as those classified as safety-related.

TVA also considers that cables are reliable and available to meet their associated regulatory requirements.

The issues of sidewall bearing pressure,

jamming, pullbys, bend radius, and vertical supports were addressed sufficiently based on the broad scope of walkdowns associated with BFN Unit 2.

E-8

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REFERENCES 1.

TVA letter to NRC dated July 18,

1988, Browns Ferry Nuclear Plant (BFN) Resolution of Cable Installation Issues 2

~

TVA letter to NRC dated June 19,

1988, Browns Ferry Nuclear Plant (BFN) Unit 2 Electrical Cable Installation Revised Walkdown and Summary Reports (TAC No.

62260) 3.

TVA letter to NRC dated October 15,

1992,

Response

to NRC Supplemental Safety Evaluation on the Conformance of BFN with the Station Blackout (SBO) Rule 4 ~

5.

TVA letter to NRC dated June 14,

1993, Completion of Anticipated Transients Without Scram (ATWS) Rule (10 CFR 50.62)

Commitments For Unit 2.

TVA letter to NRC dated November 29, 1990, Anticipated Transient without Scram (ATWS)

Response

to NRC Followup Items During ATWS Inspection E-9

1