ML20077A313

Forwards Program for Resolving Conduit & Conduit Supports Issue Prior to Restart of Units 1 & 3 for Info,Per

ML20077A313
Person / Time
Site:	Browns Ferry
Issue date:	05/06/1991
From:	Wallace E TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9105090280
Download: ML20077A313 (6)

Text

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A leonessee Vahey Auttety i01 MAe Sreet Chatawga leonessee 3702 MAY 061991 U.S. Nucicar Regulatory Commission ATTN Document Control Desk Washington, D.C. 20555 Centlemen:

In the Matter of ) Docket Nos. 50-259 Tennessee Valley Authority ) 50-296 BROUNS FERRY NUCLEAR PLANT (BFN) - PROGRAM FOR RESOLVING CONDUlT AND CONDUIT SUPPORTS ISSUE PRIOR TO THE RESTART OF UNITS 1 AND 3

Reference:

TVA letter, dated January 9,1991, Plans for the Return to Service of BFN Unit.s 1 and 3 As part of the referenced letter, TVA committed to provide the NRC Staff with the action plan for dispositioning the conduit and conduit supports issue at BFN Units 1 and 3. Enclosure 1 to this letter provides a summary of this issue, a review of the Unit 2 resolution, a discussion of lessons learned, and a description of how this issue will be resolved on Units 1 and 3. This submittal is provided for informational purposes only. No NRC action is specifically requested.

A summary list of commitments contained in this letter is provided in Enclosure 2. If you have any questions, please telephone Joesph E. McCarthy, Unit 3 Licensing Manager, at (205) 729-3604.

Very truly yours, TENNESSEE VALLEY AUTHORITY

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Nuclea Li ensing and Regulal y Affairs Enclosures

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

Ms. S. C. Black, Deputy Director Project Directorato 11-4 U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike, Rockville, Maryland 20852 NRC Resident inspector I Browns Ferry Nuclear Plant l Route 12 Box 637 Athens, Alabama 35609-2000 i

Mr. Thierry M. Ross, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Project Chief U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323

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e ENCLOSURE 1 BROWNS. FERRY NUCLEAR PLANT (BFN) - UNITS 1 AND 3

' CONDUIT AND CONDUIT SUPPORTS CORRECTIVE ACTION PLAN ISSUE

SUMMARY

concerns regarding the adequacy of conduit and conduit supports were originally raised in NRC Inspection Repnre 83-09, dated April 18, 1983. The inspection identified a concern regarding the construction practice for the installation of field routed electrical conduit supports not being in accordance with the applicable General Construction Specification. Conduit supports which did not meet the field routing criteria were identified.

Therefore, the adequacy of conduits to perform their safety function after a design basis earthquake could not be assured.

The following is a summary of the more significant TVA/NRC correspondence which documents the resolution of this issue. This summary is provided in order to assist the NRC Staff if additional detailed historical information is required.

By letter dated July 31, 1986, NRC requested TVA provide background information and a description of the corrective actions for the BFN conduit qualification program. TVA submitted the requested background information and a description of TVA's corrective action program by letter, dated April 8, 1987. Supplemental programmatic information and a copy of the interim criteria for conduit and conduit supports was provided by TVA letter, dated May 27, 1988. NRC approved the interim operability criteria for conduits in a Safety Evaluation, dated July 26, 1988. By letter dated August 23, 1988, TVA responded to the Safety Evaluation open items and concerns.

Monitoring and evaluation of TVA's corrective actions in documented in:

Inspection Report 88-13, dated October 3, 1988, Inspection Report 88-38, dated April 19, 1989, Inspection Report 89-21, dated June 15, 1989, Inspection Report 89-29, dated September 20, 1989, and Inspection Report 89-42, dated February 26, 1990.

TVA responded to the open items in Inspection Report 88-13, by letter, dated January 18, 1989. The acceptability of TVA's program to evaluate the adequacy of conduite and conduit supports for Unit 2 was documented in Section 2.2.2.3 of NUREG-1232,. Volume 3, Supplement 1, dated October 24, 1989, and in the same section of Supplement 2, dated January 23, 1991. By letter dated April'16, 1991, TVA notified NRC that the-conduit support modifications required to satisfy the interim operability criteria -for Unit _2 restart were

-complete.

REVIEW OF THE UNIT 2 RESOLUTION OF CONDUlT AND OONDUiT SUPPORTS

'_In order _to resolve the concern regarding the adequacy of conduit and conduit supports,1TVA implemented an interim seismic qualification program. This program reviewed the conduit and-conduit supports required for Unit 2 operation, which were installed prior to May 1984. After May 1984, engineered conduit support drawings were utilized for conduit support installation. The engineered conduit: support drawings were produced in accordance with seismic design criteria and did not require re-inspection.

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l Page 2 of 3 ENCLOSURE 1 (CONTINUED)

BROWNS FERRY NUCLEAR PLANT (BFN) - UNITS 1 AND 3 CONDUIT AND CONDUIT SUPPORTS CORRECTIVE ACTION PLAN The interim conduit and conduit support evaluation program at BFN involved the walkdown and evaluation of approximately 100 miles of conduit and 20,000 supports. Trained and experienced walkdown personnel visually reviewed each conduit and conduit support and made a determination (using good engineering judgement) of the seismic adequacy of the installed configuration. If, in the evaluators opinion, the adequacy of the commodity being evaluated was questionable, a discrepancy was written for further evaluation.

The inspection required to return Unit 2 to service covered the majority of the conduite at the BFN site. This inopection included common plant areas and the specific areas of the Reactor Building which contained conduits required to achieve hot shutdown of Unit 2 in the event of a design basis earthquake.

All conduits and conduit supports in these areas were inspected regardless of the conduits safety classification or unit. The common plant areas inspected were

1) Diesel Generator Building,

2) Intake Pumping Station and associated tunnels,

3) Control Bay,

4) Off Gas Treatment Building, and the

5) Standby Gas Treatment Building.

Initially, the conduit and conduit supports were evaluated against the requirements of the original TVA General Construction Specification.

Subsequently, TVA initiated a full-scale shaker table test to develop a more realistic acceptance criteria. Each discrepancy was evaluated against thin new criteria.

In June 1986, the Seismic Qualification Utility Group (SQUG) along with the Senior Seismic Review Advisory Panel (SSRAP) decided to include cable tray and conduit systems in the scope of the program for the resolution of Unresolved Safety Issue (USI) A-46, Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors. The prog am to resolve USI A-46 is based on screening criteria and data gathered from previous earthquakes.

This program has been accepted in principle by NRC as documented in Generic Letter 87-02, dated February 19, 1987.

TVA's identified discrepancies were compared to this seismic experience data base. All outliers were corrected by modifications or were addressed by other ongoing qualification programs. At the conclusion of these activities, 430 modifications were required to bring Browns Ferry Unit 2 into compliance with the interim criteria. Approximately 230 of these modifications were in the Reactor Building. As documented in NUREG-1232, Volume 3, Supplement 2, the following Unit 2 post-restart actions remain open:

1) TVA will evaluate and upgrade, as needed, the aluminum conduit and supporte qualified to the interim criteria against the Unresolved Safety Issue (USI) A-46 program guidelines, and

2) TVA will evaluate and upgrade, as needed, the steel conduit and supports qualified to the interim criteria against the Unresolved Safety Issue (USI) A-46 program guidelines.

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ENCLOSURE 2 BROWNS FERRY NUCLEAR PLANT - UNITS 1 AND 3

SUMMARY

OF COMMITMENTS TVA's interim program for the esiemic qualification of the remaining Unito 1 and 3 conduit and conduit suppvrts will consist of engineering evaluations of these commodities with a focus on the attributes =which resulted in modifications on the Unit 2 program. The resolution of identified discrepancies will be implemented prior to the restart of Unita 1 and 3, respectively.

- TVA's final program for the seismic qualification of the remaining Unito 1 and 3 conduit and conduit supporte will be an evaluation and upgrade, as needed, of the Units 1 and 3 aluminum and steel conduit and supporte against the USI A-46 program guidelines.

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ENCLOSURE 1 (CONTINUED)

BROWNS FERRY NUCLEAR PLANT (BFN) -

UNITS 1 AND 3 CONDUIT AND CONDUIT SUPPORTS CORRECTIVE ACTION PLAN i

i DISCUSSION OF LESSONS LEARNED FROM UNIT 2 CONDUlT AND CONDUli SUPPORTS l TVA's program for the resolution of conduit support discrepancies resulted in modifications for the following generic attributes o Conduit Overspan Conditions a Between supports e Cantilevers e In-line junction boxes e Support Deficiencies e Unistrut frames and welds e Angle framos e Multiple cantilever supports  ;

l e Hardware Deficiencies The conduit itself was determined to be of rugged construction and no modifications to conduit were required.

DESCRIPTION OF THE UNITS 1 AND 3 PROGRAM FOR CONDUlT AND CONDUIT SUPPORTS TVA's interim program for the setemic qualification of the remaining Units 1 and 3 conduit and conduit supports will consist of engineering evaluations of these commodities with a focus on the attributes which resulted in

modifications in the Unit 2 program. These inspections will include the l Units 1 and 3 drywells and the areas of the Reactor Building which were not included in the Unit 2 program. Discrepancies will be evaluated against the I criteria and meismic experience database used in the Unit 2 program. The resolution of identified discrepancies will be implemented prior ta the

! restart of Unita 1 and 3, respectively.

l TVA's final program for the seismic qualification of the remainiig Unito 1 i and 3 conduit and conduit supports will be in accordance with the Unit 2

! post-restart commitmente. TVA will evaluate and upgrade, ao needed, the l Unita 1 and 3 aluminum and steel cenduit and supports against the USI A-46 l

program guidelines. When the generic resolution of USI A-46 is issued, TVA l

may evaluate the implementation the final program for the seismic qualification of conduit in lieu of the interim qualification.

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