ML20077N573

Final Deficiency Rept Re Westinghouse DS-416 Reactor Trip Switchgear Breakers.Initially Reported on 830331. Westinghouse Will Replace Undervoltage Trip Attachments. Unit 1 Breakers Repaired.Also Reported Per Part 21

ML20077N573
Person / Time
Site:	Vogtle
Issue date:	09/06/1983
From:	Foster D GEORGIA POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
REF-PT21-83 10CFR-050.55E, 10CFR-50.55E, GN-254, NUDOCS 8309130167
Download: ML20077N573 (3)

Text

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• Geo#g;a Power C7mpany 333 Piedmont Avenue Attanta. Georgia 30308 4 , , Sn Telephone 404 526-7726 'i ' O ' -

Maihng Address- [ ]j Post Office Box 4545 g8 <t, Atlanta Georg a 30302 /) '

cgyia Power Vic Pre rd nt and General Manager Vogt!e Project September 6,1983 United States Nuclear Regulatory Commission File: X7BG03-M40 Office of Inspection and Enforcement Log: GN-254 Region II-Sutie 3100 101 Marietta Street Atlanta, Georgia 30303

Reference:

Vogtle Electric Generating Plant-Units 1 and 2 50-424, 50-425; Westinghouse DS-416 Reactor Trip Breakers, GPC Letter GN-235, dated June 13, 1983 Attention: Mr. James P. O'Reilly Gentlemen:

Georgia Power Company has completed its evaluation and determined that the above referenced concern represents a significant deficiency for the Vogtle Electric Generating Plant-Units 1 and 2. Westinghouse had pre-vinusly informed the NRC of the existence of this problem in their letter NS-EPR-2744, dated March 31,1983. Since Vogtle was referenced in this letter, Georgia Power Company considers this Westinghouse letter to constitute notification of a substantial safety hazard as required in Part 10 CFR 21. Enclosed is a copy of our evaluation.

This response contains no proprietary information and may be placed in the NRC Public Document Room upon receipt.

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D. O. Foster D0F/REF/cc enclosure xc: U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C. 20555 l R. J. Kelly R. H. Pinson E. D. Groover R. E. Conway B. M. Guthrie L. T. Gucwa G. F. Head R. A. Thomas M. Malcom J. T. Beckham Jr. J. A. Bailey G. Bockhold D. N. Mactemore 0. Batum P. D. Rice D. E. Dutton H. H. Gregory III J. L. Vota i W. F. Sanders R. E. Fo1ker OniiCLgG6 8309130167 830906 t

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e g EVALUATION FOR A SIGNIFICANT DEFICIENCY Westinghouse DS-416 Reactor Trip Switchgear Breakers Initial Report:

On May 5,1983, Georgia Power Compan) notified the NRC of a potential de-ficiency concerning the reactor trip switchgear breakers. In an interim report dated 6/13/83, Georgia Power. Company stated a final report would be submitted by September 9,1983. ,

• Background Information:

In their letter US-EPR-2744 dated 3/31/83, Westinghouse informed the NRC that operating utility customers had been informed of the potential for intermittent malfunction of the reactor trip.switchgear that employs the DS-416.undervoltage (UV) trip device. ~In this letter,' Westinghouse stated that they were requesting additional information from the operating utilities to assist in their evaluation of this unreviewed safety question.

Westinghouse also enclosed a table indicating all units under construction or currently operating:that would employ the DS-416 breakers. Vogtle Electric Generating Station-Units 1 and 2 was included on this list.

On April 20, 1983, Westingh 'se advised the NRC that the potential for mis-operation of the DS-416 ret or trip switchgear undervoltage attachments

. was reportable under 10 CFR 21 and 10 CFR 50.55(e).

Additional -information is also contained in I & E Information Notice 83-18,

" Failures of the Undervoltage Trip Function of Reactor Trip System Breakers."

I & E Bulletin 83-04 was directed to plants using RTS breakers with under-voltage trip devices other than those using Westinghouse DB-type breakers (see I & E Bulletin 83-01). Failures of Westinghouse type DS-416 breakers were experienced during the tests required by Bulletin 83-04. At McGuire, a Westinghouse DS-416 breaker intermittently failed to trip on successive tests.

Engineering Evaluation:

The' design of the reactor trip switchgear for the Vogtle Electric Generating Station feeds the automatic protection signals to the undervoltage trip attachment of the reactor trip breakers. The manual signals are fed to the undervoltage trip and to a shunt trip coil of each breaker. The undervoltage trip attachment on the reactor trip switchgear allows for a safe shutdown of the reactor when power to the switchgear is below acceptable limits.

A potential for misoperation exists based on the reported malfunctions. .The deviations from the recommended clearances could increase the potential for misoperation of the attachment, thereby creating a condition wherein the reactor trip switchgear might not open on automatic demand from the reactor protection system.

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The Westinghouse evaluation also indicated a discrepancy in the design of "the retaining ring. The groove in the shaft receiving the retaining ring was not increased in width to be consistent with an earlier (1972) retaining ring design change. The new retaining ring'is wider than the original design and does not seat properly in the existing grooves. This discrepancy increases

-the potential for malfunction of the DS-416 undervoltage attachment thereby creating a condition wherein the reactor trip switchgear might not open on

- automatic demand from the reactor protection system.

Review.for Reportability:

Part 10 CFR 50.55(e) requires the reporting of. a deficiency found in design and construction which, were it to have remained uncorrected, could have adversely affected the safety of operation of the nuclear power plant at any time through- ,

.out the expected lifetime of the plant. The data in the bulletins and informa-tion notice indicated that a breaker problem does exist that could affect plant safety.

This event also represents a significant deficiency in final design as approved and released for construction such that the final design does not conform to the criterion and bases stated in the safety analysis report.

Conclusion:

This 'conceni is reportable under 10 CFR 50.55(e). Westinghouse has already reported tha concern to the NRC as a Part 10 CFR 21 through their referenced correspondence to the NRC.

Corrective Action:

(1) Westinghouse has issued a technical bulletin addressing testing procedures for undervoltage and shunt trip mechanisms for model DB and DS circuit breaker shunts and undervoltage coils. Georgia Power Company will in-corporate the Westinghouse technical bulletin into' plant maintenance pro-cedures.

(2) Westinghouse has committed to replace the undervoltage trip attachments on DS-416 reactor trip switchgear.

(3) Unit 1 breakers have been repaired. Unit 2 breakers are being held at the jobsite pending Westinghouse instructions. Georgia Power Company expects to have the Unit 2 breakers repaired and returned to the jobsite by July 31, 1984

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