ML20112H007

Ro:On 960528,detected Abnormal Metallic Impact Sounds. Caused by Confirmed Loose Part in Steam Generator. Engineering Evaluation Performed & Repairs & Modifications Scheduled for Next Refueling Outage

ML20112H007
Person / Time
Site:	Vogtle
Issue date:	06/10/1996
From:	Woodard J GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LCV-0797, LCV-797, NUDOCS 9606140081
Download: ML20112H007 (3)

Text

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• Georgia Power Company ,

333 Piedmont Avenue 4' ' Atlanta. Georgia 30308 Telephone 404 526-3195

• l Mailing Address 40 Inverness Center Parkway ,

l Post Of6ce Box 1295 Birmingham. Alabama 3s201 l i

Telephone 205 868-5086 'I J. D. Woodat d

• 8 0"*" **"" Y**

Senior Vice President LCV-0797 Docket No. 50-424 l

U. S. Regulatory Commission '

ATTN: Document Control Desk Washington, D. C. 20555 q Gentlemen:

1 VOGTLE ELECTRIC GENERATING PLANT l CONFIRMED LOOSE PART 14-DAY REPORT l l

In accordance with the requirements of the Vogtle Electric Generating Plant Final Safety Analysis Report and Regulatory Guide 1.133, Georgia Power Company submits the enclosed report concerning the discovery of a loose part. l Sincerely, J

JDW/TEW/ JAB

Enclosure:

Confirmed Loose Part Report xc: Georgia Power Comnany Mr. J. B. Beasley, Jr.

Mr. M. Sheibani NORMS U. S. Nuclear Regulatory Commission l Mr. S. D. Ebneter, Regional Administrator Mr. L. L. Wheeler, Licensing Project Manager, NRR l Mr C. R. Ogle, Senior Resident Inspector, Vogtle I

1400'.B 9606140081 960610 PDR ADOCK 05000424 PDR

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i VOGTLE ELECTRIC GENERATING PLANT - UNIT 1 l l CONFIRMED LOOSE PART 14-DAY REPORT i

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A. REQUIREMENT FOR REPORT 4

This report is required in accordance with the Vogtle Electric Generating Plant

[ Final Safety Analysis Report, Chapter 1.9, and Regulatory Guide 1.133, Section i C6. This regulatory guide requires the submittal of a follow-up report within 14 days of the initial notification of the confirmation of a loose part. The regulatory guide requires the report to include the following information:

1) a summary of data obtained in the manual and automatic data acquisition

modes;

2) a summary of the analysis, inspections, and correlations with operating data that were performed to evaluate data from the loose part detection program;

3) a summary of conclusions and a description of modifications or other actions planned or already performed to evaluate the safety implication of a loose part or to ensure that system and component safety functions are not impaired.

B. DESCRIPTION OF EVENT On May 28,1996, at 0648 EDT, a digital metalimpact monitoring system (DMIMS) alarm annunciator began to continuously alarm in the control room.

Various methods were employed to confirm the existence of a loose part in steam generator (SG) # 4. After obtaining a high confidence factor that a loose part existed, the NRC Operations Center was notified at 2157 EDT, and the unit was shutdown. Information required by Regulatory Guide 1.133, Section C6, is provided as follows:

1) An audio check detected abnormal metallic impact sounds and the DMIMS system report registered a high number ofimpacts above the alarm setpoint for channel 760 (SG #4 primary side). A tape recording was made and sent to a vendor for analysis. In addition, a printout from a test instrument recorded hits that resembled " textbook" examples of metal impacts. The vendor analysis concluded that a loose metal object was the cause of the impacts.

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VOGTLE ELECTRIC GENERATING PLANT - UNIT 1 CONFIRMED LOOSE PART 14-DAY RIi.PORT l

2) The SG #4 hot leg manway was removed and a loose metal object was found l inside. This object was a support pin nut from a control rad guide tube l assembly. The nut's locking device was found usaged into the bottom of a  ;

tube and was subsequently removed. A tidrd object believed to be a fragment i from the support pin nut, was fev.nin the SG #4 cold leg side. The support 4

pin from which the nut cmx is believed to be intact and captured in place in the reactor vessel. . A dowel pin that was attached to the nut could not be I

located. An ir.spection was performed of the SG #4 reactor coolant system hot )

leg with no loose parts found. The SG #4 lower tubesheet on the hot leg side l warimpacted by the loose object and numerous indications were noted. The I 4

other 3 SG hot leg side interior surfaces were examined with no signs of l damage.

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3) An engineering evaluation was performed to determine weld / pressure {

boundary integrity at the SG #4 lower tubesheet. The evaluation found no  !

defects that would preclude safe operation of the SG under both normal and accident conditions and the unit is being returned to power operation. Repairs and/or modifications to both the tubesheet and the control rod guide tube assemblies will be considered. Any such repairs / modifications would be likely to occur at the next refueling outage and a revision to this report would be submitted following their implementation.