ML20148S314

Ro:On 970422,Oconee Unit 2 Was Shut Down Due to Leak in Rcs. Leak Was Caused by Crack in Pipe to safe-end Weld Connection at RCS Nozzle for HPI Sys A1 Injection Line.Unit 1 Was Shut Down to Inspect Hpis Injection Lines & Implement Ldst Mods

ML20148S314
Person / Time
Site:	Oconee
Issue date:	06/30/1997
From:	Hampton J DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9707080183
Download: ML20148S314 (5)

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• • *Dukehrr Contpany J W Herrna .

OconnNucle'arSite Ike hesutent P O. Box M39 (8641634990ifice Senna, SC292  ;

(864)M3564 Fax 1 DUKEPOWER l

June 30, 1997 l

U. S.: Nuclear Regulatory Commission  !

Attention: Document Control Desk l 4' Washington, DC 20555 '

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Subject:

Oconee Nuclear Station Docket Nos. 50-269, -270, -287 j Closure of Oconee Unit 1 High Pressure Injection (HPI) System JCO Oconee Unit 2 was shut down on April 22, 1997 due to a leak in the Reactor Coolant System (RCS). The leak was caused by a crack in the pipe to safe-end weld connection at-the RCS nozzle for the HPI System Al injection line. By letter dated April.28, 1997, Duke Energy Corporation (Duke) submitted a Justification for Continued Operation (JCO) of Oconee Units 1 and 3 based on the Oconee Unit 2 HPI line leak. Further information was supplied by Duke letters

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dated May 2, 3, 7, 8, 9, 12, 13, 16, 19, 20, and 22, 1997.

Following the shutdown of Oconee Unit 3 on May 3, 1997, the JCO-related information became applicable to Oconee Unit 1 only. In addition, submittals subsequent to the May 3, 1997, Unit 3 shutdown included commitments resulting from 'k the Letdown Storage Tank (LDST) level control' problem on Unit 3. I Region II issued a Confirmation of Action Letter (CAL) for j 1).

Units 1, 2, and 3 on May 5, 1997. At a public meeting at

'Oconee on May 16, 1997, Duke presented the actions that'were l

.being implemented to support restart of Oconee Units 2 and 3 l and the continued. safe operation of Oconee Unit 1. In a letter dated May 20, 1997, Duke confirmed that the actions requested in the May 5, 1997 CAL had been completed. By i letter dated May 22, 1997, the Region II Administrator I 9707080183 970630  ;

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i U. S. Nuclear Regulatory Commission June 30, 1997 Page 2 updated the CAL by indicating concurrence for restart of .

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! Oconee Units 2 and 3, and the compensatory actions for operation of Oconee Unit 1. In a letter dated May 29, 1997, f the staff stated that it judged Duke's commitment to shut >

down Oconee Unit 1 no later than June 14, 1997 to conduct L

L radiographic and ultrasonic examinations of the HPI .4ystem ,

injection linea and to perform compensatory actions associated with the LDST level monitoring system to be  ;

j prudent.

The commitments associated with the Unit 1 JCO have been ,,

completed. Unit i was shut down on June 13, 1997 to inspect l.

the HPI System injection lines and implement LDST l

! modifications. During this outage, radiographic tests of I the Unit 1 thermal sleeves verified that the sleeves were in '

position and that there has been no change in the thermal sleeve to safe-end gaps since 1983. Radiographic tests of the nozzle to safe-end welds, safe-end to pipe welds and pipe to valve welds were performed. Ultrasonic tests of the above welds, intermediate piping and nozzle inner radius were performed. Penetrant tests of the above welds, safe- >

end, and intermediate piping, as well as the warming line attachment welds on the Al and A2 injection lines, were completed. All inspection results were acceptabl2.  ;

These inspections exceed Generic Letter 85-20 requirements and the augmented inspection program recommendations of a B&W Owner's Group task force that were provided to the staff in a Duke letter dated February 15, 1983. Based on these ,

comprehensive inspections, Duke concludes that thers has l been no degradation in the thermal sleeves, nozzler, or adjacent piping associated with t;- HPI System injection lines on Unit 1. .

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U .' S. Nuclear Regulatory Commission l

June 30, 1997 l Page 3

.A modification has been implemented on oconee Unit 1 to add L separate reference legs for the LDST_ level transmitters and l add a redundant LDST pressure transmitter. Prior to the Unit 1 shutdown, Operations had implemented administrative-

[ controls to minimize thermal cycles on the HPI nozzles, l enhance, reactor coolant leakage detection measures, and i neriodically monitor the LDST level reference legs. Based on the corrective actions implemented during the outage, ^

these interim administrative controls are no longer considered as commitments. However, as described in previous correspondence to the staff, Duke has now implemented a temperature monitoring program for the HPI nozzles on-all three units. Data collected from this program will be used to establish a periodic inspection program for the-HPI nos les and adjacent piping and to evaluate changes in operating practices to assure that thermal cycling on these injection lines is appropriately

[ managed. Duke has also inspected all of the Unit-1 HPI System mil m.um flow orifices and. replaced the orifices for the 1A and 1B HPI pumps.

In addition _to closing the JCO, Duke would like to provide an update on the status of another commitment associated with the subject HPI System events. In a letter dated May 7, 1997, Duke stated'that, depending on the complexity of the computational fluid dynamics . (CFD) analysG.9, our expectation was that these analyses would be co mpleted by the end of June, 1997. The purpose of these analyses was to assist in the assessment of the time to initiate and propagate a flaw through the piping 11 of HPI nozzle l

j_ components. Based on a discussion with the vendor which is l performing these analyses, the work will not be completed by l the end of June, 1997. . Duke expects the CFD analyses to be

[ . completed by December 15, 1997. ,

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U. S. Nuclear Regulatory Commission .

June 30, 1997

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Page 4 l In summary, Duke has completed the actions necessary to close the JCO for Oconee Unit 1. Duke will continue to keep l

the staff apprised of the status of longer-term commitments )

associated with the HPI System events of April 22, 1997, and I May 3, 1997.

Please address any questions to J. E. Burchfield, Jr. at (864) 885-3292. l 1

Very Truly Yours, l

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7 J. W. Hampton i Site Vice President l l

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U. S. . Nuclear Regulatory Commission June 30, 1997 Page 5 ,

xc: L. A. Reyes, Region II l Regional Admistrator I M. A. Scott, Region II Senior Resident Inspector lP D. E. LaBarge, ONRR Project Manager ,

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