ML20038B190

Forwards LER 81-016/01T-0.Detailed Event Analysis Encl

ML20038B190
Person / Time
Site:	Oconee
Issue date:	11/13/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20038B191	List: ML20038B190 ML20038B193
References
NUDOCS 8111240838
Download: ML20038B190 (2)

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31 NOV 18 ^8: 04 WILLIAM Q. PA R M C R, J R.

Vier Pecs.ocut 7gtg,no,ec AntA 704 aco paoouct.o November 13, 1981 373..o.3 Mr. James P. O'Reilly, Director U. S. Nuclear Regulatory Commission i Region II 101 Marietta Street, Suite 3100 l Atlanta, Georgia 30303 Re: Oconee Nuclear Station Docket No. 50-270 i

Dear Mr. O'Reilly:

Please find' attached Reportable Occurrence Report R0-270/81-16. .This report.is submitted pursuant to Oconee Nuclear Station Technical Specifi-cation 6.6.2.1.a(3), which concerns an abnormal degradation of the reactor coolant pressure boundary. This report describes an incident which is considered to be of no significance with respect to its effect on the health and safety of the public.

Reportable Occurrence Report R0-270/81-17 has been separated from.t ' y' / r report for clarity and is forwarded under separate cover. \

Ve y truly yours, (h(ft,; r 1), [ }s 3

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William O. Parker, Jr.

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Mr. W. T. Orders NRC Resident Inspector Oconee Nuclear Station 5

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DUKE POWER COMPANY OCONEE UNIT 2 Report Number: R0-270/81-16 Report Date: November 13, 1981 Occurrence Date: September 18, 1981 Facility: Oconee Unit 2, Seneca, South Carolina Identification of Occurrence: Tube leak in 2B Steam Generator Conditions Prior to Occurrence: Oconee 2 94% FP Description of Occurrence: On September 18, 19S1 at 1030 a steam generator (OTSG) tube leak of approximately 0.03 GPM was indicated by the Condensate Steam Air Ejector (CSAE) Offgas Radiation Monitor (2RIA-40). The CSAE Offgas Radiation Monitor indicated a step increase in the leak rate, to approximately 25 to 30 GPM, at 1529 that day.

Apparent Cause of Occurrence: The apparent cause of the OTSG tube leak was a circumferential crack of Tube 77-2 at the 15th tube support plate. This determination is based on a detailed analysis of the eddy current signal from Tube 77-2, and the previous history of this type of tube failure.

Analysis of Occurrence: The last eddy current test of Tube 77-2 was performed during the last refueling outage in March 1980. No indications were found on Tube 77-2 at the 15th tube support plate. Attempts were made to view the damaged area of the tube with fiber-optics. However, the equipment was unable to reach the damaged area of the tube. Assuming the tube is cracked 360 , a 10 mil separation has been calculated to give a leak of the magnitude seen during this event (25 to 30 GPM).

Personnel and systems adequately controlled this event and the releases were well within regulatory requirements. Thus, it is considered that the health and safety of the public were not adversely affected.

Corrective Action: A rapid unit shutdown was commenced at the time the step increase in the leak rate was indicated. The incident was declared an

" Unusual Event" due to the indicated leak rate of approximately 25 GPM. The unit was shut down, cooled down, and the reactor coolant loops were drained to stop the leak.

The leaking tube was identified to be Tube 77-2 which is the second tube from the outside periphery on the inspection lane. Eddy current testing of the lane region was conducted, which consisted of 3 rows on both sides of the

! inspection lane (approximately 360 tubes) . Tube 77-2 indicated a 100% thru-wall indication at the 15t' tube support plate.

The leaking tube was stabilized from the top and explosively plugged from the bottom. The leak test performed after plugging Tube 77-2 confirmed the leak was repaired. The eddy current testing of the inspection lane region confirmed that no other tubes were unacceptably degraded.