ML20009F494

Forwards LER 81-013/01T-0.Detailed Event Analysis Encl

ML20009F494
Person / Time
Site:	Oconee
Issue date:	07/14/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009F495	List: ML20009F494 ML20009F501
References
NUDOCS 8107310237
Download: ML20009F494 (2)

Text

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V DUKE Powmn COMPANY Powen rivatonwo 422 SouTu Cnuncu Stazzr. Caunt.otTz, N. C. asa42 0. 7C/

4 4'COpp W e L LI A M Q. PARKER.JR.

WCr P8ESictm? It'.C8MONg; Amta 704 sr c.. a.oovewo July 14, 1981 a n-4oe s Mr. James P. O'Reilly, Director G 4

U. S. Nuclear Regulatory Commission Region II

%~ t 4 101 Marietta Street, Suite 3100 j[,

Atlanta, Georgia 30303 97 JULyd 1981* 3 Re: Oconee Nuclear Station y,si"tawe# d Docket No. 50-269 g /

Dear Mr. O'Reilly:

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. to Please find attached Reportable Occurrence Report R0-269/81-13. This report is submitted pursuant to Oconee Nuclear Station Technical Specification 6.6.2.1.a(2) which. concerns operation less conservative than the least conservative aspect of a LCO, and describes an incident which is considered to be of no significance

with respect to its effect on the health and safety of the public.

Ve truly yours, /y -

G~

' William O. Pa er, Jr.

../>c 4 t

~# s JLJ:pw k

Attachment i

cc: Director Mr. Bill Lavallee Office of Management CProgram Analysis Nuclear Safety Analysis Center U. S. Nucle'ar Regulatory Commission P. O. Box 10412 Washington, D. C. 20555 . Palo Alto, CA 94303 4

sf 8107310237 E10714 PDR ADOCK G5000269.

5 FOR',

DUKE POWER COMPANY OCONEE NUCLEAR STATION Report Number: R0-269/81-13 Report Date: July 14, 1981 Occurrence Date: June 30, 1981 Facility: Oconee Nuclear Station, Seneca, South Carolina Identification of Occurrence: Deficiency Discovered in " Normal Power" Procedure Conditions Prior to Occurrence: Oconee 1 - Cold S/D Oconee 2 '100% FP Oconee 3 100% FP Dggeription of Occurrence: On three separate occasions _(October 29, 1980, April 9, 194t, and April 26, 1981) the backup function of the Isolating and Transfer Diodes 7 in the 125 VDC Instrumentation and Control System was disabled for all four channels on all three Oconee Units. It is conceded that this was also done at other times not mentioned here. By Frocedure OP/1,2,3/A/1107/02 " Normal Power", these diodes were taken out of service in order to detect the location of a ground on the 125 VDC system. By disabling these diodes, the redundancy of one unit's batteries backing up another unit's DC loads is defeated on more than one DC string as de-fined in Technical Specification 3.7.2(d)3. This procedure is performed when a ground is detected on one Oconee unit, but the procedure itself affects the isolating and transfer diodes on all three Oconee Units. Therefore, the event occurred on all three units at the same time. This is in violation of Technical Specifications 3.7.1(e) and 3.7.2.d(3) and is thus reportable pursuant to Technical Specification 6.6.2.1.a(2).

Apparent Cause of Occurrence: The apparent cause of the incident is a misinter-pretation of Technical Specification 3.7 when the procedure was criginally written in 1974.

Analysis of Occurrence: The only place that a single failure could occur that would-affect both batteries of any Oconee Unit's I&C DC system would be in the battery

. room. During the time that the units were separated there was no fire, explosion, or other single failure of sufficient magnitude to disable any units I&C DC systems.

It should be noted that the normal period of time for the units to be separated is less than I hour. Therefore, the probability of a failure during this-short time period is quite low. Thus, the health and safety of'the public were not endangered.

Corrective Action: The immediate corrective action was,the initiation of a pro-posed change to Occnee Technical Specification 3.7 which would allow the separation of all three units' I&C, DC system via the isolating and transfer diodes for a period not'to exceed 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This proposal is still under review by NRC'. A means of physical separation for batteries CA and CB will be investigated to deter-mine its practical justification. A change to the " Normal Power" procedure that verifies that the unit's batteries CA and CB are not tied together through the DC tie breaker when isolating the unit from its backup unit vill be processed.

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