05000338/LER-1981-007-99, Plug Found Missing from Tube at Row 1,column 12.On 810202,two More Plugs Found Missing.Caused by Bad Seals.One Tube Was Replugged on 810124.Other Two Tubes Replugged on 810303

Plug Found Missing from Tube at Row 1,column 12.On 810202,two More Plugs Found Missing.Caused by Bad Seals.One Tube Was Replugged on 810124.Other Two Tubes Replugged on 810303

ML19350B976
Person / Time
Site:	North Anna
Issue date:	03/18/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19350B975	List: 05000338/LER-1981-007, Forwards Updated LER 81-007/99X-1 05000338/LER-1981-007-99, Plug Found Missing from Tube at Row 1,column 12.On 810202,two More Plugs Found Missing.Caused by Bad Seals.One Tube Was Replugged on 810124.Other Two Tubes Replugged on 810303
References
LER-81-007-99X, LER-81-7-99X, NUDOCS 8103240561
Download: ML19350B976 (2)

LER-1981-007, Plug Found Missing from Tube at Row 1,column 12.On 810202,two More Plugs Found Missing.Caused by Bad Seals.One Tube Was Replugged on 810124.Other Two Tubes Replugged on 810303

Event date:
Report date:
3381981007R99 - NRC Website

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UPDATE REPORT - PREVIOUS REPORT DATE 02-04-81

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U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT

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DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

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/ During the last refueling outage, the first row of tubes in each steam generator /

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/ was explosively plugged to decrease potential for primary to secondary leakage.

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/ On January 15, 1981, "C" steam generator tube inspections revealed that a plug

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/ was missing from the tube at row I column 12. On Feb. 2, row 1 plugs from columns /

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/ 42 and 63 were also discovered to be missing. The tube in column 12 was replugged/

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/ on January 24th and the other two were replugged on March 3,1981. This informa-/

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/ tion is being submitted to satisfy the reporting requirements of T.S. 4.4.5.5.a. /

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ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP. COMPONENT

.TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUB. SUPPLIER MANUFACTURER

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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/.The tube plugs fell out during unit operation because of bad seals which can

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/ result when plugs are installed by explosive-charge. Corrective action was to

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/ replug all three tubes mechanically. Also, each of the plugs which vibrated

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/ loose was located and removed.

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FACILITY METHOD OF STATUS

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Inservice Inspection

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LOCATION OF RELEASE (36)

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PUBLICITY ISSUED DESCRIPTION-(45)

NRC USE ONLY

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NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 8108240 %

Virginia Electric and Power Company North Anna Power Station, Unit 1 Attachment: Page 1 of I Docket No. 50-338 Report No. LER 81-007/99X-1

Description of Event

On January 15, 1981, inservice inspection of "C" steam generator tube bundle revealed that the tube plug at row 1 column 12 had fallen out.

Subsequently, it was determined on Feb. 2 that two additional plugs in row 1 (column 12 and 42) had also become dislodged. These particular tubes were explosively plugged during the last refueling outage to decrease

' potential for fut",re primary to secondary leakage. All other tubes in the first row of each steam genertor were also plugged during the outage. On Janua ry 24, 1981, the tube at row I column 12 was mechanically replugged.

The tubes at row I column 42 and row I column 63 were mechanically replugged on March 3, 1981. This information is being submitted to satisfy the 15 day reporting requirement of T.S. 4.4.5.5.a.

Probable Consequences of Occurrence The steam generator tubes involved were not defective and therefore with their plugs missing a release of radioactive material to the environment due to primary to secondary leakage did not occur.

Because the discrepancies were found and corrected prior to return to power, the health and safety of the general public were not affected.

Cause of Event

It.is believed that the tube plugs fell out during unit operation due to an improper fit which can occur when plugs are installed by an explosive charge.

Immediate Corrective Action

The steam generator tube at row 1 column 12 was mechanically replugged on January' 24,1981 and the tubes at row I column 42 and row I column 63 were both mechanically replugged on March 3, 1981. All three tube plugs which vibrated loose were also located and removed from the primary system.

4 Scheduled Corrective Action No scheduled corrective action is required.

- Actions Taken to Prevent Reccurrence No further actions are required.

- Generic Implications There are no generic implications associated with this event.