ML19257A731

LER 79-021/01T-0:on 791211,during Normal Operation, Increasing Steam Generator Primary to Secondary Leakage Noted.Caused by Leaking Tube in Steam Generator B.Plugs Welded & Repaired

ML19257A731
Person / Time
Site:	Point Beach
Issue date:	12/22/1979
From:	Burstein S WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19257A730	List: ML19257A729 ML19257A731
References
LER-79-021-01T, LER-79-21-1T, NUDOCS 8001070480
Download: ML19257A731 (5)

Text

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. LICENSEE EVENT REPORT ,

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'l 9 l7l4 @ '30 EVENT OESCRIPTION AND PROB A8LE CONSECUENCES h o 2 l nm. 4 ,7 n n -, , 7 nun. n7n ,o en n, ,,_,,_yn 4.n.n,c4,7 e.n,, 7,,nn,.n. l f iTil I crimarv-to-cecondarv leakace was notea. secondarv water samoles I o 4 I indicated a leak rate of aoproximatelv 250 cnd, of which aceroximatelvI o s i 200 cod was calculated to be from the "B" steam generator. Shutdown I o 6 I of the unit becan at 1713 hours0.0198 days <br />0.476 hours <br />0.00283 weeks <br />6.517965e-4 months <br /> on 12-11-79. This event is renortableI o 7 I cer T.S. 15.6.9.2.A.3 and similar to orevious LER's 78-001/0lT-0, I a s I 78-010/0lT-1, 79-003/0lT-0, 79-012/OlT-0, 79-013/0lT-0, and 79-017/0lT-l 7 8 9 0 80 SYSTEM CAUSE CAUSE COYP VALVE CODE COCE SUSCODE CCMPONENT CODE SUSCODE SUSCOCE l'oT9l l C l B l @ (_E,jh l D l h l H l T l E l X l C l H lh [J_j@ W h 3 6 9 10 11 12 13 te 19 20 SE QUE N TI A L OCCURAENCE REPORT REVISION R pg EVENT YE AR R EPOR T NO. CODE TYPE NO.

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47 42 44 CAUSE DESCRIPTION AND CCARECTIVE ACTIONS h i O I An 800 osi secondarv side leak test was cerformed in both steam I i i l cenerators on 12-14-79. No leaks were observed in "A". One leakinc I i 2 tube was found in "B", together with dries in one exolosiva cluc and I i 3 l one welded clug. The leakinc tube was mechanically plugged on 12 !

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December 22, 1979 ATTACIIMENT TO LICENSEE EVENT REPORT 79-021/0lT-0 Wisconsin Electric Power Company Point Beach Nuclear Plant Unit 1 Docket 50-266 At 2137 hours0.0247 days <br />0.594 hours <br />0.00353 weeks <br />8.131285e-4 months <br />, December 11, 1979, Unit 1 was taken off line for steam generator primary-to-secondary leakage repair.

Indications of minor primary-to-secondary leakage were evident when Unit 1 returned to service on December 1, 1979, after recovery from refueling, which included extensive steam generator testing and repair (see Licensee Event Report 79-017/0lT-0). The leakage, at approximately 55 gallons per day was typical of Unit 1 minor leakage which has been experienced continually for several years.

The leakage remained stable until 1613 hours0.0187 days <br />0.448 hours <br />0.00267 weeks <br />6.137465e-4 months <br /> on December 11, 1979, at which time R15, the air ejector nonitor, rose from 45,000 cpm to 200,000 cpm. Secondary side water samples were taken, and the preliminary results indicated a leak rate of 250 gallons per day, of which approximately 200 gallons per day were calculated to be from the "B" steam generator. Analysis of a second sample taken to verify the results of the first sample confirmed that primary-to secondary leakage was 250 to 260 gallons per day. At the time,

.r.e Duty and Call Superintendent and the Superintendent-Operations ccincluded that the leak was typical of deep-crevice restrained cracking because of the sudden increase and subsequent leveling off of the leak rate at about 250 gpd. At 1713 hours0.0198 days <br />0.476 hours <br />0.00283 weeks <br />6.517965e-4 months <br />, operating personnel commenced an orderly shutdown of the unit. Unit 1 achieved cold shutdown at 1210 hours0.014 days <br />0.336 hours <br />0.002 weeks <br />4.60405e-4 months <br />, December 12, 1979.

An 800 psi secondary side leak test was performed in both steam generators on December 14, 1979. No leaks were noted in the "A" steam generator. One leaking tube was found in the "B" steam generator at a point 20" deep in the crevice, together with drips in one explosive plug and one welded plug.

The leaking tube was mechanically plugged on December 15, 1979, and the dripping plugs were weld-repaired on December 17, 1979.

Although not required by our Technical Specifications or the Confirmatory Order of November 30, 1979, an eddy current test program was developed to inspect all tubes in regions where deep crevice tube failures have been found in the past. The program began in the "A" steam generator on December 15, 1979, and in the "B" steam generator on December 18, 1979. In both programs the new latest state of the art was used for the eddy current work.

Approximately 950 tubes in each steam generator were tested in this manner.

Of the tubes inspected in the "A" steam generator, 19 were identified in the hot leg inlet as having indications in the deep-crevice region. No eddy current indications were detected at, or above, the tubesheet. Another detailed comparison of the eddy current data collected in October 1979, utilizing improved 1693 271

Attachment to LER 79-021/01T-0 December 22, 1979 techniques, showed that 12 of the 19 tubes had undefinable signals in October. Mechanical plugging of the 19 tubes in the "A" steam generator was performed on December 19, 1979. One additional tube in the "A" steam generator was plugged by mistake. See Table 1 for details.

Of the tubes eddy-current inspected in the "B" steam generator, 15 were identified as having indications in the hot-leg inlet deep-crevice region. tio eddy current indications were detected at, or above, the tubesheet. The detailed comparison of the eddy current data collected in October 1979 showed that six of these fifteen tubes had undefinable signals in October. Three of the remaining nine tubes had signals which could not be positively identified as defects due to the complexity of the eddy current signals. These three tubes were plugged as a conservative measure.

See Table 2 for details.

The 15 tubes in the "B" steam generator identified as having indications in the crevice region were explosively plugged on December 20, 1979.

All tubes having any eddy current indication were plugged, irrespective of depth of indicatien. No eddy current indication was found within two inches of the top of the tubesheet; as noted, none was found above the tubesheet. All tests went up to the first tube support plate.

The "B" steam generator was successfully leak-tested on the evening of December 20, 1979.

The unit is expected to return on line on December 22, 1979.

This event is reportable in accordance with Technical Specification 15.6.9.2.A.3.

1693 272

December 22, 1979 TABLE 1 "A" STEAM GENERATOR TUBES PLUGGED Tube Defect Location R8C19 81% 8" above tube end (new)

R10C20 42% 20" above tube end R7C21 95% 13" above tube end R18C21 85% 15-21" above tube end R8C25 85% 15-20" above tube end R9C28 92% 6" above tube end (new)

R20C31 92% 15-21" above tube end R18C32 92% 12" above tube end R19C32 60% 20" above tube end R18C33 88% 12" above tube end R7C34 88% 2-1/2 - 5" above tube end (new)

R23C40 69% 10" above tube end R27C42 <20% 12" above tube end R24C47 <20% 8" above tube end (new)

R19C51 37% 6" above tube end (new)

R12C57 83% 20" above tube end (new) 24C59 94% 17" above tube end R6C33 84% 5" above tube end (new)

R9C54 - Undefinable indication; not identified as a defect R18C45 0 Plugged accidentally i693 273

Deccmber 22, 1979 TABLE 2 "B" STEAM GENERATOR TUBES PLUGGED Tube Defect Location RllC25 74% 12" above tube end (new)

R12r26 <20% 20" above tube end R18C28 88% 5" above tube end (new)

R4C38 92% 5" above tube end (new)

R12C38 94% 20" above tube end (new)

R13C44 - Undefinable indication; 19" above tube end R13C46 87% 21" above tube end R26C46 89% 19" above tube end RllC47 - Undefinable indication; 13-20" above tube end (new)

R25C54 85% 7" above tube end (new)

R6C60 82% 9" above tube end (new)

R3C66 - Undefinable indication; 2-1/2 - 5" above tube end R3C67 91% 2-1/2 - 11" above tube end R3CG8 86% 2-1/2 - 5" above tube end (new)

R2C71 100% Detected leaking tube; 3" above tube end (new)

"B" STEAM GENERATOR WELD REPAIR (HOT LEG)

R12C55 Previously explosively plugged (1972) and welded (1977).

R20C55 Previously explosively plugged (1972) 1693 274

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