ML19317F329

LER 77-012/01X-0:on 770927,primary to Secondary Leak Found Coming from 2B once-through Steam Generator.Cause Undetermined.Leak Plugged

ML19317F329
Person / Time
Site:	Oconee
Issue date:	10/07/1977
From:	Ken Wilson DUKE POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19317F325	List: ML19317F324 ML19317F329
References
LER-77-012-01X, LER-77-12-1X, NUDOCS 8001100704
Download: ML19317F329 (7)

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DUKE POWER Ont!'A!W OCONCE Ut;IT 2 Report Number: R0-270/77-12 Occurrence'Date: October 7,1977

. Report Date: February 15, 1978 Facility: Unit 2, Seneca, South Carolina

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Identifica' tion of Occurrence: Primary-to-Secondary Leak through B Once Through SteamcGenerator (OTSG)

Conditions Prior to Occurrence: 80 percent Full-Power Description of Occurrence:

' On September 27, 1977 air injector radiation monitor RIA-40 indicated a primary-to-secondary Icak of approximately 0.2 gpm. Power was reduced .

to 67 pc.rcent to ' reduce powdex contamination. Subsequently, because

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of an apparently incrcasing Icak rate the unit was shut down on October 7, 1977. . Af ter a 21 day outage and several unsuccessful attempts to find the leak the unit was -returned to power operation on October 28, 1977. A second unsuccessful attempt to-locate the leak was made from November,3 to 12, 1977. On December 29, 1977 the unit was shut down to repair a-_ control rod stator, remove install.ed steam generator instrumentation 'and make -another attempt at 71 ocating the indicated leak. .Tub e-77-25 was discovered to be leaking. Fiber optic and eddy-current examinations indicated a 90 circumferential' crack near.

the upper tube sheet. The tube;was stabilized and plugged. The instrumented ' tubes (6), which showed considerable wall thinning, were also plugged A11 -(7) previously plugged tubes were re-plugged as a precautionary measure., Hydrostatic tests showed no further Icaks and the unit was- returned to power operation on January 16, 1978.

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Apparent Cause of.0ccurrence:

The exact cause of_tlue incident cannot be determined. The primary-to-secondary 11cak could have been _ caused.by either' tube 77-25 or any of '

the:seven replugged. tubes. The Nucicar Steam Supply System supplier, Babcock 'and Wilcox, and Duke Power Company are continuing to investigate the ' tube. leak problem. ' '

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DI KE l'O',il:R Co*tt'ANY OCONCE UNIT 2 (Cont'd)

Analysis of Occurrence:

All liquid and gaseous waste releasts were controlled and accounted for within applicabic criteria. Plant personnel exposure totalled 11.48 man-rem. The reactor coolant boundary was re-established by the tube repair. Therefore, the health and safety of the public were not endan-gered.

Corrective Action:

Tube 77-25 was stabilized and plugged. Previously instrumented tubes which showed appreciable wall thinning were also plugged. All pre-viously plugged tubes were re-plugged.

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SUMMARY

OF HAJOR OTSG TUBE EXPER1ENCE AT OCONEE~

.# TUBESLEXAMINED LANE. (excludes.. leakers) .

- ACTION RO# ,

1DATE TUBE . LEAKER CONDITION

GENERATOR ROR . TUBE . ELEVATION

' R0-269/76-17 153

'ths . Crack Plugged

.17j Tubesheet ~10/31/76 Yes 1-AL '7 7 '

No . Distorted Eddy Plugged Tubesheet. 10/31/76 Yes-1-A 77 18 Current Signal R0-269/76-19 139 No Yes No Visual ' Nailed-1-B 114. 109- 14th. Plate 12/8/76 Inspection No Distorted Eddy- Plugged No 1-B 113 115

• 14th Plate 12/8/76 Currant Signal No No Similar to Nailed 1-B 113 110 14th Plate 12/8/76 114/109 .

Yes No 300 Crack Nailed 1-B ' 75 18 Tubesheet 12/8/76 Nailed R0-269/77-2 '140 1/15/77 Yes Yes 350 . Crack

1-B '75 12 .Tubesheet No Eddy Current Nailed .

1-B 81 128 Tubesheet 1/15/77 RNo Indication RO-269/77-8 3%

No Yes Eddy Current Nailed 1-B 32 13 14th Plate 2/28/77 I.ndication No No Eddy Current Nailed ,

1-B 33 14 14th Plate 2/28/77 Indication Eddy Current P.emoved 25 14th Plate 2/28/77 Yes No 1-B 77 Indication No Eddy Current Plugged 13th Plate 2/28/77 No 1-B 2 7 Indication ,

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No No Eddy Current Plugged 1- 3 2 8 13th Plate 2/28/77 Indication No No Eddy Current Plugged 1- B 101 40 4th Plate 2/28/77 Indication

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SUMMARY

OF MMOR OTSG TUBE EXPERIENCE AT OCONEE (CONT'D) .

1. TUB'ES EXAMINED ..

LANE ACTION . ROP (excludes leakers)

TUBE. ELEVATION :DATE TUBE LEAKER CONDITION , ,

l GENERATOR ' ROW, 100 Yes Weld Crack Replugged R0-269/77-11 1-B - 77- 25 Tubesheet 3/22/77 .Yes Yes Distorted Plugged 1-BL .77 3,5,8' --- .3/22/77 1No Eddy Current

-Signal

• Plugged R0-269/77-16 507 5/7/77 Yes Yes Crack 1-B. 77 15. Tubesheet ,

No --- Removed 18 --- 5/7/77 Yes 1-B !77 ~

~No Distorted Plugged ,

5/7/77 -No ,

1-B ' 17 5 ---

• Eddy Current Signal Removed R0-270/76-15 133 Yes Yes 270 Crack, 2-B 77 23 Tubesheet 12/4/76 Hole Yes No Wear Appearance Removed 2-B ,

77- 27 15th Plate 12/4/76 No Eddy Current Flugged 2-B 124 42 12th Plate 12/4/76 No Indication, 40-60%

No Similar to Left 2-B 118 52 12th Plate 12/4/76 No 124/42, 15%

Plugged R0-287/76-10 9 11 15th Plate 7/21/76 Yes Yes No Visual 3-8 77 Inspection Nailed R0-287 /77-2 142 19 15th Plate 2/14/77 Yes .Yes Eddy Current 3-B 77 45 Crack 12,13,14,15 2/14/77 Yes No Eddy Current Nailed L3-8 77 16,17,18,20, .

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2 2/14/77 Yes No Eddy Current Nailed 3-B 75

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k-- CONEE'(CONT'D) ' '

SUMMARY

OF MAJOR OTSG TUBE EXPERIENCE AT O '# TUBES EXAMINED '

LANE - RO # (excludes leakers) ~

_ . ' ..j ACTION -

DATE TUBE JLEAKER CONDITION

- GENERATOR'. ROW , TUBE ELEVATION q.

133 JRO-287/77-8' No Yes. ~90 Crack 6-1/8" Nailed.

3-B T78' 1 f15th Plate-' 6/10/77' longitudinal

'120 Nailed R0-287 /77-10 Yes Yes 60 -90 ' Crack 2 Tubesheet 7/14/77-B . . 77 Nailed' 7/14/77 Yes .No '

3-B. . 77 1- ' R0-270 /7 7 90 Crack Nailed Yes Yes 2-B ,77 25' Tubesheet 1/14/78 Eddy Current Plugged Yes No 1/14/78- Indication, SOAK 2-B 75 - 21 ---

Eddy Current Plugged Yes No 4 --- 1/14/78 Indication, SOAK B 77 Eddy Current Plugged Yes No 77 18 --- 1/14/78 Indication, SOAK .

2-B-Eddy' Current Plugged Yes No 19 --- 1/14/78 Indication, SOAK 2-B 77 Eddy Current Plugged Yes No 21 --- 1/14/78

• Indication, SOAK 2-B 77 Eddy Current Plugged Yes No 4 -- 1/14/78 Indication, SOAK 2-B 78 Y

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.. Evt r e rt lolil e e h ified as coning 3 f EVENT DESCmFTION AND PRCS A8L$ CONSECUE**CESa primary-to-secondary leak wa o 2 l_On September 27. 1977 j down on October 7 for 21 days but the was begun on j QJ 2] I f rom the 2B OTSG.Another ' The unsuccessful unit was shut shutdown o 4 l_ leak could not he located. d stator the y During an unscheduled outage to repair a control ro y lo1511 November 3. 13 other tubes were 1eak was located an (the Icaking tube was plugged. (see  ;

@l This is the 13th OTSG tube Icak at Oconee

@ l_niunood or renlunned. i h d by the repairs.

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The corrective action, CAcss cesemencN ANocometenvt AcncNs g i The cause of OTSG tube leaks at Oconec tisd tubes. undetermined. Future g the olunninn of leaking or previously instrumen e i

i l_taken was 3 gj l_ action will be determined by research now in progress. 1 1

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Total exposure of 11.48 man-rem during t

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i fit 51 L.xl@7"3c ,,ne;h33y,'"*"l Erel,,n,t i nn of unscheduled (704) 373-8197 outanes

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