ML19340D841

LER 80-014/01T-0:on 801211,results of Ongoing Refueling Outage Steam Generator Eddy Current Insp Indicated Defective Tubes.Eight Tubes W/Crevice Defects Taken Out of Svc.Caused by Corrosion.Defects Plugged

ML19340D841
Person / Time
Site:	Point Beach
Issue date:	12/23/1980
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19340D827	List: ML19340D826 ML19340D841
References
LER-80-014-01T, LER-80-14-1T, NUDOCS 8101050448
Download: ML19340D841 (4)

Text

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? 8 3o $ l60L l@l0 l 510 61 l 01 Ol 2161668 l@l DOCKET NUM8ER 69 11211111810 EVENT DATE 74 l@ll 12REPORTDATE 75 l2 l 3 l 8 l 0l@ 80 EVENT DESCRIPTION AND PRO 8A8LE CONSEQUENCFS h t o 121 l On 12-11-80 initial results from an ongoing refueling outage steam gen-l l o I31 l erator eddy current inspection were received indicating the existence l 1014 l l of some defective tubes. Prior to initiating the eddy current l tO 5l l inspection, a 2000 psid primary-to-secondary and a 800 psid secondary- l l o is 1 1 to-primary leak check was performed and no leaks were detected. This l t

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h

{ l i 10 l l A 100 % inspection to the first support and a full tube length inspectioni 1

I l i l i l I of 3% was conducted during the outaae. Three defects and five un- I ii i2; [ definable indications were found in the "A" SG and five defects and twcj tii3l l unde finable indications were found in "B"; all within the tube shee t . l t i l 41 [ The de fects in "A" and all the indications in "B" have been plugged. l 7 8 9 80 STA S  % POWER OTHER STATUS 015 0 RY DISCOVERY DESCRIPTION ITT 1 LG_l@ l ol o I 01@l N/A l l Cl@l Eddy current examination l ACTivlTY CO TENT aELEASEo OP aELEASE AMOUNT OF A' .s vlTV LOCATION OP RELE ASE llt is l8 W 7 9 @ l toZl@l N/A l l N/A l is 44 45 80 PERSONNEL EXPOSURES r

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NAME OF PREPARER C. W. Fay 414/277-2811 PHONE: {

ATTACHMENT TO LICENSEE EVENT REPORT NO. 80-014/0lT-0 Wisconsin Electric Power Company Point Beach Nuclear Plant Unit 1 Docket No. 50-266 On December 11, 1980, at about 1400 hvues, initial results from an ongoing steam generator ed.ay current inspection were received. At that time, two defects and one degraded tube had been found in the "A" steam generator and one defect was

, found in the "B" steam generator. The unit was shut down at the

( time for Refueling 8 and steam generator eddy current inspections.

While cooling down the plant for the refueling outage, a 2000 psid primary-to-secondary hydrostatic condition was established and after draindown, a 800 psig secondary-to-primary leak check was conducted. A detailed inspection of the tubesheet during the secondary-to-primary hydrostatic leak check showed no evidence of any leakage from the steam generator tubes, although two previously plugged tubes in the "A" steam generator and two previously plugged tubes in the "B" steam generator were observed to have " wet" tube plug ends.

The eddy current inspection program performed consisted of examination of 100% of the tubes up to the first support plate on the hot leg side; greater than 3% of the tubes plus all previously degraded tubes in the cold leg were inspected over their entire length. A list of all eddy current indications of degraded tubes found in the "A" and "B" steam generator is l provided as an attachment. Three tubes in the "A" steam generator l

and five tubes in the "B" steam generator were identified as having crevice defects which exceeded the 40% tube plugging limit of Technical Specification 15.4.2.A.5. These tubes have l been taken out-of-service with mechanical plugging devices.

l The attachment provides a comparison of the eddy current signals observed during this inspection with those signals recorded during the past three inspections. Continued refinement l of the eddy current interpretation techniques, including use i of a super-imposed 200 over a 100 KHZ signal during this inspection, have permitted licensee to identify extremely small volume defects which were present in previous inspections but could not be identified due to size and noise. We elso have listad five tubes in the "A" steam generator and two tubes in the "B" steam generator which had very small volume but otherwise undefinable indications. These indications cannot be quantified as a tube defect but have been recorded as an abnormal signal.

The two tubes in the "B" steam generator have been plugged but the five tubes in the "A" steam generator were left unplugged as potential sleeving candidates in the event of a demonstration program.

1 i

In August 1980, two tubes in the "A" steam generator, R10C54 and R33C54, had been identified with 34% small volume indications at or slightly above the tubesheet. Since these indications did not exceed the tube plugging criteria and the indications had remained essentially unchanged since at least the October 1979 inspection, these tubes were not plugged. We specifically re-examined these tubes during this outage. The results are provided as part of the attachment. We interpret these results as confirmation that the indication in these tubes are essentially unchanged. A similar tube, R27C30, was identified in steam generator "B" during this inspection and has remained essentially unchanged. Nc indications within the cold leg tubesheet region were observed and only one greater than 20%

(28%) indication was observed above the tubesheet on the cold leg side. The 28% indication was previously identified as a degraded cold leg tube.

A total of 11 tube ends and 55 first tube support restrictions were encountered with a 0.720 probe. All except one tube end and eight first support restrictions passed a 0.700 probe, however. Only ten restrictions at various cold leg supports were encounter d while performing the full tube length tube inspection.

Based on the results of this inspection and inspections conducted in July and March 1980, it appears that the rate of corrosion of the steam generator tubes in the tubesheet crevice region has been substantially reduced. The results of these inspections indicate that the condition of the steam generator has not changed significantly since the March 1980 inspections.

The NRC Resident Inspector was notified of these findings. This event is reportable in accordance with Technical Specification 15.6.9.2.3, and is similar to others.

Unit 1 return-to-power is scheduled for about December 29, 1980.

POINT BEACH NUCLEAR PLANT UNIT 1

• STEAM GENERATOR INSPECTION RESULTS NOVEMBER, 1980 Tube Indication Comparison to Previous Inspections Identification Size / Location 08-80 03-80 12-79 i

Inlet - "A" Steam Generator R24C33 71%/11" ATE Same NDD NDD R11C35 63%/13" ATE Same *

• R29C5 3 65%/11-13" ATE

• NDD NDD R11C43 UDI/18-20" ATE

• NDD NDD R25C44 UDI/13-15" ATE NDD NDD NDD R25 C47 UDI/13-18" ATE * *

• R08C55 UDI/17" ATE NDD NDD NDD R10C54 <20%/TTS 34% Same Same R33C54 22%/ " ATS 34% NT NT R15C60 UDI/14-18" ATE * *

• R2 8C4 8 28%/l" ATS Cold Leg Same NT NT Inlet - "B" Steam Generator R14 C2 8 62%/21" ATE Same

• NDD R19C30 UDI/20" ATE Same

• NDD R26C37 UDI/12" ATE NDD NQD NDD R24C52 80%/5" ATE Same NDD NDD R03C60 80%/l" ATE Same

• NDD R20C60 87%/19" ATE

• NDD NDD R21C62 74%/20-21 " ATE Same Same Same R27C30 29%/ " ATE Same NT NT ATE = Above tube end NDD = No detectable defect ATS = Above tubesheet Same = Signal observed same as November 1980 signal UDI = Undefinable indication NT = Not tested

= The signal appears to be the same, but it is not possible to say for sure because the small signal is masked by noise.

l TUBES PLUGGED DURING THIS OUTAGE

" A" Steam Generator - R24C33, RllC35, R29C53 l

"B" Steam Generator - R14C28, R24CS2, R03C60, R20C60, R21C62, R19C30, R26C37 i

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