ML20009D497

LER 81-008/01T-0:on 810710,four Tubes in Steam Generators Were Verified to Have Degradation Greater than 40% Which Exceeds Plugging Limit of Tech Specs.Caused by Intergranular Attack Due to Caustic.Defective Tubes Plugged

ML20009D497
Person / Time
Site:	Point Beach
Issue date:	07/16/1981
From:	Burstein S WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20009D494	List: ML20009D493 ML20009D497
References
LER-81-008-01T, LER-81-8-1T, NUDOCS 8107240120
Download: ML20009D497 (4)

Text

NRC FORM DG U. S. EdUCLEAR REGULATORY COMMISSION (F 77) S LICENSEE EVENT REPORT CONTROL BLOCK: l i

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(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATIONI o i l Wl I l P l B l H j 1 l@l 0 l 0 l - l 0 l 0 l 0 l 0 l 0 l -l 0 l 250 l@l 4 l 1l 1l 1l 1l@l$7 CAT l 58 l@

F 8 9 LICENSEE CODE 14 15 LICENSE NUMBEH 26 LICEN3E TYPE JO CoWT "7

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? 8 60 61 DOCKET NUMBER 68 69 EVENT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h lo121IThe unit was shut down on 7-4-81 for the 150 EFPD steam generator eddy I On 7-10-81 verification of all initial eddy lo lal l current examination. ,

Current data of tubes with indication exceeding the plugging limit was  ;

completed. Two tubes in each the "A" and "B" SG's had indicationn y Prior to eddy current examination a 2000 psid primary-to-g g , >40%. ,

,g,,, , secondary and an 800 psig secondary-to-primary leak test was done. This, event is similar to others and reportable per T.S. 15.6.9.2.A.3. ,

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CAUSE DESCRIPTION AND CORF.ECTIVE ACTIONS h

i ;o,[Three of the indications were within the crevice and are considered to  ;

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tubesheet and is believed to be a remnant of phosphate wastage. The ,

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,,,3, lfour tubes with defects have been plugged. A crevice flush will be l

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ATTACHMENT TO LICENSEE EVENT REPORT NO. 81-008/0lT-0 Wisconsin Electric Power Company Point Beach Nuclear Plant, Unit 1 Docket No. 50-266 Thi July 10, 1981, verification of all initial steam generator eddy current data-for tubes with indications exceeding the plugging limit was completed. Two tubes in the "A" steam generator and two tubes in the "B" steam generator were verified to.have degradation greater than 40%, which is the plugging limit of Technical Specification 15.6.2.A.S.

1 On July 4, 1981, Unit 1 was shut down for steam l generator eddy. current inspection. The 2000 psid primary-

.to-seconRO:y hydrostatic test condition was established while the unit sas~being cooled down. An 800 psig secondary-to-primary leak check-was performed on July 6 and 7. Detailed inspections of the tubesheets with remote video equipment showed a total of nine e. plosive plugs which were either wet, boric acid coated, or dripping at a s.1.ow rate-(less than one drop every one and one-half minutes). Of the nine plugs, five had similar obser-vations ncted in previous outages. Based upon the low leak rate before shut-down_(four gallons per day) and potential steam generator demonstration sleeving during the fall 1981 Tefueling outage, the plugs were not repaired during this outage. The fact that weld repair of an explosive plug involves a relatively high personnel radiation exposure was also a major factor in deciding not.to repair the explosive plugs at this time. The specific conditions noted during the leak check are noted below.

"A" Steam Generator R03C09 explosive plug, wet, less than 1 drip /2 minutes R19C33 explosive plug, wet, less than 1 drip /2 minutes R24C37 explosive plug, wet, 1 drip /1.5 minutes R33C50 explosive plug, boric acid coated R21C49 explosive plug, wet end, no drips R04C59 mechanical plug, boric acid ring, appears wet inside R08C50 mechanical plug, boric acid ring, appears wet inside "B" Steam Generator R23C53 explosive plug, wet end, no drips R29C35 explosive plug, wet, 1 drip /2 minutes R04C46 mechanical plug,-boric acid coated, appears wet inside R29C41 weld repair, boric acid coated R28C39 explosive plug, boric acid coated R29C37 explosive plug, boric acid coated l

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Of the wet end and dripping plugs, the following have been noted in previous inspections:

R19C33 "A" steam generator R24C37 "A" steam generator R21C49 "A" steam generator R23C53 "B" steam generator R29C35 "B" steam generator The eddy current inspection consisted of remote inspection of all-readily accessible tubes to the first tube support plate. Of the 2,853 open tubes in the "A" steam generator, 2,814 were inspected and 2,816 of the 2,861 open tubes in the "B" steam generator were inspected. The tubes that were not inspected are tubes under the eddy current fixture foot (19 in "A" and 17 in "B"), the tubes that contain template plugs (17 in both "A" and "B", randomly located), and tubes with restricted tube ends which prevented the insertion of a .720 probe (3 in "A" and 11 in "B"). These tubes were not inspected because of the exposure associated with moving template plugs, hand probing, and opening tube ends. The non-inspected tubes constitute lens than 2% of the unplugged tubes, most are not located in the zone where large numbers of defects have occurred and the overall eddy current results did not indicate that it would be necessary to inspect the tubes. Cae overall eddy current results and comparison with the December 1980 tapes are listed below:

"A" Steam Generator December 1980 Comparison With Tube Indication Reported December 1980 Tapes R15C29 43%, 21" ATE NDD 31%, small change R23C36 49%, 8" ATE NDD small change R20C20 <20%, 5" ATE NDD NDD, small change R05C07 UDI, 15" ATE NDD no change R18C37 UDI, 8" ATE NDD small change RllC43 UDI, 18-20" ATE UDI no change R23C43 DDI, 5-7" ATE NDD small change R25C44 UDi, 13-15" ATE UDI no change

-R25C47 UDI, 13-18" ATE UDI no change R08C55 UDI, 17" ATE UDI nc whange R15C60 UDI, 14-18" ATE UDI no change Rl8C68 UDI, 15-17" ATE NDD small change R10C54 32%, TTS <20% 34% in July 1980 F'3C54 <20%, 1/2" ATS 22% 34% in July 1980 ATE - Above Tube End NDD - No Defect Detected UDI - Undefinable Indication ATS - Above Tubesheet

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"B" Steam Generator December 1980 Comparison With Tube Indication Reported December 1980 Tapes R03C25 80%, 17" ATE NDD small change R06C43 33%, 21" ATE NDD no change

-R16C47 52%, 1/2" ATS NDD no change R27C30 29%, 1/2" ATS 29%

ATE - Above Tube End NDD - No Defect Detected '

UDI - Undefinable Indication ATS - Above Tubesheet As in the past, all indications were rmall volume.

Besides the above listed indications, a number of restrictions were encountered with the .720 eddy current probe. In the "A" steam generator three tube ends and 23 first tube support plate restrictions were encountered. In the "B" steam generator 11 tube ends and 40 first tube support plate restrictions were encountered. Most of the same restrictions were noted in the July and December 1980 inspections. During the December 1980 inspection all but seven of the restrictions passed a .700 eddy current probe. Based on this experience, the restricted tubes were not gauged. Gauging of restricted tubes may be done during the refueling outage inspection.

The four cubes with indications greater than 40%

were' plugged on July 11, 1981. In addition, tube R06C43 in the "B" steam generator was also plugged. Correct plugging was visually' verified the same day.

A crevice flush will be performed before the unit is returned to service in an attempt to remove impurities from the tubesheet crevice. Operation of the unit at a reduced temperature in' order to reduce the corrosion rate will continue.

However, the unit-will be returned to service at a slightly higher temperature than.that at which it has been operated since December 1979, assuming the results of the crevice flushing are satisfactory.

The NRC Resident Inspector was notified of these findings. This event is reportable in accordance with Technical Specification 15.6.9.A.3 and is similar to others.

Unit 1 return to power is scheduled for about July 20, 1981.

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