ML19257C264

LER 80-003/01T-0:on 800109,while Conducting Eddy Current Examination of Steam Generator,Row 1 Column Hot Leg Tube Found Defective.Caused by Wearing of Tube Lane Blocking Device Against Tube.Device Modified to Prevent Movement

ML19257C264
Person / Time
Site:	Prairie Island
Issue date:	01/23/1980
From:	Hunstad A NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19257C263	List: ML19257C262 ML19257C264
References
LER-80-003-01T, LER-80-3-1T, TAC-12657, NUDOCS 8001250447
Download: ML19257C264 (1)

Text

NRC FORM 366 U.1. NUCLEAR REGULATORY COMMISSION

<= %0 6081 LICENSEE EVENT REPORT ,.

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(PLE ASE PRINT OR TYPE ALL REQUIRED INFORMtJION) 0 l0 0 0l0 -

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REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h O 2 l See Attached. l ITTT1 1 ITTT1 1 _

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_ SEQUE NTI AL OCCURRENCE REPORT REVISION LER EVENTYEAR REPORT NO CODE TYPE NO.

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SA S  % POWER OTHER STATUS 015 O RY DISCOVERY DESCRIPTION y W@ l 0l0 l0 l@l N/A l l,,,B_j@l Eddy current testing l ACTivlTY CO TENT AMOUNT OF ACTIVITY LOCATION OF RELEASE i 6 [.Z_j RELEASE @D OF RELE ASE@l NA NA l 7 8 9 10 11 44 45 80 P8pSONNEL EXPOSURES NUMBER TYPE DESCRIPTION i 7 l010 O l@[Zj@l NA l PE RSONNE L INJU IES NUMBER DESCRIPTION 7

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LOSS OF OR DAMAGE TO FACILITY T TYPE DESCRIPTION

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Atachment to LER P-RO-80-3

_ Event Description While conducting eddy current examination of tubes in No. 21 Steam Generator, the Row 1 Column 1 tube in hot leg was found defective. Visual inspect iot, thru the steam generator handhole revealed the thinning was caused by movement of the tube lane blocking device against the tube. No other indications in the hot leg sample were seen. Examination of peripheral and first row tubes was then done in the cold leg. Several indications of thinning were seen at the first and second tube supports. The examanation was expanded to include tubes near the periphery and other tubes at random.

Of 723 tubes examined in the cold leg, 30 showed less than 20% thinning, 9 had 20 to 40% thinning, and one tube indicated greater than 50% thinning. The affected tubes are on the outside edge of the tube bundle.

A simils e and further expanded examination was done on No. 22 Steam Generator cold leg. Of 1143 tubes examined, 54 were found with less than 20% thinning, 21 had 20 to 40% thinning, four had 40-45% thinning, eight with 45-50%

thinning and four greater than 50% chinning. Again, the affected tubes are on the outside of tne tube bundle and the indications are at the first and second tube supports. Examination of hot leg tubes in No. 22 Steam Generator showed 12 tubes with minor denting (less than 2.5 mils).

Cause Description and Corrective Actions Thinning of the tube in No. 21 Steam Generator hot leg was caused by wearing of the tube lane blocking device against the tube. Deaign of the device does not provide adequate means of holding the parts together tightly during assembly of the device. The device has been modified to provent movement. In both generators, tubes which could be af fected by movement of the device will be plugged.

Cause of the thinning at the first and second support plates in the cold legs is not known at this time. Visus 1 inspections were inconclusive. One affected tube will be removed from No. 22 Steam Generator for further examination.

An update report will ha issued.

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