ML19338D778

LER 80-025/01T-0:on 800904,during Refueling Shutdown, Ultrasonic Exam of Steam Generator Support Bolts Revealed Crack Indications.Unit 2 Also Inspected.Caused by Environ Assisted Cracking.All Unit 1 Bolts Will Be Replaced

ML19338D778
Person / Time
Site:	Prairie Island
Issue date:	09/18/1980
From:	NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19338D774	List: ML19338D773 ML19338D778
References
LER-80-025-01T, LER-80-25-1T, NUDOCS 8009230741
Download: ML19338D778 (1)

Text

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[NRC FORM 386 : v U. S. NUCLEAR REIULATORY COMMtsSION

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h .

110121 lWith Unit 1 in refueling shutdown,' ultrasonic examination of ' steam generator support 1

- frm l bolts revealed that most ~o'f the bolts had crack ' indications. Several bolts failed l.

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Lo_.LJ l when' detensioning was" attempted. Unit 2 was operating at 100% power when the discoveryl.

I' :10,61 lwas made. Unit >2 was, shut down the evening of 9-4-80 to perform similar inspections. l O 6 l Unit 2 b' o lts were found pre-tensioned and 3 of the total of' 48 were found cracked. I ITT71 1 Remaining Unit,2- bolts were detensioned and inspected. All support pads were l o i8 i I provide / with' at least 5 bolts which is sufficient for LOCA plus DBE loading. l 1 i$ SO E ,

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44 47 CAUSE DESCRIPTION AND CO"1RECTIVE ACTIONS h L1_Lo_j IFourVascomax 250 CVM bolt heads and one comnlete bolt were forwarded to Westinehouse 1

- Li,,J,,1,j ~lResearch and~ Development Center for analysis. Pre 14minnrv ann 1vsis inrti r aroe I L1_j,,y_l lenvironmentally assisted cracking. The cracks can be prevented bv a reduction in I i l installation torque. All Unit I bolts will be replaced and installed with a l

-- I minimum of pre-tensieri. A followun report will be submitted. l

.7- 8 9 80 ST ' % POWE R ' OTHER STATUS . DI O RY DISCOVERY DESCRIPTION j,,1.,,,j,,s,,,j l - Hl@ l O l 01 012.l@l NA l-lBl@l Inservice Inspection l 7

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NUMPER ' DESCRIPTION L l 1 l a l- l e l 0 ' ; Qj@l NA' l

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