ML19347A943

Updated LER 80-025/01T-1:on 800904,ultrasonic Examination of Steam Generator Support Bolts Revealed That Most Had Crack Indications.Preliminary Cause Suggests Environmentally Assisted Cracking

ML19347A943
Person / Time
Site:	Prairie Island
Issue date:	09/25/1980
From:	Hunstad A NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19347A938	List: ML19347A937 ML19347A943
References
LER-80-025-01T, LER-80-25-1T, NUDOCS 8009300558
Download: ML19347A943 (1)

Text

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O t] NRC FORM 384 Updats Rsport - Previous R port DIts 091880 U. 5. NUCLEA~4 REIULATORY COMMISSION (7 77)

LICENSEE EVENT REPORT l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATIONI CONTROL BLOCK: l 1

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lh f Tl l8 M 7 9 l NLICENSEE I P lCODE Il Nl 1l@l0 l0 l- l 0 lLICENSE le 15 0 l 0NuMSERl 4 l 0 l -l Ol 250l@26 4 lLICENSE 1 l1 TYPE l1l1l@l Jo S7 i.AT 68 l

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CON'T ITTT'l g', "C l_IJ@l0 i s loDOCKET l o lNUM8ER o l ? l a l68' l@l ni EVENT al nlDATE el al nl@l a l aREPOR l ? TlDATE si a l ol@

7 8 60 Gl 69 14 75 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h 1012l l with unie 1 in 7,r,,,14ng .h,, canon. ,,1ernonn4, o,,m4,,,4m, nr ,me.

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0 3 l bolts revealed that most of the bolts had crack indications. Several bolts fn41ed i 10141 I when detensioninst was attemnted. Unit 2 was onerneing ne 100Y nouar uhan cho l i

IOI5Ildiscovery was made. Unit 2 was shut down the evening nf 4-4-RO en norfnrm aimilar 1 0 8 l<nanocrinnn_ tinf e ? kn1ro uovo rn,,na nro ,oo.4moma ema 3 of the total of 48 were I

[TT71 i found cracked. Remaining Unit 2 bolts were dete7sioned and ir.spected. All supportI iOial l pads were provided with at least 5 bolts which is sufficient for I.OCA nlus DBE loading.

7 8 9 80 E CO E SUSC E COMPONENT CODE SUS ODE SU E 7

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h U_Lo_j IFour Vascomax 250 CVM bolt heads and one comolete bolt were forwarded to Weseinohntide W IResearch and Develonment conter for nnn1v=4a. pr,14minnrv a n 21,.e 4 . <na4re,,e I

, , l environmentally assisted cracking. The cracks can be prevented by a reduction in I g l installation torque. All Unit I bolts will be replaced and installed with a 1 i 4 l minimum of pre-tensiot. A followup report will be submitted. I 7 8 9 80

$ 5  % POWER OTHER STATUS DISC RY DISCOVERY DESCRIPTION 8 5 (JJJ@ l Ol 01 d@l NA l [,,B_j@l Inservice Inspection l ACTIVITY CO TENT REuASto OP RELEASE LOCATION O, RELEASE @

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7 i a 8 9 InInInl@l n 11 12 80 I

LOSS TYPE OP DESCRIPTION OR DAMAGE TO FACILtTV h v

7 i 9 8 9 W @l 10 m l 80 DESCRIPflON _ _ _ _ _ . .

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(_y ro . r,1.,=o. nonaan nna og11an. I IIIIllIIIIIIl5 7 8 9 10 68 69 80 3 A A Hunstad 612-388-4767 0 N AME OF PREPARER PHONE: $

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