PNO-III-80-170, on 800904,efforts to Remove Bolts from Steam Generator Upper Supports Resulted in Breaking Two Bolts. Ultrasonic Examination of All of Bolts Identified Addl Defects.Cause Could Be Stress Corrosion Cracking

PNO-III-80-170:on 800904,efforts to Remove Bolts from Steam Generator Upper Supports Resulted in Breaking Two Bolts. Ultrasonic Examination of All of Bolts Identified Addl Defects.Cause Could Be Stress Corrosion Cracking

ML20148D729
Person / Time
Site:	Prairie Island
Issue date:	09/05/1980
From:	Feierabend C, Heishman R, Little W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-80-170, NUDOCS 8010090302
Download: ML20148D729 (1)

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l l PRI L IF.t hw Nui a i s uo a v.,

l Date: Septembur 5, 1980 -

PPille.it ARY NOTir1CA110N OF EVEN1 OR UNUSUAL OCCURENct--PHO 111-80 This preliminary notification constitutes LARLY 1he infnotice of events onnation of POSSIBLE prese_n_te'd "153

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sifety or public interest significance.

[ initially received Without verification or evaluation and is basical'ly a))

that is known by lE staf f as of this date.

Facility: Northern Staten Power Company (Prairic Teland 1)

Docket No. 50-282-Red Wing, MN Silhj,*,c,t,1, FATT.imE OF "VASCOMAX 250 - Ib TNCII TIELT-COIL SCREWS", STEAM ,

GENER/ TOR UPPER SUPPORTS The li(anane initiated action to detension the 14" bolts between the steam generator supports and the wteam generator as a result of recommendations related to evaluullons per formed per NUREG-0577. Efforts to remove the bolts resulted in hrnnking ruo holte on one support column. The licensee suspended ef fortu Lu remove remair.ing bolen And ennducted UT examination nt' all the bolts for both ste.am p,enerators.

The llT examination identified addit.lunal defects. Uult 1 is currently shutdown for refuelit" The licenvee shut down Unit 2 at 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> on September 4,1980, to perform UT examin-nriou uf these bultw. ,

Preliminary evaluation indicates that the cause could be stress corrosion cracking an discussed in NUREG-0577 and NRR ictter dated May 19, 1980, which forwarded NUREC-0577 for comment.

The licensen hn's resumed ef forts to remove bolts for further examluation, and la ex-pinring nnurens for replacement bnits, as thern are no spares available.

Unit 2 would be expected to be shut down for approximatcly 3 days to completc the inspection.

The licensec made a prenn relenna during the af ternoon on Scpremher 4,1980. The NRC does not plan to make a press relesso at this ti:ne. This inf ormation is current as of 9:00-61,2/388- 2 j W. L1 le,.712/384-2552; R nhman, :112/'184-2%

Conta Distr Ibuti. F.eierdDAhsmitted on Comissioner Hendrie S. J. Chilk. SECY Chairman Ahearne {ssioner Bradford C. a e C Comissioner Gilinsky  :

I P. Bldg. IE:XOOS (1E:HQ Dis-Transmitted: MNBB __

W. J. Dircks, EDO H. R. Denton. NRR (6 min / pag:

R. H. Vollmer. NRR Landow C. Michelson, AEOD J. J. Cummings DIA J. J. fouchard, PA R. J. Mattson, NRR N. M. Haller, MPA D. F. Ross, NRR D. Eisenhut, NRR MAIL

c. W. Kerr, osy

5. H. Hanauer R. Minogue, 50 H. K. Shapar, ELD IE:X005 i Willste Bldg. Document Mgt. Br. (ForPDRi J. G. Davis, NMSS Regional Offices _ T. E. Murley, RES n 7 R PREllMINARY NOTIFICATION 8010090302