ML19332A814

RO 80-25:on 800904,w/unit in Refueling Shutdown,Ultrasonic Examination of Steam Generator Support Bolts Revealed Most Bolts Had Crack Indications.Several Bolts Failed When Detensioning Was Attempted.Cause Not Determined

ML19332A814
Person / Time
Site:	Prairie Island
Issue date:	09/05/1980
From:	Tierney F NORTHERN STATES POWER CO.
To:
References
RO-80-25, NUDOCS 8009180422
Download: ML19332A814 (2)

Text

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NGP NORTHERN STATES POWER COMPANY PIIAIRIE ISLAND NUCLEAR GENERATING PLANT 1111 # 2 Welch, SIN 35089 Sept. 5, 1980 Mr. James G. Keppler, Director Region III Of fice of Inspection & Enforcement U S Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 ATTN:

W. S. Little Reportable Occurrence No. 80-25 On 9/4/80, with Unit 1 in refueling shutdown, ultrasonic examination of steam generator support bolts revealed that most of the bolts had crack indications.

Several bolts failed when detensioning was attempted.

Unit 2 was operating at 100% power when the discovery was made.

Unit 2 was shutdown the evening of 9/4 to perform similar inspections.

Three or the 48 bolts have indications of defects.

Investigation is continuing.

These steam generator support bolts are not needed for normal operation but were installed to mitigate the effects of the postulated LOCA and the desig;n basis earthquake.

Sincerely,

,Yl&$ 1 >14;r k F. P. Tierney, Jr.

Plant Manager Prairie Island Nuclear Plant FPT/=jh cc:

L. O. Mayer Director, MIPC (2)

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