ML20127H367

Forwards Dro Bulletin 3, Failure of Structural or Seismic Support Bolts on Class I Components, to Provide Util W/Info Reported by Connecticut Yankee as AO at Haddam Neck.Action Requested Is Identified in Section B of Bulletin

ML20127H367
Person / Time
Site:	Monticello, Haddam Neck  File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	04/02/1974
From:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:	Wachter L NORTHERN STATES POWER CO.
References
NUDOCS 9211180494
Download: ML20127H367 (3)

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UNITED OTATE3

, o , ATOMIC ENERGY COMMICOION

% ' DIRECTORATE OF REGULATORY OPERATIONS REGION lil

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%rts 08 " 799 ROOSEVELT ROAD ym

, GLEN ELLYN, ILLINOIS 6o137 011) 858-286J April 2, 1974 Northern States Power ceapany Docket No. 50-263 ATTN: Mr. Leo Wachter, Vice President Power Production and System Operation 414 Nicollet Mall Minneapolis, Minnesota 54501 Gentlemen The enclosed DRO Bulletin No. 3 " Failure of Structural or Seismic Support Bolts on Class I Components". is sent to provide you with information reported by Connecticut Yankee as an abnormal occurrence at The Haddam Neck reactor facility. .

This information may have applicability at your facility (ies). Action requested en your part is identified in Section B of the enclosed Bulletin.

Sincerely yours, James G. Keppler Regional Director Anclosures l DRO Bulletin No. 74-03 l

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DRO Bulletin No. 73-04 l FAILURE OF STRUCTURAL OR SEISMIC SUPPORT BOLTS ON CLASS I COMPONENTS 1 ,

{ We recently received information from-the Connecticut Yankee Atomic

}- Power Company describing bolt failures found during routine in-service r l inspections at the Haddam Neck pressurized-water reactor which may relate to the installation and serviceability of seismic support bolts >

or other seismic support structures'at your facility.

i Description of Circumstances i A. During a visual _ inspection, several steam generator seismic support-l- holddown bolts were observed to be loose. Subsequent inspections

by ultrasonic and impact testing of all 256 bolts identified a total i

of-24 which had failed and were unable to perform their design function. '

l A preliminary evaluation indicated the bolts'had failed in tension, i apparently from over-torque during the original installation.- It was 4

later ascertained by metallurgical and-electron microscopic techniques-that the failures were_the result of stress corrosion, associated j,_ with the high pre-stressing, stress risers at the root of the bolt threads, and the presence of moisture originally _from the concrete and j continuing from miscellaneous spills,_ leakages or high humidity

!- commonly found within containment areas, i

l. In reviewing this problem, it was- noted that Section:XI' of the Boiler and Pressure Vessel. Code _does not specifically address the inspection i of support structures for vessels except for the " support attachment i (vessel support skirts) which includes the welds to the' vessel and the base metal beneath the veld zone and along the support attachment i

for a distance of two base metal thicknesses."1/ Support members and structures for piping, valves, and: pumps within the system j boundary "whose structual integrity is relied upon to withstand i the design lo j examination.2,pdsandseismic?induceddisplacements"aresubjectto t

!' B. Action Requested i

1. Since the various support structures:for vessels within con-l tainment'are subject to the same environment as'other support 1

1/ ASME Boiler and Pressure Vessel Code;Section XI; Table IS-251; Para.-H.

,2/ lbid; Para. K-2.

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structures described above, but are not subject to the same examinatien, it is requested that during your next scheduled re-fueling or~ maintenance outage, you selectively examine a repre-sentative portion of the vessel support members and structures, including the bolting material for two Seismic Category I vessels (as defined in Regulatory Guide 1.29) whose structural integrity

, relied upon to withstand design and seismic displacements. This examination should include sufficient coverage of each support structure to provide confidence of serviceability.

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2. It is requested that you notify this office is writing within 20 days of your proposed schedule for this inspection, including the date that your detailed written programs and procedures will be available for RO inspection. Your program should include, but not be limited to: structures to be examined; inspection methods to 4 be used; and number of bolts per structure examined.

3. If failures are revealed during your inspections, you are instructed to promptly report these as " Abnormal Occurrences" in accordance with the requirements of your license.

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