ML20037B383
| ML20037B383 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, Zion  |
| Issue date: | 04/02/1974 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8009240820 | |
| Download: ML20037B383 (1) | |
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UNITED STATES h.
ATOMIC ENERGY COMMISSION l
o DIRECTORATE OF REGULATORY OPERATIONS
. j\\),g REGION lli
- *f s o' "f 799 ROOSEVELT ROAD g.
GLEN ELLYN, ILLINOIS 60137 (312) ess-2sso April 2, 1974 Cosmomenalth Edison Company DoaketEe.50-10/
l ATTE: Mr. Byron Lee, Jr.
Dookat No. SC-237 vies President Doaket No. 50-249 F. O, Pax 767 Doaket No. 50-256 Chicago. T111mata 60690 Doeket Bo. 50-265 Doaket Bo. 50-295 Docket No. 50-304 Gentlement h enclosed Dao Bulletin No. 3 " Failure of Structural or Sata-te Support Bolts on Class I C-- ;--e=" La samt to provida you with information l
reported by Connecticut.1(ankee as an abnormal occurremos at h Beiden Beck reactor facility.
This information may have applisability at your fasility(ims). Action requested on your part is identified La Sestian B of the===1 h Bulletin.
Simeerely yours, James G. Espplar Regional Director Enclosure Dao Bulletin No. 74-03 bce: 10 Films DR Central F41-PDR.
Local PDE OGC, Neth, F-506A
- 1. Ranfrow, QC, (2) soona 0 820 o
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April 2, 1974 DRO Bulletin No. 73-04 FAILURE OF STRUCTURAL OR SEISMIC SUPPORT BOLTS ON CLASS I COMPONENTS We recently received information from the Connecticut Yankee Atomic Power Company describing bolt failures found during routine in-service inspections at the Haddam Neck pressurized water reactor which may I,
relate to the installation and serviceability of seismic support bolts or other seismic support structures at your facility.
Description of Circumstances A.
During a visual inspection, several steam generator seismic support holddown bolts were observed to be loose.
Subsequent inspections by ultrasonic and impact testing of all 256 bolts identified a total of 24 which had failed and were unable to perform their design function.
A preliminary evaluation indicated the bolts had failed in tension, apparently from over-torque during the original installation.
It was later ascertained by metallurgical and electron microscopic techniques that the failures were the result of stress corrosion, associated with the high pre-stressing, stress risers at the root of the bolt threads, and the presence of moisture originally from the concrete and continuing from miscellaneous spills, leakages or high humidity co=monly found within containment areas.
In reviewing this problem, it was noted that Section XI of the Boiler and Pressure Vessel Code does not specifically address the inspection of support structures for vessels except for the " support attachment (vessel support skirts) which includes the welds to the vessel and the base metal beneath the veld zone and along the support attachment for a distance of two base metal thicknesses."1/ Support members and structures for piping, valves, and pumps within the system boundary "whose structual integrity is relied upon to withstand examination.2.,pds and seistic induced displacements" are subject to the design lo B.
Action Recuested 1.
Since the various support structures for vessels within con-tainment are subject to the same environment as other support 1/ ASME Boiler and Pressure Vessel Code;Section XI; Table IS-251; Para. H.
2/ Ibid; Para. K-2.
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2-structures described above, but are not subject to the same examination, it is requested that during your next scheduled re-fueling or maintenance outage, you selectively examine a repre-sentstive portion of the vessel support members and structures,
' including the bolting material for two Seismic Category I vessels i
(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.
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 vill be available for RO inspection.
Your program should include, but not be limited to:
structures to be examined; inspection methods to be used; and number of bolts per structure examined.
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3.
If failures are revealed during your inspections, you are instructed to pro =ptly report these as " Abnormal Occurrences" in accordance with the requirements of your license.
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