Bulletin 74-003: Failure of Structural or Seismic Support Bolts on Class I Components
BL74003 UNITED STATES ATOMIC ENERGY COMMISSION WASHINGTON, D.C. 20545 J. P. O'Reilly, Director of Region I N. C. Moseley, Director of Region II J. G. Keppler, Director of Region III E. M. Howard, Director of Region IV R. H. Engelken, Director of Region V RO BULLETIN #74-3 "FAILURE OF STRUCTURAL OR SEISMIC SUPPORT BOLTS ON CLASS I COMPONENTS" The enclosed RO Bulletin #74-3 is forwarded for dispatch to all BWR and PWR licensees with Operating Licenses and those licensees having an anticipated fuel load date prior to January 31, 1975. Harold D. Thornburg, Chief Field Support & Enforcement Branch Directorate of Regulatory Operations Enclosure: As stated cc: D. F. Knuth, RO J. G. Davis, RO B. H. Grier, RO A. Giambusso, L J. Hendrie, L D. J. Skovholt, L . To All BWR and PWR with current Operating Date: 3/22/74 Licenses and those having an anticipated DRO Bulletin #74-3 fuel load date prior to January 31, 1975. 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 Haddon Neck reactor facility. This information may have applicability at your facility(ies). Action requested on your part is identified in Section B of the enclosed Bulletin. Sincerely, Director Enclosure: DRO Bulletin #74-3 . 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 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 commonly 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 weld zone and along the support attachment . - 2 - for a distance of two base metal thicknesses."1/ Support members and structures for piping, valves, and pumps within the system boundary "whose structural integrity is relied upon to withstand the design loads and seismic induced displacements" are subject to examination.2/ B. Action Requested 1. Since the various support structures for vessels within containment are subject to the same environment as other support structures described above, but are not subject to the same examination, it is requested that,during your next scheduled outage, you selectively examine a representative 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 is 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 the RO Regional Office in 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 shall include, but not be limited to: structures to be examined; inspection methods to be used; and number of bolts per structure examined. 1/ASME Boiler and Pressure Vessel Code; Section XI; Table IS-251: Para. H. 2/ Ibid; Para. K-2. . - 3 - 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. . ENCLOSURE Directorate of Regulatory Operations Information Request No. 74-2 PWR MAIN STEAM LINE ISOLATION VALVES In the past several months Regulatory Operations has received notification of a number of abnormal occurrences involving main steam isolation valves at various PWR facilities. Licensees' investigations following preoperational tests and spurious valve closures have indicated that these valves, particularly those of the check-valve type, may be subject to generic failures. To permit evaluation of the extent of the problem, the suitability of specific valves for isolation purposes under postulated steam line rupture accident conditions, and the appropriateness of possible remedial measures, you are requested to provide the following specific information: 1. Facility name and unit number. 2. A line diagram or sketch showing the locations of the isolation valve(s) with some identification of the type of each valve (check; globe, gate; etc.). 3. Assembly or sectional drawings of each valve type with dimensions and identification of material. 4. Name of the manufacturer of each valve type. 5. Steam line pressure at full power and at hot stand-by conditions, compared with valve design pressure. 6. Functional design requirements contained in the original design specifications for each valve. 7. An assessment of the adequacy of each valve type to perform the isolation function under postulated steam line rupture accident conditions. 8. Discussion of any operational malfunctions of each valve. In your response to this request, please also include information relating to modifications or other methods of resolution which are planned or which may have been made to valves of this type installed, or scheduled to be installed, in your facility(ies). 8011060831
Page Last Reviewed/Updated Tuesday, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021