ML20056C238
| ML20056C238 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 04/30/1993 |
| From: | Schrage J COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0313, RTR-NUREG-313 NUDOCS 9305120130 | |
| Download: ML20056C238 (6) | |
Text
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Downers Grove, lilinois 60515 April 30,1993 Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 Attn: Document Control Desk
Subject:
Quad Cities Nuclear Power Station Unit 2 Request for NRC Approval of a Non-Code Repair for a Recirculation System Pipe Flaw NRC Docket No. 50-265
References:
(a)
Teleconference between CECO (J. Schrage, et. al.)
and NRC (C. Patel, et. al.) on April 15,1993 (b)
Teleconference between CECO (J. Schrage, et. al.)
and NRC (D. Lynch, et. al.) on April 22,1993
Dear Dr. Murley:
During the current refueling outage for Quad Cities Station Unit 2 (O2R12),
Commonwealth Edison Company (CECO) identified an IGSCC flaw in a twelve-inch Recirculation System riser. This flaw, the proposed repair method (full structural weld overlay), and sample expansion plans, were discussed with the NRC Staff in the referenced teleconferences. This proposed repair is not an ASME Code Section XI approved repair.
NUREG 0313 Rev 2, provides NRC Staff guidance for acceptable repair procedures for IGSCC flaws. Section 3.2.1 of that document provides guidance for installation of weld overlays as a long term repair for IGSCC flaws.
Based on the guidance found in NUREG 0313, Rev 2, CECO requests NRC approval to implement the non-code repair.
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r Dr. Thomas E. Murley April 30,1993 A description of the flaw and the proposed non-code repair are provided in Attachment A. A description of the sample expansion which was implemented upon identification of the flaw is provided in Attachment B. CECO respectfully requests review and approval of the proposed non-code repair by May 15,1993. This schedule request is based upon the current schedule of outage activities (unit start-up is scheduled for May 26,1993).
If there are any questions concerning this matter, please contact John L. Schrage at (708) 663-7283.
Sincerely,
,f Q
John L..
chrage Nuclear Licensing Administrator dhj Attachments cc:
A. Bert Davis, Regional Administrator-Rill C. P. Patel, Project Manager-NRR T. E. Taylor, Senior Resident inspector-Quad Cities R. A. Hermann-NRR Office of Nuclear Facility Safety-lDNS a:\\JLSMisc\\2
ATTACHMENT A Quad' Cities Station Unit 2 Recirculation System Pipe Flaw Description of Flaw and Proposed Repair CIRCUMSTANCES AND DESCRIPTION OF FLAW On March 27,1993, in-Service inspection (ISI) of Intergranular Stress Corrosion Cracking (lGSCC) susceptible piping was being conducted on Quad Cities Unit 2 in accordance with Generic Letter (GL) 88-01. An ultrasonic examination of the Reactor Recirculation System riser line 2-0201C-12"-A, on ISI weld number 02C-F7, (see Figure 1) revealed crack-like indications in the heat affected zone of the pipe material. Weld 02C-F7 is a Category *C" weld, as defined in GL 88-01. A Category "C" weld is defined as a weld of non-resistant materials that has been stress improved after two years of operation. The stress improvement method used on 02C-F7 was Induction Heating Stress Improvement (IHSI).
Supplemental examinations of this area by Commonwealth Edison (CECO) confirmed the -
presence of three cracks. The deepest crack propagation was approximately 75% through-wall. The sample was expanded to include additional welds of similar susceptibility (see Attachmert B for a description of sample expansion). No additional indications were detected -
in the original or expanded samples.
All ultrasonic examinations were performed by technicians who have been qualified by the Electric Power Research Institute (EPRI) after September 10,1985. The results of the ultrasonic examinations were reviewed by a Commonwealth Edison Level til examiner.
DESCRIPTION OF PROPOSED REPAIR This weld will be repaired with a " full structural" design weld overlay (see Figure 2). This.
repair has been designed per the requirements of NUREG-0313 Rev. 2 and the ASME Boiler and Pressure Code Section XI. The' overlay will then be surface finished to permit performance of iiDE inspections. These will include a liquid penetrant exam, along with an ultrasonic examination of the weld overlay material and the top 25% of the base material. A hydrostatic test at 1110 psig will be conducted prior to the unit startup.
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ATTACHMENT B Quad Cities Station Unit 2 Recirculation System Pipe Flaw l
Sample Expansion Activities l
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As described in Attachment A, weld 02C-F7 is a Generic Letter (GL) 88-01 Category "C" weld
.1 on a twelve-inch Recirculation system riser. A Category "C" weld is defined as a weld of non-resistant materials that has been stress improved after two years of operation. The stress improvement method used on weld 02C-F7 was induction Heating Stress improvement (IHSI).
There are a total of 134 Category "C" welds on Quad Cities Unit 2. Of this total,51 have f
been stress improved using the IHSI method. The remainder (83) have been stress improved using the Mechanical Stress improvement Process (MSIP) method, or a load leveling weld overlay.
During the current Quad Cities Unit 2 refuel outage (O2R12),45 welds were scheduled for the i
GL 88-01 10-year Category "C" inspection requirement. An additional 31 Category *C" welds j
were scheduled for post-stress improvement inspection (within two cycles of MSIP).
GL 88-01 and NUREG 0313 Rev. 2 provide requirements for sample expansion if cracked welds are found by sample inspection during the 10-year interval. This guidance states that an additional sample of the welds in the category should be inspected, approximately equal in number to the original sample. This additional sample should be similar in distribution to the original sample, unless it is determined that there is a technical reason to select a different distribution.
Based upon the inspection results for Category *C" weld 02C-F7, and the stress improvement -
method used on the weld (IHSI), Commonwealth Edison expanded the Category "C" weld inspections to include the remaining Category "C" welds of similar IGSCC susceptibility (welds which were stress improved using the IHSI method (29 welds)). No additional indications were detected in the original or expanded samples.
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l Together_ with the post-stress improvement inspection (31 Category *C" welds), this sample -
expansion resulted in the inspection of an additional 60 Category "C" welds.~ Therefore, the total number of Category "C" welds inspected during O2R12 was 105 (initial 45 plus 31 plus J
29). This represents 78% of the total Category *C" welds, and 100% of the IHSI Category "C" welds.' The remaining Category "C" welds which were not inspected during O2R12 include 28 l
MSIP welds, which were inspected during O2R10, and one IHSI weld with a load leveling weld overlay.
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FIGURE 2 Quad Cities Unit 2 Weld O2C-F&
Weld Overlay Repair Design SWEEPOLET PIPE t WELD
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I U.S. PATENT NO. 4,624,402 WELD OVERLAY REPAIR DESIGN uom (1)
THIS REPAIR SHALL COMPLY WITH THE TECHNICAL REQUIREMENTS CONTAINED IN DOCUMENT NO. COE-107-500, REVISION O.
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EXTEND OVERLAY AS FAR AS PRACTICAL TOWARD SWEEPOLET, HOWEVER *A* DIMENSION NEED NOT EXCEED 2.0".
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