ML070430027
| ML070430027 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  (DPR-053) |
| Issue date: | 03/16/2007 |
| From: | Pickett D NRC/NRR/ADRO/DORL/LPLI-1 |
| To: | Spina J Calvert Cliffs |
| Pickett D, NRR/DORL, 415-1364 | |
| References | |
| TAC MD2351 | |
| Download: ML070430027 (4) | |
Text
March 16, 2007 Mr. James A. Spina, Vice President Calvert Cliffs Nuclear Power Plant, Inc.
Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657-4702
SUBJECT:
CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NO. 1 - FLAW EVALUATION OF DISSIMILAR METAL WELDS (TAC NO. MD2351)
Dear Mr. Spina:
By letter dated May 31, 2006 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML061580433), supplemented by letter dated December 22, 2006 (ADAMS Accession No. ML070040095), Calvert Cliffs Nuclear Power Plant, Inc. submitted a flaw evaluation of the indications detected in three dissimilar metal welds in the reactor coolant system of Unit No. 1 during the 2006 refueling outage. As required by Subarticle IWB-3600 of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),
Section XI, flaw evaluations that exceed the acceptance standards of Subarticle IWB-3500 of the ASME Code,Section XI, must be provided to the regulatory authority (i.e., the Nuclear Regulatory Commission (NRC)).
The welds are located in the hot leg surge nozzle to safe-end weld, hot leg drain nozzle to safe-end weld, and pressurizer relief valve to safe-end weld. The two circumferential indications in the surge nozzle weld and drain nozzle weld (each nozzle has an indication) exceeded the acceptance standards of Subarticle IWB-3500 of the ASME Code,Section XI. The axial indication in the pressurizer relief nozzle weld satisfied the acceptance standards of Subarticle IWB-3500. All three indications are suspected to be caused by primary water stress-corrosion cracking (PWSCC) because they are located in the inside surface of the pipe.
In addition to the flaw evaluation, you implemented a mechanical stress improvement process (MSIP) on all three nozzle locations during the 2006 refueling outage to induce compressive stresses on the inside surface and inner wall of the pipe to mitigate any further crack propagation due to PWSCC.
As allowed by the ASME Code, you performed a flaw evaluation of the above three indications in accordance with the rules of Subarticle IWB-3600 and the analytical procedures of Appendix C of the ASME Code,Section XI, to determine if the as-found flaws are within the Code allowable. You considered crack growth due to fatigue and PWSCC, and found crack growth to be negligible because of the compressive stresses generated by the MSIP over the entire length of the flaw. Furthermore, you have demonstrated that the circumferential indications in the surge line and drain line nozzle welds satisfy the allowable limits of Subarticle IWB-3600 and Appendix C of the ASME Code,Section XI. The indications were found to satisfy the normal operating and faulted condition loading in the pre-outage operating condition.
This demonstrates that the plant was in an operable condition with respect to the indications during the previous operating cycle.
J. Spina The NRC staff observes that you have satisfied the ASME Code requirements If you have any questions, please contact me at 301-415-1364.
Sincerely,
/RA/
Douglas V. Pickett, Senior Project Manager Plant Licensing Branch I-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-317 cc: See next page
ML070430027 NRR-106 OFFICE PDI-1/PE PDI-1/PM PDI-1/LA CPNB/BC PDI-1/BC(A)
NAME MDavid DPickett SLittle TChan JBoska DATE 2 / 23 / 07 3/16/ 07 3 / 15 / 07 2 / 27 / 07 3/15/ 07
Calvert Cliffs Nuclear Power Plant, Unit No. 1 cc:
President Calvert County Board of Commissioners 175 Main Street Prince Frederick, MD 20678 Mr. Carey Fleming, Esquire Sr. Counsel - Nuclear Generation Constellation Generation Group, LLC 750 East Pratt Street, 17th floor Baltimore, MD 21202 Mr. Jay S. Gaines Director, Licensing Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657-4702 Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 287 St. Leonard, MD 20685 Mr. R. I. McLean, Manager Nuclear Programs Power Plant Research Program Maryland Department of Natural Resources 580 Taylor Avenue (B wing, 3rd floor)
Tawes State Office Building Annapolis, MD 21401 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Ms. Kristen A. Burger, Esquire Maryland People's Counsel 6 St. Paul Centre Suite 2102 Baltimore, MD 21202-1631 Ms. Patricia T. Birnie, Esquire Co-Director Maryland Safe Energy Coalition P.O. Box 33111 Baltimore, MD 21218 Mr. Roy Hickok NRC Technical Training Center 5700 Brainerd Road Chattanooga, TN 37411-4017