RS-08-044, Additional Information Regarding Braidwood Station Relief Request I2R-48

Additional Information Regarding Braidwood Station Relief Request I2R-48

ML080950362
Person / Time
Site:	Braidwood
Issue date:	04/01/2008
From:	Simpson P Exelon Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
I2R-48, RS-08-044
Download: ML080950362 (2)

Text

Exelon Generation www.exe]oncorp.com 4300 Winfield Road Nuclear Warrenville, IL 60555 10 CFR 50.55a RS-08-044 April 1, 2008 U. S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457

Subject:

Additional Information Regarding Braidwood Station Relief Request 12R-48

References:

(1) Letter from T. Coutu (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission, "Second 10-Year Inservice inspection Interval, Relief Request 12R-48, Structural Weld Overlays on Pressurizer Spray, Relief, Safety and Surge Nozzle Safe-ends and Associated Alternative Repair Techniques," dated February 23,2007 (2) Letter from R. Gibbs (U. S. Nuclear Regulatory Commission) to C. M.

Crane (Exelon Generation Company, LLC), "Braidwood Station, Units 1 and 2 Evaluation of Inservice Inspection Program Relief Request 12R-48 Pertaing to Structural Weld Overlays on Pressurizer Spray, Relief, Safety, and Surge Nozzle Safe Ends (TAC Nos. MD4590, and MD4591)," dated September 17, 2007 In Reference 1, Exelon Generation Company, LLC (EGC) requested NRC approval of an alternative to the repair/replacement requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, 1989 Edition, no Addenda, IWA-4000, for the structural weld overlays on pressurizer spray, relief, safety and surge nozzle safe-ends.

The approval of this alternative was required to support the installation of full structural weld overlays (SWOLs) on all Braidwood Station pressurizer Alloy 82/182 nozzle safe-end to nozzle welds.

During preparation work for the installation of SWOLs on the Byron Station Unit 2 pressurizer Alloy 82/182 nozzle safe-end to nozzle welds during the Spring 2007 refueling outage, EGC, Westinghouse Electric Company, LLC (Westinghouse), and PCI Energy Services, identified a process improvement that will enhance the installation and insure the acceptability of the Braidwood Station Unit 2 SWOLs. Specifically, the welding installation process for the SWOLs at Braidwood Station Unit 2 will incorporate a single sacrificial layer as a buffer between the base metal and the Alloy 52/152 overlay.

April 1,2008 U. S. Nuclear Regulatory Commission Page 2 The sacrificial layer will use Alloy 52 material over the ferritic pressurizer nozzle material as well as over the existing 82/182 nozzle-to-safe-end weld. The remaining portion of sacrificial layer will use a layer of austenitic stainless steel (Le., 309L) over the existing austenitic stainless steel safe-end material and existing austenitic stainless steel weld and pipe components. EGC contends that the use of the 309L material as a sacrificial buffer layer over the existing austenitic stainless steel components will lessen the occurrences of "hot cracking."

The use of this buffer layer is consistent with the intent of the Reference 1 request and the Reference 2 evaluation as well as the with the requirements of ASME Code Case 504-2, "Alternative Rules for Repair of Classes 1, 2, and 3 Austenitic Stainless Steel Piping," in that this layer (either the Alloy 52 portion or 309L portion) will be considered sacrificial and will not be considered weld reinforcement and will not be credited as part of the required overlay thickness.

This process improvement was used on the structural weld overlays for the pressurizer spray, relief, safety, and surge nozzle safe ends at Byron Station Unit 2 (Spring 2007) and Braidwood Station Unit 1 (Fall 2007).

This letter contains no new commitments nor revises any previous commitments. This submittal does not require any formal review by the NRC but was requested by the NRC Project Manager to document an EGC position originally discussed during an NRC Region IlIlnservice Inspection review at Braidwood Station.

Should you have any questions concerning this letter, please contact David Gullott, Regulatory Assurance Manager, at (815) 417-2800.

Respectfully, ,

Patrick R. i pson Manager - icensing