ML083540626

St. Lucie, Unit 1 - Corrected Page to Safety Evaluation of Relief Request to Use Structural Weld Overlay and Alternative Examination Techniques on Safe End Dissimilar Metal Welds

ML083540626
Person / Time
Site:	Saint Lucie
Issue date:	12/24/2008
From:	Mozafari B L Plant Licensing Branch II
To:	Stall J A Florida Power & Light Co
Moroney B T, NRR/DORL, 415-3974
References
TAC MD9256
Download: ML083540626 (3)

Text

UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 December 24, 2008 Mr. J. A. Stall Senior Vice President, Nuclear and Chief Nuclear Officer Florida Power and Light Company P.O. Box 14000 Juno Beach, Florida 33408-0420 S1. LUCIE, UNIT 1 -CORRECTED PAGE TO SAFETY EVALUATION OF RELIEF REQUEST TO USE STRUCTURAL WELD OVERLAY AND ALTERNATIVE EXAMINATIOI\J TECHNIQUES ON SAFE END DISSIMILAR METAL WELDS (TAC NO. MD9256)

Dear Mr. Stall:

On November 3,2008, the U.S. Nuclear Regulatory commission (NRC) authorized an alternative to the repair requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, for S1. Lucie, Unit 1. The alternative uses a full structural weld overlay with temper bead welding for repair and the Performance Demonstration Initiative program for inspection as alternatives to the requirements of ASME Code,Section XI. On November 19, 2008, following discussion with the S1. Lucie staff, the NRC issued a correction to the discussion of delta ferrite measurements on page 9 of the safety evaluation (SE). Subsequently, it was determined that the correction did not address all of the licensee's comments and an additional clarification is needed regarding the heat of the welding wire. The enclosed SE page 9 corrects the error and is annotated to show the correction.

This page should be placed in the SE to replace the previously issued page. Sincerely, I ftl/ Brenda L. Mozafari, Senior' roject Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No.: 50-335

Enclosure:

Revised SE page cc w/enclosure:

Distribution via ListServ

-9 years on piping of both boiling and pressurized-water reactors to inhibit the growth of flaws while establishing a new structural pressure boundary.

The SWOLs will control growth in PWSCC flaws and maintain weld integrity by producing compressive stress in the DMW. The full SWOLs will be sized to meet all structural requirements independent of the existing weld and will produce a favorable surface for UT examination.

Due to their close proximity adjacent SS safe end-to-piping SMW will be incorporated into the area of the weld overlay. 4.1 General Requirements ASME Code Case N-504-3 and Nonmandatory Appendix Q (a contingent requirement of Code Case N-504-3 in accordance with RG 1.147, Revision 15) of ASME Code Section XI, require certain specification and surface conditions of the applicable base metal (LAS, CS, SS, and Alloy 82/182), the weld overlay filler metal (Alloy 52M) and the Cr content of weld overlay deposits.

Section 1 of Attachment 2 to RR-2, Rev. 1, provides corresponding requirements, with modifications.

FPL will deposit a barrier layer of ER308L or ER309L SS filler metal on the base metal prior to weld overlay as a contingency for preventing possible hot cracking, which may result from high sulfur content in austenitic SS base material.

The tendency of certain metals to exhibit hot cracking is caused by the segregation at grain boundaries of low-melting constituents (e.g., sulfur) in the weld metal. This may result in grain-boundary tearing under thermal contraction stresses.

Hot cracking may be minimized by employing low impurity welding metals. FPL stated that a SS barrier layer of alloy ER308L or ER309L, will be utilized over the appropriate base materials due to the uncertainty in establishing impurity thresholds for successful Alloy 52M SWOLs. FPL also stated that the proposed SWOL design does not take structural credit for the buffer/barrier weld layer. FPL will install the barrier layer on the austenitic SS pipe and safe end only and stop short of the Alloy 82/182 weld material.

The final tie-in to the existing nickel Alloy 82/182 weld may be performed with nickel Alloy 82 weld metal. Welding over the nickel base ENiCrFe-3 (Alloy 182) joint with an iron based ER308L or ER309L electrode may cause cracking in the SS barrier layer. FPL stated further that the SS barrier layer will be deposited with a welding procedure that has been qualified in accordance with the ASME Code,Section IX. Liquid penetrant (PT) examinations will be performed on the barrier layer surface and its volume will be included in the final UT of the overlay. Delta ferrite (FN) measurements are not required per Attachment 2 of RR-2, Rev. 1, for weld overlay repairs made of Alloy 52/52M weld metal. Welds of Alloy 52/52M are 100 percent austenitic and contain no delta ferrite due to their high nickel composition (approximately 60 percent nickel). FPL's vendor performed a mockup and the Cr content of the first overlaid layer was verified at the 24 percent minimum Cr value specified in accordance with Section 1 (e) of Attachment 2 to RR-2, Rev. 1. Furthermore, FPL states the same heat of wire, or a wire heat with equal or greater Cr content than that used in qualification, will be used in situ for the first layer and the same welding parameters will be specified in the welding procedure specification as were used in the mockup for the first layer. Correction Letter dated December 24, 2008 December 24, 2008 Mr. J. A. Stall Senior Vice President, Nuclear and Chief Nuclear Officer Florida Power and Light Company P.O. Box 14000 Juno Beach, Florida 33408-0420 SUB..ST. LUCIE, UNIT 1 -CORRECTED PAGE TO SAFETY EVALUATION OF RELIEF REQUEST TO USE STRUCTURAL WELD OVERLAY AND ALTERNATIVE EXAMINATION TECHNIQUES ON SAFE END DISSIMILAR METAL WELDS (TAC NO. MD9256)

Dear Mr. Stall:

On November 3,2008, the U.S. Nuclear Regulatory commission (NRC) authorized an alternative to the repair requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, for St. Lucie, Unit 1. The alternative uses a full structural weld overlay with temper bead welding for repair and the Performance Demonstration Initiative program for inspection as alternatives to the requirements of ASME Code,Section XI. On November 19, 2008, following discussion with the St. Lucie staff, the NRC issued a correction to the discussion of delta ferrite measurements on page 9 of the safety evaluation (SE). Subsequently, it was determined that the correction did not address all of the licensee's comments and an additional clarification is needed regarding the heat of the welding wire. The enclosed SE page 9 corrects the error and is annotated to show the correction.

This page should be placed in the SE to replace the previously issued page. Sincerely, IRA BMoroney fori Brenda L. Mozafari, Senior Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No.: 50-335

Enclosure:

Revised SE page cc w/enclosure:

Distribution via ListServ DISTRIBUTION:

PUBLIC RidsAcrsAcnw_MailCTR Resource RidsNrrPMBMozafari Resource RidsNrrLABClayton Resource (hard copy) LPL2-2 R/F RidsNrrDorlLpl2-2 RidsOgcRp Resource TFarnholtz, EDO RidsRgn2MailCenter Resource RidsNrrDciCpnb Resource KHoffman, NRR ADAMS Accession No' ML083540626 NRR-106 OFFICE LPL2-2/PM LPLlI-2/PM LPLII-2/LA CPNB/BC LPLlI-2/BC NAME BMoroney BMoroney for BMozafari BClayton CNove for TChan BMozafari for TBovce DATE 12/23/08 12/23/08 12/22/08 12/23/08 12/24/08 OFFICIAL RECORD COPY