RC-08-0009, Supplemental Information Relative to Request to Use Alternatives to ASME Code Section Xl Requirements for Application of Weld Overlay Repairs (RR-III-05)

Supplemental Information Relative to Request to Use Alternatives to ASME Code Section Xl Requirements for Application of Weld Overlay Repairs (RR-III-05)

ML080230050
Person / Time
Site:	Summer
Issue date:	01/18/2008
From:	Archie J South Carolina Electric & Gas Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RC-08-0009
Download: ML080230050 (7)

Text

Jeffrey B. Archie Vice President, Nuclear Operations 803.345.4214 A SCANA COMPANY January 18, 2008 RC-08-0009 Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS)

DOCKET NO. 50/395 OPERATING LICENSE NO. NPF-12 SUPPLEMENTAL INFORMATION RELATIVE TO REQUEST TO USE ALTERNATIVES TO ASME CODE SECTION Xl REQUIREMENTS FOR APPLICATION OF WELD OVERLAY REPAIRS (RR-III-05)

Reference:

J. B. Archie (SCE&G) letter, RC-07-0085, to Document Control Desk (NRC) - Request to Use Alternatives to ASME Code Section Xl Requirements for Application of Weld Overlay Repairs, June 1, 2007 South Carolina Electric & Gas (SCE&G) submitted the referenced request for using an alternative to the requirements of ASME Code,Section XI IWA-4330 for mitigating primary water stress corrosion cracking (PWSCC) on dissimilar metal welds using full structural weld overlays (SWOL) on June 1, 2007. This request is based on ASME Code Case N-740 and is applicable to VCSNS.

SCE&G has subsequently identified a material discrepancy in the pressurizer nozzle material as stated in the subject relief request. This discrepancy was relative to the carbon steel nozzle material SA-508 CL 2, which was inconsistently identified as SA-508 CL 2a.

This discrepancy was investigated and evaluated. The material was confirmed to be SA-508 CL 2 as noted on the ASME Code Data Sheet N-1A form and the Certified Material Test Reports (CMTR) for the respective nozzles.

With this material discrepancy, potential impacts were investigated relative to MRP-216.

The material discrepancy of SA-508 CL 2 versus 2a was determined to have no affect on the finite element analysis (FEA) contained in the EPRI-Advanced FEA Results for VCSNS.

A telephone conference was held on November 15, 2007 between SCE&G, the NRC VCSNS Project Manager, and the respective NRC technical reviewer of the referenced relief request. During this call, SCE&G described the material discrepancy issue and noted that there was no impact on the VCSNS SWOL design.

SCE&G I Virgil C. Summer Nuclear Station 'P. 0. Box 88. Jenkinsville, South Carolina 29065

• T (803) 345.5209

• www.sceg.com

Document Control Desk CR-07-00439 RC-08-0009 Page 2 of 2 The NRC indicated that this was not a significant issue and would not impact the SER for the relief request. The NRC did request that SCE&G address certain items identified during the discussion in a supplemental submittal. This requested information, along with corrected material information, is provided as attachment to this letter.

Should you have any questions, please call Mr. Bruce Thompson (803) 931-5042.

Very truly yours, ke

. Arc' ie JWT/JBA/dr Attachment - Relief Request RR-111-05 Supplemental Information c:

K. B. Marsh S. A. Byrne N. S. Carns J. H. Hamilton, Jr.

R. J. White V. M McCree R. E. Martin K. M. Sutton F. A. Miller D. G. Dobson S. C. Smith T. A. McAlister NRC Resident Inspector NSRC RTS (CR-07-00439)

File (810.19-2)

PRSF (RC-08-0009)

Document Control Desk Attachment CR-07-00439 RC-08-0009 Page 1 of 5 Relief Request RR-III-05 Supplemental Information As Requested Through Teleconference With NRC November 15, 2007

1. Errors were made in the original relief request submittal relative to material classification, Class 2a versus Class 2.

Relief Request, RR-III-05, for the Pressurizer Structural Weld Overlay (SWOL) project is impacted by the documentation discrepancy identified subsequent to the June 1, 2007, submittal by SCE&G through letter RC-07-0085. The following pages are impacted by this discrepancy and are marked to identify the affected text:

Attachment I, page 13 of 16, 12 th line - Class 2a should be Class 2 Attachment II, page 1 of 2 - The material for the nozzles should be changed to SA-508 CL 2' w/SST Clad.

Attachment II, page 2 of 2 - The existing nozzle has "A 508 Class 2 or 2A".

Change this to SA-508 Class 2.

These discrepancies have no impact on the technical content of RR-l11-05 or the results of the SWOL sizing or inspections.

Marked-up copies of the affected pages providing the correct material information are contained in pages 3 through 5 of this attachment.

2. Sufficient margin exists in the calculations for the overlay and there is no impact on design; only documentation correction.

The design of the SWOL utilized Code stress allowables for SA-508 CL 2, which are more conservative (lower) than those of SA-508 CL 2a. There is no impact on the SWOL design for the pressurizer.

3. Finite element analysis (FEA) was reviewed and there is no impact as a result of the errors.

The material discrepancy of SA-508 CL 2 versus CL 2a does not affect the EPRI-Advanced FEA Results as they apply to VCSNS, specifically with respect to the conclusions in MRP-216. This was determined by both a detailed site review and discussion with the Westinghouse expert panel member.

Document Control Desk Attachment CR-07-00439 RC-08-0009 Page 2 of 5

4. NRC reviewer (John South) asked what materials would be used in the buffer layer if needed.

Welding Services Incorporated (WSI) has identified in the respective procedure for application of a buffered layer (if required at VCSNS), that the weld metal will be 308L.

Attachment Ill, Step 1.f of RR-111-05 identifies that a stainless steel buttering (buffer layer) may be applied to the stainless steel piping prior to the application of the Alloy 52M overlay to preclude sensitivities to impurities such as sulfur.

5. NRC reviewer asked that SCE&G include reference to Code Case 504-2, paragraph e.

Attachment V of RR-111-05 identifies the specific paragraphs of Code Case 504-2 and the proposed alternatives in Attachment III of RR-III-05. The proposed "existing" alternative (specific to Code Case 504-2, e) does not address the delta ferrite content limits as identified in the Code Case since SCE&G's focus is on the 52M alloy rather than the application of a stainless steel buffer layer.

The statements considering the ferrite content would apply if the structural weld overlay were composed of austenitic stainless steel instead of nickel alloy 52M. The application of an austenitic stainless steel layer may be applied as a buffer layer to seal the base material if required. The application of an austenitic stainless steel buffer, if used, will not be credited to the structural weld overlay thickness required in the design. Thus, the ferrite content requirements of Code Case 504-2, e do not apply. The buffer layer, if applied, will not be applied to the carbon steel nozzle nor the dissimilar metal weld.

6. NRC reviewer asked that SCE&G add a statement of no impact on finite element analysis.

A statement of no impact on finite element analysis is provided in response to item 3 above.

Document Control Desk Attachment CR-07-00439 RC-08-0009 Page 3 of 5 Document Control Desk Attachment I CR-07-00439 RC-07-0085 Page 13 of 16 basis for starting the 48-hour hold after completing the third temperbead weld layer rather than waiting for the weld overlay to cool to ambient temperature. (Weld layers beyond the third layer are not designed to provide tempering to the ferritic HAZ when performing ambient temperature temperbead welding.) EPRI has documented their technical basis in technical report 1013558, Temperbead Welding Applications - 48 Hour Hold Requirements for Ambient Temperature Temperbead Welding (Ref. 12).

The technical data provided by EPRI in their report is based on testing performed on SA-508, Class 2 low alloy steels and other P-Number 3, Group 3 materials, which is the nozzle material at VCSNS. This point is important b us the VCSNS Pressurizer nozzles are manufactured from SA-.50, lass 3, Group 3) carbon steel. After evaluating the issues relevant to y r

• gen cracking such as microstructure of susceptible materials, availability of hydrogen, applied stresses, temperature, and diffusivity and solubility of hydrogen in steels, EPRI concluded the following on page 5-2 of the report: "There appears to be no technical basis for waiting 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after cooling to ambient temperature before beginning the NDE of the completed weld. There should be no hydrogen present, and even if it were present, the temperbead welded component should be very tolerant of the moisture." Page 5-2 of the report also notes that over 20 weld overlays and 100 repairs have been performed using temperbead techniques on low alloy steel components over the last 20 years. During this time, there has never been an indication of hydrogen cracking by the nondestructive examination performed after the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold or by subsequent inservice inspection.

In addition, the ASME Section X1 Committee approved Revision 4 to Code Case N-638 (i.e., N-638-4) in October 2006 to allow the 48-hour hold to begin after completing the third weld layer when using austenitic filler metals. Paragraph 4(a)(2) of the code case states in part: "When austenitic materials are used, the weld shall be nondestructively examined after the three tempering layers (i.e., layers 1, 2, and 3) have been in place for at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />." The ASME Section XI technical basis for this change is documented in the White Paper in ASME C&S Connect for Code Case N-638-4. The ASME White Paper points out that introducing hydrogen to the ferritic HAZ is limited to the first weld layer since this is the only weld layer that makes contact with the ferritic base material. While the potential for introducing hydrogen to the ferritic HAZ is negligible during subsequent weld layers, these layers provide a heat source that accelerates the dissipation of hydrogen from the ferritic HAZ in non-water backed applications.

Furthermore, the solubility of hydrogen in austenitic materials such as Alloy 52M is much higher than that of ferritic materials while the diffusivitv of hydrogen in austenitic materials is lower than that of ferritic materials. As a result, hydrogen in the ferritic HAZ tends to diffuse into the austenitic weld metal which has a much higher solubility for hydrogen. This diffusion process is enhanced by heat supplied in subsequent weld layers. Like the

Document Control Desk Attachment II CR-07-00439 RC-07-0085 Page 1 of 2 w0 CDM=

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CD DISSIMILAR METAL WELD DETAILS Material Identification Nozzle Type Nozzle ISI Weld Safe End (§E)

ISI Weld Pip Pipe Size Figure No.

PZR A-508, Cl 2A' D

82J1821 3 SA-182 P8-P8 Weld, A-376, TP304 V NPS Spray Line wISST Clad 1O CGE-1-4503-Gr F316L ID CGE-1-4503-(Pipe) 46(DM) 45 PZR TA-508, Cl 2,9' DMW 82/1822 SA-182 P8-P8 Weld3 A-376, TP304 6" NPS Safety Valve w/SST Clad I0 CGE-1-4501-Gr F316L ID CGE-l-4501-(Pipe)

A I(DM) 2 PZR2 Safety Vv

-8, Cl 2.

DMW 82/182' SA-182 PB-P8 Weld' A-376, TP304 6' NPS w/SST Clad MD CGE-1-4501-Gr F316L ID CGE-1-4501-(Pipe) 12(DM) 13 PZR TA-508, Cl 2 D$'

DMW 82/182' SA-182 P8-P8 Weld 3 A-376, TP304 6" NPS Safety Valve w/SST Clad ID CGE-1-4501-Gr F316L I0 CGE-1-4501o (Pipe)

C 23(DM) 24 PZR Relief DA58 C

0MW 821182 SA-182 P8-P8 Weld' A-376. TP304 6" NPS Valve w/SST Clad ID CGE-1-4502-Gr F316L ID CGE-1-4502-(Pipe) 1(DM) 2 PZR SA-508, Cl 2 DMW 82/182' SA-182 P8-P8 Weld 3 A-376, TP304 14" NPS Surge Line w/SST Clad ID CGE Gr F316L ID CGE (Pipe) 4500A-1(DM) 4500A-2 Notes:

I Nozzle material is carbon steel.

2.

DMW includes butter and weld.

3, One full structural overlay may be applied over both the DMW (82/182 weld) and the P8-P8 weld. See Figure 1.

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VCSNS Pressurizer Alloy 600 Nozzle Welds - Structural Weld Overlay

[ ~Alley 52M OverlayI F A508 CI-,,. Z_

ozzle Allov 1R2 Butter SA-182 Grade 316L Safe-EndI Z

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FIGURE 1 TYPICAL MATERIAL/LAYOUT FOR WELD OVERLAY