NL-06-2434, Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles

Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles

ML062960237
Person / Time
Site:	Vogtle, Farley
Issue date:	10/20/2006
From:	Grissette D Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-06-2434
Download: ML062960237 (31)

Text

Don E. Grissette Vice President Tel 205.992.6474 Fax 205.992.0341 October 20,2006 Southern Nuclear Operating Company, Inc.

40 lnverness Center Parkway Post Office Box 1295 Birmingham, Alabama 35201

\\

SOUTHERN &

COMPANY Energy to Serve Your WorldSM Docket Nos.:

50-348 50-424 50-364 50-425 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles Ladies and Gentlemen:

By letter NL-06-1713, dated August 10,2006, Southern Nuclear Operating Company (SNC) requested Inservice Inspection (ISI) Alternative (ISI-GEN-ALT-06-03) to allow the application of full-structural weld overlays over the pressurizer nozzle dissimilar metal welds.

This alternative is for the Farley Nuclear Plant (FNP) 3rd IS1 Interval extending from December I, 1997 through November 30,2007 and for the Vogtle Electric Generating Plant (VEGP) 2nd IS1 Interval extending from May 3 1, 1997 through May 30,2007.

On September 8,2006, SNC received a facsimile from the NRC containing a Request for Additional lnformation (RAI) containing 17 questions from the staff related to the proposed alternative request 1 Sf-GEN-ALT-06-03. Subsequently, on September 29,2006, SNC received a revised RAI by facsimile from the NRC containing an additional three questions related to the proposed alternative request IS1-GEN-ALT-06-03. The SNC response to the NRC questions is enclosed.

The staff requested that SNC submit the same commitments as specified in Exelon's letter dated September 14, 2006, for the contingency and preemptive weld overlay relief requests at Vogtle Units 1 and 2 and Farley Units 1 and 2. It is our understanding that NRC and industry experts are having discussions regarding inspection and repair of weld overlays. These discussions may result in different criteria that may be beneficial to future weld overlays SNC. Therefore, if industry activities result in changes that are beneficial, SNC may request an amendment to this response.

Approval is requested by January 5,2007 to support scheduled examinations performed during the planned Unit 2 outage at VEGP beginning March 2007, the Unit 2 outage at FNP beginning April 2007, and the Unit 1 outage at FNP beginning October 2007.

U. S. Nuclear Regulatory Commission NL-06-2434 Page 2 This letter contains no NRC regulatory commitments. If you have any questions, please advise.

Sincerely, Don E. Grissette

Enclosure:

Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles cc:

Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. J. R. Johnson, General Manager - Plant Farley Mr. T. E. Tynan, General Manager - Plant Vogtle RType: CVC7000, LC# 14495 U. S. Nuclear Regulatory Commission Dr. W. D. Travers, Regional Administrator Ms. K. R. Cotton, NRR Project Manager - Farley Mr. R. E. Martin, NRR Project Manager - Vogtle Mr. C. A. Patterson, Senior Resident Inspector - Farley Mr. G. J. McCoy, Senior Resident Inspector - Vogtle

Enclosure Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles

1.

NRC Request Page 1. The NOTE under the Contingency Overlay Repairs heading states that the contingency repair would only be used "If evidence of PWSCC [primary water stress-corrosion cracking] is observed during volumetric or visual examinations of one of the pressurizer dissimilar metal welds..." The visual examination cannot detect a PWSCC flaw that is not connected to the outside surface of the weld. Therefore, the result of a visual examination by itself cannot be used as a criterion in determining whether a repair should be made. There is a total of six dissimilar metal welds and six similar metal welds at each unit as shown on page 2 of the submittal.

(a) Clarify that both visual examination and ultrasonic examination will be performed on all pressurizer nozzle dissimilar metal and similar metal welds at Vogtle Unit 1 and Farley Unit 2 prior to applying contingency overlay repairs.

(b) Clarify whether a weld overlay will be applied to a similar metal weld if an ultrasonic examination will not be performed on that similar metal weld.

(c) Discuss the criteria for determining a PWSCC indication and provide the indication size (the threshold) that requires a contingency overlay repair.

(d) Discuss whether a contingency overlay repair will be performed on a dissimilar metal weld if the indication detected is not caused by PWSCC.

(e) If one of the pressurizer dissimilar metal welds in Vogtle Unit 1 or Farley Unit 2 is detected with an indication, clarify whether all the dissimilar metal and similar metal welds in Vogtle Unit 1 and Farley Unit 2 pressurizers will be repaired.

Southern Nuclear Operatinp Companv (SNC) Comment Visual examinations will be performed each refueling outage on the dissimilar metal welds until they are mitigated by weld overlay. Ultrasonic examinations are scheduled as follows (see Table 1 on page 26):

Vogtle Unit 1 is scheduled to have preemptive full structural weld overlays (FSWOLs) applied during the next refueling outage in Spring 2008. No ultrasonic examinations are scheduled prior to that time.

Vogtle Unit 2 is scheduled to have preemptive FSWOLs applied during the next refueling outage in Spring 2007. No ultrasonic examinations are scheduled prior to that time.

Farley Unit 1 is scheduled to have preemptive FSWOLs applied during the next refueling outage in Fall 2007. No ultrasonic examinations are scheduled prior to that time.

Enclosure Page 1 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles Farley Unit 2 is scheduled to have preemptive FSWOLs applied during the Spring 201 0 refueling outage. Ultrasonic examinations are scheduled during the next refueling outage in Spring 2007.

SNC Response to NRC Items l(a) throuph (el (a) If a through-wall flaw is detected on Vogtle Unit 1 or Farley Unit 2 by a visual examination, no ultrasonic examinations will be performed prior to applying a contingency overlay repair. If a PWSCC flaw is detected during the scheduled Farley Unit 2 ultrasonic examinations, a contingency overlay will be applied.

(b) Similar metal welds will be overlayed as discussed in SNC response 2. Ultrasonic examinations are not scheduled for the adjacent similar metal welds prior to applying the overlay. Many of the similar metal welds have significant examination restrictions due to their proximity to the dissimilar metal welds.

(c) Through-wall leakage during a visual examination will be attributed to PWSCC. An ultrasonic indication will be attributed to PWSCC if it meets the following conditions:

the indication is observed in the weld metal and the indication is connected to the inside diameter (ID) surface. A PWSCC indication will be repaired by applying a FSWOL.

(d) If a flaw is not attributable to PWSCC (refer to conditions in l(c) above), then an evaluation will be performed per ASME Section XI Code rules to determine the acceptability of the weld. A contingency FSWOL will be applied to unacceptable non-PWSCC flaws.

(e) Preemptive FSWOLs are scheduled for Vogtle Unit 1 and Farley Unit 2 in 2008 and 2010 respectively. If an indication is detected prior to the planned overlay outage, SNC would repair only the nozzle with the indication.

NRC Request Page 1, last two paragraphs. Under the Preemptive Overlays heading, the licensee stated that "A preemptive FSWOL [full structural weld overlay] will be applied to each of the VEGP-2 [Vogtle Unit 21 and FNP-1 [Farley Unit 11 pressurizer DSM

[dissimilar metal weld]..." However, under the NOTE for the Preemptive Overlays heading, the licensee stated that "...If Primary Water Stress Corrosion Cracking (PWSCC) is discovered at the VEGP and FNP units prior to applying the preemptive overlay, an FSWOL may be used to perform repairs, as necessary..." The second statement contradicts the first statement by applying conditions to the FSWOL. The second statement implies that the criterion of applying a preemptive overlay is the same as the criterion of applying a contingency overlay repair (i.e., an overlay will be applied based on the result of nondestructive examinations).

Enclosure Page 2 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles (a) Discuss the criteria for the application of FSWOL to the dissimilar metal and similar metal welds under the preemptive overlay strategy.

(b) Clarify whether the ultrasonic examination and visual examination will be conducted on the dissimilar metal and similar metal welds at Vogtle Unit 2 and Farley Unit 1 prior to applying preemptive overlays.

(c) Identify the number of welds that will be overlaid under the preemptive overlay strategy.

SNC Comment As a point of clarification, SNC developed proposed alternative ISI-GEN-ALT-06-03 to allow application of a preemptive FSWOL to each dissimilar metal weld. In addition, the preemptive FSWOL will be extended over each adjacent similar metal weld that is sufficiently close to the dissimilar metal weld to ensure sufficient ultrasonic examination coverage of the similar metal weld. Code Case N-740, from which technical content was used by SNC in the drafting of proposed alternative ISI-GEN-ALT-06-03, was written for "repairs," not preemptive overlays, and it states, "...flaw characterization and evaluation requirements shall be based on the as-found flaw." For a preemptive FSWOL, there is no known flaw; therefore, a flaw must be assumed. These assumptions are:

For crack-growth calculations, paragraph 2(a) of the proposed alternative, Crack Growth Considerations, states that, "a flaw with a depth of 75% and a circumference of 360 degrees will be assumed."

For design of the overlay, paragraph 2(b)(6) of the proposed alternative, Design, states that, "the flaw shall be assumed to be 100% through the original wall thickness for the entire circumference."

However, if an indication attributed to PWSCC is detected by examination prior to the application of the preemptive overlay, a "contingency" overlay is planned as a repair based on the following criteria:

If an indication attributed to PWSCC is found by ultrasonic examination, flaw characterization and evaluation requirements shall be based on the as-found flaw as discussed in Paragraph 2(a) of the proposed alternative.

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If an indication attributed to PWSCC is found by leakage, in lieu of performing ultrasonic examinations, the flaw shall be assumed to be 100% through the original wall thickness for the entire circumference.

Enclosure Page 3 of 28

Joseph M. Parley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles SNC Response to NRC Items 2(a) through (c)

(a) A preemptive FSWOL will be extended over each adjacent similar metal weld that is sufficiently close to the dissimilar metal weld to ensure sufficient ultrasonic examination coverage of the similar metal weld. This is expected to include all adjacent similar metal welds with the possible exception of those on the surge lines, where there may be sufficient separation between the dissimilar metal weld and the similar metal weld to allow examination of the similar metal weld after the dissimilar metal weld is overlaid.

(b) See SNC response to question 1 and Table 1. SNC does not plan to conduct ultrasonic or visual examinations on the similar metal welds adjacent to the dissimilar metal welds prior to applying an overlay. These will be examined after the overlay is applied.

(c) The number of welds to be overlaid is 11 or 12 per unit. The welds to be overlaid include the dissimilar metal welds listed on page two of the proposed alternative and adjacent similar metal welds associated with the spray, safety and relief nozzles. The similar metal weld on each pressurizer surge line may not be overlaid if there is sufficient separation between it and the dissimilar metal weld to allow examination of the similar metal weld after the overlay is applied.

3.

NRC Request Page 3. In the Applicable Code Requirements section, the licensee stated that examinations of pressurizer dissimilar metal and similar metal welds are performed based on the NRC-approved risk-informed program. Confirm that once the weld overlay is applied to the subject welds, the welds will no longer be part of the risk-information program. The examinations of the overlaid welds will follow the inspection strategy in the proposed alternative.

SNC confirms that it will use the inspection strategy in the proposed alternative.

4.

NRC Request Page 4. first paragraph. The licensee stated that the proposed alternative will be based on the 2001 edition of the American Society of Mechanical Engineers (ASME),

Boiler and Pressure Vessel Code (Code), Section I11 and Section XI, with Addenda through 2003. As stated in NRC Regulatory Issue Summary 2004-16, licensees need to request the NRC approval for the use of the later edition or addenda of the ASME Code (i.e., later than the edition of the Code of record).

Enclosure Page 4 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles (a) Confirm that the proposed Relief Request ISI-GEN-ALT-06-03 also contains a request to use the later edition of the Code.

(b) Confirm that the 2001 edition with addenda through 2003 of the ASME Code is used for Relief Request ISI-GEN-ALT-06-03, because this is the latest edition of the Code that the NRC has approved in 10 CFR 50.55a.

SNC R e s ~ o n s e to NRC Items 4(a) and (b) a) Per 10 CFR 50.55a (g)(4)(iv), SNC requests approval to use the 2001 Edition of the American Society of Mechanical Engineers (ASME), Boiler and Pressure Vessel Code (Code), Section I11 and Section XI, with Addenda through 2003 for this proposed alternative. The exception is that for ASME Section XI, Appendix VIII, the 2001 Edition of Section XI will be used. This exception is based on 10 CFR 50.55a(b)(2)(xxiv) which states, "The use of Appendix VIII and the supplements to Appendix VIII and Article 1-3000 of Section XI of the ASME BPV Code, 2002 Addenda through the latest edition and addenda incorporated by reference in paragraph (b)(2) of this section, is prohibited."

b) As stated in the proposed alternative, the 2001 edition with addenda through 2003 of the ASME Code is used for proposed alternative ISI-GEN-ALT-06-03.

5.

NRC Request On Page 4:

(a) To clarify the description in Section 1 (a) of the proposed alternative, provide a drawing of a typical nozzle-weld-pipe configuration including the nozzle, dissimilar metal weld, safe end, similar metal weld, pipe, and the overlay. Identify the material of each component. Provide dimensions for relief, safety, spray, and surge nozzles and piping (such as diameters and thickness) in a table. Include the thickness of weld overlays.

(b) Clarify when the overlay will be applied and will not be applied to the similar metal welds.

SNC Response to NRC Items 5(a) and (b)

(a) Figures l, 2 and 3 (pages 27-28) provide a typical sketch of the overlay and the materials for each component. Specific dimensions and the overlay thickness are proprietary information and will be in the design package available for NRC review at the plant site.

Enclosure Page 5 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles (b) Refer to the response to NRC request 2(c).

6.

NRC Request Page 5: Section 2(a) of the proposed alternative states that for a preemptive overlay, a flaw with a depth of 75 percent and a circumference of 360 degrees will be assumed.

(a) Confirm that the 75 percent depth flaw is assumed to be located in the original weld and that the flaw originates from the inside surface of the pipe.

(b) Provide the technical basis of the assumed flaw depth.

SNC Response to NRC Items 6(a) and (b)

(a) Refer to the response to NRC request 2 and the proposed alternative ISI-GEN-ALT

03. A flaw in the original weld with a depth of 75% and a circumference of 360 degrees that originates from the inside of the pipe is postulated for crack growth purposes. A flaw in the original weld having a 100% through-wall depth and a circumference of 360 degrees that originates from the inside of the pipe is assumed for design purposes for the preemptive FSWOL. The design requirement is identical to that of a repair.

(b) A 75% through-wall depth flaw is the largest flaw that could remain undetected. A preservice volumetric examination will be performed after application of the overlay using an ASME Section XI, Appendix VII:[ [as implemented through performance demonstration initiative (PDI)] examination procedure. This examination will verify there is no cracking in the upper 25% of the original weld and base material, and the assumption of a 75% through-wall crack is conservative. Otherwise, if any crack-like flaws are found during the preservice examination in the upper 25% of the original weld or base materials, the as-found flaw (postulated 75% through wall, plus the portion of the flaw in the upper 25%) would be used for the crack growth analysis.

7.

NRC Request On Pages 5 and 6:

(a) Discuss whether the thickness of the full structural weld overlay will be the same for a specific nozzle weld between the contingency overlay repair design and preemptive overlay design because the flaw assumed in the original nozzle weld between these two designs is different as shown in Section 2(b) of the alternative.

(b) Discuss how the thickness of the weld overlay is derived. Use an example to show how an actual overlay thickness is calculated.

Enclosure Page 6 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles SNC Response to NRC Items 7(a) and (b)

(a) The thickness of the weld overlay would be the same in both cases. In both cases, a 100% through-wall flaw with a circumference of 360 degrees is used for design purposes.

(b) The thickness of the overlay is determined based on the assumption of a through-wall flaw, with a length of 360 degrees in the underlying pipe. The overlay is applied, so that the criteria of IWB-3640 are met after the overlay is applied. For example, suppose that the pipe loads in the Alloy 182 region are such that an allowable depth of 75% of the pipe wall is determined from IWB-3640. The new thickness of the pipe would have to be such that the postulated flaw would now be 75% of the new total thickness. Simple math results in an overlay thickness of 33% of the original pipe wall thickness.

8.

NRC Request Page 6. Section 2(b)8 states that the effects of any changes in applied loads, as a result of weld shrinkage from the entire overlay on other items in the piping system shall be evaluated. The licensee also stated that existing flaws previously accepted by analytical evaluation shall be evaluated in accordance with IWB-3640. Confirm that these evaluation results will be completed and available for staff review prior to plant startup.

SNC Response There are no existing flaws that required acceptance by analytical evaluation. Evaluations of the weld shrinkage will be included in the outage summary report.

9.

NRC Request Page 6, last paragraph. The licensee stated that ultrasonic examination procedures and personnel shall be qualified in accordance with Appendix VIII of the ASME Code,Section XI. On Page 10, first paragraph, the licensee mentioned that the Appendix VIII ultrasonic examinations are implemented through the Performance Demonstration Initiative (PDI) program. In similar relief requests by other licensees, a comparison of the ultrasonic examination qualified by the PDI program to the requirements in Appendix VIII of the Code is included to demonstrate the compliance.

(a) Clarify why the proposed alternative did not present such comparison.

(b) Clarify whether the ultrasonic examination will be performed on the maximum extent achievable.

Enclosure Page 7 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles SNC Response to NRC Items 9(a) and (b)

(a) As stated in response to NRC request 4(a) for proposed alternative ISI-GEN-ALT-06-03, SNC intends to use Appendix VIII of the 2001 Edition of Section XI. The PDI Program Status for Code Compliance and Applicability developed in June 2005 indicates that the PDI Program is in compliance with Appendix VIII, 2001 Edition of Section XI as amended and mandated by 10 CFR 50.55a, Final Rule dated October 1, 2004. Therefore, a comparison is not regarded as necessary.

(b) The ultrasonic examination will be performed on the maximum extent achievable.

10. NRC Request Page 7, Section 3(a)2 of the proposed alternative requires that the weld overlay and the adjacent base material for at least one-half inch from each side of the weld shall be examined using the liquid penetrant method. This requirement is not consistent with Section 4.0(b) of Code Case N-638-1, which requires surface and ultrasonic examination of a band on either side of the overlay with an axial length of at least 1.5 times the component thickness or 5 inches whichever is greater. Discuss why the proposed requirement is sufficient to meet Section 4.0(b) of Code Case N-638-1.

SNC Response The examination requirements of N-638-1 are applicable to cavity type repairs and have been utilized for overlay repairs with NRC approval. The non-destructive examination (NDE) requirements in the proposed alternative are only applicable to an overlay repair.

The NDE requirements in the proposed alternative cover the area that would be affected by application of the overlay. Any PWSCC degradation would be in the alloy 8211 82 weld or the adjacent heat affected zone (HAZ). Further, the original weld and adjacent base materials have received a radiographic examination (RT) prior to initial acceptance. The proposed surface and volumetric examinations provide adequate assurance that any defects produced by welding of the overlay or by extension of pre-existing defects would be identified.

11. NRC Request Page 7. Section 3(a)3.(iii) states that any un-inspectible volume in the weld overlay shall be assumed to contain the largest radial planar flaw that could exist within that volume. The assumed flaw shall meet the standards of Table IWB-3514-2 or the requirements of IWB-3640 by evaluation. Confirm that these evaluation results will be completed and available for staff review prior to plant startup.

Enclosure Page 8 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles SNC Response An identification of the examination coverage of each overlay will be developed and available for NRC review prior to plant startup. The evaluation results of postulated flaws in these regions will be completed and will be included in the outage summary report.

12. NRC Request On Page 7:

(a) The acceptance examination of Section 3(a) is performed 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the temperature of the weld overlay reaches the ambient temperature. Discuss when the preservice inspection of Section 3(b) is performed in the sequence of the weld overlay installation.

(b) Section 3(a) contains no requirements regarding the disposition of an unacceptable indication in the weld overlay during the acceptance examination.

However, Section 3(c)6 requires repairlreplacement of the weld overlay if an unacceptable indication is detected in the overlay during inservice inspection.

Explain why similar repairlreplacement requirements are not discussed in Section 3(a), or clarify the requirements for unacceptable indications in Section 3(a).

SNC R e s ~ o n s e to NRC Items 12(a) and (b)

(a) The acceptance examination and preservice inspection are performed at the same time.

(b) For weld overlay examination volumes with unacceptable indications during the acceptance examinations, the unacceptable indications will be removed and the volume will be re-welded.

13. NRC Request Page 8. Section 3(c)(3) states that for Class 1,2, or 3 piping, the acceptance criteria of IWB-3600, IWC-3600, or IWD-3600 shall be met for the weld overlay. However, relief request ISI-GEN-ALT-06-03 is specifically requested for pressurizer piping which is Class 1. Please clarify.

SNC Response Only the acceptance criteria of Class 1 piping in accordance with IWB-3600 shall be met for the weld overlay.

Enclosure Page 9 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles

14. NRC Request On Pages 8 and 9:

(a) Section 3(c)(4) states that the 25 percent of weld overlays in the population will be examined once every ten years. Clarify whether the population of welds to be examined is based on the plant specific number of weld overlays.

(b) Justify the adequacy of the proposed successive examinations in Section 3(c)(5),

because the proposed successive examinations are not consistent with the requirements of IWB-2420 of the ASME Code,Section XI.

SNC Response to NRC Items 14(a) and (b)

(a) The population of welds to be examined is based on the plant specific number of weld overlays.

(b) The proposed overlays are mitigative structural replacements rather than analytical acceptance of indications for which IWB-2420 rules apply. There are no known indications present. The successive proposed IS1 examination schedule is adequate because in the case where cracking is observed re-examination is required within two outages. Any crack growth observed would again require successive examinations within the next two outages.

15. NRC Request Page 9, last paragraph, last sentence. The licensee stated that if a flaw is detected in the upper 25 percent of the original material during the presewice examination, the actual flaw size would be used for the crack growth evaluations. The staff thinks that this flaw size is not a consewative assumption for the crack growth calculations. The current ultrasonic examination is qualified only to detect flaws in the upper 25 percent of the pipe base metal after a weld overlay is applied. Therefore, the condition in the lower 75 percent of the pipe base metal would be unknown. The consewative assumption would be to assume existence of a crack of 75 percent throughwall depth in the lower 75 percent pipe base metal which should be added to the depth of the crack found in the upper 25 percent of the pipe base metal. This worst case crack should be used to calculate crack growth. Discuss why it is acceptable to assume the actual flaw size as you proposed when the ultrasonic examination is only qualified for the upper 25 percent of the pipe metal.

Enclosure Page 10 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles SNC Response As stated in the response to NRC request 6 (b), the as-found flaw size would be the 75%

through-wall flaw postulated, plus any flaws present in the upper 25% of the original weldment. For example, if no flaws were identified in the upper 25% of the weldment, the flaw depth for crack growth purposes would be 75% through-wall. However, if a flaw was found extending 10% of the wall thickness into the upper 25% of the original weldment, the as-found flaw for crack growth purposes would be 85% through-wall. This flaw would then be evaluated for the intended period of operation for growth by PWSCC and fatigue mechanisms.

16. NRC Request (a) Section 2(g) of Appendix 1 to the submittal is different from the corresponding Section (j) in Code Case N-638-1. Section 2(g) of Appendix 1 provides additional requirements for the case when the average lateral expansion value of the heat affected zone of Charpy V-notch specimens is less than the average value for the unaffected base metal. Discuss the technical basis for the requirements in Section 2(g) of Appendix 1.

(b) Section 3.0(c) of Appendix 1 states that the heat input of the first three layers shall not exceed 45,000 Jtinch under any conditions. Provide the technical basis for this heat input.

(c) Section 3.0(c) of Code Case N-638-1 requires that for similar metal welding, the completed weld shall have at least one layer of weld reinforcement deposited. This reinforcement shall be removed by mechanical means, so that the finished surface is flush with the surface surrounding the weld. Discuss whether this requirement should be included in Section 3.0(c) of Appendix 1.

(d) Section 3(d) of Appendix 1 states that the interpass temperature limitation of QW-406.3 does not need to be applied. This condition is not in the corresponding Section 3.0(d) of Code Case N-638-1. Discuss why this condition is included in the proposed alternative.

(e) Discuss the technical basis for the requirements in Section 3(e) of Appendix 1, which are not shown in Code Case N-638-1.

(0 Section 4.0(c) of Code Case N-638-1 requires that areas from which weld-attached thermocouples have been removed be ground and examined using a surface examination method. Discuss whether this requirement should be included in Appendix 1 to the alternative.

Enclosure Page 1 1 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles (g) In Regulatory Guide 1.147, Revision 14, the staff imposed a condition on Code Case N-638-1 regarding ultrasonic examination and associated acceptance criteria based on NB-5330 of the ASME Code, Section 111. Discuss whether this condition will be satisfied.

(h) For the case when it is impossible to measure the temperature of the weld overlay during installation, confirm that requirements in Sections 3(e)(2) and 3(e)(3) of Appendix 1 to the proposed alternative will be used in combination to determine the weld overlay temperature.

SNC Response to NRC Items 16(a) throu~h (h)

(a) This change was incorporated into Code Case N-638-2. The basis for the change is found in the ASME website C&S Connect supporting the action. See Appendix I of this response for the technical basis.

(b) The selected heat input is less than the 50,000 Jlin needed to assure the transformation product is martensite which is subsequently tempered. This was added to address an ASME Main Committee negative vote. The Main Committee negative vote and response are shown in Appendix I1 of this response.

(c) This requirement is not appropriate for inclusion. All weld filler material for this particular application is fully austenitic. This provision is applicable to femtic filler material. When using a femtic filler material, it is necessary to remove the last layer since it is not tempered. This is not a concern for the austenitic filler materials.

(d) This clarification was made due to a recent change incorporated in N-638-2. The basis from the white paper supporting the action is found in ASME C&S Connect for the action. The basis is shown in Appendix I11 to this response.

(e) This set of alternative techniques and analytical methods were included to provide a number of ways to determine interpass temperature. This change was included in N-638-2. The basis from the white paper supporting the action is found in ASME C&S Connect for the action. The basis is shown in Appendix IV to this response.

(0 Welded thermocouples will not be used in this application.

(g) The proposed alterative does not use Code Case N-638-1. The NRC staff imposed condition on Code Case N-638-1 regarding ultrasonic examination and the use of associated acceptance criteria based on NB-5330 of the ASME Code, Section 111, will not be satisfied by SNC. Code Case N-638-1 was not prepared for weld overlay applications; instead, Code Case N-638-1 (and the temper bead welding techniques in IWA-4600) was written to address repair welds where a defect in piping is excavated and the resulting cavity is filled using a temper bead technique. However, an excavated cavity configuration differs significantly from the weld overlay configuration. SNC Enclosure Page 12 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles has concluded that the proposed alternative was written to specifically address weld overlays, and not only does it adequately examine the weld overlays, but it provides more appropriate examinations and acceptance criteria than the NRC staff-imposed position. Conversely, the imposition of ASME Section I11 acceptance standards to weld overlays is inconsistent with years of NRC precedence and without justification given the evidence of past NRC approvals and operating experience. SNC's conclusion is based on the following:

i.

Weld overlays have been used for repair and mitigation of cracking in Boiling Water Reactors since the early 1980s. In Generic Letter 88-01, the NRC approved the use of Section XI acceptance standards for determining the acceptability of installed weld overlays.

ii. Weld overlays for repair of cracks in piping are not addressed by ASME Section 111. ASME Section 111, utilizes nondestructive examination procedures and techniques with flaw detection capabilities that are well within the practical limits of workmanship standards for welds. These standards are most applicable to volumetric examinations conducted by radiographic examination. Radiography (RT) of weld overlays is not appropriate because of presence of radioactive material in the Reactor Coolant system and water in the pipes. The acceptance standards are written for a range of fabrication flaws including lack of fusion, incomplete penetration, cracking, slag inclusions, porosity, and concavity.

However, experience and fracture mechanics have demonstrated that many of the flaws that are rejected using ASME Section 111 acceptance standards do not have a significant effect on the structural integrity of the component.

iii. The UT examinations performed in accordance with the proposed alternative are in accordance with ASME Section XI, Appendix VIII, Supplement 1 1 as implemented through the PDI. These examinations are considered more sensitive for detection of defects, either from fabrication or service-induced, than either ASME Section I11 RT or UT methods. Further, construction type flaws have been included in the PDI qualification sample sets for evaluating procedures and personnel.

iv. Per Section 3(a)3 of the proposed alternative, any planar flaws found during either the acceptance or preservice examination are required to meet the requirements of Table IWB-35 14-2. This approach was previously found acceptable in the NRC Safety Evaluation Report (SER) dated July 21,2004 for Three Mile Island, Unit 1.

However, within the same SER, the NRC had issues regarding the application of Table IWB-35 14-3 to laminar flaws in a weld overlay. The SER stated, "Applying Table IWB-3514-3 to a weld overlay exposes several inherent oversights. For instance, the acceptance of a laminar flaw size is independent of the weld overlay size, and the acceptance criteria is silent on the inaccessible volume beneath the lamination which may hide other flaws beneath the lamination." These issues are addressed in the proposed alternative, as follows:

Enclosure Page 13 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles Per Section 3(a)3i of the proposed alternative, Table IWB-3514-3 has been restricted so that the total laminar flaw shall not exceed 10% of the weld surface area and no linear dimension of the laminar flaw shall exceed 3.0 inches.

Per Section 3(a)3ii of the proposed alternative, the reduction in coverage due to laminations is limited to less than 10% with the dimensions of the uninspectable area based on the coverage obtained by angle beam examinations.

Due to recent overlay issues at Byron, the position stated in Section 3(a)3iii of the proposed alternative, is being altered. The new position is that an uninspectable volume in the weld overlay shall be assumed to contain the largest planar flaw that could exist within that volume. This assumed planar flaw shall meet the requirements of Table IWB-3514-2, or alternately, theflaw will be repaired.

(h) The alternative allows any one of the methods listed in Section 3(e) of Appendix 1 to the proposed alternative. A discussion of the change to N-638-2 and its basis, as well as a response to the Main Committee negative, is found in the response to NRC request 16(e) above.

NRC Request On Page 3: The code of record for both VEGP units and Farley units is the 1989 editions of the ASME Code,Section XI. On page 1, the licensee stated that the second IS1 interval for both VEGP units started on May 31,1997. For Farley Unit 1, the third IS1 interval started on December 1,1997. For Farley Unit 2, the third IS1 interval started on July 30,2001. Based on the aforementioned starting dates of the IS1 intervals, clarify why the code of record for these units is not based on the edition or addenda later than 1989 edition of the ASME Code.

SNC Res~onse 10 CFR 50.55a (g)(4)(ii) states, "lnservice examination of components and system pressure tests conducted during successive 120-month inspection intervals must comply with the requirements of the latest edition and addenda of the Code incorporated by reference in paragraph (b) of this section 12 months before the start of the 120-month inspection interval."

The VEGP 1&2 Second Ten-Year IS1 Interval began on May 3 1, 1997. The Code incorporated by reference in paragraph (b) on May 3 1, 1996 (12 months before the start of the interval), was the 1989 Edition of Section XI with no addenda.

Enclosure Page 14 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles The Farley Unit 1 Third Ten-Year IS1 Interval began on December 1, 1997. The Code incorporated by reference in paragraph (b) on December 1, 1996 (12 months before the start of the interval), was the 1989 Edition of Section XI with no addenda.

By letter dated January 9, 1997 SNC requested that Farley Unit 2 be updated to the 1989 Code at the beginning of Farley Unit 1 Third Ten-Year IS1 Interval. The intent was for the update to cover part of the second and third ten-year IS1 intervals with the next update due on December 1,2007. Refer to the NRC Safety Evaluation dated March 20, 1997 (TAC NOS. M97735 and M97736).

18. NRC Request If the pressurizer surge line in any of the Vogtle or Farley units has been approved for leak-before-break and the weld overlay is applied to the surge line, the licensee needs to confirm that the original leak-before-break analyses are still valid and associated acceptance criteria (e.g., the safety margin on crack size and leak rates as specified in Standard Review Plan 3.6.3) are still acceptable.

SNC Response SNC will confirm that the original leak-before-break analyses are still valid and the associated acceptance criteria will still be met after the weld overlays are applied.

19. NRC Request By letter dated April 28,2006, Exelon submitted a relief request for the preemptive weld overlays of the pressurizers lines at Byron and Braidwood. By letter dated September 14,2006, Exelon committed to provide the NRC, within 14 days after the completion of the ultrasonic examination of the weld overlay installations, (1) the examination results of the weld overlays, (2) a discussion of any repairs to the overlay material and/or base metal and the reason for the repair, and (3) commitment to perform the subsequent insemce examination in accordance with Subarticle Q-4300 of Appendix Q to the ASME Code,Section XI. The staff requests that Southern Nuclear submit the same commitments as specified in Exelon's letter dated September 14,2006, for the contingency and preemptive weld overlay relief requests at Vogtle Units 1 and 2 and Farley Units 1 and 2.

SNC Resvonse SNC commits to provide the NRC, within 14 days after the completion of the ultrasonic examination of the weld overlay installations, (1) the examination results of the weld overlays, and (2) a discussion of any repairs to the overlay material and/or base metal and the reason for the repair. Regarding the Inservice Inspection requirements of Subarticle Q-Enclosure Page 15 of 28

Joseph M. Farley Nuclear Plant Vogtle Electric Generating Plant Response to Request for Additional Information Regarding Proposed Alternative for Application of Full Structural Weld Overlays on Pressurizer Nozzles 4300 of Appendix Q, the proposed alternative has essentially incorporated these Inservice Inspection requirements. A comparison of 4-4300 versus the proposed alternative is provided in Appendix V to this response. The only substantive difference is in Q-4300(e),

where Appendix Q states, "Weld overlay examination volumes that show no additional indication of crack growth or new cracking shall be placed into a population to be examined on a sample basis. Twenty-five percent of this population shall be examined once every ten years." There is not a corresponding statement in paragraph 3(c)5 of the proposed alternative that would allow the use of a sample basis; however, SNC agrees to the use the sample basis.

20.

NRC Request If the presewice inspection (ultrasonic examination) of the installed weld overlay detected indications that are unacceptable per the acceptance criteria of Table IWB-3514-2 of the ASME Code,Section XI, discuss the disposition of the unacceptable indications prior to restart of the plant.

For weld overlay examination volumes with unacceptable indications detected during the preservice inspections, the unacceptable indications will be removed and the volume will be re-welded.

Enclosure Page 16 of 28

APPENDIX I Clarification of Impact Testing Acceptance Criteria and Provisions for an Adjustment Temperature A. Clarification of Acceptance Criteria The current text in paragraph 2.1 (j) of Code Case N-638-1 states: "The average of the three HAZ impact tests shall be equal to or greater than the average values of the three unaffected base metal tests." The current Charpy V-notch test acceptance criteria in Code Case N-638-1 is misleading and inconsistent with the specified acceptance criteria in Section XI applicable to other Class 1 components, since it implies that all three parameters - lateral expansion, absorbed energy, and percent shear fracture - have to be equal or exceed the base material values. This was never the intent of this requirement.

Under the proposed change, the Charpy V-notch acceptance criteria will be revised to read as follows: "The average of the three HAZ Charpy V-notch lateral expansion values shall be equal to or greater than the average value of the three unaffected base metal lateral expansion values... " This change clarifies the intent of the Code Case and aligns its Charpy V-notch acceptance criteria with that of Sections 111 and XI as demonstrated in the code references provided below.

Section XI - IWA-4620, Temper Bead Welding of Similar MaterialsSection XI - IWA-4630, Temper Bead Welding of Dissimilar Materials Section 111 - NB-4330, Impact Test Requirements B. Charpy V-notch Adjustment Temperatures NB-4335 of Section I11 establishes impact testing requirements for welding procedure qualifications that include provisions to determine and apply an "Adjustment Temperature". Although not specifically defined in Section 111, the "Adjustment Temperature" of a welding procedure is the temperature added to the RTNDT or Lowest Service Temperature of materials to compensate for degradation of base material impact properties due to the welding process. Provisions to utilize an "Adjustment Temperature" have existed in Section 111, NB-4335 since the Winter 1974 Addenda of the 1974 Edition.

Where impact testing is required, the acceptability of a welding procedure qualification is based in part on Charpy V-notch testing of the weld heat affected zone. The welding procedure qualification is acceptable if the average lateral expansion value of the heat affected zone specimens is equal to or greater than the average lateral expansion value of the unaffected base material specimens. However, if the heat affected zone average lateral expansion value is less than that of the unaffected base material, an "Adjustment Temperature" must be determined. Alternatively, the welding procedure may be requalified.

According to the 2001 Edition, 2002 Addenda of NB-4335.2(~)(5), (6), or (7) of Section 111, the Adjustment Temperature for the welding procedure may be determined using any of the three methods described below. It should be noted that the Adjustment Temperature determination method described in NB-4335.2(~)(5) has been in the code since the Winter 1974 Addenda; whereas, the NB-4335.2(~)(6) and (7) methods were added to the code by the 2002 Addenda.

Enclosure Page 17 of 28

APPENDIX I (Continued)

NB-4335.2(~)(5): "Additional Charpy V-notch tests shall be performed either on the heat affected zone or the unaffected base material, or both, at temperatures where the lateral expansion value of all three specimens tested is not less than 35 mils. The average lateral expansion value for each test meeting this requirement shall be plotted on a lateral expansion verses temperature graph. The difference in temperature THAZ and TUBM where the heat affected zone and the unaffected base material average lateral expansion values are the same and not less than 35 mils shall be used to determine the Adjustment Temperature TADJ where: TAD, = THAZ

- TUBM If TADJ I 0, then TAD, = 0.

NB-4335.2(~)(6): "As an alternative to NB-4335(c)(5), if the average lateral expansion value of the heat affected zone is no less than 35 mils and the average of the heat affected zone specimens is not less than 5 mils below the average lateral expansion value of the unaffected base material specimens, TADJ may be taken as 15OF."

NB-4335.2(~)(7): "As a second alternative to NB-4335(c)(5), if the average lateral expansion value of the heat affected zone specimens is no less than 35 mils, the difference between the average lateral expansion value of the heat affected zone and the unaffected base material specimens shall be calculated as described in NB-4335.2(e)(3)."

Once determined, the "Adjustment Temperature" must be applied to compensate for the degradation of heat affected zone toughness due to the welding procedure. According to NB-4335.2(e) of the 2001 Edition, 2002 Addenda of Section 111, any of the following three methods may be used.

NB-4335.2(e)(l): "The RTNDT temperature established in NB-233 1 or NB-2332(b) or the lowest service temperature specified in the Design Specification [NB-2332(a)] for all of the material to be welded in production welding procedure specifications (WPSs) supported by this PQR shall be increased by the adjustment temperature TADJ-"

NB-4335.2(e)(2): "The specified testing temperature for the production material may be reduced by the adjustment temperature TADJ."

NB-4335.2(e)(3): "The materials to be welded may be welded using the WPS provided they exhibit Charpy V-notch values that are no less than the minimum required lateral expansion value required by NB-2300 plus the difference in average lateral expansion values established in NB-4335.2(~)(7) or NB-4335.2(d)(5)."

Addition of Adiustment Temperature Provisions to Code Case N-638 Code Case N-638-1 does not presently address utilization of an Adjustment Temperature.

The proposed change will add provisions for determining and applying an Adjustment Temperature that will be consistent with Section 111. This change should also eliminate questions that could result in unwarranted procedure re-qualifications that are costly and time consuming. The proposed change would revise paragraph 2.1 Cj) as follows:

Enclosure Page 18 of 28

APPENDIX I (Continued)

"The average lateral expansion value of the three HAZ Charpy V-notch specimens shall be equal to or greater than the average lateral expansion value of the three unaffected base metal specimens. However, if the average lateral expansion value of the HAZ Charpy V-notch specimens is less than the average value for the unaffected base metal specimens and the procedure qualification meets all other requirements of this Case, either of the following shall be performed:

(1) The welding procedure shall be requalified.

(2) An Adjustment Temperature for the procedure qualification shall be determined in accordance with the applicable provisions of NB-4335.2 of Section 111,2001 Edition with 2002 Addenda. The RTNDT or lowest service temperature of the materials for which the welding procedure will be used shall be increased by a temperature equivalent to that of the Adjustment Temperature."

Enclosure Page 19 of 28

APPENDIX I1 MC Nepative Ballot: # 05-7 Record: # BC04-998 FeldsteinJ (Disapproved)

Date Posted: 02/06/05 Item 5 in the Explanation for this action (The present version of the code case does not contain a requirement to monitor process temperatures during the welding operation) does not mention the elimination of the Section LY interpass temperature variable Q W-406.3 or the fact that computational rather than actual measurements would be permitted for determining the production interpass temperature. Since this code case is specifically written for a non-preheated/PWHT repair when it is impractical to drain the component, the owner or repair organization likely performed the weld procedure qualification with both preheat/interpass temperatures close to room temperature to simulate a water back repair. Section LY limits the application of this PQR to a WPS that does not have an increase of more than 1 OOF in interpass temperature because of the potential effect on notch toughness. What data has SCXI to justlfi eliminating this requirement and to support the use of ANY heat flow computational model for controlling the production maximum interpass temperature?

I believe that given the changes to the welding aspects of this code case a review by SC IX is appropriate.

After discussing this vote with you on the phone, yesterday, 2/24/05, I understand that there are two aspects to your negative vote. The first deals with metallurgical data to support a 350F maximum interpass procedural temperature while the PQR is performed with a maximum 150F interpass temperature.

The second challenges the level of specificity in the method for alternatively computing a maximum interpass temperature rather than by actual measurement.

The following is the basis for the position that employing preheat or interpass conditions up to 350 F would still produce the desired toughness in the weld HAZ in SA 508/533 materials.

Begin with a basis assumption that the desired toughness is produced via the desired HAZ microstructure, and that is a structure of tempered martensite. This is generally supported in the literature, and is stated in conclusion 8a, in NUREG/CR-3873. This NUREG document is an extensive study of the transformation behavior of SA 508 and SA 533 steels for cooling rates associated with weld thermal cycles. In this study, it was determined that there is a critical cooling rate for the formation of this desired structure. Cooling rates slower than this critical cooling rate would produce greater proportions of bainite. The critical cooling rate for SA 508 is approximately 30 dgF/sec, and for SA 533 approximately 40dgF/sec. Any cooling rate higher than this would produce, then, the desired HAZ microstructure. This is shown graphically on page 72 of the above referenced NUREG document.

Setting aside the condition that affects the tempering of the HAZ, the weld bead placement, then, the object of the effort is to select a set of welding conditions that will produce a cooling rate that is greater than the critical cooling rate. This effort is favored by low welding energy input, and "low" preheat and interpass temperature conditions. Furthering this examination, there would logically be a set of welding parameters, albeit lower, that would support an interpass temperature of; say, 350 F.

Enclosure Page 20 of 28

APPENDIX I1 (Continued)

The work of Signes (Welding Journal, 1972, A Simplified Method for calculatina coolina rates in Mild and Low Alloy Steel Weld Metals) shows a table of welding conditions and the attendant cooling rates. In this table, table I, a series of weld energy inputs, base metal thicknesses and initial temperatures is given. From this table it can be clearly seen that for base metal thicknesses of 2 inches or greater and for initial temperatures (either preheat or interpass, as the case may be) above 300 F, that cooling rates are always greater that 40dgF/sec ifthe weld energy input is less than 60 kJ,/in.

A quick extrapolation of these data presented by Signes show that if an upper limit of 5OkJ/in were applied to apreheat or interpass temperature of 350F or less, then a critical cooling rate of 40dgF/sec would never be exceeded. Thus, if such limits were imposed, the beneficial martensitic condition would always be produced in the HAZ.

A practical side note is in order here. The only process permitted for Sec XI ambient temperbead welding is GTAW. The Framatome ANP experience is the maximum energy input that will produce quality ambient temperbead overlays is 36kJ/in. This would be true regardless ofthe organization conducting the work, as it is limited by weld metal quality more so than the condition of the weld HAZ.

Regarding the second concern, I agree with your observation regarding the lack of detail in the methodology used in the heat flow computational alternative. After a review of heat flow calculations used by Framatome ANP, reference, Sindo Kou, Welding Metallurm Copyright 1970, and Warren M. Rohsenow, James P. Harnett, and Ejup N. Ganic, Handbook of Heat Transfer Fundamentals - Second Edition, Copyright 1985, I propose we clarzh this alternative with the following:

"Heat flow calculations shall include, as a minimum, the following variables:

I. Welding heat input (voltage, current, travel speed, including primary and secondarypulse widths, when applicable).

2. Initial or ambient temperature of the item@) being welded.

3. ConJiguration and mass of the item(s) being welded and weld location with respect thereto.

4. Thermal conductivity and diffusivity of the materials being welded.

5. Arc time per pass and delay time between each pass.

6. The total arc time to complete the weld. "

In conclusion, I appreciate the thoroughness of your concerns and trust that the above response and Code Case clarification will enable you to withdraw your negative vote.

David E. Waskey Section X WG-WSRP Chairman Enclosure Page 2 1 of 28

APPENDIX 111 Clarified Existing Interpass Temperature Provision of Paragraph 3.O(D)

ASME IX, QW-256 specifies that the interpass temperature used during production welding shall not be more than 100°F above the interpass temperature used in the procedure qualification. This interpass temperature limitation is a Section IX supplementary essential variable. Code Case N-638 takes exception to thisSection IX supplemental essential variable requirement. Paragraph 2.1 (e) of the Code Case specifies that the maximum interpass temperature for the first three layers of the procedure qualification shall not exceed 150°F; paragraph 3.0(d) specifies that the maximum interpass temperature of the welding procedure shall be 350°F regardless of the interpass temperature during qualification.

Paragraph 2.1 (e) of the Code Case limits the interpass temperature to 1 50°F (maximum) during the procedure qualification. This limitation on interpass temperature was included in the Code Case to ensure that cooling rates obtained during the procedure qualification were more severe than those to be experienced in production welding. In other words, the 150°F (maximum) interpass temperature requirement of paragraph 2.l(e) ensures that cooling rates obtained during the procedure qualification are not slower than those achievable during production welding.

Additionally, the 350°F maximum interpass temperature requirement of paragraph 3.0(d) "for field applications" allows for slower (i.e. less severe) cooling rates which are helpful in producing more ductile transformation products in the heat affected zone.

The proposed change to paragraph 3.0(d) was made to clarify the intent of this requirement. It does not amend or change the original intent of this requirement.

Enclosure Page 22 of 28

APPENDIX IV Requirement to Monitor Process Temperatures during the Welding Process The present revision of Code Case N-638 does not clearly address the monitoring of process temperatures during the production welding operation. The proposed change adds the following requirement in new paragraph 3.0(e):

"The interpass temperature shall he controlled by one of the following methods:

(1) Temperature measurement (e.g. pyrometers, temperature indicating crayons, thermocouples) during welding; (2) Heat flow calculations using the maximum heat input permitted by the welding procedure; (3) Mock-up testing using the maximum heat input permitted by the welding procedure."

The proposed change will allow the use of any temperature monitoring or analytical method that ensures that process temperatures are controlled within the interpass temperature limitations of the welding procedure. Because this Code Case is generally used to perform repair welding on Reactor Coolant System (RCS) components where radiological exposure is a significant concern, temperature monitoring has been generally performed remotely using devices such as infrared thermometers. While thermocouples' are certainly allowed under the proposed change, the radiological exposure associated with their installation and removal (which includes NDE) make them a less attractive option. As an alternative to temperature monitoring methods, analytical evaluations that provide assurance that process temperatures will remain within welding procedure variables can be performed.

Although the use of thermocouples and recording instruments are critical when using traditional temper bead welding procedures that are based on elevated preheat and postweld bake temperatures, their use is not critical to ambient temperature temper bead procedures.

It should be noted that the analytical method included is more specific than that stated above.

See response to (b) above in resolving MC negative.

Enclosure Page 23 of 28

APPENDIX V COMPARISON OF APPENDIX Q-4300 TO THE PROPOSED ALTERNATIVE Q-4300(a) The weld overlay examination volume in Fig. 4-4300-1 shall be added to the inspection plan and shall be ultrasonically examined during the first or second refueling outage following application.

3(c)l The weld overlay examination volume A-B-C-D in the aforementioned Figure 2 shall be added to the applicable inspection plans and shall be ultrasonically examined during the first or second refueling outage following application.

Q-4300(b) The weld overlay examination volume in Fig. 4-4300-1 shall be ultrasonically examined to determine if any new or existing cracks have propagated into the upper 25% of the pipe base material or into the overlay. The angle beam shall be directed perpendicular and parallel to the pipe axis, with scanning performed in four directions.

3(c)2 The weld overlay examination volume in the aforementioned Figure 2 shall be ultrasonically examined to determine if any new or existing cracks have propagated into the upper 25% of the base material or into the overlay. The angle beam shall be directed perpendicular and parallel to the piping axis, with scanning performed in four directions.

Q-4300(c) The inservice examination acceptance standards of Table IWB-3514-2 shall be satisfied for the weld overlay. Alternatively, for Class 1, 2, or 3 piping systems, the acceptance criteria of IWB-3600, JWC-3600, or JWD-3600, as applicable, shall be satisfied for the weld overlay. Cracks in the outer 25% of the pipe base metal shall meet the design analysis requirements of 4-3000.

3(c)3 The inservice examination acceptance standards of Table IWB-35 14-2 shall be met for the weld overlay. Alternatively, for class 1,2, or 3 piping systems, the acceptance criteria of IWB-3600, IWC-3600, or IWD-3600, as applicable, shall be met for the weld overlay. Cracks in the outer 25% of the base metal shall meet the design analysis requirements as addressed in Section 2, "Crack Growth Considerations and Design," of this proposed alternative.

Q-4300(d) Weld overlay examination volumes that show no indication of crack growth or new cracking shall be placed into a population to be examined on a sampling basis. Twenty-five percent of this population shall be examined once every ten years.

3(c)4 Weld overlay examination volumes that show no indication of crack growth or new cracking shall be placed into a population to be examined on a sample basis. Twenty-five percent of this population shall be examined once every ten years.

Q-4300 (e) If inservice examinations reveal crack growth or new cracking, meeting the acceptance standards, the weld overlay examination volume shall be reexamined during the first or second refueling outage following discovery of the growth or new cracking. Weld overlay examination volumes that show no additional indication of crack growth or new cracking shall be placed into a population to be examined on a sample basis. Twenty-five percent of this population shall be examined once every ten years.

3(c)5 If inservice examinations reveal crack growth, or new cracking, meeting the acceptance standards, the weld overlay examination volume shall be reexamined during the first or second refueling outage following discovery of the growth or new cracking.

Enclosure Page 24 of 28

Appendix V (Continued)

COMPARISON OF APPENDIX Q-4300 TO THE PROPOSED ALTERNATIVE Q-4300 (t) For weld overlay examination volumes with unacceptable indications as described in Q-4300(b) and (c), the weld overlay shall be removed, including the original defective piping weldment, and corrected by a repairlreplacement activity in accordance with MA-4000.

3(c)6 For weld overlay examination volumes with unacceptable indications as described above in Paragraphs 3(c)2 and 3(c)3, the weld overlay shall be removed, including the original defective weld, and the item shall be corrected by a repairlreplacement activity in accordance with IWA-4000.

Enclosure Page 25 of 28

Table 1 - Pressurizer Inspection 1 Mitiaation Schedule & Status

...- r--"---

r-------

u------

Identification History I -schedule I Schedule I

APP Vlll APP Vlll 1 1201-~6-002-W; 7 I

I 4 0 %

11 (Spring)

1. 2 - 6" SahtvlRelief I NIA 11 1R1412008 21201-~6-002-~~7 I

I 4 0 %

(Spring)

NIA 1 2R1212007 I

I

<SOX I (Spring) r 1 NI A I

2R12 I2007 21201-~6-002-WIQ

<SO%

(Spring)

1. 4-6"hfdyIRt I

NI A 2R12 12007 21201 -V&O02-W20

• SO%

(Spring)

1. 5 - 4" S ~ n v NIA 2R12 I 2007 21201$6062-i21 I

'90%

C 6 - 14" Sume 1 2R12 12007 I

(Spring)

1. 1 - 6" SlhtylRsIid N/A 1R2112007 Ul-4501-1DM 4 0 %

(Fall)

1. 2 - 6" SlwlRdkf r

NIA r 1R21/2007

~~~1%502-14811-

• SO%

1 (Fall)

NIA 1 R2112007

• SO%

(Fall)

NIA 1 1R2112007

<SO%

1 (Fall)

1. 5-4"Spr89 NIA 1 R2112007 AI&l-4205-35DM

>90%

(Fall)

1. 6 - 14" Surge 1

1 R2112007 1 R2112007 Notes:

) APR 1-4500-7~6 I

1

>90% (Note 1) 1 (Spring)

I (1) Anticipated coverage. Minor surface conditioning may be necessary.

Page 26 of 28

Figure 1 - Typical sa&y / relief nozzle configurdon Figwe 2 - Typical ~psdty node cianfigwation Page 27 of 28

&we 3 -Typical sur e nozzle configuration 42

--.%.,, J, '

Enclosure Page 28 of 28