Text

Revision to Third Ten-Year Inservice Inspection (ISI) Interval Requests ISI-3-27 and ISI-3-28, Use of Structural Weld Overlay and Associated Alternative Repair Techniques
	ML083220131
Person / Time
Site:	San Onofre
Issue date:	11/12/2008
From:	Scherer A; Southern California Edison Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	Download: ML083220131 (52)
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J SOUTHERN CALIFORNIA EDISON An EDISON INTERNATIONAL@ Company A. Edward Scherer Director Nuclear Regulatory Affairs November 12, 2008 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

Docket Nos. 50-361 and 50-362 Revision to Third Ten-Year Inservice Inspection (ISI)

Interval Requests ISI-3-27 and ISI-3-28 Use of Structural Weld Overlay and Associated Alternative Repair Techniques San Onofre Nuclear Generating Station, Units 2 and 3

References:

See Enclosure 1

Dear Sir or Madam:

Pursuant to 10 CFR 50.55a(a)(3)(i), Southern California Edison (SCE) requests approval of Revision 1 to ISI-3-27 (Enclosure 2) and Revision 1 to ISI-3-28 (Enclosure 3) to use alternatives to the requirements of the American Society of Mechanical Engineers (ASME) Code, Section Xl, 1995 Edition through 1996 Addenda, IWA-4000, for repair/replacement activities related to the performance of structural weld overlays at San Onofre Nuclear Generating Station (SONGS)

Unit 2 and Unit 3 for the third 10-year Inservice Inspection (ISI) interval. Revision 1 of these Relief Requests is necessary to increase the applicability to include an additional component.

By letter dated February 21, 2007 (Reference 1), as supplemented by letter dated September 21, 2007 (Reference 2), Southern California Edison (SCE) submitted ISI Relief Request ISI-3-27 in support of performing Structural Weld Overlays on Dissimilar Metal Welds (DMWs) on certain nozzles of the Hot Leg of the Reactor Coolant System (RCS) at San Onofre Units 2 and 3. This request was approved by letter from the NRC dated December 13, 2007 (Reference 3).

By letter dated August 1, 2007 (Reference 4), SCE submitted ISI Relief Request ISI-3-28. This submittal requested approval to begin the 48-hour hold period prior to post-weld Non-Destructive Examination (NDE) following application of the third temperbead layer. Relief Request ISI-3-28 applied to the weld overlays described in Reference 1 as well as additional weld overlays for the Pressurizer surge nozzles. This request was approved by letter from the NRC dated December 13, 2007 (Reference 5).

P.O. Box 128 San Clemente, CA 92674 X cw-r

Document Control Desk November 12, 2008 The weld overlays for the Unit 3 RCS Hot Leg nozzles must be implemented during the current Unit 3 Cycle 15 Refueling Outage. During implementation of these weld overlays, SCE has discovered that the physical configuration of the Unit 3 RCS Hot Leg Surge Line includes additional Code-allowed weld build-up that is not specifically detailed on the engineering drawings. The weld overlay was designed to cover the RCS Hot Leg Surge nozzle to safe end dissimilar metal weld and the adjacent stainless steel weld joining the safe end to the pipe.

The pipe adjacent to the stainless steel weld, however, was found to be slightly shorter than was shown on the engineering drawings and it contains bands of weld material build-up on either end of the pipe. With this configuration, the weld overlay as originally designed would have ended on top of a weld build-up rendering the buildup, as well as the adjacent pipe to elbow weld impossible to inspect via Ultrasonic Testing (UT). To resolve this issue, the design of the weld overlay has been modified to increase the length of the overlay and fully cover.

the pipe weld material build-up to elbow weld as well as the pipe to elbow weld and provide an overlay that is UT inspectable. The purpose of Revision 1 to ISI-3-27 and Revision 1 to ISl-3-28 is to include this additional pipe-to-elbow weld in the scope of the Relief Requests.

SCE is implementing the revised design of the overlay during the current refueling outage. A review of the ASME Section III and Fatigue Crack Growth calculations was made, and compared against the geometry of the modified weld overlay. Although some specific stress values may change as a result of the comprehensive analysis which will be completed for the modified geometry following Mode 4 entry, the conclusions of the current analysis will remain valid for the modified geometry, and the modified weld overlay configuration is acceptable for a minimum of one cycle. The current calculation will be revised to reflect the modified design. Due to the emergent nature of the overlay design modification, the revision to the calculation will not be available until after Mode 4 entry. SCE will submit a summary report of the calculation and its conclusions as soon as it becomes available. Based on the review of the calculations, it is not expected that any of these changes affect the conclusions of References 1 and 4 or the associated Safety Evaluation Reports (SERs).

This situation was not foreseen because of the difficulties (i.e., the dose impact) associated with walking down the actual configuration of the RCS Hot Leg Surge Line nozzle.

In addition, Reference 1 contained inconsistencies that are corrected by Revision 1. These include:

Reference 1 referred inconsistently to the base material of the RCS Hot Leg Surge, Drain, and Shutdown Cooling Surge nozzles as P1 or P3 ferritic steel. The base material for these nozzles consists of P1 ferritic steel.

Document Control Desk November 12, 2008

" A footnote in Reference 1 referred to the recording criteria of the UT examination procedure for examination of the pressurizer overlays.

Reference 1 applied to RCS Hot Leg overlays, not the pressurizer.

" Reference 1, Table 3 stated that the weld overlay would extend to the transition taper of the low alloy steel nozzle. The RCS Hot Leg nozzles that were the subject of Reference 1 consist of carbon steel.

SCE has reviewed References 1 and 4 and the associated Safety Evaluation Reports (SERs) as they relate to these errors and has determined that the conclusions of our requests are not changed.

SCE requests approval of Revision 1 to Relief Requests ISI-3-27 and ISI-3-28 prior to Mode 4 entry for the current Unit 3 Cycle 15 Refueling Outage. Mode 4 is currently forecast for November 21, 2008.

Should you have any questions, please contact Ms. Linda T. Conklin at (949) 368-9443.

Sincerely,

Enclosures:

1. References

2. Revision 1 to Relief Request IS1-3-27

3. Revision 1 to Relief Request ISI-3-28

4. Drawings cc:

E. E. Collins, Regional Administrator, NRC Region IV N. Kalyanam, NRC Project Manager, San Onofre Units 2 and 3 G. G. Warnick, NRC Senior Resident Inspector, San Onofre Units 2 and 3 References

References

1. Letter from A. E. Scherer (SCE) to Document Control Desk (NRC) dated February 21, 2007,

Subject:

Docket Nos. 50-361 and 50-362, Third Ten-Year Inservice Inspection (ISI) Interval Relief Request, ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques, San Onofre Nuclear Generating Station, Units 2 and 3.

2. Letter from A. E. Scherer (SCE) to Document Control Desk (NRC) dated September 21, 2007,

Subject:

Docket Nos. 50-361 and 50-362, Response to Request for Additional Information Regarding Third Ten-Year Inservice Inspection (ISI) Interval Relief Request ISI-3-27, San Onofre Nuclear Generating Station, Units 2 and 3 3 Letter from T. G. Hiltz (NRC) to R. M. Rosenblum (SCE) dated December 13, 2007,

Subject:

San Onofre Nuclear Generating Station, Unit 2 and Unit 3 - Re: Request Approval to Use Alternatives to the Requirements of the American Society of Mechanical Engineers Code, Section Xl, IWA-4000, for Repair/Replacement Activities Related to the Performance of Structural Weld Overlays (TAC Nos. MD4580 and MD4581)

4. Letter from A. E. Scherer (SCE) to Document Control Desk (NRC) dated August 1, 2007,

Subject:

Docket Nos. 50-361 and 50-362, Third Ten-Year Inservice Inspection (ISI) Interval Request ISI-3-28, 48-hour Hold Period, San Onofre Nuclear Generating Station, Units 2 and 3

5. Letter from T. G. Hiltz (NRC) to R. M. Rosenblum (SCE) dated December 13, 2007,

Subject:

San Onofre Nuclear Generating Station, Unit 2 and Unit 3 - Re: Request Approval to Use Alternatives to the Requirements of the American Society for Mechanical Engineers Code, Section Xl, IWA-4000, for Repair/Replacement Activities Related to the Performance of Structural Weld Overlays (TAC Nos. MD6256 and MD6257)

Southern California Edison (SCE)

San Onofre Nuclear Generating Station (SONGS), Units 2 and 3 Docket No. 50-361 and 50-362 Revision 1 to Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques CONTENTS 1.0 REASON FOR THE REQUEST.................................

2 2.0 CODE COMPONENTS FOR WHICH RELIEF IS REQUESTED..............

3 3.0 CODE REQUIREMENTS FOR WHICH RELIEF IS REQUESTED..........

4 4.0 PROPOSED ALTERNATIVES AND SUPPORTING INFORMATION......

5 5.0 DURATION OF THE PROPOSED RELIEF REQUEST...........................

13 6.0 P R E C E D E N T S......................................................................................

.. 14 7.0 R E F E R E N C E S.......................................................................................

. 14 8.0 C O N C LU S IO N........................................................................................

.. 15 ATTACHMENT 1 Table 1:

Modifications To Code Case N-504-2 and Corresponding Nonmandatory Appendix Q Requirements Table 2:

Alternatives To Appendix VIII. Supplement 11 Table 3:

Modification To Code Case N-638-1 ATTACHMENT 2 Chemical Analyses of Incremental Milling of Weldment ATTACHMENT 3 Comparison of Code Cases N-504-2 and N-504-3 and Discussion of Differences SONGS Unit 2 and Unit 3 Page 1 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(i)

- Alternative Provides Acceptable Level of Quality and Safety -

1.0 REASON FOR THE REQUEST Currently, there are no comprehensive criteria for a licensee to apply a structural weld overlay repair to a dissimilar metal weld that is constructed of Alloy 82/182 weld material, which is susceptible to primary water stress corrosion cracking (PWSCC). Although the American Society of Mechanical Engineers (ASME)

Boiler and Pressure Vessel Code, Section Xl, 1995 Edition through 1996 Addenda, IWA-4000 (Reference 1), is used for the San Onofre Nuclear Generating Station (SONGS) Unit 2 and Unit 3 Section Xl repair/replacement program, it does not have the needed requirements for this type of repair. The latest Nuclear Regulatory Commission (NRC) approved ASME Code also does not have the needed requirements for this type of repair. Repair/replacement activities associated with a structural weld overlay repair of this type are requi'red' to address the materials, welding parameters, ALARA concerns, operational constraints, examination techniques, and procedure requirements. Thus, this is the reason for this relief request.

Revision 1 to ISI-3-27 is necessary to increase the applicability of the Relief Request to include additional components.

The weld overlays for the Unit 3 RCS Hot Leg nozzles must be implemented during the current Unit 3 Cycle 15 Refueling Outage. During implementation of these weld overlays, SCE has discovered that the physical configuration of the Unit 3 RCS Hot Leg Surge Line includes additional Code-allowed weld build-up that is not specifically detailed on the engineering drawings. The weld overlay was designed to cover the RCS Hot Leg Surge nozzle to safe end dissimilar metal weld and the adiacent stainless steel weld ioining the safe end to the pipe.

The pipe adiacent to the stainless steel weld, however, was found to be slightly shorter than was shown on the engineering drawings and it contains bands of weld material build-up on either end of the pipe. With'this configuration, the weld overlay as originally designed would have ended on top of a weld build-up rendering the buildup, as well as the adiacent pipe to elbow weld impossible to inspect via Ultrasonic Testing (UT). To resolve this issue, the design of the weld overlay is being modified to increase the length of the overlay and fully cover the pipe weld material build-up to elbow weld as well as the pipe to elbow weld and provide an overlay that is UT inspectable.

In addition, Revision 0 of ISI-3-27 contained miscellaneous inconsistencies in reference to components and the associated materials. Revision 1 to ISI-3-27 also corrects these inconsistencies.

Page 2 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques 2.0 CODE COMPONENTS FOR WHICH RELIEF IS REQUESTED Group: High safety significant (HSS) Class 1 dissimilar metal piping welds with Alloy 82/182 weld metal are susceptible to PWSCC and adjacent stainless steel welds.

a)

Name of Components:

1. Reactor Coolant System Hot Leg surge nozzle to safe end HSS dissimilar metal welds (ISI Designation Number 02-006-010/03-006-010) with Alloy 82/182 weld material subject to PWSCC.

2. Reactor Coolant System Hot Leg surge nozzle adjacent stainless steel welds (ISI Designation Number 02-016-016/03-016-016) and adiacent pipe-to-elbow stainless steel welds (ISI Designation Number 02-016-015/03-016-015).

3. Reactor Coolant System Hot Leg drain nozzle to safe end HSS dissimilar metal welds (ISI Designation Number 02-006-011/03-006-011) with Alloy 82/182 weld material subject to PWSCC.

4. Reactor Coolant System Hot Leg drain nozzle adjacent stainless steel welds (ISI Designation Number 02-030-001/03-030-010).

.5.

Shutdown Cooling System Hot Leg nozzle to safe end HSS dissimilar metal weld (ISI Designation Number 02-007-009/03-007-009) with Alloy 82/182 weld material subject to PWSCC.

6. Shutdown Cooling System Hot Leg nozzle adjacent stainless steel welds (ISI Designation Number 02-021-001/03-021-010).

Except where noted differently in item 2, above, the "adiacent" stainless steel weld refers to the safe-end-to-pipe stainless steel weld.

The Unit 2 stainless steel pipe to elbow weld (ISI 02-016-015) is included in this request contingent upon final inspection and confirmation of sizing of the Unit 2

,eVo I

-weld overlay.

b) ASME Code Class:

These welds are all ASME Code Class 1 welds located within the reactor coolant pressure boundary c) System:

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Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Reactor Coolant System (RCS) d) Code Category:

Examination Category B-J, "Risk-Informed Piping Examinations" e.1)

Code Item No. B9.11 "Welds subject to PWSCC" (ISI Designation Numbers 02-006-010, 02-007-009, 03-006-010, and 03-007-009)

"Welds subject to Thermal Fatigue" (ISI Designation Numbers 02-006-010, 02-007-009, 02-016-015, 02-016-016, 02-021-001, 03-006-010, 03-007-009, 03-016-015, 03-016-016, and 03-021 -010) e.2)

Code Item No. B9.21 "Welds subject to PWSCC" (ISI Designation Number 02-006-011 and 03-006-011)

"Welds subject to Thermal Fatigue" (ISI Designation Numbers 02-006-011., 03-006-011, 02-030-001, and 03-030-010) 3.0 CODE REQUIREMENTS FOR WHICH RELIEF IS REQUESTED 1995 Edition through the.1996 Addenda of the ASME Code Section XI, (Reference 1), IWA-4610(a).

1995 Edition with the 1996 Addenda, of the ASME Code, Section Xl, Appendix VIII, Supplement 11 (Reference 2).

Modification to the Nuclear Regulatory Commission (NRC) approved Code Case N-504-2 (see below) with the 2005 Addenda, Nonmandatory Appendix Q j *- -

(Reference 3).

Code Case N-638-1 (Reference 4)., Tables 1, 2, and 3 provide details of relief requested from each of the above requirements.

The Weld Overlays will be performed in accordance with the requirements of American Society of Mechanical Engineers (ASME) Code Case N-504-2, with modifications described below and in Attachment 1. When Revision 0 of Relief Page 4 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Request ISI-3-27 was originally submitted, Code Case N-504-2 was the latest version of this Code Case approved by the NRC as stated in NRC Regulatory Guide 1.147, Revision 14. Revision 0 of ISI-3-27 was approved by the NRC allowing, in part, use of Code Case N-504-2 with the modifications proposed by SCE. In October of 2007, NRC issued Revision 15 of RG 1.147, which endorses Code Case N-504-3.

SCE has performed a review of Code Case N-504-3 to determine the differences between the two revisions of the Code Case. This review determined that the changes incorporated into Code Case N-504-3 either do not apply to the proposed Weld Overlays or are met by the modifications Code Case N-504-2 that were proposed by SCE and approved by the NRC as ISI-3-27, Revision 0. provides a description of the differences between Code Case N-504-2 and N-504-3 and a discussion of how the proposed Relief Request is consistent with Code Case N-504-3 or the previously approved modifications to Code Case N-504-2.

Page 5 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques 4.0 PROPOSED ALTERNATIVES AND SUPPORTING INFORMATION Full Structural Weld Overlay Desian Criteria A structural weld overlay repair is proposed for the dissimilar metal welds identified in Section 2.0 a).

in the following table.

The material of the above three nozzles is provided Dissimilar Metal Weld Nozzle Material Safe End Material Identifier Hot Leg Surge Line Unit 2: SA-105 SA-351 GR CF8M 02-006-010/03-006-010 GR II Forging Stainless Steel Cast Unit 3*: SA-541 C1 1 Forging Hot Leg Drain Line SA-105 GR II SA-182 F316 Forging 02-006-011/03-006-011 Forging Shutdown Cooling Line Unit 2: SA-105 SA-351 GR CF8M 02-007-009/03-007-009 GR II Forging Stainless Steel Cast Unit 3*: SA-541 C1 1 Forqgin Adjacent Stainless Steel Pipe Material Weld Identifier Hot Leg Surge Line SA-376 Grade TP316 02-016-016/03-016-016 Hot Leg Surge Line SA403 Grade WP 316 02-016-015/03-016-015 Hot Leg Drain SA-376 Grade TP316 02-030-001/03-030-010 Shutdown Cooling Line SA-403 Grade WP316 02-021-001/03-021-010

As described in SCE's letter dated Auaust 29, 2008, the Nozzle Material for the 6~.1..

Unit 3 forainas is SA-541. Class 1 rather than SA-1 05 GR II 4 Q"/ - 1, The overlay will be designed as a structural weld overlay in accordance with ASME Section X1 Code Case N-504-2 and Nonmandatory Appendix Q (Reference 3). The temper bead welding technique will be implemented in accordance with ASME Section Xl Code Case N-638-1 (Reference 4) for that portion of the overlay applied over the ferritic base material for which the Construction Code requires post-weld heat treatment. Temperature monitoring requirements contained within this Code Case will be performed using contact Page 6 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques pyrometers in lieu of thermocouples required by IWA-4610(a) of the ASME Code, Section Xl 1995 Edition through 1996 Addenda (Reference 1).

I The weld overlays will be sized as Full-Structural Weld Overlays designed to satisfy the ASME Section III requirements without crediting the existing pipe.

See Attachment 2 for the chromium content information of the weld material being used.

In the sizing calculations, SCE assumes the crack depth for weld overlay (WOL) sizing is equal to the original wall thickness (t orig pipe). To meet the general Section Xl requirement that no flaw of depth greater than 75% through-wall is acceptable, this requires:

crack depth / (t orig pipe + t WOL)

= 0.75, twol = 1/3 original pipe wall thickness.

SCE also considers the piping loads in the WOL sizing. The final size of each WOL will be the larger of these two calculations.

The planned full-structural WOL is designed to be more conservative than an "optimized "WOL that assumes a crack depth equivalent to 75% of the original wall thickness only.

Crack growth calculations will be performed to determine the time for any observed flaw indications to grow to the overlay design basis in the structural sizing calculations (through wall flaw) due to fatigue and stress corrosion crack growth. These calculations will use as an initial flaw size the flaw depth detected by NDE (if any) prior to the weld overlay. If no flaws are detected, the initial flaw size will be assumed to be 10% of the original wall thickness, based on a conservative estimate of the detection threshold for the NDE.

This structural weld overlay (weld reinforcement) will completely cover the existing Alloy 82/182 weld metal and will extend onto the ferritic and austenitic stainless steel material on each end of the weld. To avoid stress risers, the weld material is extended and tapered across the pipe and nozzle side. The end slope is required to be no steeper than 45 degrees to minimize stress concentration.

Sufficient overlay length is provided to allow for adequate transfer of axial loads between the pipe and the weld overlay. Therefore, the length of the actual structural weld overlay will exceed the minimum length required by ASME Code Case N-504-2 and Section XI Appendix 0 for load redistribution and inspection purposes.

It is important to note that inspection requirements are a controlling factor in the structural weld overlay repair design. The length of the structural weld overlay Page 7 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques must be sufficient for inspection of an area that is 1/2 inch beyond the required repair length and the outer 25% of the original wall thickness. It should be noted that the length of the structural weld overlay may be extended and blended into the low alloy steel nozzles outer diameter taper to permit UT inspection of the weld and minimize stress concentration on the nozzle outer diameter. Since generally the outside diameter of the nozzle is larger than that of the safe end, the structural weld overlay thickness on the safe end will be increased to allow a smooth transition surface for UT inspection. Therefore, the final structural weld overlay length and thickness after taking into consideration the UT inspection requirements will exceed the length required for a structural weld overlay repair in accordance with the ASME Code Case N-504-2 and Section XI Appendix Q.

In summary, the combination of deposition of PWSCC resistant weld reinforcement on the outside surface of the dissimilar metal weld, with favorable axial and hoop residual compressive stress produced on the inside diameter due to shrinkage will result in acceptable assurance for long term crack mitigation. In addition, inservice inspection is facilitated because of the enhanced ability to inspect the joint.

Code Case N-504-2(g) Flaw Evaluations and Shrinkage Stress Effects Analyses Flaw evaluations and shrinkage stress effects evaluations will be completed prior to returning Unit 2 and Unit 3 to service from their respective Cycle 15 refueling outage. The evaluation records will be maintained on site and available for NRC review at any time.

Pre-Weld Overlay Non-Destructive Examinations (NDE)

SCE will perform NDE to meet the requirements of Appendix VIII, Supplement 10, as modified by the Performance Demonstration Initiative (PDI) Program.

However, because the material of the hot leg surge line safe end and the shutdown cooling line safe end is cast austenitic stainless steel SCE will perform the qualified Appendix VIII, Supplement 10, as modified by the PDI Program UT exam, on the Alloy 82/182 welds from the nozzle side, which is ferritic steel.

Appendix VIII, Supplement 9 "Qualification Requirements for Cast Austenitic Piping Welds" is in the course of preparation and is not required by 10CFR50.55a(g)(6)(ii)(C).

Therefore, to meet the RI-ISI UT examination requirement of the hot leg surge line and shutdown cooling line nozzles, SCE will perform UT examination from the cast austenitic stainless steel side in accordance with ASME Section Xl, Appendix Ill. Additionally, the UT examination of the stainless steel weld adjacent to the hot leg surge line and shutdown cooling line nozzles will be performed in accordance with ASME Section XI, Appendix III from the cast austenitic stainless steel side and Appendix VIII, Supplement 2, as modified by the PDI Program UT exam, from austenitic stainless steel side. As the hot leg surge line stainless steel pipe-to-4 Page 8 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques elbow weld consists of austenitic steel only the UT examination has been performed in accordance with Appendix VIII, Supplement 2, as modified by the PDI Proqram UT exam.

Post Weld Overlay NDE The examinations of the completed full structural weld overlay and heat affected zone beneath the weld overlay will be performed in accordance with the requirements of Code Case N-504-2 and Appendix Q, including the flaw acceptance standards specified in Article Q-4000. These inspections, and associated acceptance standards provide full assurance that the weld and adjoining base material are fully capable of performing their intended function.

Thus it is SCE's intent to meet the condition specified in Regulatory Guide 1.147 for the use of Code Case N-504-2. The following discussion is provided to clarify how SCE will comply with the condition specified in Regulatory Guide 1.147.

ASME Section XI pre-service acceptance standards, as specified in Appendix0Q, are the appropriate standards for pre-service ultrasonic examinations of weld' overlay repairs to nuclear plant components. These standards are consistent with the highly sensitive ultrasonic examination procedures being used, which are qualified in accordance with ASME Section Xl, Appendix VIII, Supplement 11 as implemented via the EPRI Performance Demonstration Initiative (PDI). The post-repair inspection volume includes the full thickness of the weld overlay plus 25% of the underlying base metal/weldment thickness. The specimen sets -for PDI qualification of weld overlay examinations include construction type flaws in the overlays in addition to simulated service flaws in the underlying base metal and weldment. Therefore, use of PDI-qualified personnel and procedures will result in the reliable detection of construction type flaws.

The ASME Section Xl flaw acceptance standards are based on fracture mechanics principles that evaluate the potential effect of flaw indications on the safe operation of a component. ASME Section III ultrasonic standards, on the other hand, are derived from radiographic standards in earlier construction codes and tend to be workmanship-based, addressing flaws occurring in the original construction process that are likely to be detected by radiography. The ASME Section III acceptance criteria do not allow the presence of any cracks or crack-like indications, regardless of their size, and are geared more towards construction-type welds. Many indications that are detectable by PDI qualified ultrasonic techniques, and thus require evaluation, would not be detected by the radiographic examinations required by the original construction Code or Section Ill.

The Section X1 pre-service examination standards were developed for exactly the above-stated reasons, and consider the materials in which the flaw indications are detected, the orientation and size of the indications, and ultimately their I Page 9 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques potential structural impact on the component. They are the logical choice for evaluation of potential flaw indications in post-overlay examinations, in which unnecessary repairs to the overlays would result in additional personnel radiation exposure without a compensating increase in safety and quality, and could potentially degrade the effectiveness of the overlays by affecting the favorable residual stress field that they produce.

Acceptance of ultrasonic indications in weld overlay repairs using Section XI acceptance criteria has been approved by NRC in past weld overlay applications (e.g. References 1, 2).

Qualification requirements for full structural overlaid wrought austenitic piping welds, (i.e., ASME Section XI, Appendix VIII, Supplement 11 as modified by the PDI program).are not currently qualified for cast austenitic stainless steel. The hot leg surge line and shutdown cooling line nozzle safe end are cast austenitic stainless steel. For the 25% of the underlying cast austenitic stainless steel of the structural weld overlay SCE will perform an UT examination using the best available technique for the pre-service and inservice inspections for these welds-This is consistent with information provided to support previously approved relief requests ISI-3-18 and ISI-3-24.

Code Case N-638-1 addresses the use of the temper bead welding technique including those welds made in deep cavities in ferritic material. In the case of weld overlays to be applied at SONGS Unit 2 and Unit 3, this technique will be used to apply a non-ferritic overlay to the P1 ferritic nozzle base material adjacent to the dissimilar metal weld (DMW). The PDI qualified ultrasonic examination procedure is designed and qualified to examine the entire volume of the overlay weld as well as the region of the P1 material containing the weld heat I¢,,.-I affected zone (HAZ) and a volume of unaffected base material beyond the HAZ.

In addition to verifying the soundness of the weld, a purpose of these examinations is to assure that delayed cracking that may be caused by hydrogen introduced during the temper bead welding process is not present. In the unlikely event that this type of cracking does occur, it would be initiated on the surface on which the welding is actually performed or in the HAZ immediately adjacent to the weld. The most appropriate technique to detect surface cracking is the surface examination technique that SCE will perform on the weld overlay and the adjacent base material in a band at least 1.5 times the thickness of the base material on either side of the overlay. The maximum achievable inspection volume is 100 percent of the volume susceptible to weld induced flaws.

While it would be possible to extend the examination volume to a larger extent on either side of the weld overlay, it would not be possible with current technology to ultrasonically inspect 100 percent of the volume within 1.5 times the thickness of the base material because of geometric considerations. Inspection of an increased volume would result in increased dose to inspection personnel without Page 10 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques a compensating increase in safety or quality because there is no plausible mechanism for formation of new flaws or propagation of existing flaws in the region. The overlay volume is small relative to the volume of the underlying pipe and does not present the same concerns as those related to welds in deep cavities contemplated by the requirements of Code Case N-638-1. Therefore, the examinations tailored for overlay inspection and required by Code Case N-504-2 and Appendix Q, as modified in the request for relief, provide full assurance that the weld and adjoining base material are fully capable of performing their intended function.

Later revisions to Code Case N-638-1 (N-638-2 and N-638-3), approved by ASME Code in 2005 and 2006 respectively recognize that inspection of the larger volume is not necessary to assure quality and safety.

The NRC has previously granted relief on this specific issue for temper bead welding for use at other plants for the reasons mentioned above. Specifically, San Onofre Nuclear Generating Station Unit 2 in December of 2006, Millstone Power Station, Unit No. 3 in January 2006, and Three Mile Island Unit 1 in Fall, 2003 have received approval to use inspection methods essentially identical to those proposed by SCE for San Onofre Unit 2 and Unit 3 by ISI-3-27.

Page 11 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Post Weld Overlay NDE Report A report that summarizes the results of the examinations will be submitted to the NRC within fourteen days of completion of the final UT examination. The report will include the following details as applicable, S

S 0

S a listing of indications detected1 the disposition of all indications using the standards of ASME Section Xl, IWB-3514-2 and/or IWB-3514-3 criteria and, if possible, the type and nature of the indications,2 and a discussion of any repairs to the overlay material and/or base metal and the reason for the repair.

'The recording criteria of the ultrasonic examination procedure to be used for the examination of the SONGS RCS Hot Leg overlays will require that all indications, regardless of amplitude, be investigated to the extent necessary to provide accurate characterization, identity, and location.

Additionally, the procedure requires that all indications, regardless of amplitude, that cannot be clearly attributed to the geometry of the overlay configuration be considered flaw indications.

2 The ultrasonic examination procedure requires that all suspected flaw indications are to be plotted on a cross sectional drawing of the weld and that the plots should accurately identify the specific origin of the reflector.

Page 12 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Comprehensive Criteria of the Weld Overlays Tables 1, 2, and 3, when used with the ASME Code,Section XI, 1995 Edition through 1996 Addenda, Article IWA-4000 (Reference 1), provide a comprehensive package of proposed detailed criteria with requirements, proposed alternatives, methodologies, modifications, and the bases for these differences, to support this relief request.

This SONGS Unit 2 and Unit 3 structural weld overlay repair of a piping weld with Alloy 82/182 weld material will be performed as a repair/replacement activity in accordance with IWA-4000 of the 1995 Edition, through 1996 Addenda, of ASME Section XI (Reference 1) with the exception of the requirements in IWA-4610(a).

In lieu of the weld-attached thermocouple requirements and recording instruments in IWA-4610(a), contact pyrometers and manual recording of the process temperatures will be used at SONGS Unit 2 and Unit 3. These contact pyrometers will be calibrated in accordance with the measuring and test equipment program and will be capable of monitoring the process temperatures from 50 0F, minimum preheat temperature to 350'F, maximum interpass temperature. Additionally, the methodology of Code Case N-504-2 (Reference 3), as modified and shown in Table 1,.will be used.

The ultrasonic examination of the completed structural weld overlay will be accomplished in accordance with ASME Section XI, 1995 Edition with the 1996 Addenda, Appendix VIII, Supplement 11 (Reference 2) with the alternatives used to comply with the Performance Demonstration Initiative (PDI) program as shown in Table 2.

The temper bead weld technique requirements in accordance with Code Case N-638-1 (Reference 4) will be applied to the ferritic nozzle base material with the modifications described in Table 3. Code Case N-638-1 specifies a limit of 100 square inches for a temper bead weld. Approval to exceed this limit will be needed for the hot leg surge line and the shutdown cooling line nozzles. The intent of the code case is clarified to limit the area of an individual weld over the ferritic material. Electric Power Research Institute Technical Report 1003616 (reference 6) provides justification fdr a maximum area of 500 square inches.

The hot leg surge line and shutdown cooling line nozzle weld area can be assumed to not exceed 300 square inches. SCE is anticipating the weld overlays on ISI Designation 02-006-010, 03-006-010, 02-007-009, and 03-007-009 will exceed 100 square inches. The weld overlays on 02-006-011 and 03-006-011 will not exceed 100 square inches.

Any applicable requirements not addressed by Tables 1, 2, and 3 will be met as described in Section XI, 1995 Edition through 1996 Addenda, IWA-4000 Page 13 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques (Reference 1); Appendix VIII, Supplement 11 (Reference 2); Code Case N-504-2 (Reference 3); and Code Case N-638-1 (Reference 4).

Code Case N-504-2 (Reference 3) is approved for use for austenitic stainless steel material in NRC Regulatory Guide 1.147, Revision 14, August 2005, provided it is used with Nonmandatory Appendix Q, of ASME Section Xl, 2005 Addenda. Provided in Table 1 are SCE's proposed modifications for structural weld overlay repair of nickel based and ferritic materials due to the specific construction of the SONGS Unit 2 and Unit 3 dissimilar metal welds. Therefore, SCE intends to follow the methodology of Code Case N-504-2 (Reference 3),

except for the modifications identified in Table 1.

5.0 DURATION OF PROPOSED RELIEF REQUEST This request will be applied for the remainder of the current SONGS Unit 2 and Unit 3 third 10-year ISI interval that started on August 18, 2003. Once these structural weld overlays are installed they will remain in place for the design life; of the repair that is defined by the evaluation required in paragraph (g) of Code Case N-504-2 and corresponding requirements in Nonmandatory Appendix Q (Reference 3). The structural weld overlays are also subject to the satisfactory examination requirements of Article Q-4000 for inservice inspection. Those requirements include adding anyinstalled structural weld overlay repairs into the SONGS Unit 2 and Unit 3 ISI plan per Subarticle 0-4300 for at least one inservice examination to be completed within the next 2 refueling cycles.

Page 14 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques 6.0 PRECEDENTS

1.

Letter from Richard J. Laufer, NRC, to Christopher M. Crane, AmerGen, "Three Mile Island Nuclear Station, Unit 1 (TMI-1) Request for Relief from Flaw Removal, Heat Treatment, and Nondestructive Examination Requirements for the Third 10-year Inservice Inspection (ISI) Interval (TAC.No. MC1201)," Accession Number ML041670510, dated July 21, 2004.

2.

Letter from Richard J. Laufer, NRC, to Bryce L. Shriver, PPL Susquehanna, "Susquehanna Steam Electric Station, Unit 1 - Relief from American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (ASME Code), Section Xl, Appendix VIII, Supplement 11, Requirements and Code Cases N-504-2 and N-638 Requirements (TAC Nos. MC2450, MC2451 and MC2594)," Accession Number ML051220568, dated June 22, 2005.

3.

Letter from L. Raghavan, NRC, to Mano K. Nazar, I&M, "Donald C. Cook Nuclear Plant, Unit 1 - Alternative to Repair Requirements of Section Xl of the American Society of Mechanical Engineers Code (TAC No.

MC06751)," Accession Number ML051720006, dated June 27, 2005.

4.

Letter from Richard J. Laufer, NRC, to George Vanderheyden, Calvert Cliffs, "Calvert Cliffs Nuclear Power Plant, Unit No. 2 - Relief Request for Use Weld Overlay and Associated Alternative Inspection Techniques (TAC Nos. MC6219 and MC6220)," Accession Number ML051930316, dated July 20, 2005.

5.

Letter from Leslie N. Darrell J. Roberts, NRC, to David A. Christian Dominion Nuclear Connecticut, Inc., "Millstone Power Station, Unit No. 3 -

Issuance of Relief from Code Requirements (TAC No. MC8609),"

Accession Number ML053260012, dated January 20, 2006.

6.

Letter from David Terao (NRC) to Richard M. Rosenblum (SCE), "San Onofre Nuclear Generating Station, Unit 2 - Re: Request for Relief From the Requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (TAC No. MD0191) dated December 14, 2006.

Page 15 of 16

Relief Request ISI-3-27, Revision 1 Use of Structural Weld Overlay and Associated Alternative Repair Techniques

7.0 REFERENCES

(1) 1995 Edition through 1996 Addenda, ASME Code, Section Xl, IWA-4000.

(2) 1995 Edition, ASME Code, Section Xl, with the 1996 Addenda, Appendix VIII, Supplement 11.

(3)

ASME Code Case N-504-2, Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Section Xl, Division 1, March 12, 1997, including ASME Code Section Xl, 2005 Addenda, Nonmandatory Appendix Q, Weld Overlay Repair of Class 1L, 2, and 3 Austenitic Stainless Steel Piping Weldments.

(4)

ASME Code Case N-638-1, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique Section Xl, Division 1, February 13, 2003.

(5)

Letter from A. E. Scherer (SCE) to the U. S. Nuclear Regulatory Commission dated February 22, 2006;

Subject:

Docket Nos. 50-361 Third Ten-Year Inservice Inspection (ISI) Interval Relief Request ISI 18 Use of Structural Weld Overlay and Associated Alternative Repair Techniques, San Onofre Nuclear Generating Station, Unit 2 (6)

Electric Power Research Institute Technical Report 1003616, "Additional Evaluations to Extend Repair Limits for Pressure Vessels and Nozzles," March 2004.

8.0 CONCLUSION

SCE has determined that the approach described in this relief request includes available operating experience (OE) related to previously approved NRC requirements that have been used to produce acceptable structural weld overlay repairs when applied to a dissimilar metal weld with Alloy 82/182 weld material.

The basis for this determination is the application of this same type of structural weld overlay repair at Three Mile Island, Donald C. Cook, Calvert Cliffs, Millstone, and SONGS Unit 2 and Unit 3. Those structural weld overlay repairs were based on, and this relief request includes, the NRC approved ASME Code requirements and Code Cases. SCE believes that the use of this relief request for a structural weld overlay repair at SONGS Unit 2 and Unit 3 will result in an acceptable level of quality and safety that meets the requirements of 10 CFR 50.55a(a)(3)(i).

Page 16 of 16

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques San Onofre Nuclear Generating Station, Unit 2 and Unit 3, Comprehensive Criteria For Structural Weld Overlay of Welds Contains Modifications and Alternatives for the Use Of Relief Request ISI-3-27 Tables 1, 2, and 3

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 1 Modifications To Code Case N-504-2 and Corresponding Non-Mandatory Appendix Q Requirements Code Case N-504-2 Modification/Basis Reply: It is the opinion of the Committee that, in lieu of the Modification. Code Case N-504-2 will be used for weld overlay requirements of IWA-4120 in Editions and Addenda up to and repairs to the ferritic (P1) and nickel alloy (F43/P43) material as including the 1989 Edition with the 1990 Addenda, in IWA-well as the austenitic stainless steel (P8) material.

4170(b) in the 1989 Edition with the 1991 Addenda up to and Basis: Code Case N-504-2 is accepted for use along with including the 1995 Edition, and in IWA-4410 in the 1995 Edition Nonmandatory Appendix Q in the current NRC Regulatory with the 1995 Addenda and later Editions and Addenda, defect Guide 1.147 Rev. 14. For the weld overlay of the identified in austenitic stainless steel piping may be reduced to a flaw of welds at SONGS Unit 2 and Unit 3 the base material will be acceptable size in accordance with IWB-3640 from the 1983 ferritic material (P1) with existing nickel alloy weld metal Edition with the Winter 1985 Addenda, or later Editions and (F43/P43) to which an austenitic stainless steel (P8) safe end is Addenda, by deposition of weld reinforcement (weld overlay) welded. Industry operational experience has shown that on the outside surface of the pipe, provided the following PWSCC in Alloy 82/182 will blunt at the interface with stainless requirements are met. [Essentially same as Scope of steel base metal, ferritic base metal, or Alloy 52/52M weld Appendix Q]:

metal. SONGS Unit 2 and Unit 3 plans to apply a 360-structural weld overlay to control growth in any PWSCC crack and maintain weld integrity. The weld overlay will induce compressive stress in the weld, thus impeding growth of any reasonably shallow cracks. Furthermore, the overlay will be sized to meet all structural requirements independent of the existing weld.

(b) Reinforcement weld metal shall be low carbon (0.035%

Modification. In lieu of austenitic stainless steel filler material, max.) austenitic stainless steel applied 360- around the the reinforcement weld metal will be a nickel alloy.

circumference of the pipe, and shall be deposited in Basis: The weld metal used may be ERNiCrFe-7A (Alloy 52M, accordance with a qualified welding procedure specification UNS N06054) or ERNiCrFe-7 (Alloy 52 UNS N06052). This identified in the Repair Program. [Same as Q-2000(a)]

weld metal is assigned F43 by ASME per Code Case 2142-2.

The requirements of ASME-Section Ill, NB-2400 will be applied to all filler material. The chromium content of Alloy 52M is 28-31'.5%, identical to that of Alloy 52. The main difference in Alloy 52 vs. Alloy 52M is a higher Niobium content (0.5-1 %). The Page.1 of 2

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 1 Modifications To Code Case N-504-2 and Corresponding Non-Mandatory Appendix Q Requirements difference in chemical composition between Alloy 52 and Alloy 52M improves the weldability of the material and pins the grain boundaries thus preventing separation between the grains and hot tearing during weld puddle solidification. These filler materials were selected for their improved resistance to PWSCC. Alloys 52 and 52M contain about 30% chromium that imparts excellent corrosion resistance. The existing Alloy 82/182 weld and the Alloy 52/52M overlay are nickel base and have ductile properties and toughness similar to austenitic stainless steel piping welds at pressurized water reactor operating temperature. These filler materials are suitable for welding over the ferritic nozzle or pipe Alloy 82/182 weld and the austenitic stainless steel pipe or safe ends.

(e) The weld reinforcement shall consist of a minimum of two Modification: Delta ferrite (FN) measurements will not be weld layers having as-deposited delta ferrite content of at least performed for weld overlay repairs made of Alloy 52/52M weld 7.5 FN. The first layer of weld metal with delta ferrite content of metal.

least 7.5 FN shall constitute the first layer of the weld Basis: Welds of Alloy52/52M are 100% austenitic and contain reinforcement design thickness. Alternatively, first layers of at no delta ferrite due to the high nickel composition least 5 FN may be acceptable based on evaluation. [Same as (approximately 60% nickel).

0-2000(d)]

K-Page 2 of 2

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 2 Alternatives to Appendix VIII, Supplement 11 Appendix VIII of Section Xl cannot be used for NDE of a structural weld overlay repair. Relief is requested to use the PDI program implementation of Appendix VIII. A detailed comparison of Appendix VIII and PDI requirements is summarized-below.

Relief is requested to allow closer spacing of flaws provided they don't interfere with detection or discrimination. The specimens used to date for qualification to the Tri-party (NRC/BWROG/EPRI) agreement have a flaw population density greater than allowed by current Code requirements. These samples have been used successfully for all previous qualifications under the Tri-party agreement program. To facilitate their use and provide continuity from the Tri-party agreement program to Supplement 11, the PDI program has merged the Tri-party test specimens into their structural weld overlay program.

SUPPLEMENT 11 - QUALIFICATION REQUIREMENTS PDI PROGRAM:

FOR FULL STRUCTURAL OVERLAID WROUGHT The Proposed Alternative to Supplement 11 AUSTENITIC PIPING WELDS Requirements 1 0 SPECIMEN REQUIREMENTS 1.1 General. The specimen set shall conform to the following requirements.

(b) The specimen set shall consist of at least three specimens Alternative: (b) The specimen set shall include specimens with having different nominal pipe diameters and overlay overlays not thicker than 0.1 in. more than the minimum thicknesses. They shall include the minimum and maximum thickness, nor thinner than 0.25 in. of the maximum nominal nominal pipe diameters for which the examination procedure is overlay thickness for which the examination procedure is applicable. Pipe diameters within a range of 0.9 to 1.5 times a applicable.

nominal diameter shall be considered equivalent. If the Basis: To avoid confusion, the overlay thickness tolerance procedure is applicable to pipe diameters of 24 in. or larger, the contained in the last sentence was reworded and the phrase specimen set must include at least one specimen 24 in. or "and the remainder shall be alternative.flaws" was added to the larger but need not include the maximum diameter. The next to last sentence in paragraph 1.1 (d) (1) specimen set must include at least one specimen with overlay thickness within -0.1 in. to +0.25 in. of the maximum nominal overlay thickness for which the procedure is applicable.

Page 1 of 7

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 2 Alternatives to Appendix VIII, Supplement 11 (d) Flaw Conditions (1) Base metal flaws. All flaws must be cracks in or near the -

Alternative: (1)... must be in or... intentional overlay butt weld heat-affected zone, open to the inside surface, and fabrication flaws shall not interfere with ultrasonic detection or extending at least 75% through the base metal wall. Flaws may characterization of the base metal flaws. Specimens containing extend 100% through the base metal and into the overlay intergranular stress corrosion cracking shall be used when material; in this case, intentional overlay fabrication flaws shall available. At least 70% of the flaws in the detection and sizing not interfere with ultrasonic detection or characterization of the tests shall be cracks and the remainder shall be alternative cracking. Specimens containing/ GSCC shall be used when flaws. Alternative flaw mechanisms, if used, shall provide crack-available, like reflective characteristics and shall be limited by the following:

(a) The use of alternative flaws shall be limited to when the implantation of cracks produces spurious reflectors that are uncharacteristic of actual flaws.

(b) Flaws shall be semi elliptical with a tip width of less than or equal to 0.002 inches.

Basis: This paragraph requires that all base metal flaws be cracks. Implanting a crack requires excavation of the base material on at least one side of the flaw. While this may be satisfactory for ferritic materials, it does not produce a useable axial flaw in austenitic materials because the sound beam, which normally passes only through base material, must now travel through weld material on at least one side, producing an unrealistic flaw response. To resolve this issue, the PDI program revised this paragraph to allow use of alternative flaw mechanisms under controlled conditions. For example, alternative flaws shall be limited to when implantation of cracks precludes obtaining an effective ultrasonic response, flaws shall be semi elliptical with a tip width of less than or equal to 0.002 inches, and at least 70% of the flaws in the detection and sizing test shall be cracks and the remainder shall be alternative flaws. To avoid confusion, the overlay thickness tolerance contained in paragraph 1.1(b) last sentence, was Page 2 of 7

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 2 Alternatives to Appendix VIII, Supplement 11 reworded and the phrase "and the remainder shall be alternative flaws" was added to the next to last sentence.

Paragraph 1.1 (d)(1) includes the statement that intentional overlay fabrication flaws shall not interfere with ultrasonic detection or characterization of the base metal flaws.

(e) Detection Specimens (1) At least 20% but less than 40% of the flaws shall be oriented within +/-209 of the pipe axial direction. The remainder shall be oriented circumferentially. Flaws shall not be open to any surface to which the candidate has physical or visual access.

The rules of IWA-3300.shall be used to determine whether closely spaced flaws should be treated -as single or multiple flaws.

Alternative: (1) At least 20% but less than 40% of the base metal flaws shall be oriented within +/-209 of the pipe axial direction. The remainder shall be oriented circumferentially.

Flaws shall not be open to any surface to which the candidate has physical or visual access.

Basis: The requirement for axially oriented overlay fabrication flaws was excluded from the PDI Program as an improbable scenario. Weld overlays are typically applied using automated GTA W techniques with the filler metal applied in a circumferential direction. Because resultant fabrication induced discontinuities would also be expected-to have major dimensions oriented in the circumferential direction axial overlay fabrication flaws are unrealistic. The requirement for using IWA-3300 for proximity flaw evaluation was excluded, instead indications will be sized based on their individual merits.

(2) Specimens shall be divided into base and overlay grading Alternative: (2) Specimens shall be divided into base metal units. Each specimen shall contain one or both types of grading and overlay fabrication grading units. Each specimen shall units.

contain one or both types of grading units. Flaws shall not interfere with ultrasonic detection or characterization of other flaws.

(a)(1) A base grading unit shall include at least 3 in. of the Alternative: (a)(1) A base metal grading unit includes the length of the overlaid weld. The base grading unit includes the overlay material and the outer 25% of the original overlaid outer 250/6 of the overlaid weld and base metal on both sides.

weld. The base metal grading unit shall extend circumferentially The base grading unit shall not include the inner 75% of the fdr. at least 1 in. and shall start at the weld centerline and be overlaid weld and base metal overlay material, or base metal wide enough in the axial direction to encompass one half of the Page 3 of 7

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 2 Alternatives to Appendix VIII, Supplement 11 to-overlay interface.

original weld crown and a minimum of 0.50" of the adjacent base material.

Basis: The phrase "and base metal on both sides," was inadvertently included in the description of a base metal grading unit, The PDI program intentionally excludes this requirement because some of the qualification samples include flaws on both sides of the weld. To avoid confusion several instances of the term "cracks" or "cracking" were changed to the term "flaws" because of the use of alternative Flaw mechanisms. Modified to require that a base metal grading unit include at least1 in. of the length of the overlaid weld, rather than 3 inches.

i (a)(2) When base metal cracking penetrates into the overlay material, the base grading unit shall include the overlay metal within 1 in. of the crack location. This portion of the overlay material shall not be used as part of any overlay grading unit.

Alternative: (a)(2) When base metal flaws penetrate into the overlay material, the base metal grading unit shall not be used as part of any overlay fabrication grading unit.

(a)(3) When a base grading unit is designed to be unflawed, at least 1 in. of unflawed overlaid weld and base metal shall exist on either side of the base grading unit. The segment of weld length used in one base grading unit shall not be used in another base grading unit. Base grading units need not be uniformly spaced around the specimen.

Alternative: (a)(3) Sufficient unflawed overlaid weld and base metal shall exist on all sides of the grading unit to preclude interfering reflections from adjacent flaws.

Modified to require sufficient unflawed overlaid weld and base metal to exist on all sides of the grading unit to preclude interfering reflections from adjacent flaws, rather than the 1 inch requirement.

(b)(1) An overlay grading unit shall include the overlay 2material Alternative: (b)(1) An overlay fabrication grading unit shall and the base metal-to-overlay interface of at least 6 in. The include the overlay material and the base metal-to-overlay overlay grading unit shall be rectangular, with minimum interface for a length of at least 1 in.

dimensions of 2 in.

Modified to require sufficient unflawed overlaid weld and base metal to exist on all sides of the grading unit to preclude interfering reflections from adjacent flaws, rather than the I inch requirement (b)(2) An overlay grading unit designed to be unflawed shall be Alternative: (b)(2) Overlay fabrication grading units designed Page 4 of 7

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 2 Alternatives to Appendix VIII, Supplement 11 surrounded by unflawed overlay material and unflawed base metal-to-overlay interface for at least 1 in. around its entire perimeter. The specific area used in one overlay grading unit shall not be used in another overlay grading unit. Overlay grading units need not be spaced uniformly about the specimen.

to be unflawed shall be separated by unflawed overlay material and unflawed base metal-to-overlay interface for at least 1 in.

at both ends. Sufficient unflawed overlaid weld and base metal shall exist on both sides of the overlay fabrication grading unit to preclude interfering reflections from adjacent flaws. The specific area used in one overlay fabrication grading unit shall not be used in another overlay fabrication grading unit. Overlay fabrication grading units need not be spaced uniformly about the specimen.

Basis: Paragraph 1.1 (e)(2)(b)(2) states that overlay fabrication grading units designed to be unflawed shall be separated by unflawed overlay material and unflawed base metal-to-overlay interface for at least 1 in. at both ends, rather than around its entire perimeter.

(b)(3) Detection sets shall be selected from Table VIII-$2-1.

Alternative:...base metal grading units, ten unflawed base The minimum detection sample set is five flawed base grading metal grading units, five flawed overlay fabrication grading units, ten unflawed base grading units, five flawed overlay units, and ten unflawed overlay fabrication grading units. For grading units, and ten unflawed overlay grading units. For each each type of grading unit, the set shall contain at least twice as type of grading unit, the set shall contain at least twice as many many unflawed as flawed grading units. For initial procedure unflawed as flawed grading units.

qualification, detection sets shall include the equivalentof three personnel qualification sets. To qualify new values of essential variables, at least one personnel qualification set is required.

(f) Sizing Specimen (1) The minimum number of flaws shall be ten. At least 30% of Alternative: (1) The...least 40% of the flaws shall be open to the flaws shall be overlay fabrication flaws. At least 40% of the the inside surface. Sizing sets shall contain a distribution of flaws shall be cracks open to the inside surface.

flaw dimensions to assess sizing capabilities. For initial procedure qualification, sizing sets shall include the equivalent of three personnel qualification sets. To qualify new values of essential variables, at least one personnel qualification set is required.

(3) Base metal cracking used for length sizing demonstrations Alternative: (3) Base metal flaws used.. circumferentially.

Page 5 of 7

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 2 Alternatives to Appendix VIII, Supplement 11 shall be oriented circumferentially.

(4) Depth sizing specimen sets shall include at least two distinct Alternative: (4) Depth sizing specimen sets shall include at locations where cracking in the base metal extends into the least two distinct locations where a base metal flaw extends overlay material by at least 0.1 in. in the through-wall direction.

into the overlay material by at least 0.1 in. in the through-wall direction.

2.0 Conduct of Performance Demonstration The specimen inside surface and identification shall be Alternative: The specimen...prohibited. The overlay concealed from the candidate. All examinations shall be fabrication flaw test and the base metal flaw test may be completed prior to grading the results and presenting the results performed separately.

to the candidate. Divulgence of particular specimen results or candidate viewing of unmasked specimens after the performance demonstration is prohibited.

2.1 Detection Test.

Flawed and unflawedgrading units shall be randomly mixed.

Alternative: Flawed...(base metal or overlay Although the boundaries of specific grading units shall not be fabrication)...each specimen.

revealed to the candidate, the candidate shall be made aware of the type or types of grading units (base or overlay) that are present for each specimen.

2.2 Length Sizing Test (d) For flaws in base grading units, the candidate shall estimate Alternative: (d) For... base metal grading.., base metal wall the length of that part of the flaw that is in the outer 25% of the thickness.

base wall thickness.

2.3 Depth Sizing Test.

For the depth sizing test, 80% of the flaws shall be sized at a Alternative: (a) The depth sizing test may be conducted specific location on the surface of the specimen identified to the separately or in conjunction with the detection test.

candidate. For the remaining flaws, the regions of each (b) When the depth sizing test is conducted in conjunction with specimen containing a flaw to be sized shall be identified to the the detection test and the detected flaws do not satisfy the candidate. The candidate shall determine the maximum depth requirements of 1.1 (f), additional specimens shall be provided of the flaw in each region.

to the candidate. The regions containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the maximum depth of the flaw in each region.

(c) For a separate depth sizing test, the regions of each specimen containing a flaw to be sized shall be identified to the Page 6 of 7

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 2 Alternatives to Appendix VIII, Supplement 11 candidate. The candidate shall determine the maximum depth of the flaw in each region.

3.0 ACCEPTANCE CRITERIA 3.1 Detection Acceptance Criteria Examination procedures, equipment, and personnel are qualified for detection when the results of the performance demonstration satisfy the acceptance criteria of Table VIII-S2-1 for both detection and false calls. The criteria shall be satisfied separately by the demonstration results for base grading units and for overlay grading units.

Alternative: Examination procedures are qualified for detection when:

a. All flaws within the scope of the procedure are detected and the results of the performance demonstration satisfy the acceptance criteria of Table VIII-S2-1 for false calls.

b. At least one successful personnel demonstration has been performed meeting the acceptance criteria defined in (c).

c. Examination equipment and personnel are qualified for detection when the results of the performance demonstration satisfy the acceptance criteria of Table VIII-S2-1 for both detection and false calls.

d. The criteria in (b) and (c) shall be satisfied separately by the demonstration results for base metal grading units and for overlav fabrication aradina units.

3.2 Sizing Acceptance Criteria (a) The RMS error of the flaw length measurements, as Alternative: (a) The...base metal flaws is...position.

compared to the true flaw lengths, is less than or equal to 0.75 inch. The length of base metal cracking is measured at the 75%

through-base-metal position.

(b) All extensions of base metal cracking into the overlay Alternative: This requirement is omitted.

material by at least 0.1 in. are reported as being intrusions into Basis: The requirement for reporting all extensions of cracking the overlay material.

into the overlay is omitted from the PDI Program because it is redundant to the RMS calculations performed in paragraph 3.2(c) and its presence adds confusion and ambiguity to depth sizing as required by paragraph 3.2(c). This also makes the weld overlay program consistent with the supplement 2 depth sizing criteria Page 7 of 7

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 3 Modification To Code Case N-638-1 Code Case N-638-1 Modification/Basis i

1.0 (a) The maximum area of an individual weld based on the finished surface shall be 100 sq. in., and the depth of the weld shall not be greater than one-half of the ferritic base metal thickness.

Modification: The maximum area of an individual weld based on the finished surface over the ferritic material will not exceed 300 square inches, and the depth of the WOL shall not be greater than one-half of the ferritic base metal thickness.

Basis: The maximum finished area of the WOL for the hot leg surge line and shutdown cooling line nozzles will exceed 100 sq-in over the ferritic material. EPRI Technical Report 1003616 provides technical justification for extending the size of the temper bead repairs up to a finished area of 500 sq-in over the ferritic material. The area of the finished overlays will be substantially less than this.

The WOL will extend to the transition taper of the carbon steel nozzle so that qualified UT of the required volume can be performed'. There have been a number of temper bead WOL repairs applied to safe-end to nozzle welds in the nuclear industry, and a WOL repair having a 300 sq. in. surface was recently approved for the Susquehanna Steam Electric Station and the D. C. Cook (Precedents 2 and 3).

Results of industry analyses and testing performed to date have indicated that there is no direct correlation of amount of surface area repaired when comparing residual stresses using temper bead welding. Residual stresses associated with larger area repairs (> 100 sq in) remain compressive at an acceptable level.

(Referenced below in 4.0(b) para. 1.0(d) Prior to welding the area to be welded and a band around the area of at least 11/2 times the component thickness or 5in., whichever is less shall beat least 50 0F.)

4.0(b) The final weld surface and a band around the area defined in para. 1.0 (d) shall be examined using a surface and ultrasonic methods when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months . The ultrasonic examination shall be in accordance with Appendix 1.3 Modification: In lieu of the required ultrasonic examination of 4.0(b) only the required liquid penetrant examination will be performed. The ultrasonic examination will be in accordance with N-504-2 and Appendix Q.

Basis: For the application of the weld overlay repair addressed in this request it is not possible to perform a meaningful ultrasonic examination of the required band of base material because of the existing nozzle configurations. This Code Case applies to any type of welding where a temper bead technique is to be employed and is not specifically written for a weld overlay repair. However, it is believed that for this type of repair that Page 1 of 2

Relief Request ISI-3-27 Use of Structural Weld Overlay and Associated Alternative Repair Techniques Table 3 Modification To Code Case N-638-1 3Refer to the 1989 Edition with the 1989 Addenda and later Editions and Addenda any major base material cracking would take place in the HAZ directly below the weld overlay or in the underlying Inconel 82/182 weld deposit and not in the required band of material out beyond the overlay. Therefore, it is assumed that if this cracking were to occur it would be identified by the ultrasonic examination of the weld overlay and not performing the required base material ultrasonic examination should be considered acceptable.

4.0(c) requires temperature monitoring by welded thermocouples per IWA7461 0(a)

Modification: Preheat and interpass temperatures for the weld pad will be measured using a contact pyrometer. Interpass temperature will be monitored for the first three layers at each

repair location. On the first repair location, the interpass temperature measurements will betaken every three to five passes. After the first three layers, interpass temperature measurements will be taken every six to ten passes for the subsequent layers. The heat input from layers beyond the third layer will not have a metallurgical affect on the low alloy steel HAZ.

Basis: Due to the location of the repair and area radiation dose rate, the placement of welded thermocouples for monitoring weld interpass temperature is determined to be not beneficial based on dose savings. Therefore, welded thermocouples are not planned for use to monitor interpass temperature during weldinq.

Page 2 of 2

ATTACHMENT 2 CHEMICAL ANALYSES OF INCREMENTAL MILLING OF WELDMENT SONGS Unit 2 and Unit 3 The data shown below are typical of several mockups that are representative of the weld overlays to be installed. These data are from an overlay on carbon steel base material and testing has confirmed that the chromium content of overlays on stainless steel base materials is similar. The data supports the current overlay design, which specifies a single sacrificial layer that is not credited in the structural analysis of the overlay.

Chromium Content (wt. %)

For Orbital Welding Utilizing Alloy 52M Alloy 52M 2 nd Layer 1 st Layer Ist Layer 0.035" wire by X-ray by X-ray by Electron Diffraction from CMTR Fluoroscope Fluoroscope Spectroscopy Element/

SFA 5.14 Near Quadrant ER NiCrFe-Near Surface Near Surface Near Mid-l Base 7A Surface layer Metal Chromium 00 28.8 26.3 27.3 27.4 27.5 Chromium 900 29.5 26.9 29.1 28.0 27.4 Chromium 1800 29.1 26.6 28.0 27.5 27.5 Chromium 2700 29.4 27.0 26.7 26.9 26.4 Avg. % Cr 29.3 29.2 26.7 27.8 27.5 27.2 NOTE: These data are representative of the alloy 52M structural weld overlay repair to be at SONGS. Subsequent layers will have %Cr equal to or greater than the 2nd layer Page 1 of 1

ATTACHMENT 3 COMPARISON OF CODE CASES N-504-2 AND N-504-3 AND DISCUSSION OF DIFFERENCES SONGS Unit 2 and Unit 3 The purpose of this attachment is to describe the changes between Code Case N-504-2, which had been approved by the NRC at the time of submittal of Relief Request ISI-3-27, Revision 0, and Code Case N-504-3, which is currently endorsed by the NRC, to show that ISI-3-27, Revision 1, is consistent with Code Case N-504-3 or the modifications previously approved to Code Case N-504-2.

The differences between the two revisions of the Code Case are as follows:

1. In the Reply to Inquiry that introduces the Code Case, N-504-2 states that, "It is the opinion of the Committee that, in lieu of the requirements of IWA-4120 in Editions and Addenda up to and including the 1989 Edition with the 1990 Addenda, in IWA-4170(b) in the 1989 Edition with the 1991 Addenda up to and including the 1995 Edition, and in IWA-4410 in the 1995 Edition with the 1995 Addenda and later Editions and Addenda, defect in austenitic stainless steel piping may be reduced...".

Code Case N-504-3 states in the same section, "It is the opinion of the Committee that, in lieu of the requirements of IWA-4120 in Editions and Addenda up to and including the 1989 Edition with the 1990 Addenda, in IWA-4170(b) in the 1989 Edition with the 1991 Addenda up to and including the 1995 Edition, in IWA-4410 in the 1995 Edition withthe 1995 Addenda up to and including the 1996 Addenda, and in IWA-4420 in the 1995 Edition with the 1997 Addenda and later Editions and Addenda, in IWA-4810(a) in the 1992 Edition with the 1994 Addenda through the 1995 Edition, and in IWA-4520(a) in the 1995 Edition with the 1995 Addenda and later Editions and Addenda, a defect in austenitic stainless steel piping may be reduced...".

The effect of this change to the language of the Code Case was to broaden the applicability. As the proposed relief in ISI-3-27 Revision 0 met the applicability requirements of Code Case N-504-2, it would also meet the applicability requirements of Code Case N-504-3.

2. Paragraph (g)(2) of Code Case N-504-2 states in part, "When structural credit is taken for [Submerged Arc Welding] SAW or [Shielded Metal Arc Welding] SMAW weld metal in the original pipe weldment or the weld overlay, the evaluation requirements of Tables IWB-3641-5 and IWB-3641-6 shall be applied."

Page 1 of 3

Paragraph (g)(2) of Code Case N-504-3 states in part, "When structural credit is taken for [Submerged Arc Welding] SAW or [Shielded Metal Arc Welding] SMAW weld metal in the original pipe weldment or SMAW weld metal in the weld overlay, the evaluation requirements of Tables IWB-3640 for SAW or SMAW welds, as applicable, shall be applied."

The proposed overlay is designed as a full structural weld overlay, rather than excavating a defect and performing a cavity repair. The overlay thickness was determined assuming a 100% through-wall flaw in the original pipe weldment, with the thickness of the overlay material meeting the design acceptance criteria. As such, no structural credit is taken for the weld metal in the original pipe weldment. In addition, the Gas-Tungsten Arc Welding (GTAW) technique will be used for application of the weld overlay, not the Submerged Arc Welding (SAW) technique or the Shielded Metal Arc Welding (SMAW) technique.

Because no structural credit is taken for the original pipe weldment and because the overlay will not be SAW or SMAW weld metal in the weld overlay, this requirement of Code Case N-504-3 does not apply to the proposed weld overlays of this Relief Request.

3. Paragraph (i) of Code Case N-504-2 states, "Preservice examination of the completed repair shall be performed in accordance with IWB-2200.

For all classes of components, liquid penetrant and ultrasonic examination of the completed weld repair shall be performed. Examination procedures shall be specified in the Repair Program. The acceptance standards of Table IWB-3514-2 shall apply. Ultrasonic examinations shall verify the integrity of the newly applied weld reinforcement. Examinations shall also be performed to identify the original flaws in the outer 25% of the underlying pipe wall as a benchmark for subsequent examinations of the overlay. Grinding and machining of the as-welded overlay surface may be used to improve the surface finish for such examinations, when the overlay thickness is not reduced below design requirements.

Paragraph (i) of Code Case N-504-3 states, "Preservice examination of the completed repair shall be performed in accordance with IWB-2200.

For all classes of components, liquid penetrant and ultrasonic examination of the completed weld repair shall be performed. Examination procedures shall be specified in the Repair Program. The acceptance standards of Table IWB-3514-2 shall apply for planar flaws. The acceptance standards of Table IWB-3514-3 shall apply for laminar flaws provided the reduction in coverage of the examination volume is less than 10%. The dimensions of the uninspectable volume are.dependent on the coverage achieved with the angle beam examination. Additionally, any uninspectable volume in Page 2 of 3

the weld overlay shall be assumed to contain the largest radial planar flaw that could exist within that volume. The assumed planar flaw shall meet the inservice examination acceptance standards of Table IWB-3514-2.

Both axial and circumferential flaws shall be assumed. As an alternative to the assumed planar flaw, radiography in accordance with the Construction Code shall be used to examine the uninspectable volume in the weld overlay. The radiographic acceptance criteria of the Construction Code shall apply. Ultrasonic examinations shall verify the integrity of the newly applied weld reinforcement. Examinations shall also be performed to identify the original flaws in the outer 25% of the underlying pipe wall as a benchmark for subsequent examinations of the overlay. Grinding and machining of the as-welded overlay surface may be used to improve the surface finish for such examinations, when the overlay thickness is not reduced below design requirements."

Relief Request ISI-3-27, Revision 0, stated that Examination and Inspection would be performed in accordance with ASME Section Xl, Non mandatory Appendix Q, "Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments," Article Q-4000, "Examination and Inspection," as required per Regulatory Guide 1.147 Revision 14, Table 2, Conditionally Acceptable Section Xl Code Cases for the Code Case N-504-2. Examination and Inspection requirements of Appendix Q, Article Q-4000 meet the preservice examination requirements as specified in Code Case N-504-3. Therefore ISI-3-27, Revision 1, is consistent with the preservice examination requirements specified in Code Case N-504-3.

==

Conclusion:==

The changes from Code Case N-504-2 and N-504-3 do not apply to the proposed weld overlays of Relief Request ISI-3-27, Revision 1, with the exception of the requirements of paragraph (i), regarding Preservice examination. ASME Section Xl, Non mandatory Appendix Q, "Weld Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments," Article Q-4000, "Examination and Inspection, that was originally proposed and approved as part of ISI-3-27, Revision 0, meets the preservice examination requirements of Code Case N-504-3.

SCE concludes that performance of the proposed weld overlays in accordance with Code Case N-504-2 with the modifications previously approved by the NRC as part of Relief Request ISI-3-27, Revision 0, would be consistent with either Code Case N-504-3 or the previously approved modifications to Code Case N-504-2.

Page 3 of 3 Southern California Edison (SCE)

San Onofre Nuclear Generating Station (SONGS), Units 2 and 3 Docket No. 50-361 and 50-362 Revision 1 to Relief Request ISI-3-28 48-Hour Hold Period Following Application of the Third Temperbead Layer

Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(i)

- Alternative Provides Acceptable Level of Quality and Safety -

1.0 REASON FOR THE REQUEST Southern California Edison (SCE) will be performing full structural weld overlays to reduce dependence on the Alloy 82/182 welds as a pressure boundary weld and to mitigate any potential primary water stress corrosion cracking in the future. SCE has submitted Relief Requests ISI-3-25 and ISI-3-27 by letters dated July 14, 2006 and February 21,.2007, respectively. The NRC issued approval of ISI-3-25 by letter dated June 12, 2007.

Relief Requests ISI-3-25 and ISI-3-27. as currently approved, require that the j

final weld surface be examined using surface and ultrasonic methods when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months .

Research and industry experience show that starting the 48-hour hold period following completion of application of the third temperbead layer provides an acceptable level of quality and safety. Thus, this is the reason for Relief Request ISI-3-28.

Revision 1 of ISI-3-28 is necessary to increase the applicability of the Relief Request to include additional components.

The weld overlays for the. Unit 3 RCS Hot Leg nozzles must be implemented during the current Unit 3 Cycle 15 Refueling Outage. During implementation of these weld overlays, SCE has discovered that the physical configuration of the Unit 3 RCS Hot Leg Surge Line includes additional Code-allowed weld build-up that is not specifically detailed on the engineering drawings. The weld overlay was designed to cover the RCS Hot Leg Surge nozzle to safe end dissimilar metal weld and the adiacent stainless steel weld ioining the safe end to the pipe.

The pipe adiacent to the stainless steel weld, however, was found to be slightly shorter than was shown on the engineering drawings and it contains bands of weld material build-up on either end of the pipe. With this confiquration, the weld overlay as originally designed would have ended on top of a weld build-up rendering the buildup, as well as the adjacent pipe to elbow weld impossible to inspect via Ultrasonic Testing (UT). To resolve this issue, the design of the weld overlay is being modified to increase the length of the overlay and fully cover the pipe weld material build-up to elbow weld as well as the pipe to elbow weld and provide an overlay that is UT insDectable.

Page 1 of 9

2.0 CODE COMPONENTS FOR WHICH RELIEF IS REQUESTED Group: High safety significant (HSS) Class 1 dissimilar metal piping welds with Alloy 82/182 weld metal are susceptible to Pressurized Water Stress Corrosion Cracking (PWSCC)..

a)

Name of Components:

Pressurizer Surge Nozzle components (ISI-3-25) 1 ?-evij

1. Unit 2 Pressurizer 821201 ME087 surge line nozzle to safe end HSS dissimilar metal weld (ISI Designation Number 02-005-031) with Alloy 82/182 weld material subject to PWSCC.

2. The adjacent Unit 2 Pressurizer S21201 ME087 stainless steel weld (ISI Designation Number 02-016-001)

3. Unit 3 Pressurizer S31201ME087 surge line nozzle to safe end HSS dissimilar metal weld (ISI Designation Number 03-005-031) with Alloy 82/182 weld material subject to PWSCC.

4. Theadjacent Unit 3 Pressurizer 831201 ME087* stainless steel weld (ISI Designation Number 03-016-001)

Note that this component was erroneously identified in ISI-3-25 as S21201 ME087.

Reactor Coolant System Hot Leg components (ISI-3-27)

5. Reactor Coolant System Hot Leg surge line nozzle to safe end HSS dissimilar metal welds (IS Designation Number 02-006-010/03-006-010) with Alloy 82/182 weld material subject to PWSCC.

6. The adjacent stainless steel welds (ISI Designation Number 02-016-016/03-016-016), and adiacent pipe-to-elbow stainless steel kv.

welds (ISI Designation Number 02-016-015/03-016-015).

7. Reactor Coolant System Hot Leg drain nozzle to safe end HSS dissimilar metal welds (ISI Designation Number 02-006-011/03-006-011) with Alloy 82/182 weld material subject to PWSCC.

8. The adjacent stainless steel welds (IS[ Designation Number 02-030-001/03-030-010).

9. Shutdown Cooling System Hot Leg nozzle to safe end HSS dissimilar metal weld (ISI Designation Number 02-007-009/03-007-009) with Alloy 82/182 weld material subject to PWSCC.

10. The adjacent stainless steel welds (ISI Designation Number 02-021-001/03-021-010).

Except where noted differently in item 6, above, the."adjacent" stainless steel weld refers to the safe-end-to-pipe stainless steel weld.

Page 2 of 9

The Unit 2 stainless steel pipe to elbow weld (ISI 02-016-015) is included in this reauest continaent upon final inspection and confirmation of sizina of the Unit 2 epzv-i weld overlay.

b) American Society of Mechanical Engineers (ASME) Code Class:

These welds are all ASME Code Class 1 welds located within the reactor coolant pressure boundary.

c) System:

Reactor Coolant System (RCS) d.1)

Code Category:

d.2)

Code Category:

Examination Category B-F, Examination Category B-J, "Risk-

"Risk-Informed Piping Informed Piping Examinations" Examinations" e.1)

Code Item No. B5.40 e.2)

Code Item No. B9.11 "Welds subject to PWSCC" (ISI "Welds subject to PWSCC" (ISI Designation Numbers 02-005-Designation Numbers 02-006-031 and 03-005-031) 010, 02-007-009, 03-006-010, and 03-007-009).

"Welds subject to Thermal Fatigue" (ISI Designation "Welds subject to Thermal Numbers 02-005-031 and 03-Fatigue" (ISI Designation 005-031)

Numbers 02-016-001, 02-006-010, 02-007-009, 02-016-015, 02-016-016, 02-021-001, 03-016-001, 03-006-010, 03-007-009, 03-016-015, 03-016-016, and 03-021-010) f N/A e.2)

Code Item No. B9.21 "Welds subject to PWSCC" (ISl Designation Number 02-006-011 and 03-006-011).

"Welds subject to Thermal Fatigue" (ISI Designation Numbers 02-006-011, 03-006-011, 02-030-001, and 03-030-010).

I

~

1.~

I

~*eLd~ :1-Page 3 of 9,

3.0 CODE REQUIREMENTS FOR WHICH RELIEF IS REQUESTED Modification to Code Case N-638-1 (Reference 4).

4.0 PROPOSED ALTERNATIVES AND SUPPORTING INFORMATION Pressurizer Surge Line (ISI-3-25)

A structural weld overlay repair has been approved by the NRC for the pressurizer S2(3)1201ME087 surge line nozzle to safe end HSS dissimilar metal welds (ISI Designation Numbers 02-005-031 and 03-005-031) and the adjacent welds (ISI Designation Numbers 02-016-001 and 03-016-001). The material of the above two nozzles is ferritic steel (P3). The pipe safe ends are austenitic stainless steel (P8). The surge line nozzles material is SA-508 Class 2 and the safe end material is SA-351 CF8M. The existing weld filler material is Alloy 82/182 (F43 equivalent to P43). The surge line pipe is stainless steel SA-376 Grade TP316. As described in NRC-approved Relief Request ISI-3-25, the overlay will be designed as a structural weld overlay in accordance with ASME Section XI Code Case N-504-2 and Nonmandatory Appendix Q (Reference 3).

The temper bead welding technique will be implemented in accordance with ASME Section Xl Code Case N-638-1 (Reference 4) for that portion of the overlay applied over the ferritic base material for which the Construction Code requires post-weld heat treatment.

Page 4 of 9

I Hot Lea Surae/Drain Line, Shutdown Coolinc Surge Line (ISI-3-27)

Dissimilar Metal Weld Nozzle Material Safe End Material Identifier I

Hot Leg Surge Line Unit 2: SA-105 SA-351 GR CF8M 02-006-010/03-006-010 GR II Forging Stainless Steel Cast Unit 3*: SA-541 C0 1 Forgqing Hot Leg Drain Line SA-105 GR II SA-182 F316 Forging 02-006-011/03-006-011 Forging Shutdown Cooling Line, Unit 2: SA-105 SA-351 GR CF8M 02-007-009/03-007-009 GR II Forging Stainless Steel Cast Unit 3*: SA-541 Cl 1 Forqinq Adiacent Stainless Steel Pipe Material Weld Identifier Hot Leg Surge Line SA-376 Grade TP316 02-016-016/03-016-016 Hot Leg Surge Line SA403 Grade WP316 02-016-015/03-016-015 Hot Leg Drain SA-376 Grade TP316 02-030-001/03-030-010 Shutdown Cooling Line SA-403 Grade WP316 02-021-001/03-021-010

As described in SCE's letter dated Auaust 29, 2008, the Nozzle Material for the Unit 3 forgings is SA-541, Class 1 rather than SA-105 GR II.

As described in Relief Request ISI-3-27, the overlay will be designed as a structural weld overlay in accordance with ASME Section Xl Code Case N-504-2 and Nonmandatory Appendix Q (Reference 3). The temper bead welding technique will be implemented in accordance with ASME Section XI Code Case N-638-1 (Reference 4) for that portion of the overlay applied over the ferritic base material for which the Construction Code requires post-weld heat treatment.

Relief Requests ISI-3-25 and ISI-3-27 cite several modifications to Code Case N-638-1 that SCE would apply during weld overlay installation. Specifically, these modifications to the Code Case are found in Table 3, of Enclosure 1, Attachment 1 of SCE's July 14, 2006 and February 21, 2007 submittals. This Relief Request ISI-3-28 proposes an additional modification to Code Case N-638-1.

Page 5 of 9

Paragraph 4.0(b) of Code Case N-638-1 states in part:

4.0(b) "The final weld surface and the band around the area defined in para. 1.0(d) shall be examined using surface and ultrasonic methods when the completed weld has been at ambient temperature for at least 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months ...."

Relief Request ISI-3-28 proposes:

A modification to the above requirement to allow the 48-hour hold time to begin following completion of the third temperbead layer.

Any applicable requirements not addressed by Relief Request ISI-3-28, or by Tables 1, 2, and 3 of ISI-3-25 and ISI-3-27, will be satisfied as described in Section Xl, 1995 Edition through 1996 Addenda, IWA-4000 (Reference 1);

Appendix VIII, Supplement 11 (Reference 2); Code Case N-504-2 (Reference 3);

and Code Case N-638-1 (Reference 4).

This modification to Code Case N-638-1 is based on the following discussion:

In December 2006, the Electric Power Research Institute (EPRI) issued Technical Report 1013558, "48-Hour Hold Requirements for Ambient Temperature Temperbead Welding" (Reference 5, ADAMS Accession No. ML070670060). Although 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, the conclusions are bounding and applicable to P-Number 1 materials such as SA-105 GR II which have a lower carbon equivalent and lower hardenability. This is important because SONGS hot leg surge line, hot leg drain and shut down cooling lines have this SA-1 05 GR II. or SA-541 Cl 1, P-Number 1 forging type nozzle material.

The technical report focuses on four key concerns associated with the 48-hour hold time. The four key concerns are:

(1)

Microstructural Issues (2)

Sources for Hydrogen Introduction (3)

Diffusivity and Solubility of Hydrogen in Steels (4)

Tensile Stress and Temperature A summary of the EPRI research results are as follows:

The microstructure in the P-3 material directly beneath the temperbead Weld Overlay (WOL) consists of a tempered martensite or tempered upper bainite that has excellent toughness, combined with a modest maximum hardness (of the order of Rockwell [Rc] 30 or lower).

The microstructure at the toe of the temperbead WOL in the P-3 weld heat affected zone (HAZ) at the outside diameter (OD) surface where tempering is Page 6 of 9

somewhat limited may have a very small HAZ with a maximum hardness of the order of Rc 36, at a distance of approximately 40 mils from the toe of the WOL.

At a depth of approximately 2 to 2.5 mm (80 to 100 mils) beneath the toe of the WOL, the hardness is reduced to less than 294 Knoop hardness (29 Rc), a hardness level well below that required to cause hydrogen cracking.

Sources'of hydrogen include moisture, poor shielding gas, and contamination. It is noted that moisture in the shielding gas or high humidity is not a problem for Gas-Tungsten Arc Welding (GTAW) temperbead welding. Contamination will affect the weld, and should be identified either during the welding process or during the subsequent Non-Destructive Examination (NDE) of the overlay. Good welding practice should eliminate this problem for the temperbead WOL.

Tensile stresses should not be an issue for cold cracking as the thermal stresses diminish with each weld overlay layer. Following the final layer, it is expected that the maximum surface temperature at the toe of the WOL in the P-3 HAZ would reach temperatures only on the order of 400 degrees Fahrenheit (OF) to 500 OF. Slow cooling to ambient temperatures from these temperatures would be expected to produce relatively small stresses.

The diffusion rate for hydrogen is greater in ferritic material than in austenitic materials, but the solubility of hydrogen in austenite is from five to seven times greater in the austenite than in the ferrite or martensite. Consequently, due to the temperatures expected during the welding of the temperbead layers, and, during the welding of the non-temperbead WOL layers, the temperature should be sufficient for the hydrogen to diffuse out of the material, either escaping the structure or diffusing into the austenite, where it can be held in much greater quantities. Thus, even if hydrogen is produced, a large hydrogen inventory in the P-3 material is not expected.

Based on the above discussion, EPRI Technical Report 1013558 concludes that there is no technical basis for waiting 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months after cooling to ambient temperature before beginning the NDE of the completed weld.

In addition to the EPRI report, the ASME Section Xl Code Committee approved Revision 4 to ASME Code Case N-638 in October 2006 to allow the 48-hour hold time 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 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months ." The ASME Section XI technical basis for this change is documented in an ASME white paper (ADAMS Accession No. ML070790679). 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 Page 7 of 9

as Alloy 52M is much higher than that of ferritic materials while the diffusivity 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 EPRI report, the ASME white paper concludes that there is sufficient delay time to facilitate detecting potential hydrogen cracking when NDE is performed 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months after completing the third weld layer.

5.0 DURATION OF PROPOSED RELIEF REQUEST This request will be applied for the remainder of the current SONGS Units 2 and 3 third 10-year ISI interval that started on August 18, 2003. Once these structural weld overlays are installed they will remain in place for the design life of the repair that is defined by the evaluation required in paragraph (g) of Code Case N-504-2 and corresponding requirements in Nonmandatory Appendix Q (Reference 3). The structural weld overlays are also subject to the satisfactory examination requirements of Article Q-4000 for inservice inspection. Those requirements include adding any installed-structural weld overlay repairs into the SONGS Units 2 and 3 ISI plan per Subarticle Q-4300 for at least one inservice examination to be completed within the next 2 refueling cycles.

6.0 PRECEDENTS

1.

Letter from Thomas H. Boyce, NRC, to William R. Campbell, Jr.,

Tennessee Valley Authority, "Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1 - Request for Relief G-RR-1 Regarding Preemptive Weld Overlays on Pressurizer Nozzles (TAC Nos. MD2381, MD2382 and MD2383)," dated June 11, 2007.

2.

Letter from David Terao, NRC, to Timothy G. Mitchell, Entergy Operations, "Arkansas Nuclear One, Unit 1 - Request for Alternative ANO1 -R&R-01 0 to Use Proposed Alternative to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code Requirements for Pressurizer Nozzle Weld Overlay Repairs (TAC No. MD4019)," dated April 6, 2007.

Page 8 of 9

7.0 REFERENCES

(1) 1995 Edition through 1996 Addenda, ASME Code, Section Xl, IWA-4000.

(2) 1995 Edition, ASME Code,Section XI, with the 1996 Addenda, Appendix VIII, Supplement 11.

(3)

ASME Code Case N-504-2, Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Section XI, Division 1, March 12, 1997, including ASME Code Section XI, 2005 Addenda, Nonmandatory Appendix Q, Weld-Overlay Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping Weldments.

(4)

ASME Code Case N-638-1, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique Section XI, Division 1, February 13, 2003.

(5).

EPRI Technical Report 1013558, "48-Hour Hold Requirements for Ambient Temperature Temperbead Welding" (ADAMS Accession No. ML070670060).

8.0 CONCLUSION

SCE has determined that the approach described in this relief request provides sufficient delay time to facilitate the detection of potential hydrogen cracking when non-destructive examination is performed 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months after completion of the third weld layer. SCE believes that the use of this relief request to begin the 48-hour hold period after application of the third temperbead layer on the pressurizer surge nozzle and RCS hot leg structural weld overlay repairs at SONGS Units 2 and 3 will result in an acceptable level of quality and safety that meets the requirements of 10 CFR 50.55a(a)(3)(i).

Page 9 of 9 Drawings

v t e Letter Sequence Request
TAC:ME0108, (Open)
Initiation Request Acceptance... Administration Questions Answers Results Approval Other:
MONTHYEAR2008-11-12 [Table View]

ML083220131

Text

Subject:

References:

Dear Sir or Madam:

Enclosures:

Subject:

Subject:

Subject:

Subject:

Subject:

7.0 REFERENCES

Subject:

8.0 CONCLUSION

7.0 REFERENCES

8.0 CONCLUSION

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