RA-19-0028, Submittal of Relief Request (19-ON-001) to Utilize Code Case N-853, PWR Class 1 Primary Piping Alloy 600 Full Penetration Branch Connection Weld Metal Buildup for Material Susceptible to Primary Water Stress

Submittal of Relief Request (19-ON-001) to Utilize Code Case N-853, PWR Class 1 Primary Piping Alloy 600 Full Penetration Branch Connection Weld Metal Buildup for Material Susceptible to Primary Water Stress

ML19084A197
Person / Time
Site:	Oconee
Issue date:	03/21/2019
From:	Burchfield J Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA-19-0028
Download: ML19084A197 (10)

Text

~ ~ DUKE J. Ed Burchfield, Jr.

~ ENERGY Vice President Oconee Nuclear Station Duke Energy ON01VP I 7800 Rochester Hwy Seneca, SC 29672 o: 864.873.3478 t* 864. 873.4208 Ed.Burchfie/d@duke-energy.com Serial: RA-19-0028 10 CFR 50.55a March 21, 2019 U.S. Nuclear Regulatory Commission A TIN : Document Control Desk Washington, DC 20555-0001 OCONEE NUCLEAR STATION, UNIT NOS. 1, 2 AND 3 DOCKET NOS. 50-269 , 50-270, 50-287 / RENEWED LICENSE NOS. DPR-38, DPR-47 AND DPR-55

SUBJECT:

Relief Request (19-ON-001) to Utilize Code Case N-853, "PWR Class 1 Primary Piping Alloy 600 Full Penetration Branch Connection Weld Metal Buildup for Material Susceptible to Primary Water Stress Corrosion Cracking Section XI, Division 1" Ladies and Gentlemen:

Pursuant to 10 CFR 50.55a(z)(1), Duke Energy Carolinas, LLC (Duke Energy) hereby submits Relief Request 19-ON-001 requesting U.S. Nuclear Regulatory Commission (NRC) approval to use an alternative to the defect removal requirements of American Society of Mechanical Engineers (ASME) Code,Section XI, Article IWA-4000 at Oconee Nuclear Station Units 1, 2, and 3 (ONS). Specifically, Duke Energy proposes to use ASME Code Case N-853, "PWR Class 1 Primary Piping Alloy 600 Full Penetration Branch Connection Weld Metal Buildup for Material Susceptible to Primary Water Stress Corrosion Cracking Section XI, Division 1" with the deviations described herein. Enclosure 1 contains details regarding this request.

This submittal contains no new regulatory commitments. To support work in the ONS Unit 3 refueling outage currently scheduled in April 2020, Duke Energy requests approval of this relief request prior to that outage . If you have questions concerning this request, please contact Art Zaremba, Manager, Fleet Licensing, at (980) 373-2062 .

Sincerely, t u &Jf:J))~

J. Ed Burchfield, Jr.

Vice President Oconee Nuclear Station

Enclosure:

1. Relief Request 19-ON-001

U.S. Nuclear Regulatory Commission RA-19-0028 Page 2 cc: (all with Enclosure unless otherwise noted)

C. Haney, Regional Administrator USNRC Region II E. L. Crowe, USNRC Resident Inspector - ONS A. L. Klett, NRR Project Manager - ONS RA-19-0028 Enclosure 1 Relief Request 19-ON-001

Relief Request Serial #19-ON-001 RA-19-0028, Enclosure 1

1. ASME Code Components Affected ONS Unit 1:

• Three 1A Hot Leg RTE Mounting Boss Alloy 600 Nozzle Welds (1-PHA-13, 1-PHA-14, & 1-PHA-15).

• Three 1B Hot Leg RTE Mounting Boss Alloy 600 Nozzle Welds.

(1-PHB-13, 1-PHB-14, & 1-PHB-15).

• Four (4) Cold Leg RTE Mounting Boss Alloy 600 Nozzle Welds (1-PIA1-12, 1-PIA2-12, 1-PIB1-12, & 1-PIB2-12).

ONS Unit 2:

• Three 2A Hot Leg RTE Mounting Boss Alloy 600 Nozzle Welds.

(2-PHA-13, 2-PHA-14, & 2-PHA-15).

• Three 2B Hot Leg RTE Mounting Boss Alloy 600 Nozzle Welds.

(2-PHB-13, 2-PHB-14, & 2-PHB-15).

• Four (4) Cold Leg RTE Mounting Boss Alloy 600 Nozzle Welds (2-PIA1-12, 2-PIA2-12, 2-PIB1-12, & 2-PIB2-12).

ONS Unit 3:

• Three 3A Hot Leg RTE Mounting Boss Alloy 600 Nozzle Welds.

(3-PHA-13, 3-PHA-14, & 3-PHA-15).

• Three 3B Hot Leg RTE Mounting Boss Alloy 600 Nozzle Welds.

(3-PHB-13, 3-PHB-14, & 3-PHB-15).

• Two 3A Hot Leg Pressure Tap Alloy 600 Nozzle Welds.

(* Nearest Nozzle Butt Welds 3-RC-287-6 & 3-RC-287-7).

• Two 3B Hot Leg Pressure Tap Alloy 600 Nozzle Welds.

(* Nearest Nozzle Butt Welds 3-RC-286-14 & 3-RC-286-15).

• Two 3A Hot Leg Flow Meter Alloy 600 Nozzle Welds.

(* Nearest Nozzle Butt Welds 3-RC-287-3 & 3-RC-287-63V).

• Two 3B Hot Leg Flow Meter Alloy 600 Nozzle Welds.

(* Nearest Nozzle Butt Welds 3-RC-286-11 & 3-RC-286-58V).

• Four (4) Cold Leg RTE Mounting Boss Alloy 600 Nozzle Welds (3-PIA1-9, 3-PIA2-9, 3-PIB1-11, & 3-PIB2-9).

• One 3B1 Cold Leg Level Tap Alloy 600 Nozzle Weld.

(* Nearest Nozzle Butt Weld 3-50-37-1).

• Three Cold Leg Drain Alloy 600 Nozzle Welds.

(3PIA1-10, 3-PIA2-10, 3-PIB2-10).

Note *: Small Bore Piping (1 NPS) Nozzle Welds are not given explicit weld IDs on the original Drawings. These nine specific Small Bore Nozzle Welds are located by the nearest documented branch connection butt weld.

Materials of construction for all locations referenced above are:

• Reactor Coolant System Piping (RCS) - SA-106 Grade B (P-No. 1)

• Alloy 600 Nozzle - SB-167 UNS N06600 (P-No. 43)

• Alloy 82/182 Dissimilar Metal Weld (DMW) - ERNiCr-3, Spec. SFA 5.14 /

ENiCrFe-3, Spec. SFA 5.11 (F-No. 43)

Page 1 of 7

Relief Request Serial #19-ON-001 RA-19-0028, Enclosure 1

2. Applicable Code Edition and Addenda

The current edition for the Inservice Inspection (ISI) interval for ONS Units 1, 2, and 3 is the American Society of Mechanical Engineers (ASME) Code,Section XI, 2007 Edition with the 2008 Addenda (Reference 1). All three units are in the fifth inspection interval with a scheduled end date of July 15, 2024.

The code of construction for ONS 1, 2, and 3 is B31.7, 1969 Edition, and was later reconciled to the ASME Code,Section III, 1983 Edition, no Addenda.

American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)

Code Case N-722-1 as conditioned by 10 CFR 50.55a (Reference 2)

American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)

Code Case N-853 (Reference 3)

3. Applicable Code Requirements Code Case N-722-1 (as conditioned by 10 CFR 50.55a) requires that piping hot leg/cold leg full penetration welds susceptible to PWSCC be inspected in accordance with Table 1 of the Code Case as part of the ISI program. Duke Energy has decided to preemptively mitigate/repair selected nozzle butt welds on the RCS piping, utilizing a welded reinforcing pad and replacement nozzle.

ASME Code,Section XI (Reference 1), Article IWA-4000 provides requirements for repair replacement activities:

IWA-4421 states, in part:

Defects shall be removed or mitigated in accordance with the following requirements...

IWA-4422.1(a) states, in part:

A defect is considered removed when it has been reduced to an acceptable size ...

IWA-4422.1(b) states, in part:

Alternatively, the defect removal area and any remaining portion of the defect may be evaluated, and the component accepted in accordance with the appropriate flaw evaluation provisions of Section XI ...

Article IWA-4000 does not provide specific guidance for the repair or mitigation of defects in dissimilar metal welds. Furthermore, the NRC in 10 CFR 50.55a(b)(2)(xxv) specifically prohibits the use of the provisions in IWA-4340, "Mitigation of Defects by Modification.

Page 2 of 7

Relief Request Serial #19-ON-001 RA-19-0028, Enclosure 1

4. Reason for Request

The welds identified in Section 1 are unmitigated full penetration welds fabricated from materials susceptible to PWSCC. As these welds are unmitigated, there exists the potential that flaws may develop at these locations and result in leakage. In accordance with Code Case N-722-1, these welds require frequent visual examination for the identification of any RCS leakage.

Duke Energy is proposing to apply a welded reinforcing pad on the Outer Diameter (OD) of the RCS piping using PWSCC resistant nickel Alloy 52M (ERNiCrFe-7A) filler metal. The new weld pad will be welded using the machine Gas Tungsten Arc Welding (GTAW)

Ambient Temperature Temper Bead (ATTB) welding technique. Duke Energy is proposing to attach a PWSCC resistant nozzle to the new weld pad with a full penetration nozzle corner weld using a non-temper bead manual welding technique, using PWSCC resistant nickel Alloy 52M filler metal, or with a "J" groove partial penetration weld as described in Code Case N-853. The welded pad will be designed and installed in accordance with Code Case N-853 except that the replacement nozzle material will be UNS S31600 or UNS N06690.

Code Case N-853 is not yet NRC-approved, but it has been reviewed by the NRC and is proposed to be approved for Unconditional Use (Reference 4 and 5). Therefore, Duke Energy is requesting relief under 10 CFR 50.55a(z)(1) from the defect removal requirements of ASME Code,Section XI, Article IWA-4000. The identified welds will be mitigated by a repair/replacement activity that meets the requirements of Code Case N-853 with the alternative nozzle material and weld joint geometry described herein. The repair/replacement activity provides an acceptable level of quality and safety.

5. Proposed Alternative and Basis for Use Figure 1a and Figure 1b provide sketches of the existing nozzle configurations described in Section 1. The Alloy 600 nozzle and Alloy 82/182 weld are materials with known susceptibility to PWSCC. The replacement of PWSCC susceptible material with material that is resistant to PWSCC provides for an acceptable level of quality and safety. The PWSCC susceptible material, at the identified locations, is currently unmitigated.

Application of a PWSCC resistant branch connection weld metal buildup will reduce the risk of a flaw propagating through the pressure boundary.

The PWSCC resistant branch connection weld metal buildup will be designed in accordance with Code Case N-853. Code Case N-853 has been reviewed by the NRC and is proposed to be approved for Unconditional Use (Reference 4 and 5). Two optional deviations may be taken to Code Case N-853 as follows: a) the new nozzle material may be manufactured from UNS S31600 material instead of UNS N06690, and b) the new nozzle may be attached by a full penetration nozzle corner weld instead of a partial penetration J groove weld.

Reference 6 provides the technical basis supporting the use of Code Case N-853.

Code Case N-853 requires the use of UNS N06690 material for the replacement nozzle.

Duke Energy proposes as an option to use UNS S31600 material for the replacement nozzle. UNS S31600 material is used in many applications for elevated temperature reactor coolant piping at ONS. UNS S31600 is an austenitic stainless steel that has demonstrated operating experience as PWSCC resistant. The applicable ASME Code allowable stresses and material properties for UNS S31600 will be used in the design of the replacement nozzle. The reason for the requested use of UNS S31600 is that UNS S31600 is a more Page 3 of 7

Relief Request Serial #19-ON-001 RA-19-0028, Enclosure 1 readily available material, given the strict ASME Code Class 1 requirements for materials, and the small volume of material required.

Code Case N-853 requires the use of a partial penetration J groove weld for the attachment of the new nozzle to the reinforcing weld metal buildup. The partial penetration J groove weld is one of many Code approved configurations for attachment of nozzles to piping. Figure 2 provides a sketch of the Code Case configuration. Duke Energy proposes to optionally use a full penetration nozzle corner weld to join the new nozzle to the weld reinforcing pad. The technical basis for Code Case N-853 (Reference 6) includes reference for the use of full penetration nozzle welds.

The full penetration nozzle corner weld configuration shown in Figure 3 is in agreement with ASME Code,Section III, Figure NB-4244(b)-1 detail (a) (Reference 7). The full penetration corner weld will be examined in accordance with Reference 7 and Code Case N-853. The reason for the requested optional use of the nozzle corner weld detail (detail (a) of Figure NB-4244(b)-1) is that field conditions of access and interferences may result in situations where the corner weld is preferable to the J-groove weld, based on dose exposure and installation sequence. Additionally, use of a full penetration corner weld eliminates the small pocket area at the base of the nozzle which over time will collect contaminants and create a radiological hot spot in the RCS piping.

In summary, Duke Energy is requesting relief under 10 CFR 50.55a(z)(1) from the ASME Code,Section XI defect removal requirements of IWA-4000. The repair/replacement activity will follow the requirements stated in Code Case N-853 and modified herein. The requested relief from IWA-4000 is based on the use of Code Case N-853 (with the noted deviations /

exceptions) that will provide an alternative with an acceptable level of quality and safety.

The subject welds will be mitigated or repaired by application of a PWSCC resistant reinforcing pad and attachment of a PWSCC resistant nozzle. The pre-service and inservice examination requirements of Code Case N-853 will be implemented. The use of Code Case N-853 as guidance for the repair/replacement activity will provide an acceptable level of quality and safety.

6. Precedents Weld metal buildups with a replacement nozzle have been performed to repair leaking nozzles on reactor pressure vessels and pressurizers. These instances formed the basis of Code Case N-853. Listed below are examples with the submitted request for alternative (RR) and safety evaluation (SE).

a. Palo Verde Nuclear Generation Station (RR Reference 8; SE Reference 9)

b. Limerick Generation Station (RR Reference 10; SE Reference 11)

Page 4 of 7

Relief Request Serial #19-ON-001 RA-19-0028, Enclosure 1

7. Duration of Proposed Alternative The duration of this relief request is for the remainder of the current licensed operating life of each ONS unit, shown below. The repairs will be designed to meet the requirements of Code Case N-853 and ASME Code,Section III (Reference 7). The design will consider operation until the end of the current operating licenses for each unit.

Docket Number License Expires Unit 1 05000269 02/06/2033 Unit 2 05000270 10/06/2033 Unit 3 05000287 07/19/2034

8. References

1. American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI, 2007 Edition with the 2008 Addenda.

2. ASME Code Case N-722-1, Additional Examinations for PWR Pressure Retaining Welds in Class 1 Components Fabricated with Alloy 600/82/182 Materials,Section XI, Division 1, Approval Date: January 26, 2009.

3. ASME Code Case N-853, PWR Class 1 Primary Piping Alloy 600 Full Penetration Branch Connection Weld Metal Buildup for Material Susceptible to Primary Water Stress Corrosion Cracking,Section XI, Division 1, Approval Date: June 27, 2016.

4. Federal Register; Proposed Rules; Vol. 83, No. 159; August 16, 2018.

5. NRC Draft Regulatory Guide DG-1342; Proposed Revision 19 to Regulatory Guide RG 1.147; August 2018 (ADAMS Accession No. ML18114A225).

6. Waskey, D., McCracken, S., (2016); Technical Basis for Code Case N-853 - A600 Branch Connection Weld Repair for SCC Mitigation; Proceedings of the ASME 2016 Pressure Vessels and Piping Conference; PVP2016; July 17-21, 2016, Vancouver, British Columbia, Canada; PVP2016-63902.

7. ASME Code Section III, 2013 Edition.

8. Arizona Public Service Company letter, American Society of Mechanical Engineers (ASME) Code,Section XI, Request for Approval of an Alternative to Flaw Removal and Characterization - Relief Request 51, dated November 8, 2013 (ADAMS Accession No. ML13317A071).

9. NRC letter, Palo Verde Nuclear Generating Station, Unit 3 - Request for Relief from ASME Code,Section XI Requirements Regarding Half-Nozzle Repair and Flaw Evaluation as an Alternative to Flaw Removal and Flaw Characterization for Flaw in Bottom-Mounted Instrument Nozzle Penetration No.3 (TAC No. MF3051), dated April 10, 2014 (ADAMS Accession No. ML14093A407).

10. Exelon Generation letter, Proposed Relief Request Associated with Reactor Pressure Vessel Nozzle Repairs, dated May 15, 2017 (ADAMS Accession No. ML17135A423).

11. NRC letter, Limerick Generating Station, Unit 2 - Relief Request I4R-17, Associated with the Alternate Repair of a 2-Inch Instrument Line Nozzle at Penetration N-16D on the Reactor Pressure Vessel (CAC No. MF9702), dated August 14, 2017 (ADAMS Accession No. ML17208A090)

Page 5 of 7

Relief Request Serial #19-ON-001 RA-19-0028, Enclosure 1 Figure 1a: Sketch of Example Existing Nozzle Configuration RCS RUN PIPE AU.DY 82/182 BUTTER (UNIT 3 ONLY)

AU.DY 82/182 WELD AU.DY 600 NOZZLE Figure 1b: Sketch of Example Fast RTE Nozzle Connection Page 6 of 7

Relief Request Serial #19-ON-001 RA-19-0028, Enclosure 1 NEW NOZZLE ALLOY 52/v\ J Prep Weld CC N-853 ALLOY 82/182/

Figure 2: Sketch of Example Repaired Nozzle Configuration with Code Case N-853 J-Groove Weld NEW NOZZLE ALLOY 52M CORNER WELD Figure NB-4244(b)-1 CJP ALLOY 82/182/ ALLOY 600 Figure 3: Sketch of Example Repaired Nozzle Configuration with Proposed Alternative Full Penetration Corner Weld Page 7 of 7