NMP1L3526, Submittal of Emergency Relief Request I5R-14 Concerning a Proposed Alternative Associated with N2E Safe End-to-Nozzle Dissimilar Metal Weld Repair with Laminar Indication
| ML23103A404 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 04/13/2023 |
| From: | David Gudger Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NMP1L3526 | |
| Download: ML23103A404 (1) | |
Text
200 Exelon Way Kennett Square, PA 19348 www.constellation.com 10 CFR 50.55a NMP1L3526 April 13, 2023 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Nine Mile Point Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-63 NRC Docket No. 50-220
Subject:
Submittal of Emergency Relief Request I5R-14 Concerning a Proposed Alternative Associated with N2E Safe End-to-Nozzle Dissimilar Metal Weld Repair with Laminar Indication
References:
- 1) Letter from D. Gudger (Constellation Energy Generation, LLC) to U.S. Nuclear Regulatory Commission, Submittal of Emergency Relief Request I5R-11 Concerning the Installation of a Weld Overlay on Reactor Pressure Vessel Recirculation Inlet Nozzle N2E Safe End-to-Nozzle Dissimilar Metal Weld (32-WD-208) dated March 24, 2023 (ML23083B991)
- 2) Letter from D. Gudger (Constellation Energy Generation, LLC) to U.S. Nuclear Regulatory Commission, Submittal of Emergency Relief Request I5R-11 Concerning the Installation of a Weld Overlay on Reactor Pressure Vessel Recirculation Inlet Nozzle N2E Safe End-to-Nozzle Dissimilar Metal Weld (32-WD-208) dated March 27, 2023 (ML23086C088)
- 3) Email from R. Guzman (U.S. Nuclear Regulatory Commission) to T. Loomis (Constellation Energy Generation, LLC), Nine Mile Point Unit 2 - Request for Additional Information - Emergent Relief Request I5R-11 Weld Overlay on RPV Recirculation Nozzle N2E DM Weld (EPID L-2023-LLR-0011), dated March 28, 2023 (ML23087A291)
- 4) Letter from D. Gudger (Constellation Energy Generation, LLC) to U.S. Nuclear Regulatory Commission, Submittal of Emergency Relief Request I5R-11 Concerning the Installation of a Weld Overlay on Reactor Pressure Vessel Recirculation Inlet Nozzle N2E Safe End-to-Nozzle Dissimilar Metal Weld (32-WD-208) dated March 29, 2023 (ML23088A165)
- 5) Letter from D. Gudger (Constellation Energy Generation, LLC) to U.S. Nuclear Regulatory Commission, Submittal of Emergency Relief Request I5R-11 Concerning the Installation of a Weld Overlay on Reactor Pressure Vessel Recirculation Inlet Nozzle N2E Safe End-to-Nozzle Dissimilar Metal Weld (32-WD-208) dated March 30, 2023 (ML23089A230)
Emergency Relief Request I5R-14 April 13, 2023 Page 2
- 6) Email from R. Guzman (U.S. Nuclear Regulatory Commission) to T. Loomis (Constellation Energy Generation, LLC), Verbal Authorization for NMP1 Proposed Alternative Weld Overlay N2E Safe-end to nozzle DM Weld (EPID L2023-LLR-0011), dated March 31, 2023 (ML23090A130)
In the Reference 1 letter, Constellation Energy Generation, LLC (CEG) requested emergency approval of a proposed alternative associated with the repair of the recirculation inlet nozzle N2E safe end-to-nozzle dissimilar metal (DM) weld. In the Reference 6 email, the U.S. Nuclear Regulatory Commission provided approval of this proposed alternative.
During the acceptance examination of the N2E weld overlay repair, three laminar indications were identified with two of the indications meeting the acceptance criteria of the previously approved alternative, which is based on Code Case N-740-2. One indication exceeded the acceptance criteria of Code Case N-740-2 due to the length exceeding 10% of the pipe circumference. This indication is located approximately 1.5 inches from the toe of the dissimilar metal weld in the stainless-steel safe end at the interface between the safe-end base material and the buffer layer. This laminar indication is located away from the original axial flaw location and does not impact the ability to examine the required NDE volume including the susceptible material. The indication was evaluated and determined to meet the acceptance criteria of Non-Mandatory Appendix Q. Additionally, an analysis was performed to compare the stress results with and without the presence of the laminar indication and showed insignificant difference in applied stresses; therefore, no adverse impact from the indication. The use of the Appendix Q acceptance criteria and the additional evaluation performed provide reasonable assurance of the adequacy of the weld overlay with the presence of the laminar indication.
Attached is an emergency proposed alternative to allow the laminar indication to remain in place until the next refueling outage (N1R28). CEG requests verbal approval of this revision by Noon, April 15, 2023 to permit startup from the current refueling outage.
If you have any questions concerning this letter, please contact Tom Loomis at Thomas.Loomis@constellation.com.
Respectfully, David T. Gudger Senior Manager - Licensing & Regulatory Affairs Constellation Energy Generation, LLC
Attachment:
- 1) Relief Request I5R-14 cc: Regional Administrator, Region I, NRC NRC Senior Resident Inspector, NMP Project Manager NRC, NMP A. L. Peterson, NYSERDA
Nine Mile Point Nuclear Station, Unit 1 Proposed Alternative Associated with N2E Safe End-to-Nozzle Dissimilar Metal Weld Repair with a Laminar Indication RELIEF REQUEST I5R-14
10 CFR 50.55a Proposed Alternative I5R-14 Revision 0 (Page 1 of 6)
Proposed Alternative Associated with N2E Safe End-to-Nozzle Dissimilar Metal Weld Repair with a Laminar Indication In Accordance with 10 CFR 50.55a(z)(1) 1.0 ASME CODE COMPONENT(S) AFFECTED Code Class:
1 Examination Category:
R-A Item Number:
Description:
Reactor Pressure Vessel (RPV) Recirculation Inlet Nozzle N2E Safe End-to-Nozzle DM Weld Materials:
Nozzle - SA-336 with buttering Weld Material - Alloy 82/182 Safe End - SA-182 F316 Size:
Nominal 29 Inches (Outer Diameter)
Component Number(s):
Weld No. 32-WD-208 Drawing Numbers:
ISI-NOZ-002 2.0 APPLICABLE CODE EDITION AND ADDENDA The fifth interval of the Nine Mile Point Nuclear Station, Unit 1 Inservice Inspection (ISI) Program is based on the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel (B&PV) Code,Section XI, 2013 Edition. The fifth ISI interval began on August 23, 2019 and is scheduled to conclude on August 22, 2029.
The applicable ASME Section III, Construction Codes Edition and Addenda are as follows:
Safe-End: ASME Section III, 1977 Edition through Summer 1977 Addenda Piping: ASME Section III, 1980 Edition through Winter 1980 Addenda Installation: ASME Section III, 1977 Edition through Summer 1978 Addenda The nondestructive examination method and acceptance criteria of the 1992 Edition or later of Section III shall be met.
3.0 APPLICABLE CODE REQUIREMENTS IWA-4411 of the ASME Code,Section XI states that Welding, brazing and installation shall be performed in accordance with the Owners Requirements and, except as modified below, in accordance with the original Construction Code of the item.
10 CFR 50.55a Proposed Alternative I5R-14 Revision 0 (Page 2 of 6)
IWA-4411(a) of the ASME Code,Section XI states in part, that Later Editions and Addenda of the Construction Code, or a later different Construction Code, either in its entirety or portions thereof, and Code Cases may be used, provided the substitution is as listed in IWA-4221(c).
IWA-4411(b) of the ASME Code,Section XI states that Revised Owners Requirements may be used, provided they are reconciled in accordance with IWA-4222.
IWA-4412 states Defect removal shall be accomplished in accordance with the requirements of IWA-4420.
IWA-4611 specifies requirements for defect removal and examination following defect removal.
IWB-3640 provides the evaluation procedures and acceptance criteria for flaws in austenitic and ferritic piping. In particular, IWB-3642, IWB-3643, and IWB-3644 state that (f)laws with depths greater than 75% of the wall thickness are unacceptable.
This alternative proposes to follow the guidance in Non-Mandatory Appendix Q in lieu of the requirements in ASME Code Case N-740-2 for acceptance of a laminar indication in the weld overlay to the N2E safe end-to-nozzle DM weld at NMP1. The following is a discussion of the N-740-2 and Appendix Q requirements:
As discussed in Code Case N-740-2 3(a)(3)(-a) regarding acceptance of laminar flaws in the weld overlay, The acceptance standards of IWB-3514 shall be met, with the additional limitation that the total laminar flaw area shall not exceed 10% of the weld surface area and that no linear dimension of the laminar flaw area shall exceed the greater of 3 in. (76 mm) or 10% of the pipe circumference.
ASME Section XI, Non-Mandatory Appendix Q, Section Q-4100, has been accepted by the NRC for defining laminar flaw acceptance criteria for stainless steel weld overlay repairs.
4.0 REASON FOR REQUEST Dissimilar Metal (DM) welds containing nickel welding Alloys 82 and 182 have experienced Intergranular Stress Corrosion Cracking (IGSCC) in components operating at boiling water reactor temperatures.
On March 18, 2023, during automated encoded UT examination of the N2E safe end-to-nozzle DM weld (32-WD-208) one relevant indication was recorded. The indication is axially oriented and is located in the DM weld and adjacent safe end material. The indication is located approximately 14 inches clockwise from top of center. The
10 CFR 50.55a Proposed Alternative I5R-14 Revision 0 (Page 3 of 6) indication is inner diameter connected with attributes that are indicative of IGSCC.
This flaw did not meet the acceptance standards of IWB-3500 and could not be accepted by analytical evaluation in accordance with IWB-3600; therefore, a repair/replacement activity was required in accordance with IWA-4000.
As provided in an approval from the U.S. Nuclear Regulatory Commission on March 31, 2023, CEG was granted approval for a leak barrier weld overlay (Email from R.
Guzman (U.S. Nuclear Regulatory Commission) to T. Loomis (Constellation Energy Generation, LLC), Verbal Authorization for NMP1 Proposed Alternative Weld Overlay N2E Safe-end to nozzle DM Weld (EPID L2023-LLR-0011), dated March 31, 2023 (ML23090A130)).
During the acceptance examination of the weld overlay, a laminar indication (bolded, indication 2) with a length exceeding 10% of the pipe circumference (91.3 inches) was identified, which does not meet the acceptance criteria of Code Case N-740-2.
Indications 1 and 3 were determined to meet the acceptance criteria. The dimensional parameters of all identified laminar indications are as follows:
Length (in.) Width (in.)
Depth (in.)
Meets Appendix Q Meets N-740-2 1
4.3 0.3 0.55 Yes Yes 2
12.2 0.3 0.56 Yes No 3
7.1 0.2 0.51 Yes Yes
10 CFR 50.55a Proposed Alternative I5R-14 Revision 0 (Page 4 of 6)
The following is an approximate location of indication 2:
The following figure shows the location of all laminar indications relative to the axial flaw:
All three laminar indications meet the acceptance standards of Appendix Q, IWB-3514, and the total area of all identified laminar indications does not exceed 10% of the weld surface area. Indication 2 is located approximately 1.5 inches from the toe of the dissimilar metal weld on the stainless-steel safe-end at the interface between
10 CFR 50.55a Proposed Alternative I5R-14 Revision 0 (Page 5 of 6) the safe-end base metal and the buffer layer. Indication 2 is located approximately 22.5 clockwise from the original axial flaw location and does not impact the ability to examine the required NDE volume including the susceptible material.
An analysis of indication 2 was performed assuming a laminar indication 0.3 inches wide by 360 degrees and was evaluated for internal pressure and a piping moment.
The analysis was performed to compare the stress results with and without the presence of the laminar indication and showed insignificant difference in applied stresses; therefore, no adverse impact from the indication. The use of the Appendix Q acceptance criteria and the additional evaluation provide reasonable assurance of the adequacy of the weld overlay with the presence of the laminar indication. The preservice examination of the weld overlay was completed and meets the acceptance criteria of the previously approved alternative and achieved the examination coverage of essentially 100% including all susceptible material. Following the application of the weld overlay, the original axial flaw was confirmed to be less than 75% through wall.
5.0 PROPOSED ALTERNATIVE AND BASIS FOR USE Pursuant to 10 CFR 50.55a(z)(1), CEG proposes an alternative to the ASME Code requirements stated in Section 3.0 to permit a laminar flaw (indication 2) to remain in place for the upcoming cycle at NMP1.
The laminar flaw acceptance criteria of Code Case N-740-2 will not be used for indication 2. In lieu of these requirements, the flaw acceptance criteria of ASME Section XI, Non-Mandatory Appendix Q, Section Q-4100 will be met. The laminar flaw acceptance criteria of Appendix Q are consistent with Code Case N-740-2 with respect to the requirement to satisfy the acceptance standards of IWB-3514.
Additionally, N-740-2 requires that the total laminar flaw area shall not exceed 10%
of the weld surface area and that no linear dimension of the laminar flaw area shall exceed the greater of 3 in. (76 mm) or 10% of the pipe circumference. The total laminar flaw area (indications 1, 2, and 3 combined) has been determined to be significantly less than 10% of the weld surface area.
Indication 2 exceeds the N-740-2 requirement to be less than 10% of the pipe circumference but meets the acceptance criteria of Non-Mandatory Appendix Q.
Additionally, an analysis of indication 2 was performed assuming a laminar indication 0.3 inches wide by 360 degrees long and was evaluated for internal pressure and a piping moment. The analysis was performed to compare the stress results with and without the presence of the laminar indication and showed insignificant difference in applied stresses; therefore, no adverse impact from the indication. Indication 2 is relatively narrow at 0.3 inches wide and exceeds the length acceptance criteria of Code Case N-740-2 by a small amount (13.4% versus 10%) with no detected through wall dimension. This laminar indication is not near the original axial flaw to cause any impact
10 CFR 50.55a Proposed Alternative I5R-14 Revision 0 (Page 6 of 6) to the flaw or the inspection of it. The use of the Appendix Q acceptance criteria and the additional evaluation of indication 2 provides reasonable assurance of the adequacy of the weld overlay with the presence of the laminar indications and that leaving indication 2 in place for the upcoming cycle will provide an acceptable level of quality and safety.
6.0 DURATION OF THE PROPOSED ALTERNATIVE This alternative is proposed for use until the end of Unit 1 refueling outage N1R28 in 2025 during which a full structural weld overlay repair shall be performed on the N2E safe end-to-nozzle weld.
7.0 PRECEDENTS None
8.0 REFERENCES
- 1. ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," 2013 Edition.
- 2. ASME Code Case N-740-2, Full Structural Dissimilar Metal Weld Overlay for Repair or Mitigation of Class 1, 2, and 3 Items,Section XI, Division 1, dated November 10, 2008.