RS-22-127, Submittal of Sixth Inservice Inspection Interval Relief Request I6R-10 Reactor Pressure Vessel Penetration N-11B Repair
| ML22348A205 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 12/14/2022 |
| From: | Simpson P Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RS-22-127, EPID L-2017--LLR-0004, CAC. MF9286 | |
| Download: ML22348A205 (1) | |
Text
4300 Winfield Road Warrenville, IL 60555 630 657 2000 Office December 14, 2022 10 CFR 50.55a(z)(1)
RS-22-127 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Quad Cities Nuclear Power Station, Unit 2 Renewed Facility Operating License No. DPR-30 NRC Docket No. 50-265
Subject:
Submittal of Sixth Inservice Inspection Interval Relief Request I6R-10 Reactor Pressure Vessel Penetration N-11B Repair
References:
- 1.
Letter from D.J. Wrona (U.S. NRC) to B.C. Hanson (Exelon Generation Company, LLC), "Quad Cities Nuclear Power Station, Unit 2 - Approval of Alternatives to the ASME Code Regarding Reactor Vessel Penetration N-11B - Relief Request I5R-11, Revision 3 (CAC. No. MF9286; EPID L-2017--LLR-0004)
(RS-17-014)," dated January 24, 2018 (ADAMS Accession No. ML18022A616)
- 2.
Letter from R.F. Kuntz (U.S. NRC) to D.P. Rhoades (Constellation Energy Generation, LLC), "Clinton Power Station, Unit No. 1; Dresden Nuclear Power Station, Units 2 and 3; James A. Fitzpatrick Nuclear Power Plant; Lasalle County Station, Units 1 and 2; Limerick Generating Station, Units 1 and 2; Nine Mile Point Nuclear Station, Units 1 and 2; Peach Bottom Atomic Power Station, Units 2 and 3; and Quad Cities Nuclear Power Station, Units 1 and 2 - Proposed Alternative for Repair of Water Level Instrumentation Partial Penetration Nozzles (EPIDs L-2021--LLR-0057 and L-2021-LLR-0058) (RS-17-014)," dated April 15, 2022 (ADAMS Accession No. ML22094A001)
In accordance with 10 CFR 50.55a, "Codes and standards," paragraph (z)(1), Constellation Energy Generation (CEG), LLC requests U.S. Nuclear Regulatory Commission (NRC) approval of the attached relief request I6R-10, Revision 0, for Quad Cities Nuclear Power Station (QCNPS), Unit 2. CEG has determined that the proposed alternative provides an acceptable level of quality and safety as required by 10 CFR 50.55a(z)(1). The prior authorization for relief request I5R-11, Revision 3 (Reference 1), remains in effect only until the end of Cycle 27 in the spring of 2024. The attached relief request I6R-10, Revision 0, seeks continued relief for the existing penetration N-11B repair and uses Q2R26 non-destructive examination (NDE) data to justify extension such that the next evaluation of the
U.S. Nuclear Regulatory Commission December 14, 2022 Page 2 alternative would be required during the 2030 refueling outage rather than the spring 2024 outage as currently required by Reference 1. The proposed NDE and flaw evaluation methods are consistent with the prior QCNPS approval in Reference 1 as well as a newer generic fleet approval (Reference 2) for application of this repair and evaluation technique to other water level instrumentation penetrations.
CEG requests authorization of this request by December 14, 2023.
There are no regulatory commitments contained within this letter. Should you have any questions concerning this letter, please contact Ms. Rebecca L. Steinman at 630-657-2831.
Respectfully, Patrick R. Simpson Sr. Manager Licensing Constellation Energy Generation, LLC
Attachment:
10 CFR 50.55a Relief Request I6R-10, Revision 0 cc:
Regional Administrator - NRC Region III NRC Senior Resident Inspector - Quad Cities Nuclear Power Station
10 CFR 50.55a Request Number I6R-10, Revision 0 Page 1 of 9 Request for Relief for Unit 2 Reactor Pressure Vessel Penetration N-11B Repair In Accordance with 10 CFR 50.55a(z)(1),
"Alternate Provides Acceptable Level of Quality and Safety"
- 1.
ASME Code Components Affected Code Class:
1
Reference:
IWB-2500, Table IWB-2500-1 Examination Category:
B-P Item Number:
B15.10
==
Description:==
Reactor Pressure Vessel (RPV) Water Level Instrument Penetration - 2" Nominal Pipe Size Component Number:
RPV Penetration N-11B
- 2.
Applicable Code Edition and Addenda
The code of record for the sixth 10-year Inservice Inspection (ISI) Program interval at Quad Cities Nuclear Power Station (QCNPS) is the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code),Section XI, 2017 Edition. The sixth 10-year interval is effective from April 2, 2023, through April 1, 2033.
The code of construction for the RPV is the ASME Code,Section III, 1965 Edition through Summer 1965 Addenda.
The code of construction for the instrument penetration nozzle is the ASME Code,Section III, 1965 Edition through Summer 1969 Addenda.
- 3.
Applicable Code Requirement
The specific ASME Code requirements for which use of the proposed alternative is being requested are listed below. These requirements are in the 2017 Edition of the ASME Code. It should be noted that the repair and initial flaw analysis were both completed during the fourth 10-year ISI Program interval and the governing code for the fourth interval was the 1995 Edition through 1996 Addenda. The repair was re-evaluated during the fifth 10-year ISI Program interval when the governing code was the 2007 Edition through 2008 Addenda.
Flaw Removal Paragraph IWA-4412 of the ASME BPV Code,Section XI, states: Defect removal shall be accomplished in accordance with the requirements of IWA-4420.
Subparagraph IWA-4611.1(a) of the ASME BPV Code,Section XI, states: Defects shall be removed in accordance with IWA-4422.1. A defect is considered removed when it has been reduced to an acceptable size.
10 CFR 50.55a Request Number I6R-10, Revision 0 Page 2 of 9 Subarticle IWA-5250(a)(3) of the ASME BPV Code,Section XI, states: Components requiring corrective action shall have repair/replacement activities performed in accordance with Article IWA-4000 or corrective measures performed where the relevant condition can be corrected without a repair/replacement activity.
N-528 of Section III, 1965 Edition through Summer 1965, requires repair of weld defects including removal of defects detected by leakage tests.
Flaw Evaluation Subparagraph IWB-3522.1 of the ASME BPV Code,Section XI, states, in part, that: A component whose visual examination (IWA-5240) detects any of the following relevant conditions shall meet IWB-3142 and IWA-5250 prior to continued service...
Subparagraph IWB-3142.1(b) of the ASME BPV Code,Section XI, states: A component whose visual examination detects the relevant conditions described in the standards of Table IWB-3410-1 shall be unacceptable for continued service, unless such components meet the requirements of IWB-3142.2, IWB-3142.3, or IWB-3142.4.
Subarticle IWA-3300(a) of the ASME BPV Code,Section XI, states, in part, that: Flaws detected by the preservice and inservice examinations shall be sized.
Subarticle IWA-3300(b) of the ASME BPV Code,Section XI, states, in part, that: Flaws shall be characterized in accordance with IWA-3310 through IWA-3390, as applicable.
IWB-3610(b) states "For purposes of analytical evaluation, the depth of flaws in clad components shall be defined in accordance with Figure IWB-3610-1 as follows" Subarticle IWB-3420 of the ASME BPV Code,Section XI, states: Each detected flaw or group of flaws shall be characterized by the rules of IWA-3300 to establish the dimensions of the flaws. These dimensions shall be used in conjunction with the acceptance standards of IWB-3500.
- 4.
Reason for Request
During QCNPS Unit 2 refueling outage Q2R21 (i.e., spring 2012), and because of leakage indications on the RPV penetration N-11B, Constellation Energy Generation, LLC (CEG)
(which was Exelon Generating Company, LLC (EGC) at the time) partially replaced the existing RPV penetration N-11B nozzle assembly with a nozzle penetration that is resistant to Intergranular Stress Corrosion Cracking (IGSCC). This repair was performed in accordance with ASME and construction codes applicable at the time, except as noted in relief request I4R-19 submitted for U.S. Nuclear Regulatory Commission (NRC) review on April 6, 2012 (ADAMS Accession No. ML12100A012). Relief Request I4R-19 was authorized by the NRC on January 30, 2013 (ADAMS Accession No. ML13016A454).
As described in I4R-19, a welded pad was applied to the outside surface (OD) of the RPV using IGSCC resistant nickel Alloy 52M (ERNiCrFe-7 or -7A) filler metals and was welded using the machine gas tungsten arc welding (GTAW) ambient temperature temper bead (ATTB) welding technique. An IGSCC resistant nozzle was attached to the new weld pad with a partial penetration weld using a non-temper bead manual welding technique. The original partial penetration attachment weld and a remnant of the original nozzle remained in place. A
10 CFR 50.55a Request Number I6R-10, Revision 0 Page 3 of 9 failure assessment was completed prior to startup from refueling outage Q2R21 to demonstrate the acceptability of leaving the original partial penetration attachment weld, with a maximum postulated flaw, in place for the operating cycle, which ended in April 2014.
The repair was performed by installing a welded pad using ATTB welding in accordance with ASME Code Case N-638-4. At the time of the repair, the NRC had conditionally approved ASME Code Case N-638-4 to allow ATTB welding of ferritic materials without the requirement for preheat or post-weld heat treatment.
Relief Request I5R-11 Revision 1 was submitted to demonstrate the acceptability of leaving the original partial penetration attachment weld, with a maximum postulated flaw, in place for two additional cycles (i.e., through Unit 2 Cycle 24). This relief request was authorized by the NRC on February 28, 2014 (ADAMS Accession No. ML14055A227).
IWA-4412 and IWA-4611 contain requirements for the removal of, or reduction in size of defects. The defect on N-11B will remain in service without removal or reduction in size; therefore, relief is sought from these requirements.
IWB-3400 and IWB-3600 were written with the expectation that nondestructive examination techniques such as ultrasonic testing (UT) would be used to determine the flaw size and shape. In support of the flaw evaluation and application of applicable acceptance criteria, paragraphs IWA-3300, IWB-3420, and IWB-3600 require characterization of the flaw in the leaking penetration. When I5R-11 Revision 1 was submitted, there was no qualified or demonstrated technique to perform volumetric nondestructive examination of the partial penetration weld in this configuration that can be used to accurately characterize the location, orientation, or size of a flaw in the weld. However, since approval of I5R-11 Revision 1, a demonstrated technique has been developed and was successfully used during refueling outage Q2R23 (i.e., spring 2016).
Relief Request I5R-11 Revision 3 was submitted to demonstrate the acceptability of the repair performed in Q2R21 for an additional 9 years (i.e., through Unit 2 Cycle 27 currently scheduled to end in spring 2024). This relief request was authorized by the NRC on January 24, 2018 (ADAMS Accession No. ML18022A616).
This relief request is being submitted to demonstrate the continued acceptability of the repair performed in Q2R21 for an additional 9 years (i.e., through Unit 2 Cycle 30 currently scheduled to end in spring 2030).
- 5.
Proposed Alternative and Basis for Use Proposed Alternative In accordance with 10 CFR 50.55a(a)(3)(i), CEG proposes the following alternatives to the ASME Code Section XI requirements specified in Section 3 above.
A.
As an alternative to flaw removal or reduction in size to meet the applicable acceptance standards, CEG implemented an OD repair of the RPV instrument nozzle N-11B utilizing an OD weld pad as described in the Q2R21 repair of nozzle penetration section below.
No additional repairs are proposed in this relief request.
B.
As an alternative to performing the nondestructive examination required to characterize the flaw under IWB-3420 and IWB-3610(b) in RPV instrument nozzle N-11B, CEG
10 CFR 50.55a Request Number I6R-10, Revision 0 Page 4 of 9 proposes analyzing a maximum postulated flaw that bounds the range of flaw sizes that could exist in the J-groove weld and nozzle. The maximum postulated flaw size assumed in the analysis will be verified using demonstrated nondestructive examination techniques.
Basis for Use A.
Background
The QCNPS Unit 2 RPV is manufactured from SA-302, Grade B, modified by Code Case 1339, carbon steel that is clad with stainless steel. The RPV water level instrument penetrations are fabricated with Alloy 600 components. IGSCC of Alloy 600 components and welds exposed to boiling water reactor (BWR) cooling water has been historically observed. In particular, dissimilar metal welds (DMWs) made with nickel Alloy 182 weld metal exposed to elevated operating temperatures, such as nozzle J-groove welds, pose a heightened propensity for IGSCC.
During refueling outage Q2R21, EGC (at that time) discovered a leak in water level instrument penetration nozzle N-11B located on the RPV upper shell. The examination that detected the defect consisted of a visual examination in which active leakage was observed at the nozzle interface with the RPV OD during the Class 1 system leakage test.
This observation necessitated repair of this water level instrument nozzle using the methodology described below.
B.
Q2R21 Repair of Nozzle Penetration EGC (now CEG) replaced the existing nozzle assembly with a nozzle penetration that is resistant to IGSCC, meeting Section XI and Code Case N-638-4 as conditionally approved by the NRC in Regulatory Guide 1.147, Revision 17. Figure 1 provides a diagram of a typical RPV water level instrument nozzle repair. A welded pad was applied to the OD of the RPV using IGSCC resistant nickel Alloy 52M (ERNiCrFe-7 or -7A) filler metals and was welded using the machine GTAW ATTB welding technique. The IGSCC resistant nozzle was attached to the new weld pad with a partial penetration weld using a non-temper bead manual welding technique. The original partial penetration attachment weld and a remnant of the original nozzle currently remain in the RPV, and will continue to remain, in place. A weld flaw evaluation, described below, was completed to demonstrate the acceptability of leaving the original partial penetration attachment weld in service.
C.
Examination of J-Groove Weld BWRVIP-IP-1 Mockup The nondestructive examination mockup was fabricated from a section of material that the Electric Power Research Institute (EPRI) obtained from a cancelled BWR/6 RPV. The Boiling Water Reactor Vessel and Internals Project (BWRVIP) requested and received fabrication drawings from several BWRVIP members and selected two different penetration configurations to include in the mockup design. The mockup design included two BWR instrument penetrations. Both consisted of Alloy 600 penetration tubes that are joined to the inside surface of the RPV using an Alloy 82/182 partial penetration J-groove weld. One penetration configuration was based on site-supplied information provided by QCNPS Units 1 and 2, Dresden Units 2 and 3, Peach Bottom Units 2 and 3, and Browns Ferry Units 1 and 2. The other penetration was similar, except that the penetration tube and weld joint configuration represented later BWR designs. Both penetrations contained
10 CFR 50.55a Request Number I6R-10, Revision 0 Page 5 of 9 three manufactured cracks located in the Alloy 82/182 J-groove welds. Some of the cracks propagate into the low-alloy RPV material.
A more detailed description of the BWRVIP-IP-1 nondestructive examination mockup can be found in Section 14.5.1 of BWRVIP-03, Revision 20, BWR Vessel and Internals Project, Reactor Pressure Vessel and Internals Examination Guidelines (Product ID 3002010675).
BWRVIP H9 Weld Mockups In addition to the BWRVIP-IP-1 mockup, three flaws in the series of BWRVIP H9 shroud support plate weld mockups were also used during the nondestructive examination demonstration. These three flaws propagate out of the H9 welds, into the low-alloy RPV material to represent flaws that have propagated out the top of BWRVIP instrument penetration J-groove welds. These flaws were selected to increase the number of demonstration flaws that initiate within dendritic Alloy 82/182 weld material and propagate into fine-grain low-alloy RPV material.
Additional information regarding the BWRVIP H9 mockups and their flaws is provided in Section 5.3.2 of BWRVIP-03, Revision 20, BWR Vessel and Internals Project, Reactor Pressure Vessel and Internals Examination Guidelines (Product ID 3002010675).
NDE Demonstration Using the lessons learned during the initial BWRVIP development of the ultrasonic examination techniques for BWR instrument penetration J-groove welds, CEG coordinated with their inspection vendor to begin developing a fully field-deployable examination procedure. Using the BWRVIP-IP-1 and BWRVIP H9 weld mockups (BWRVIP-E, BWRVIP-E1, and BWRVIP-E2 mockups), CEG's inspection vendor developed and demonstrated a manual phased array ultrasonic examination technique.
This technique used longitudinal waves as the primary examination technique and shear waves as a supplemental examination technique. The longitudinal wave technique is used to locate flaws contained within the dendritic structure of the Alloy 82/182 J-groove weld. Similar to the BWRVIP developed examination techniques, the inspection vendor used the shear wave examination technique to enhance the ability to reliably determine if flaws have propagated into the low-alloy steel RPV material. Ultrasonic shear waves do not readily penetrate the dendritic Alloy 82/182 weld structure but are much more sensitive to locate flaws present in fine grain ferritic base material. There were five flaws in the demonstration set that initiate within Alloy 82/182 weld material and propagate into low-alloy RPV material. The shear wave technique detected all the flaws that propagated into the low-alloy RPV material.
Additional information regarding the new BWRVIP nondestructive examination demonstration is provided in Section 14.6 of BWRVIP-03, Revision 20, BWR Vessel and Internals Project, Reactor Pressure Vessel and Internals Examination Guidelines (Product ID 3002010675).
The NDE examination technique described above remains unchanged from the last approval.
10 CFR 50.55a Request Number I6R-10, Revision 0 Page 6 of 9 Manual Phased Array Examination During refueling outage Q2R23, the instrument penetration was examined using both the longitudinal and shear wave techniques. A refracted longitudinal wave probe was used to interrogate the Alloy 82/182 weld material and a shear wave probe was used to interrogate the ferritic material surrounding the J-groove weld. The instrument penetration was re-examined in refueling outage Q2R26 using the same examination techniques.
In both outages, the Alloy 82/182 J-groove weld material was examined using the manual phased array technique that was demonstrated in accordance with BWRVIP-03 requirements because there are no qualification criteria in ASME Code,Section XI, 2007 Edition through 2008 Addenda, Mandatory Appendix VIII for BWR instrument penetrations. The ferritic material surrounding the Alloy 82/182 J-groove weld was interrogated by personnel who have successfully completed a Performance Demonstration for ASME Code,Section XI, 2007 Edition through 2008 Addenda, Mandatory Appendix VIII, Supplement 4 for detection and sizing of flaws located in the ferritic material at nozzle inner-radius locations.
In preparation for performing the Q2R23 examination, the examiner performed an ultrasonic examination of the full-scale NDE instrument penetration NDE mockup, using the demonstrated phased array procedure. This was intended to familiarize the examiner with the BWR instrument penetration configuration. However, given the configuration differences between the instrument penetration and a nozzle inner-radius, the qualified nozzle inner-radius technique was modified as necessary so that it could be applied to the QCNPS N-11B instrument penetration configuration. The technique modifications were captured in a new proprietary inspection vendor examination procedure and validated using the BWRVIP mockups. EPRI/BWRVIP independently reviewed and documented the vendor's validation in accordance with BWRVIP-03 requirements.
Results During Q2R23, an inside surface connected indication was identified within the Alloy 82/182 J-groove weld material. The indication initiates at the toe of the J-groove weld and connects to the J-groove weld root at the annulus between the instrument nozzle N-11B and the RPV. The indication progresses perpendicular to the RPV surface, along the J-groove weld to penetration tube interface. No indications were present in the low-alloy RPV base metal. The inner nozzle is no longer part of the credited pressure boundary due to repairs made in 2012. A total of two indications were found within the bounded volume of the J-groove weld. No propagation has occurred into the low-alloy RPV base metal. The indications are characterized as follows:
- 1. The first indication was identified at approximately 202.5 degrees from top dead center in the clockwise direction. The indication was oriented circumferentially and was sized at approximately 0.25 inches in length. The indication initiates from the inside surface of the J-groove weld and propagates perpendicular to the RPV surface along the Alloy 600 penetration tube -to - Alloy 82/182 J-groove weld interface. The ultrasonic indication exhibited characteristics that are consistent with stress corrosion cracking.
The indication is the apparent origin of the leakage that was identified and repaired during the Q2R21 refueling outage as the indication connects the inside surface of the J-groove weld to the penetration tube-to-RPV penetration bore hole annulus. The indication intersects the J-groove weld root at the penetration tube annulus location,
10 CFR 50.55a Request Number I6R-10, Revision 0 Page 7 of 9 so it does not intersect the low-alloy RPV material.
- 2. The second indication was identified at approximately 90 degrees from top dead center in the clockwise direction. This indication was wholly contained within the J-groove weld and did not propagate into the low-alloy RPV base metal. It was sized at approximately 0.25 inches in length circumferentially with no measurable axial depth. The indication was not connected with the ID of the RPV and was below recording criteria for the procedure. The indication does not connect to the low-alloy steel RPV base metal. The embedded nature of this indication would not provide a path for the leakage that was identified during the Q2R21 refueling outage.
The Q2R26 exam results did not show any change from the Q2R23 results.
Validation The entire circumference of the J-groove weld was interrogated with the supplemental shear wave examination technique that was demonstrated using the full-scale mockups.
No indications were identified during either the Q2R23 or the Q2R26 examinations to suggest that a flaw has propagated into the low-alloy steel RPV base metal. The apparent planar flaw identified from the longitudinal wave examination was not identified during the shear wave examination, which provides additional evidence that the flaw tip is contained within the dendritic structure of the Alloy 182 weld material. If the flaw tip had propagated into the fine grain microstructure of the low-alloy steel RPV base metal, it is expected that a recognizable response would have been present during the shear wave examination. Therefore, it was concluded based on the Q2R23 and Q2R26 results that the utilized UT examination demonstrates reliable capability in identifying flaws in J-groove welds in RPV instrument nozzles.
Flaw Evaluation A flaw evaluation based on Linear Elastic Fracture Mechanics (LEFM) analysis was used to determine the acceptability of the postulated flaws in the remnant J-groove weld. This flaw evaluation is documented in AREVA NP Inc. document 32-9215236-002, "Quad Cities Unit 2 Instrument Nozzle J-Groove Weld LEFM Flaw Evaluation," which was previously submitted to the NRC as Attachment 1 of a letter dated December 20, 2013 (ADAMS Accession No. ML13358A401). The NRC's review of the flaw evaluation is documented in a letter dated February 28, 2014 (ADAMS Accession No. ML14055A227).
Based on the original LEFM flaw evaluation describe above, postulated circumferential and axial flaws were determined to be acceptable for at least nine years of operation using BWRVIP-60-A crack growth rates. Examination of the J-groove weld flaw during refueling outage Q2R26 (i.e., spring 2022) using the available NDE technique showed no indication is extending out into the ferritic low-alloy RPV base metal, same as the Q2R23 examination results. This stable condition (i.e., no indication of flaw growth) supports an additional nine-year period of operation from the spring 2022 refueling outage, which would require re-evaluation during the 2030 refueling outage rather than the spring 2024 refueling outage as currently authorized by the NRC.
Conclusion 10 CFR 50.55a(z)(1) states: "Alternatives to codes and standards requirements.
Alternatives to the requirements of paragraphs (b) through (h) of this section or portions
10 CFR 50.55a Request Number I6R-10, Revision 0 Page 8 of 9 thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation, or Director, Office of New Reactors, as appropriate. A proposed alternative must be submitted and authorized prior to implementation. The applicant or licensee must demonstrate that:
(1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety; or (2) Hardship without a compensating increase in quality and safety. Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety."
The LEFM analysis projects a conservative growth rate of nine years after refueling outage Q2R21 (i.e., spring 2012) if the indication is connecting to the low-alloy RPV base metal. Initial examination demonstrated that the indication is located within the J-groove weld and is not in contact with the low-alloy RPV base metal. Recent examinations in 2018 and 2022 show no change in the indication. Since the initial conditions that act as inputs to the LEFM analysis are unchanged the predicted nine year grown rate is unchanged. Therefore, based on the successful examination in refueling outage Q2R26 it is appropriate to re-evaluate in refueling outage Q2R30 (i.e., Spring 2030) to ensure the approved analysis remains bounded.
CEG concludes that the proposed alternative of this request provides an acceptable level of quality and safety. The weld pad on the RPV was installed using Nickel Alloy 52M filler metal using a qualified ATTB welding procedure. The RPV penetration was replaced with an IGSCC resistant nozzle welded to the OD of the RPV with Alloy 52M. The supporting flaw evaluation demonstrates that the RPV is acceptable without removal of the original nozzle remnant and partial penetration weld. Recent nondestructive examination of the flaw shows no flaw progression beyond the J-groove weld into the low-alloy RPV base metal. Therefore, CEG requests that the NRC authorize the proposed alternative in accordance with 10 CFR 50.55a(z)(1).
- 6.
Duration of Proposed Alternative Relief is requested for three (3) additional cycles following the Unit 2 Spring 2022 refueling outage (i.e., through Unit 2 Cycle 30 currently scheduled to end in Spring 2030). This supports the nine (9) years beyond the Unit 2 Spring 2022 refueling outage when the NDE technique was last performed.
- 7.
Precedent As noted above, a relief request was previously authorized for Quad Cities Unit 2 (I5R-11, Revision 1) by the NRC in a Safety Evaluation dated February 28, 2014. (ADAMS Accession No. ML14055A227).
A request to renew the relief was subsequently authorized for Quad Cities Unit 2 (I5R-11, Revision 3) by the NRC in a Safety Evaluation dated January 24, 2018. (ADAMS Accession No. ML18022A616).
Similar to this relief request, both of these prior authorizations were based on the original flaw evaluation reviewed by the NRC in 2014.
10 CFR 50.55a Request Number I6R-10, Revision 0 Page 9 of 9 Figure 1 Typical Reactor Pressure Vessel Water Level Instrument Nozzle Repair Detail C