ML25175A344
| ML25175A344 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 06/24/2025 |
| From: | Ameren Missouri |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML25175A342 | List: |
| References | |
| ULNRC-06956 | |
| Download: ML25175A344 (1) | |
Text
Enclosure 1 to Relief Request I5R-02 ULNRC-06956 Page 1 of 14 Proposed Alternative In accordance with 10 CFR 50.55a(z)(1)
Alternative Provides Acceptable Level of Quality and Safety
- 1. ASME Code Component Affected:
Components:
Reactor Vessel Bottom Head (RVBH) Bottom Mounted Instrumentation (BMI)
Nozzles 30, 35, 48, and 57 Code Class:
ASME Section III Class 1 Examination Category:
B-P, American Society of Mechanical Engineers (ASME) Code Section XI Code Item Number:
B15.10, Table IWB-2500-1 (B-P)
B15.80, Code Case N-722-1, Table 1 There are 58 RVBH BMI nozzles welded to the inside surface of the reactor vessel with partial penetration J-groove welds.
2. Applicable Code Edition and Addenda
Callaway's Inservice Inspection (ISI) Program complies with the 2019 Edition of the ASME Boiler and Pressure Vessel Code (BPVC),Section XI.
Callaway's fifth ISI interval began December 19, 2024, and ends on December 18, 2036. Callaway moved from the ten-to the twelve-year ISI interval as allowed by ASME Code Case N-921.
The Code of Construction for the reactor vessel is ASME Code Section III, 1971 Edition with Addenda through Winter 1972.
The Code of Construction for the RVBH BMI nozzle repair modification installation is ASME Code,Section III, 2015 Edition.
3. Applicable Code Requirement
Flaw Removal IWA-4412, Defect Removal, states, "Defect removal shall be accomplished in accordance with the requirements of IWA-4420.
IWA-4420, Defect Removal Requirements IWA-4421, General Requirements, states, in part, "Defects shall be removed in accordance with the following requirements: "
to Relief Request I5R-02 ULNRC-06956 Page 2 of 14 Flaw Characterization and Evaluation IWA-3300, Flaw Characterization, states, in part, "(b) Flaws shall be characterized in accordance with IWA-3310 through IWA-3390, as applicable."
IWB-3142.4, Acceptance by Evaluation, states, in part, "(b) A component containing relevant conditions is acceptable for continued service if an evaluation demonstrates the component's acceptability."
IWB-3420, Characterization, 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."
IWB-3660, Evaluation Procedure and Acceptance Criteria for PWR Reactor Vessel Head Penetration Nozzles, states, in part, "PWR reactor vessel upper and lower head penetration nozzles containing flaws may be evaluated to determine acceptability for continued service in accordance with the evaluation procedure and acceptance criteria of this paragraph."
Successive Examinations IWB-2420, Successive Inspections, states, in part, "(a) The sequence of component examinations which was established during the first inspection interval shall be repeated " and "(b) If a component is accepted for continued service in accordance with IWB-3132.3, the areas containing flaws shall be reexamined during the next three inspection periods listed in the schedule of the Inspection Program of IWB-2400 "
ASME Code Case N-722-1, Additional Examinations for PWR Pressure Retaining Welds in Class 1 Components Fabricated With Alloy 600/82/182 Materials, Item No. B15.80, RPV bottom-mounted instrument penetrations, requires visual examination every other refueling outage with IWB-3522 acceptance standards.
4. Reason for Request
On May 6, 2025, during Callaway's refueling outage (RFO), i.e., Refuel 27, Quality Control inspectors were performing a visual (VT-2) exam of the reactor vessel bottom head (RVBH) bottom mounted instrument (BMI) nozzles. During this exam, the inspectors identified dry white residue, resembling boric acid, coming from the annulus between BMI Nozzle 48 and the penetration through the RVBH. (See Figure 4-1.) The area was cleaned, with no active boric acid leak observed, and the condition was entered into Callaway's Corrective Action Program. Additionally, operators transitioned the plant back down to cold shutdown to satisfy reactor coolant system (RCS) operational leakage Technical Specification requirements.
As part of the extent-of-condition investigation, ultrasonic testing (UT) exams and visual (VT-1) exams were performed on all 58 BMI nozzles. Figure 4-3 depicts the locations of the nozzles. UT exams were performed inside the bore of the BMI nozzles. Underwater cameras were used to perform VT-1 exams. Eddy current (EC) exams were attempted on two nozzles that showed indications (Nozzles 48 and 57); however, due to tooling difficulties associated with nozzle geometry, no meaningful data could be obtained. From the analysis of the UT and VT-1 data, it was determined that four BMI nozzles (30, 35, 48, and 57) require repair. Figure
to Relief Request I5R-02 ULNRC-06956 Page 3 of 14 4-2 depicts the repair modification, which is described later in this section. The examinations verified no other unacceptable indications in the other nozzle penetrations.
The analysis of the UT and VT-1 data for BMI Nozzles 30, 35, 48, and 57 are summarized below:
- BMI Nozzle 30: UT data shows an axially oriented Stress Corrosion Cracking (SCC) indication located in the center of the partial penetration J-groove weld that has slightly propagated into the nozzle tube material. The indication has a length of 0.220" and a depth of 0.073". UT data shows that the indication is located within a grouping of J-groove weld fabrication flaws. A VT-1 surface anomaly coincides with the UT indication. The jagged nature of the surface anomaly is consistent with SSC.
- BMI Nozzle 35: UT data shows an axially oriented SCC indication located on the toe of the partial penetration J-groove weld that has propagated into the nozzle tube material. The indication has a length of 0.200" and a depth of 0.129".
- BMI Nozzle 48: UT data shows weld fabrication flaws in the partial penetration J-groove weld, which have not propagated into the nozzle tube material. The UT data shows a leak path pattern consistent with water flowing through the annulus between the outer diameter of the BMI nozzle tube and inside surface of the RVBH bore hole. The leak path pattern initiates at the location of one of the J-groove weld fabrication flaws. The J-groove weld fabrication flaw may therefore contain a SCC flaw which cannot be detected using UT techniques. A VT-1 surface anomaly coincides with the leak path signature.
- BMI Nozzle 57: UT data shows no evidence of SCC in the nozzle tube material. VT-1 data shows an approximate 0.04" diameter pit observed on the surface of the partial penetration J-groove with linear like indications propagating from it. SCC flaws could not be ruled out from the observed surface anomaly on the J-groove weld.
As a result of the RCS leakage, Ameren is performing a half-nozzle repair modification of BMI Nozzle 48 using ASME Section XI, Code Case N-638-11, and ASME Section III. The same modification is being performed for BMI Nozzles 30, 35, and 57 to preemptively prevent RCS leakage. Figure 4-1 depicts the existing configuration of the BMI nozzles. The modification will consist of removing the lower portion of the existing Alloy 600 nozzle, applying an Alloy 52M weld pad on the outer surface of the RVBH, and installing a replacement Alloy 690 nozzle with an Alloy 52M partial penetration J-groove weld. Figure 4-2 depicts the repair modification. The new weld pad will be welded to the outer surface of the RVBH using machine Gas Tungsten Arc Welding (GTAW) Ambient Temperature Temper Bead (ATTB) welding with inert shielding gas.
The new Alloy 690 half nozzle will be inserted into the bore and welded to the Alloy 52M weld pad with an Alloy 52M partial penetration J-groove weld using a manual GTAW welding technique. It is noted that Relief Request I5R-01 allows non-destructive examination (NDE) of the new Alloy 52M weld pad for Nozzles 30, 35, 48, and 57 to be performed without applying the required 48-hour hold time per Code Case N-638-11.
Therefore, elimination of the 48-hour NDE hold time and its basis (for Nozzles 30, 35, 48, and 57) is not within the scope of this relief request.
As a result of the modification of BMI Nozzles 30, 35, 48, and 57, the nozzle penetration pressure boundary will move from the original partial penetration J-groove weld that is inside the RVBH to the new partial penetration J-groove weld outside the RVBH (i.e., the original BMI nozzles and J-groove welds will no longer perform a pressure boundary function). In support of this new configuration, a one-cycle ASME Section III design analysis of the modification, along with a corrosion evaluation describing potential corrosion
to Relief Request I5R-02 ULNRC-06956 Page 4 of 14 mechanisms at the affected BMI nozzle locations, has been performed. A separate relief request, containing analyses beyond one cycle of operation (i.e., "life of repair"), will be submitted at a later date to justify continued use of the new configuration for BMI Nozzles 30, 35, 48, and 57 for the remainder of the current ISI interval (per 10 CFR 50.55a).
The modification will leave in place, for each affected nozzle, the upper portion of the original BMI nozzle and original partial penetration J-groove weld containing the flaw, i.e., remnant nozzle and remnant weld.
While the axial flaws in the BMI nozzles were characterized, there is not a Performance Demonstration Initiative (PDI) qualified technique that can accurately perform non-destructive examinations (NDE) to fully characterize the location, orientation, or size of flaws in the original J-groove welds. Therefore, since IWA-3300 and IWB-3420 require flaw characterization, and since IWA-4412 requires flaw removal of an identified flaw, an alternative is proposed for BMI Nozzles 30, 35, 48, and 57 to leave in place the remnant nozzles and welds. A flaw evaluation, using a maximum postulated flaw, and a loose parts discussion, will demonstrate the acceptability of leaving in place the remnant welds for one cycle. As previously noted, a separate relief request, containing "life of repair" analyses, will be submitted at a later date to justify leaving in place the remnant nozzles and welds for the remainder of the current ISI interval (per 10 CFR 50.55a).
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Enclosure l to Relief Request ISR-02 ULNRC-06956 Page 6 of 14 Figure 4-2 Bottom Mounted Nozzle
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to Relief Request I5R-02 ULNRC-06956 Page 8 of 14
- 5. Propose Alternative and Basis for Use:
In accordance with 10 CFR 50.55a, Codes and Standards, paragraph (z)(1), Ameren proposes alternatives to the flaw characterization requirements of Section XI IWA-3300 and IWB-3420 and to the flaw removal requirements of IWA-4412 on the basis that performing the alternatives stated below provides an acceptable level of quality and safety.
Half-Nozzle Repair Modification As explained in Section 4, Ameren is performing a half-nozzle repair modification of BMI Nozzles 30, 35, 48 and 57 using ASME Section XI, Code Case N-638-11, and ASME Section III. This modification will result in the nozzle penetration pressure boundary being moved to the new partial penetration J-groove weld outside the RVBH. This means, as previously stated, that the remnant nozzles and J-groove welds no longer perform a pressure boundary function. Additionally, the remnant nozzles will be physically separated from the new Alloy 690 nozzles. The planned steps of the proposed repair are described below. This plan may change due to varying conditions present during the work. Changes to the plan, as detailed below, will remain in compliance with applicable Code requirements, except where NRC approval has been granted (e.g., Relief Request IR5-01).
- 1. Sever nozzle and thimble guide tube.
- 2. Clean and perform surface and volumetric exams of weld pad region.
- 3. Machine to thin existing Alloy 600 nozzle, as specified in final implementing drawings.
- 4. Roll expand the existing Alloy 600 nozzle (optional).
- 5. Machine original RVBH bore to remove the lower portion of the existing Alloy 600 nozzle.
- 6. C1ean RVBH bore.
- 8. Deposit new Alloy 52M weld pad, as specified in final implementing drawings*.
- 9. Perform liquid penetrant surface and UT exams on new Alloy 52M weld pad.
- 10. Install wedge dam.
- 11. Machine and clean final RVBH bore.
- 16. Perform progressive surface exams as the J-groove weld is deposited, to include a final surface exam.
- 17. Prep end of thimble guide tube.
- A minimum of three (3) layers of Austenitic Nickel-Alloy 52M (SFA-5.14, ERNiCrFe-7A) filler material in accordance with the temper bead requirements in Case N-638-11.
One-Cycle Justification Section III Analysis In accordance with the design requirements of ASME Code Section III, Subsection NB, 2015 Edition, a design analysis has been performed for the half-nozzle repair modification of BMI Nozzles 30, 35, 48, and 57. The
to Relief Request I5R-02 ULNRC-06956 Page 9 of 14 analysis demonstrates that all primary stresses, primary plus secondary stresses, fatigue criteria and sizing requirements are satisfied per NB-3200, NB-3300, and NB-3600 for at least one cycle of operation. The analysis confirms that the new nozzles will not eject from the reactor vessel under design conditions and all service level conditions. A conservative, sustained, corrosion rate was applied, and the resultant increase in bore diameter, due to the half-nozzle repair modification, was considered in the reinforcement calculation (per NB-3330) as part of the ASME Section III analysis. Relief Request I5R-02, Attachment 1 (contained in to ULNRC-06956) includes the one-cycle Section III analysis.
Due to the emergent nature of the half-nozzle repairs for BMI Nozzles 30, 35, 48, and 57, it was anticipated that the Section III analysis, originally provided in Enclosure 2 in ULNRC-06948, may warrant updates if there were field implementation changes. Therefore, a commitment (COMN 50441), identified in the Relief Request I5R-02 transmittal letter, ULNRC-06948, was established to submit the additional information in a timely manner. The half-nozzle repairs for BMI Nozzles 30, 35, 48, and 57 are complete, therefore, the one-cycle Section III analysis contained in Enclosure 2 to ULNRC-06956 satisfies (closes out) this commitment.
As noted above, the current analyses for Relief Request I5R-02 are based on one cycle of operation. This was due to the emergent nature of the modification such that there was not sufficient time to perform a "life of repair"Section III analysis. A "life of repair" analysis will be performed to demonstrate the acceptability of the repaired penetrations for operation beyond one cycle, which will be included in a separate relief request to be submitted at a later date.
Corrosion Evaluation Due to the nozzle penetration pressure boundary being moved to the outside the RVBH, the half-nozzle repair modification results in the RVBH low alloy steel being exposed to reactor coolant. Therefore, a corrosion evaluation has been performed to address potential corrosion mechanisms due to the half-nozzle repair modification of BMI Nozzles 30, 35, 48, and 57. Corrosion mechanisms evaluated include general corrosion, crevice corrosion, galvanic corrosion, stress corrosion cracking, and hydrogen embrittlement of the exposed RVBH. The corrosion evaluation also evaluated potential corrosion mechanisms for the new Alloy 690 nozzle and the new Alloy 52M weld pad used in the modification. Relief Request I5R-02, Attachment 2 (contained in Enclosure 2 to ULNRC-06956) includes the corrosion evaluation.
Due to the emergent nature of the half-nozzle repairs for BMI Nozzles 30, 35, 48, and 57, it was anticipated that the corrosion evaluation, originally contained in Enclosure 2 in ULNRC-06948, may warrant updates if there were field implementation changes. Therefore, a commitment (COMN 50441), identified in the Relief Request I5R-02 transmittal letter, ULNRC-06948, was established to submit the additional information in a timely manner. The half-nozzle repairs for BMI Nozzles 30, 35, 48, and 57 are complete; therefore, the corrosion evaluation contained in Enclosure 2 to ULNRC-06956 satisfies (closes out) this commitment.
Flaw Evaluation As described in Section 4, the half-nozzle repair modification will leave in place, for each affected nozzle, the upper portion of the original BMI nozzle and original partial penetration J-groove weld containing the flaw. As an alternative to performing NDE to characterize the original J-groove weld to meet the requirements of IWA-3300 and IWB-3420, and as an alternative to flaw removal or a reduction in size of the original J-groove weld to meet the requirements of IWA-4412, an analysis has been performed in which a maximum postulated flaw that bounds the range of flaw sizes that could exist in the original J-groove weld was assumed.
to Relief Request I5R-02 ULNRC-06956 Page 10 of 14 This analysis is summarized in the "As-Left J-Groove Weld One-Cycle Justification section below. A loose parts discussion is also provided below.
As-Left J-Groove Weld One-Cycle Justification The assumptions of IWB-3600 of ASME Section XI for analytical flaw evaluations are that cracks are fully characterized in accordance with IWB-3420 in order to compare the calculated parameters to the acceptable parameters addressed in IWB-3500. There are no qualified NDE techniques for examining the original nozzle-to-shell RVBH J-groove weld. Therefore, since it is impractical to characterize the flaw geometry that may exist therein, it is conservatively assumed that the as-left condition of the remaining J-groove weld includes flaws extending through the entire J-groove weld and buttering.
Since uphill and downhill hoop stresses in the J-groove weld are the highest at the nozzle penetration, the preferential direction for cracking is radial relative to the RVBH shell. Therefore, a radial-axial flaw (radial with respect to the nozzle axis) in the J-groove weld and buttering is postulated and would propagate through the weld and buttering to the interface with the low alloy steel RVBH material. Any growth of the postulated as-left flaw into the PWSCC (primary water stress corrosion cracking) resistant low alloy steel would be primarily by fatigue crack growth under cyclic loading conditions.
The J-groove flaws are evaluated using a worst-case BMI nozzle outermost penetration configuration. The outermost penetration is modeled due to the applied loading conditions being the same or worse than all other locations in the RVBH. The initial flaw size for the J-groove weld is conservatively assumed to include all of the weld and buttering. Fatigue crack growth for cyclic loading conditions, using operational stresses, and crack growth rates from ASME Section XI for ferritic material are calculated. Based on the results of LEFM analysis only, a postulated flaw remaining in the original J-groove weld and buttering for the modified RVBH nozzle is shown to be acceptable. Additionally, the transients applicable for the as-left J-groove weld crack growth are those due to normal and upset conditions only.
Relief Request I5R-02, Attachment 3 (contained in Enclosure 2 to ULNRC-06956) includes the as-left J-groove weld justification for one cycle of operation. This one-cycle evaluation is based on a comparative analysis between a similar previously performed RVBH BMI half-nozzle modification at another plant and Callaway's half-nozzle modification of BMI Nozzles 30, 35, 48, and 57. Specifically, this comparative analysis was performed against a prior "life of repair" BMI nozzle analysis performed for another plant that is most representative and bounding relative to Callaway's half-nozzle modification, considering geometry, materials, and transient loading conditions as well as a conservative crack growth prediction for one cycle of operation. This qualitative justification shows that the "as-left" J-groove weld postulated flaw for Callaway's modification meets the acceptance criteria of IWB-3612 for normal/upset and emergency/faulted operating conditions during one cycle of operation. "Life of repair" analyses, performed for similar half-nozzle repairs in the industry, have resulted in a fatigue crack growth life for the "as-left" J-groove flaw of 50 years (per linear elastic fracture mechanics (LEFM)). Similarly, prior analyses of similar repair configurations have demonstrated that fatigue crack growth is acceptable, and the crack-like indications remain stable, satisfying the ASME Section XI criteria.
Due to the emergent nature of the half-nozzle repairs for BMI Nozzles 30, 35, 48, and 57, it was anticipated that the flaw evaluation of the "as-left" J-groove weld, originally contained in Enclosure 2 to ULNRC-06948, may warrant updates if there were field implementation changes. Therefore, a commitment (COMN 50441),
identified in the Relief Request I5R-02 transmittal letter, ULNRC-06948, was established to submit the
to Relief Request I5R-02 ULNRC-06956 Page 11 of 14 additional information in a timely manner. The half-nozzle repairs for BMI Nozzles 30, 35, 48, and 57 are complete, therefore, the flaw evaluation contained in Enclosure 2 to ULNRC-06956 satisfies (closes out) this commitment.
Again, as noted previously, due to the emergent nature of the modification, there was not sufficient time to perform a detailed "life of repair" finite element analysis for the "as-left" J-groove weld. A "life of repair" analysis for Callaway's half-nozzle modification of BMI Nozzles 30, 35, 48, and 57 will be performed, which will be included in a separate relief request to be submitted at a later date.
Loose Parts Discussion The potential for debris from the cracked remnant J-groove welds was considered. Radial cracks (relative to the nozzle) were postulated to occur in the J-groove weld due to the dominance of higher hoop stresses relative to axial stresses. The possibility of transverse cracks occurring that could subsequently intersect the radial cracks is considered remote as there are minimal driving forces for cracks in the transverse direction. The radial cracks would relieve the driving forces for any potential transverse cracks. There are no known service conditions that could drive radial cracks and transverse cracks to intersect to produce a loose part. There is extensive operating experience with remnant J-groove welds, for which there are no known cases of debris generation (loose parts) due to PWSCC of the remnant J-groove weld. Therefore, cracking of the J-groove weld resulting in debris (loose parts) is not expected.
A detailed loose parts analysis for operation beyond one cycle will be performed to demonstrate the acceptability of the remnant nozzles and welds, which will be included in a separate relief request to be submitted at a later date.
RCS Leak Detection The following information is provided to describe the methods used to identify RCS leakage at Callaway, to provide confidence that should a leak develop, it would be identified in a timely manner.
The RVBH BMI nozzles are inspected during refueling outages in accordance with ISI, Boric Acid Corrosion Control, and Alloy 600 Management plans/programs. Collectively, these routine outage-based inspections are performed descending into and ascending from every RFO and are the primary method of detecting extremely small amounts of RCS leakage. As described in Section 4, the pressure boundary leakage associated with BMI nozzle 48 was identified by an outage ISI inspection.
During power operations, Technical Specification (TS) 3.4.15 establishes the limiting condition for operation (LCO) for RCS leakage detection instrumentation. This TS requires instruments, of diverse monitoring methods, to be available to rapidly detect small RCS leaks in time to place the plant in a safe condition when needed. The RCS leakage detection instrumentation is described in the Callaway's Final Safety Analysis Report (FSAR) Section 5.2.5.
Also, during power operations, TS 3.4.13 establishes RCS leakage criteria. The safety significance of RCS leakage varies widely depending on its source, rate, and duration. Therefore, detecting and monitoring RCS leakage into the containment area is necessary. Quickly separating the identified leakage from the unidentified leakage is necessary to provide quantitative information to the operators, allowing them to take corrective
to Relief Request I5R-02 ULNRC-06956 Page 12 of 14 action should a leak occur that is detrimental to the safety of the facility and the public. Depending on the source identified, a shutdown could be required. TS LCO 3.4.13 has the following leakage limits:
- a. No pressure boundary leakage;
- b. 1 gpm unidentified leakage;
- c. 10 gpm identified leakage; and
- d. 150 gallons per day primary to secondary leakage through any one steam generator (SG).
Should any of the above limits be exceeded, the appropriate Condition under LCO 3.4.13 would be entered, and the associated Required Action(s) would be performed within the specified Completion Time(s),
including plant shutdown, if required.
Finally, during power operations, in the event that unidentified leakage increases greater than 0.10 gallons per minute (gpm) above the normal, steady state value for a given plant condition during the performance of a routine RCS water inventory balance, operating procedures require that various actions be implemented to investigate the increased leakage. If an unacceptable increase in unidentified leakage were to occur, Callaway would shut down the plant in a controlled manner prior to a BMI nozzle failure.
6. Duration of Proposed Alternative
Authorization of the proposed alternatives is requested for the duration of the Callaway Plant Unit 1 Cycle 28, which begins upon restart from the current refueling outage (RF27) and scheduled to conclude in the Fall of 2026. A separate relief request will be submitted, prior to the end of Cycle 28, to justify continued use of the half-nozzle repair modification for the duration of the current ISI twelve-year interval. This future relief request will contain the appropriate analyses and justification in support of operation for the remainder of current plant licensing.
7. Precedents
- Arizona Public Service Company (APS) letter, "Palo Verde Generating Station (PVNGS) Unit 1 - Relief Request 76 - Proposed Alternative for Pressurizer Lower Shell Nozzle," dated April 23, 2025 (ADAMS Accession No. ML25113A296) o NRR E-mail Capture, "
Subject:
NRC Verbal Authorization to Arizona Public Service Accepting the Provisions of Relief Request 76 for one Cycle of Operation," dated April 27, 2025 (ADAMS Accession No. ML25118A063)
- Arizona Public Service Company (APS) letter, "Palo Verde Generating Station (PVNGS) Unit 1 - Relief Request 70 - Proposed Alternatives for Pressurizer Lower Shell Temperature Nozzle," dated October 23, 2023 (ADAMS Accession No. ML23296A254) o NRR E-mail Capture, "
Subject:
Palo Verde Unit 1 - Verbal Authorization of Relief Request 70, Proposed Alternatives for Pressurizer Lower Shell Temperature Nozzle," dated October 27, 2023 (ADAMS Accession No. ML23303A011) o NRC Safety Evaluation letter, " Palo Verde Nuclear Generating Station, Unit 1 Re: Relief Request 70 Proposed Alternatives for Pressurizer Lower Shell Temperature Nozzle (EPID L-2023-LLR-0057)," dated September 9, 2024 (ADAMS Accession No. ML24197A199).
to Relief Request I5R-02 ULNRC-06956 Page 13 of 14
- Exelon Generating Company letter, "Peach Bottom Atomic Power Station, Unit 2 - Proposed Relief Request Associated with N-16A Reactor Pressure Vessel Instrument Nozzle Repairs," dated November 4, 2020 (ADAMS Accession No. ML20309B020) o NRR E-mail Capture, "
Subject:
Peach Bottom Verbal Relief for Penetration Nozzle (EPID: L-2020-LLR-0144)," dated November 6, 2020 (ADAMS Accession No. ML20314A028) o NRC Safety Evaluation letter, "Peach Bottom Atomic Power Station, Unit No. 2 - Approval of One-Time Alternative to Flaw Characterization and Removal Requirements for N-16A Nozzle (EPID L-2020-LLR-0144," dated April 23, 2021 (ADAMS Accession No. ML21110A680)
- Exelon Generating Company letter, "Limerick Generating Station, Unit 2 - Proposed Relief Request Associated with Reactor Pressure Vessel Nozzle Repairs," dated May 15, 2017 (ADAMS Accession No. ML17135A423) o NRR E-mail Capture, "Verbal Authorization by the Office of Nuclear Reactor Regulation for Relief Request I4R Alternative Repair of Instrument Nozzle N-16D on the Reactor Vessel -
Limerick Generating Station, Unit 2," dated May 17, 2017 (ADAMS Accession No. ML17137A307) o NRC Safety Evaluation letter, "Limerick Generating Station, Unit 2 - Relief Request I4R-17, Associated with the Alternative 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)
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) o NRR E-mail Capture, "
Subject:
Palo Verde Nuclear Generating Station, Unit 3 - Summary of Telephone Conference Re: Verbal Authorization for Relief Request 51 (TAC NO. MF3051)," dated December 5, 2013 (ADAMS Accession No. ML13330A573) o NRC Safety Evaluation 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. ML3051)," dated April 10, 2014 (ADAMS Accession No. ML14093A407)
- Exelon Generation Company letter, "Quad Cities Nuclear Power Station, Unit 2 - Relief Request I4R-19 Associated with the Reactor Pressure Vessel Nozzle Repairs," dated April 6, 2012 (ADAMS Accession No. ML12100A012) o NRR E-mail Capture, "
Subject:
NRC Verbal Approval for Quad Cities Nuclear Power Station, Unit 2 Relief Request I4R-19," dated April 16, 2012 (ADAMS Accession No. ML12107A472) o NRC Safety Evaluation letter, "Quad Cities Nuclear Power Station, Unit 2 - Safety Evaluation in Support of Request for Relief Associated with the Reactor Pressure Vessel Nozzle Repairs (TAC NO. ME8347)," dated January 30, 2013 (ADAMS Accession No. ML13016A454)
to Relief Request I5R-02 ULNRC-06956 Page 14 of 14
- 8. References ASME Code,Section XI, "Rules for Inspection and Testing of Components of Light-Water-Cooled Plants,"
Division 1, 2019 Edition.
ASME Code,Section XI, Case N-638-11, "Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique," Division 1, dated August 2, 2019.
ASME Code,Section III, "Nuclear Power Plant Components," 1971 Edition including Addenda through Winter 1972.
ASME Code,Section III, "Rules for Construction of Nuclear Facility Components," Division 1, 2015 Edition.