ML21034A576
| ML21034A576 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 02/03/2021 |
| From: | Richard Guzman NRC/NRR/DORL/LPL1 |
| To: | Sinha S Dominion Energy Nuclear Connecticut |
| Guzman R | |
| References | |
| EPID L-2020-LLR-0097 | |
| Download: ML21034A576 (9) | |
Text
From:
Guzman, Richard To:
Shayan.Sinha@dominionenergy.com
Subject:
Millstone Unit 2 - REQUEST FOR ADDITIONAL INFORMATION - Alternative Request RR-05-06 Inspection Interval Extension for SG Pressure Retaining Welds and Full-Penetration Welded Nozzles (EPID: L-2020-LLR-0097)
Date:
Wednesday, February 03, 2021 2:41:00 PM
- Shayan,
On January 22, 2021, the U.S. Nuclear Regulatory Commission (NRC) staff sent Dominion Energy Nuclear Connecticut, Inc. (DENC, the licensee) the subject Request for Additional Information (RAI) as a draft e-mail. This RAI relates to the licensees July 15, 2020, alternative request (ADAMS Accession No. ML20198M682), to the inservice inspection (ISI) requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code for steam generator pressure-retaining welds and full-penetration welded nozzles for Millstone Power Station, Unit No. 2 (MPS2).
On February 2, 2021, the NRC staff and DENC held a conference call to discuss clarifications on the draft RAI. Updated below is the official (final) RAI. As agreed on the call, please respond to this RAI within 45 days of this e-mail communication, or no later than March 22, 2021. A publicly available version of this message will be placed in the NRCs ADAMS system. Please contact me if you have any questions in regard to this request.
Thank you,
Richard V. Guzman Senior Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov
From: Guzman, Richard <Richard.Guzman@nrc.gov>
Sent: Friday, January 22, 2021 4:57 PM To: Shayan Sinha (Services - 6) <Shayan.Sinha@dominionenergy.com>
Subject:
[EXTERNAL] Millstone Power Station, Unit 2 - DRAFT Request for Additional Information -
Alternative Request RR-05-06 Inspection Interval Extension for SG Pressure Retaining Welds and Full Penetration Welded Nozzles (EPID: L-2020-LLR-0097)
- Shayan,
By letter dated July 15, 2020 (ADAMS Accession No. ML20198M682), Dominion Energy Nuclear Connecticut, Inc., submitted a proposed alternative to the inservice inspection (ISI) requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code for steam generator pressure-retaining welds and full-penetration welded nozzles for Millstone Power Station, Unit No. 2 (MPS2).
The NRC staff has determined that additional information is needed to complete its review, as described in the request for additional information (RAI) shown below. This RAI is identified as DRAFT at this time to confirm your understanding of the information needed by the NRC staff to complete its evaluation. If youd like to have a clarification call, please let me know and I will coordinate availabilities w/the NRC technical staff. I intend to send out the questions below as official no later than February 3rd, if possible.
- Thanks, Richard Guzman Sr. PM, Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov
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REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING ALTERNATIVE REQUEST RR-05-06, INSPECTION INTERVAL EXTENSION FOR STEAM GENERATOR PRESSURE-RETAINING WELDS AND FULL-PENETRATION WELDED NOZZLES FOR MILLSTONE POWER STATION, UNIT NO. 2 DOCKET NO. 50-336 (EPID:L-2020-LLR-0097)
By letter dated July 15, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20198M682), Dominion Energy Nuclear Connecticut, Inc. (DENC, the licensee), submitted to the U.S. Nuclear Regulatory Commission (NRC) a proposed alternative to the inservice inspection (ISI) requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for steam generator (SG) nozzle-to-shell welds (NSWs), SG head welds (HWs), SG tubesheet-to-head welds (THWs), SG shell welds (SWs), and SG nozzle inside radius (NIR) sections of Millstone Power Station, Unit No. 2 (MPS2).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Paragraph 50.55a(z)(1), the licensee proposed to increase the ISI interval for the subject components to 30 years, from the current ASME Code Section,Section XI requirement of 10 years. In 10 CFR 50.55a(z)(1), the licensee is required to demonstrate that the proposed alternative provides an acceptable level of quality and safety. The licensee referred to the analyses in non-proprietary Electric Power Research Institute (EPRI) Report No. 3002015906 "Technical Bases for Inspection Requirements for PWR [Pressurized Water Reactor] Steam Generator Class 1 Nozzle-to-Vessel Welds and Class 1 and Class 2 Vessel Head, Shell, Tubesheet-to-Head and Tubesheet-to-Shell Welds," 2019 (ADAMS Accession No. ML20225A141) and non-proprietary EPRI Report No. 3002014590, "Technical Bases for Inspection Requirements for PWR Steam Generator Feedwater and Main Steam Nozzle-to-Shell Welds and Nozzle Inside Radius Sections", April 2019 (ADAMS Accession No. ML19347B107) to support the proposed alternative in the submittal. The licensee also included an applicability evaluation of the EPRI reports to MPS2. The NRC staff has
determined that additional information as requested below is needed to complete its review of the licensee's proposed alternative.
RAI-1
Regulatory Basis The NRC has established requirements in 10 CFR Part 50 to protect the structural integrity of structures and components in nuclear power plants. Among these requirements are the ISI requirements of Section XI of the ASME Code incorporated by reference in 10 CFR Part 50.55a to ensure that adequate structural integrity of the SG vessel is maintained through the service life of the vessel. Therefore, the regulatory basis for the followingRAI has to do with demonstrating that the proposed alternative ISI requirements would ensure adequate structural integrity of the SG vessel welds of MPS2 for which EPRI report 3002015906 is referenced, and thereby providing an acceptable level of quality and safety per 10 CFR 50.55a(z)(1) for these components Issue The NRC staff noted that the probabilistic fracture mechanics (PFM) software used in EPRI report 3002015906 is PROMISE Version 2.0, while in EPRI report 3002014590, the PFM software used is PROMISE Version 1.0. The NRC staff audited PROMISE Version 1.0 and issued the audit report by letter dated December10, 2020 (ADAMS Accession No. ML20258A002). One of the objectives of the NRC staff's audit was to ensure that PROMISE Version 1.0 received adequate verification and validation (V&V). The NRC staff has not audited PROMISE Version 2.0, and therefore, has determined that an understanding of the difference between PROMISE Version 2.0 and PROMISE Version 1.0 and the V&V performed for its difference is needed to support its review of the licensees submittal.
Request To ensure that PROMISE Version 2.0 received adequate V&V for use in the referenced analyses for the SG vessel welds of MPS2, describe the difference between PROMISE Version 2.0 and PROMISE Version 1.0 and the V&V performed for its differenceto ensure that (1) cases intended for the difference between PROMISE Version 2.0 and PROMISE Version 1.0 reflected the change; and (2) that cases not intended for thedifference were not affected.
RAI-2
Regulatory Basis Similar to RAI-1, the regulatory basis for the followingrequests has to do with demonstrating that the proposed alternative ISI requirements would ensure adequate structural integrity of the "Stay Cylinder Base to Hemisphere (Head)" (SG-1-BHC-1-A and SG-2-BHC-1-A) and "Stay Cylinder to Tube Sheet" welds (SG-1-TSS-3-A and SG-2-TSS-3-A) identified as Examination Category B-B, Item No. B2.31 in Section 1.0 of Attachment 1 to the submittal, and thereby providing an acceptable level of quality and safety per 10 CFR 50.55a(z)(1) for these welds.
Issue (a) Figure A2 in Attachment 2 to the licensee's submittal shows the configuration of the "Stay Tube to Head Weld" and "Stay Tube to Tubesheet Weld." It is not clear to the NRC staff
whether "Stay Tube to Head Weld" is the same as the "Stay Cylinder Base to Hemisphere (Head)" (SG-1-BHC-1-A and SG-2-BHC-1-A) and whether "Stay Tube to Tubesheet Weld" is the same as "Stay Cylinder to Tube Sheet" (SG-1-TSS-3-A and SG-2-TSS-3-A). Also, "Stay Tube to Head Weld" and "Stay Tube to Tubesheet Weld" in Figure A2 in Attachment 2 to the licensee's submittal do not seem to be represented by any of the paths in Figure 7-24 of EPRI report 3002015906.
(b)In addition, theNRC staff noted that the configuration of the "Stay Tube to Tubesheet Weld" in Figure A2 appears to include a tube attached to the tubesheet, rather than a plate attached to the tubesheet as shown in Figure 7-24 of EPRI report 3002015906.
Request (a) Clarify if the "Stay Tube to Head Weld" in Figure A2 in Attachment 2 of the submittal is the same as the "Stay Cylinder Base to Hemisphere (Head)" (SG-1-BHC-1-A and SG-2-BHC-1-A) and whether "Stay Tube to Tubesheet Weld" in Figure A2 is the same as "Stay Cylinder to Tube Sheet" (SG-1-TSS-3-A and SG-2-TSS-3-A).
(b) Discuss which paths in Figure 7-24 of EPRI report 3002015906 represent the "Stay Cylinder Base to Hemisphere (Head)" (SG-1-BHC-1-A and SG-2-BHC-1-A) welds of MPS2 and "Stay Cylinder to Tube Sheet" (SG-1-TSS-3-A and SG-2-TSS-3-A) welds of MPS2, and justify that the stresses in the selected paths are appropriate for these welds.
RAI-3
Regulatory Basis The regulatory basis for the followingrequests has to do with demonstrating that the proposed alternative ISI requirements would ensure adequate structural integrity of the SG vessel welds of MPS2 for which EPRI report 3002015906 is referenced, and thereby providing an acceptable level of quality and safety per 10 CFR 50.55a(z)(1) for these welds.
Issue Regarding the applied stresses determined in EPRI report 3002015906; (a) The through-wall stress distribution plots in Figures 7-25 through 7-28 of EPRI report 3002015906 for the B2.31, B2.40, C1.10, C1.20, and C1.30 welds do not show the stress distributions for the unit pressure case. Thus, the NRC staff cannot verify if the pressure stress dominates in these welds. Sections 4.3.3 and 4.6 of EPRI report 3002015906 state the dominance of the radius-to-thickness (R/t) ratio, which reflect the dominance of the pressure stress.
(b) The through-wall stress distribution plots for the thermal transients in Figures 7-17 and 7-18 of EPRI report 3002015906 for the B3.130 welds show compressive stresses at the inner surface (except the Heatup/Cooldown transient). Tensile stresses at the inside surface are typically expected for transients that have temperature drops, such as Reactor Trip which has a temperature drop of 75°F in 10 seconds as described in Section 5.2.2 of EPRI report 3002015906.
(c) Figures A2 and A3 in Attachment 1 to the submittal show that the B2.31, B2.40, and B3.130 welds of MPS2 requested in the submittal are cladded. Figures 7-15 and 7-16 of EPRI report 3002015906 (B3.130 welds) and Figure 7-24 (B2.31 and B2.40) show that the stress paths for these welds include the clad. However, the NRC staff noted that clad residual
stress is not included as a separate applied stress in EPRI report 3002015906. The NRC staff noted that in a similar EPRI report for cladded welds in the pressurizer vessel, non-proprietary EPRI Report No. 3002015905, "Technical Bases for Inspection Requirements for PWR Pressurizer Head, Shell-to-Head, and Nozzle-to-Vessel Welds", December 2019, clad residual stresses are included as a separate applied stress (Section 8.2.2.4 of EPRI report 3002015905).
Request (a) Show that the pressure stress dominates the thermal transient stresses for the B2.31, B2.40, C1.10, C1.20, and C1.30 welds requested in the submittal for MPS2.
(b) Explain if the thermal stresses on the inside surface shown in the plots in Figures 7-17 and 7-18 of EPRI report 002015906 become tensile at times other than those shown in the figures.
(c) Justify how excluding the clad residual stress as a separate applied stress would adequately represent thetotal applied load in the B2.31, B2.40, and B3.130 welds of MPS2 requested in the submittal.
RAI-4
Regulatory Basis The regulatory basis for the followingRAI has to do with demonstrating that the proposed alternative ISI requirements would ensure adequate structural integrity of the MPS2 cladded welds identified as Examination Category B-B, Item Nos. B2.31 and B2.40, and Examination Category B-D, Item No. B3.130 in Section 1.0 of Attachment 1 to the submittal, and thereby providing an acceptable level of quality and safety per 10 CFR 50.55a(z)(1) for these welds.
Issue For the B2.31, B2.40, and B3.130 welds of MPS2 requested in the submittal, Table A2 in of the submittal shows the minimum and maximum temperatures (70°F and 535°F, respectively) for the Heatup/Cooldown transient. Section 8.2.2.5 of EPRI report 3002015906 states that the minimum temperature (200°F) during this transient corresponds to Figure 7-22 of EPRI report 3002015906, and therefore, a fracture toughness (KIC) set at the upper shelf value of the ASME Code KIC curve, 200 ksiin, may be used. The NRC staff noted that Figure 7-22 of EPRI report 3002015906 is at the end of heatup (as noted in the figure). During the ramp periods in the beginning and ending of the Heatup/Cooldown transient, the temperatures at the subject locations of the B2.31, B2.40, and B3.130 welds of MPS2 could be lower than 200°F and thus, KIC could be lower than 200 ksiin. For instance, during the audit summary report for PROMISE Version 1.0 (ADAMS Accession No. ML20258A002, Item No. 2.e.iii), the NRC staff observed that for the SG feedwater nozzle, KIC could be as low as 130 ksiin during the Heatup/Cooldown transient and that this lower value of KIC is addressed by the sensitivity study results on fracture toughness in Tables 8-13 and 8-14 of EPRI report 3002014590. The NRC staff noted that the lowest KIC value, 80 ksiin, used in the sensitivity study on fracture toughness in EPRI report 3002015906 is the same as the lowest KIC value used in the sensitivity study on fracture toughness in EPRI report 3002014590. However, the NRC staff noted that the pressure for the B2.31, B2.40, and B3.130 welds of MPS2 is more than twice the pressure analyzed for SG feedwater nozzle in the audit report since these welds are on the primary side of the reactor coolant system. The NRC staff also noted that the probability of rupture value of 1.50E-07 per year for the limiting
case (SGPTH-P4A for aKIC value of 80 ksiin) in Table 8-14 of EPRI report 3002015906 is higher than the probability of rupture value for the limiting case value of 3.75E-08 per year for the SG feedwater nozzle for a KIC value of 80 ksiin. The NRC staff further noted in to the submittal that the B2.31 welds requested for MPS2 had an examination coverage as low as 49.58%. With this examination coverage, the probability of rupture of value for the limiting case in Table 8-14 of EPRI report 3002015906 could exceed the criterion of 1E-06 per year since 1.50E-07 per year is only about one order magnitude lower than the criterion.
Request Given the NRC staffs observations discussed above for the B2.31, B2.40, and B3.130 welds of MPS2, explain how the sensitivity study on fracture toughness in EPRI report 3002015906 addresses the lower KIC value during the ramp periods in the beginning and ending of the Heatup/Cooldown transient.
RAI-5
Regulatory Basis The regulatory basis for the followingRAI has to do with demonstrating that the proposed alternative ISI requirements would ensure adequate structural integrity of the SG vessel welds of MPS2 for which EPRI report 3002015906 is referenced, and thereby providing an acceptable level of quality and safety per 10 CFR 50.55a(z)(1) for these components.
Issue The Reactor Trip transient (see Tables 5-7 through 5-9 of EPRI report 3002015906) was selected for the SG vessel welds of MPS2for which EPRI report 3002015906 is referenced.
A sample list of reactor coolant system design transients is given in Table 5-6 of EPRI report 3002015906. The NRC staff noted that Heatup, Cooldown, Plant loading, Plant unloading, and Reactor Trip in Table 5-6 are included in the transients selectedfor analysis. The NRC staff further noted thatthe rest of the transients in Table 5-6 are not included in the transients selected for analysis. It is not clear to the NRC staff whether the Reactor Trip transient selected for analysis in EPRI report 3002015906 accounted for transients not explicitly included in the analysis.
Request Explainwhether the Reactor Trip transient selected for the SG vessel welds of MPS2,for which the EPRI report 3002015906 is referenced,boundsand includes other transients and their cyclesnot explicitly included in the analysis in EPRI report 3002015906.
RAI-6
Regulatory Basis The regulatory basis for the followingRAI has to do with demonstrating that the proposed alternative ISI requirements would ensure adequate structural integrity of the MPS2 welds identified as Examination Category B-B, Item Nos. B2.31 and B2.40, and Examination Category B-D, Item No. B3.130 in Section 1.0 of Attachment 1 to the submittal, and thereby providing an acceptable level of quality and safety per 10 CFR 50.55a(z)(1) for these welds.
Issue
Table A1 in Attachment 2 to the submittal, the licensee states that MPS2 has not resulted in an event (unheated auxiliary feedwater being introduced into a hot SG) that can result in a thermal shock of the SG vessel. The NRC noted that the auxiliary feedwater event referred to in Table A1 affects the secondary side welds and NIR sections requested for MPS2 in the submittal (Item Nos. C1.10, C1.20, C1.30, C2.21, and C2.22) in Section 1.0 in Attachment 1 to the submittal. The NRC staff noted that a thermal shock event from the primary side can affect the primary side welds requested for MPS2 in the submittal (Item Nos. B2.31, B2.40, and B3.130).
Request Similar to the thermal shock applicability discussion in Table A1 in Attachment 2 to the submittal,explain whether MPS2 has experienced a thermal shock event in the primary side of the reactor coolant system that can affect the KIC value assumed in the analysis in EPRI report 3002015906 referenced for the primary side welds requested for MPS2 in the submittal.
RAI-7
Regulatory Basis The regulatory basis for the followingRAI has to do with demonstrating that the proposed alternative ISI requirements would ensure adequate structural integrity of the SG vessel welds and NIR sections of MPS2 for which EPRI reports 3002015906 and 3002014590 are referenced, and thereby providing an acceptable level of quality and safety per 10 CFR 50.55a(z)(1) for these welds.
Issue Regarding treatment of the pressure tests in EPRI reports 3002015906 and 3002014590; (a) In Sections 5.2 of the EPRI reports, EPRI stated that it did not consider test conditions beyond asystemleakagetest in the analyses, andstated thatsinceany pressure tests will be performed at operating pressure, no separate test conditions need to be included in the analyses because the test conditions are captured in the other transients included in the analyses. Even thoughthe pressure test conditions are not included in the analyses, the NRC staff determined that the appropriate temperature conditions for an upper shelffracture toughness (KIC) value of 200ksiinassumed in the EPRI report must exist during the primary and secondary side hydrostatic and leak tests.
(b) The transients selected for analysis in Tables 5-7, 5-8, and 5-9 in EPRI report 3002015906 and Table 5-5 in EPRI report 3002014590 do not include pressure tests (system leak and hydrostatic tests). Sections 4.2.1 and 4.3.2 of the MPS2 updated final safety analysis report indicates there are 10 cycles of primary and secondary side hydrostatic testing and 200 cycles of primary and secondary side leak testing. The NRC staff has determined in a safety evaluation for a similar submittal that the hydrostatic and leak testing are reasonably accounted for by the 300 cycles of the Heatup and Cooldown transient assumed in the EPRI reports. In Tables A1, A2, and A3 in Attachment 2 in the submittal, the licensee states 121 projected 60-year cycles of Heatup and Cooldown for MPS2. This leaves 179 cycles for pressure testing. The NRC staff noted a total of 210 cycles of pressure testing (as discussed above) for MPS2 applicable to both the primary side and secondary side. The NRC staff noted that 179 cycles of these 210 cycles of pressure testing are accounted for in the analysis in the EPRI reports. However, this still leaves 31 cycles of pressure testing of MPS2
unaccounted for. To determine whether the referenced analyses account for the MPS2 pressure tests, the staff is requesting the following RAIs.
Request (a) Confirm that at the maximum primary and secondary side pressures during the hydrostatic and leak tests of MPS2, the temperature of the primary side affecting the primary side welds requested for MPS2 in the submittal and the temperature of the secondary side affecting the secondary side welds requested for MPS2 in the submittal are high enough such that the upper shelf KIC of value of 200 ksiin assumed in the EPRI reports for fracture toughness is appropriate, considering the value of the nil-ductility reference temperature (RTNDT) of 60°F assumed incalculating KICin EPRI reports 3002015906 and 3002014590.
(b) Discuss how the 31 cycles of pressure testing of MPS2 as discussed above are accounted for in the referenced analysis in the EPRI reports.
RAI-8
Regulatory Basis The regulatory basis for the followingRAI has to do with demonstrating that the proposed alternative ISI requirements would ensure adequate structural integrity of the MPS2 welds identified as Examination Category B-B, Item Nos. B2.31 and B2.40 in Section 1.0 of to the submittal, and thereby providing an acceptable level of quality and safety per 10 CFR 50.55a(z)(1) for these welds.
Issue One set of the PFM results relevant to the B2.31 and B2.40 welds requested for MPS2 in the submittal is shown in Table 8-19 of EPRI report 3002015906. The probability ofrupture statedfor these welds is 7.33E-07 per year at 80 years, which is little margin from the criterion of 1E-06 per year such that an input parameter with high uncertainty or examination coverage can easily cause the probability ofrupture value to exceed the criterion. This probability of rupture value, however, is with a stress multiplier of 1.9 that addresses the variation in radius-to-thickness (R/t) ratio from the geometric configuration modeled as discussed in Section 8.3.4.3.2 of EPRI report 3002015906. The R/t ratio applicable for Item Nos. B2.31 and B2.40 modeled in EPRI report 3002015906 is (169.75/2)/6.94 = 12.2 (dimensions from Table 4-2 of EPRI report 3002015906). The NRC staff noted that the corresponding R/t ratio for MPS2 can be calculated from the MPS2 SG lower head dimensions in Table A1 and Figure A2 in to the submittal. However, the thickness of the SG lower head in Figure A2 in to the submittal is not clearly shown in the figure. The NRC staff noted that the SG lower head diameter (165 inches), is given in Table A1 in Attachment 2 of the submittal.
A calculation of the R/t ratio for the SG lower head of MPS2 could show that there is more margin in the probability ofrupture of the B2.31 and B2.40 welds requested for MPS2 than is shown in Table 8-19 of EPRI report 3002015906.
Request In order to verify that results for MPS2 are bounded by the results in Table 8-19 of EPRI report 3002015906, clarify the thickness of the SG lowerhead of MPS2 in Figure A2 in to the submittal.
RAI-9
Regulatory Basis The regulatory basis for the followingRAI has to do with demonstrating that the proposed alternative ISI requirements would ensure adequate structural integrity of the SG vessel welds and NIR sections of MPS2 for which EPRI reports 3002015906 and 3002014590 are referenced, and thereby providing an acceptable level of quality and safety per 10 CFR 50.55a(z)(1) for these welds and sections.
Issue Section 6.0 of Attachment 1 to the submittal states that MPS2 received preservice inspection followed by four 10-year interval inspections. However, the NRC staff noted that the MPS2 inspection history in Attachment 3 to the submittal shows the examination results and coverage achieved for only the last two inspection intervals (3rd and 4th 10-year ISI intervals).
The licensee stated that the two MPS2 SGs were replaced during the 2nd 10-year ISI interval, but the top portion of the SGs were retained. The NRC staff noted that this explains why the MPS2 inspection history in Attachment 3 to the submittal shows examinations only for the 3rd and 4th 10-year ISI intervals. The NRC staff has determined that the examination results and coverage achieved for the 1st and 2nd 10-year ISI intervals for the SG vessel welds and NIR sections that were retained in the top portion of the SGs are needed to confirm that the relevant PFM results in EPRI reports 3002015906 and 3002014590 are appropriate for the subject SG vessel welds and NIR sections requested for MPS2 in the submittal.
Request (a) Provide the examination results and coverage achieved for the 1st and 2nd 10-year ISI intervals for the subject SG vessel welds and NIR sections of MPS2 that were retained.
OR (b) Confirm that the examination results for the 1st and 2nd 10-year ISI intervals for theSG vessel welds and NIR sections listed in Attachment 3 to the submittal that were retained are the same as those in the attachment and that the coverages achieved for the 1st and 2nd 10-year ISI intervals for theSG vessel welds and NIR sections listed in Attachment 3 to the submittal that were retained are not less than the smallest coverage of 56.3% shown in the attachment.
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