ML20252A026

Relief Request IR-062 Regarding Weld Examination Coverage for the Third Inservice Inspection Interval

ML20252A026
Person / Time
Site:	Perry
Issue date:	09/18/2020
From:	Robert Kuntz Plant Licensing Branch III
To:	Payne F Energy Harbor Nuclear Corp
Wall S
References
EPID L-2020-LLR-0067
Download: ML20252A026 (13)

Text

September 18, 2020 Mr. Frank R. Payne Site Vice President Energy Harbor Nuclear Corp.

Perry Nuclear Power Plant P.O. Box 97, SB306 Perry, OH 44081-0097

SUBJECT:

PERRY NUCLEAR POWER PLANT, UNIT NO. 1 - RELIEF REQUEST IR-062 REGARDING WELD EXAMINATION COVERAGE FOR THE THIRD INSERVICE INSPECTION INTERVAL (EPID L-2020-LLR-0067)

Dear Mr. Payne:

By letter dated April 17, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20108F511), Energy Harbor Nuclear Corp. (the licensee) requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI. Relief Request (RR) IR-062, Revision 0, pertains to examination coverage of Class 1 component welds at the Perry Nuclear Power Plant (PNPP).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),

the licensee requested relief from the required volumetric or surface examination coverage for inservice inspection (ISI) of the component welds on the basis that the ASME Code requirements are impractical.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). The NRC staff has determined that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest, given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. Furthermore, the NRC staff concluded that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject components. Therefore, the NRC staff grants relief from the ASME Code examination requirements for the welds included in RR IR-062 for PNPP for the third 10-year ISI interval, which began on May 18, 2009, and ended on May 17, 2019.

All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

F. Payne If you have any questions, please contact the Project Manager, Scott Wall, at 301-415-2855 or e-mail at Scott.Wall@nrc.gov.

Sincerely, Digitally signed by Robert F. Robert F. Kuntz Date: 2020.09.18 Kuntz 10:39:29 -04'00' Nancy L. Salgado, Chief (Robert Kuntz for)

Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-440

Enclosure:

Safety Evaluation cc: Listserv

ML20252A026 *via e-mail ** via memo OFFICE NRR/DORL/LPL3/PM* NRR/DORL/LPL3/LA* NRR/DNRL/NVIB/BC**

NAME SWall SRohrer (JBurkhardt for) HGonzalez DATE 09/11/2020 09/11/2020 08/26/2020 OFFICE NRR/DNRL/NPHP/BC** NRR/DORL/LPL3/BC*

NAME MMitchell NSalgado (RKuntz for)

DATE 08/26/2020 09/18/2020 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 10 CFR 50.55a REQUEST IR-062, REVISION 0 THIRD 10-YEAR INTERVAL INSERVICE TESTING INTERVAL ENERGY HARBOR NUCLEAR CORP.

PERRY NUCLEAR POWER PLANT, UNIT NO. 1 DOCKET NO. 50-440

1.0 INTRODUCTION

By letter dated April 17, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20108F511), Energy Harbor Nuclear Corp. (the licensee) requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI. Relief Request (RR) IR-062, Revision 0, pertains to examination coverage of Class 1 component welds at the Perry Nuclear Power Plant (PNPP).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),

the licensee requested relief from the required volumetric or surface examination coverage for inservice inspection (ISI) of the component welds on the basis that the ASME Code requirements are impractical.

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)(4), Inservice inspection standards requirement for operating plants, components (including supports) that are classified as ASME Code Class 1, Class 2, and Class 3 must meet the requirements in 10 CFR 50.55a throughout the service life of a boiling- or pressurized-water reactor (BWR or PWR). The exception is the design and access provisions and preservice examination requirements set forth in Section XI of editions and addenda of the ASME Code that become effective subsequent to editions specified in 10 CFR 50.55a(g)(2) and (3), which are incorporated by reference in 10 CFR 50.55a(a)(1)(ii) to the extent practical within the limitations of design, geometry, and materials of construction of the components.

Pursuant to 10 CFR 50.55a(g)(4)(ii), Applicable ISI Code: Successive 120-month intervals, inservice examination of components and system pressure tests conducted during successive 120-month inspection intervals must comply with the requirements of the latest edition and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(a) 12 months before the start of the 120-month inspection interval (or the optional ASME Code Cases listed in U.S. Nuclear Regulatory Commission (NRC) Regulatory Guide (RG) 1.147, when using ASME Enclosure

Code,Section XI, as incorporated by reference in 10 CFR 50.55a(a)(3)(ii), subject to the conditions listed in 10 CFR 50.55a(b).

Pursuant to 10 CFR 50.55a(g)(5)(iii), ISI program update: Notification of impractical ISI Code requirements, if the licensee has determined that conformance with a ASME Code requirement is impractical for its facility, the licensee must notify the NRC and submit, as specified in § 50.4, information to support the determinations. Determinations of impracticality in accordance with 10 CFR 50.55a(g)(5)(iii) must be based on the demonstrated limitations experienced when attempting to comply with the ASME Code requirements during the ISI interval for which the request is being submitted. Requests for relief made in accordance with 10 CFR 50.55a(g)(5)(iii) must be submitted to the NRC no later than 12 months after the expiration of the initial or subsequent 120-month inspection interval for which relief is sought.

Pursuant to 10 CFR 50.55a(g)(6)(i), Impractical ISI requirements: Granting of relief, the Commission will evaluate determinations under 10 CFR 50.55a(g)(5) that ASME Code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law, will not endanger life or property or the common defense and security, and are otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the NRC to grant the relief requested by the licensee.

3.0 TECHNICAL EVALUATION

3.1 Summary of Request The licensees RR IR-062 is for multiple ASME Code Class 1 component welds associated with multiple ASME Code, Examination Categories, for PNPPs third 10-year ISI interval. The licensee stated that for the subject welds in RR IR-062, it was impractical to meet the ASME Code-required examination coverage. Specifically, due to original design of these components, it was not possible to effectively perform examinations to the extent required by the ASME Code. The licensee stated that conformance would require extensive modifications to the components without a compensating increase in the level of quality and safety.

The licensee indicated that it performed the ASME Code-required examinations to the maximum extent possible. Due to design limitation there are no viable alternative examination techniques currently available to increase the coverage. Therefore, pursuant to 10 CFR 50.55a(g)(5)(iii),

the licensee requested relief on the basis that achieving the ASME Code-required volumetric surface examination coverage for the subject components in RR IR-062 is impractical.

The ASME Code of record at PNPP for the third 10-year ISI interval is the 2001 Edition through the 2003 Addenda of ASME Code,Section XI. The third 10-year ISI interval at PNPP began on May 28, 2009, and ended on May 27, 2019. Additionally, the licensee stated that PNPP adopted ASME Code Case N-460, Alternative Examination Coverage for Class 1 and Class 2 Welds,Section XI, Division 1, which defines essentially 100 percent, as greater than 90 percent coverage of the examination volume or surface area, as applicable. The licensee also cited use of ASME Code Case N-613-1, Ultrasonic Examination of Full Penetration Nozzles in Vessels, Examination Category B-D, Reactor Nozzle-To-Vessel Welds, and Nozzle

Inside Radius Section Figs. IWB-2500-7(a), (b), (c), and (d),Section XI, Division I. ASME Code Cases N-460 and N-613-1 are NRC-approved alternatives that can be used by a licensee, as referenced in RG 1.147, Revision 19, Inservice Inspection Code Case Acceptability (ADAMS Accession No. ML19128A244).

For clarity, the NRC staffs evaluation of RR IR-062 is documented according to each of the applicable ASME Code-required examination categories.

3.2 Examination Category B-O and RA, Pressure-Retaining Welds in Piping 3.2.1 Applicable ASME Code Requirements The examination requirements for Examination Category B-O, Item Number B14.10 are delineated in Table IWB-2500-1, which states, in part, that 10 percent of the peripheral Control Rod Housings shall be examined during an inspection interval. Furthermore, the examinations can be volumetric or surface and should cover the appropriate volumes or areas delineated in Figure IWB-2500-18. Table 1 below provides a summary of licensees examinations for Examination Category B-O welds for which the licensee is seeking relief.

Table 1 - Examination Category B-O Welds with Limited Surface Examination Coverage Component Pipe Item Limitation/ Examination Identification and Size Materials No. Coverage Results System (inch) 1B13-02/35-FW Control Rod Drive Limited Access/ Austenitic No Recordable B14.10 Housing 4 85% coverage Stainless Steel Indications Housing-to-Flange Weld 1B13-54/15-FW Control Rod Drive Limited Access/ Austenitic No Recordable B14.10 Housing 4 75% coverage Stainless Steel Indications Housing-to-Flange Weld The Examination Category R-A, Item Numbers R2.11 and R2.ND are related to the licensees risk-informed ISI program as well as portions of ASME Code Case N-578-1, Alternative Piping Classification and Examination Requirements,Section XI, Division 1. The NRC approved the licensees risk-informed ISI program for the third ISI interval by letter dated November 14, 2012 (ADAMS Accession No. ML12313A153). The licensee noted that it used a plant-specific item designation. Item Number R2.11 is designated for components that are subject to thermal fatigue, and Item Number R2.ND is designated for components do not have a known degradation mechanism.

For Examination Category R-A, Items Numbers R2.11 and R2.ND, the required examination consists of essentially 100 percent volumetric examination. The required examination volume for Item Number R2.ND is delineated in ASME Code,Section XI, Figure IWB-2500-8(c). For Item Number R2.11, the required examination volume is related to the licensees repair of the existing weld joint by a structural weld overlay during the refueling outage in 1999. Specifically, the NRC staff approved the licensees use of ASME Code Case N-504, Alternative Rules for

Repair of Class 1, 2, and 3 Stainless Steel Piping,Section XI, Division 1, for the repair of a circumferential indication believed to be due to intergranular stress-corrosion cracking of the Alloy 182 butter. The current ISI inspection requirements for the overlay repair weld in terms of the examination volume are essentially the same as the initial requirements at the time the safe end to nozzle weld was repaired in 1999. Table 2 below provides a summary of the examination results for PNPP Examination Category R-A welds for which the licensee is seeking relief.

Table 2 - Examination Category R-A Welds with Limited Volumetric Coverage Component Pipe Item Limitation/ Examination Identification and Size Materials No. Coverage Results System (inch)

Limited access Unchanged 1B13-N4C-KB Alloy 52 Full sided Recordable R2.11 Feedwater Nozzle 12 Structural Weld Nozzle-to-Pipe, Fabrication to Safe End Weld Overlay 70.5% coverage Indications Single sided 1B33-0028 Austenitic No Recordable R2.ND Pipe-to-Sweepolet 12x16 Safety Injection Stainless Steel Indications 50% coverage 3.2.2 Licensees Reason for Request Due to component design limitations the licensee was unable to obtain the ASME Code-required examination coverage for the components identified in its submittal, without extensive design modifications. The licensee stated that the subject welds were examined to the extent practical due to limited access. The licensee further stated that 100 percent of the accessible welds were examined. For examination Category B-O welds, the licensee performed surface examinations using the liquid penetrant. The summary of the examination results is provided in Table 1. For Examination Category R-A welds, the licensee performed ultrasonic (UT) examinations, using personnel, equipment, and procedures qualified in accordance with ASME Code,Section XI, Appendix VIII, as implemented by the Performance Demonstration Initiative (PDI). The ASME code-required volume for these welds was examined ultrasonically to the maximum extent possible. The summary of the examination results is provided in Table 2.

For the Examination Category B-O welds, 1B13-02/35-FW and 1B13-54/15-FW, the licensee performed surface examinations. These are control rod housing-to-flange welds for which due to design constraints the license was not able to achieve the ASME Code-required examination coverage (i.e., essentially 100 percent). The licensee was able to achieve 85 and 75 percent of the required examination area for welds 1B13-02/35-FW and 1B13-54/15-FW, respectively.

There were no recordable indications or flaws recoded as a result of these surface examinations.

For Examination Category R-A welds 1B13-N4C-KB and 1B33-0028, the licensee performed volumetric examinations. These welds are piping welds and, due to the design configuration, the licensee was not able to achieve the required examination volume. For weld 1B13-N4C-KB, the licensee was able to achieve 70.5 percent of the required examination volume; these examinations revealed previously identified lack of fusion fabrication flaws related to the 1999

structural weld overlay. For weld 1B33-0028, the licensee was able to achieve 50 percent of the required examination volume, with no recordable indications.

3.2.3 NRC Staff Evaluation of Examination Category B-O and R-A Welds Examination requirements for ASME Code,Section XI, Examination Category B-O, Item B14.10 call for inspection of 10 percent of the peripheral Control Rod Housings during an inspection interval by volumetric or surface examinations. The examinations require essentially 100 percent volumetric or surface examinations of the volume or surface area delineated in ASME Code,Section XI, Figure IWB-2500-18.

Examination requirements of ASME Code Case N-578-1, Examination Category R-A, Item Numbers R2.11 and R2.ND, require essentially 100 percent volumetric examinations covering the examination volume delineated in ASME Code,Section XI, Figure IWB-2500-8(c).

However, licensees volumetric examinations are restricted by component design, materials, and weld configurations. These conditions precluded the licensee from obtaining full access from both sides of these welds, resulting in limited volumetric examinations. To gain access for achieving examination coverage for the required examination volumes, the subject welds would require design modifications. This would place a burden on the licensee; therefore, obtaining essentially 100 percent of ASME Code-required volumetric examinations for the subject welds is considered impractical.

As shown in the sketches and technical descriptions included in the licensees submittal for PNPP, the subject Examination Category B-O welds are all austenitic stainless steel piping welds with physical limitations that restricted performing essentially 100 percent surface examinations for these welds. However, the licensees surface examinations on welds 1B13-02/35-FW and 1B13-54/15-FW were able to achieve 85 and 75 percent, respectively, of the required examination area with no recordable indications. The NRC staff finds that licensees achieved examination coverage on these welds, with no recordable indications, provides a reasonable assurance of structural integrity is considered justified and acceptable.

As shown on the sketches and technical description, weld 1B33-0028 is an austenitic stainless steel branch connection which limits access for volumetric scanning from the single side of the weld. The regulation in 10 CFR 50.55a(b)(2)(xv)(A)(2) requires that examinations of austenitic welds from a single side may be credited for full coverage only after completing a single-sided Appendix VIII demonstration using flaws on the opposite side of the weld. The licensee stated that this weld was examined using the latest techniques and applicable requirements including the requirements of Appendix VIII and applicable PDI requirements. These techniques have been qualified through the industrys PDI, which meets the intent of the ASME Code,Section XI, Appendix VIII requirements for flaws located on the near-side of the welds. However, far-side detection of flaws from a single-sided scan is considered to be a best effort. The NRC staff expects that had significant flaws been present on the far-side of the weld, they would have been detected by the licensee. Therefore, the NRC staff finds that the licensees achieved examination coverage of 50 percent with no detectable indications constitutes a best effort, is considered justified and acceptable.

Weld 1B13-N4C-KB is a dissimilar metal weld which was repaired during the seventh refueling outage in 1999, with a full structural weld overlay using a stress-corrosion cracking resistant material (Alloy 52). Volumetric examinations performed subsequent to the application of the full structural weld overlay revealed several indications related to the fabrication of the overlay.

These indications were determined to be laminar in nature, and the licensees evaluations confirmed that the weld overlay with these indications was acceptable for continued service.

The NRC staff reviewed licensees evaluation and, as discussed in the NRC staffs safety evaluation dated May 13, 1999 (ADAMS Accession No. ML20137N878; non-publicly available),

determined that the weld overlay with the indications, has sufficient margin and is suitable for continued service, subject to re-inspections in accordance with the inspection schedule of NUREG-0313, Revision 2, Technical Report on Material Selection and Processing Guidelines for BWR Coolant Pressure Boundary Piping, January 1988 (ADAMS Accession No. ML031470422). The licensees current volumetric examination of the weld overlay provided complete coverage of the area above the original flaw for which the overlay was applied.

Additionally, the licensee was able to verify that the weld overlay fabrication indications from the 1999 overlay repair are unchanged. The NRC staff also reviewed the licensees Owners Activity Reports and noted that the subject weld was volumetrically examined multiple times with no apparent change in the original flaw as well as the fabrication indications. While the licensees examination of weld 1B13-N4C-KB was limited to 70.5 percent, the examinations also verified that the known indications are essentially unchanged and are consequently deemed acceptable for continued service, subject to re-inspections. Therefore, the NRC staff finds that the licensees achieved examination coverage of 70.5 percent with the noted unchanged fabrication indications constitutes a best effort, is considered justified and acceptable.

Based on its review of the subject Examination Category R-A and B-O welds at PNPP, the NRC staff finds that it is impractical to meet the ASME Code-required examination coverage for the subject welds due to the design configuration of the subject components. The NRC staff also determined that the examinations performed, despite the limited coverage obtained by the licensee, provide reasonable assurance of the structural integrity for the subject component welds. Furthermore, the continued performance of the periodic required visual (VT-2) examinations through the system pressure tests provide additional assurance of structural integrity of the subject components. Hence, the NRC staff finds that the risk associated with granting the requested relief would be very low. Therefore, the NRC staff finds the licensees request acceptable.

3.3 Examination Category B-A and B-D, Pressure-Retaining Welds in Reactor Vessel and Full Penetration Welded Nozzles in Vessels 3.3.1 Applicable ASME Code Requirements The examination requirements for Examination Category B-A, Item Number B1.30 are delineated in Table IWB-2500-1, and requires the volumetric examination depicted in

Figure IWB-2500-4. Table 3 below provides a summary of licensees examinations for Examination Category B-A welds for which the licensee is seeking relief.

Table 3 - Examination Category B-A with Limited Volumetric Examination Coverage Component Limitation/ Examination Item No. Identification and Materials Coverage Results System SA-533 Gr. B Cl. 1 1B13-AE Plate w/ SS Cladding No. 4 shell ring to shell Limited Access Two acceptable B1.30 flange circumferential 70.9% coverage indications SA-508 Class II seam Forging The examination requirements for Examination Category B-D, Item Number B3.90 are delineated in Table IWB-2500-1, and requires the volumetric examination depicted in Figure IWB-2500-7. Per ASME Code Case N-613-1, item B3.90 nozzle-to-vessel welds previously ultrasonically examined using the examination volumes of Figures IWB-2500-7(a),

(b), and (c) may be examined using the reduced examination volumes as specified in ASME Code Case N-613-1 Figures 1, 2, and 3. Table 4 below provides a summary of licensees examinations for Examination Category B-D welds for which the licensee is seeking relief.

Table 4 - Examination Category B-D Welds with Limited Volumetric Coverage Component Limitation/ Examination Item No. Identification and Materials Coverage Results System SA-533 Gr. B Cl. 1 1B13-N4C-KA Limited access due Plate w/SS Cladding No Recordable B3.90 Feedwater Nozzle to to nozzle design, Indications Safe End Weld 83.2% coverage SA-508 Class II Forging SA-533 Gr. B Cl. 1 1B13-N4C-KB Limited access due Plate w/SS Cladding No Recordable B3.90 Feedwater Nozzle to to nozzle design, Indications Safe End Weld 83.2% coverage SA-508 Class II Forging SA-533 Gr. B Cl. 1 1B13-N4C-KC Limited access due Plate w/SS Cladding No Recordable B3.90 Feedwater Nozzle to to nozzle design, Indications Safe End Weld 83.2% coverage SA-508 Class II Forging SA-533 Gr. B Cl. 1 1B13-N4C-KD Limited access due Plate w/SS Cladding No Recordable B3.90 Feedwater Nozzle to to nozzle design, Indications Safe End Weld 83.2% coverage SA-508 Class II Forging

Table 4 - Examination Category B-D Welds with Limited Volumetric Coverage Component Limitation/ Examination Item No. Identification and Materials Coverage Results System SA-533 Gr. B Cl. 1 1B13-N4C-KE Limited access due Plate w/SS Cladding No Recordable B3.90 Feedwater Nozzle to to nozzle design, Indications Safe End Weld 82.7% coverage SA-508 Class II Forging SA-533 Gr. B Cl. 1 1B13-N4C-KF Limited access due Plate w/SS Cladding Three acceptable B3.90 Feedwater Nozzle to to nozzle design, indications Safe End Weld 83.2% coverage SA-508 Class II Forging 3.3.2 Licensees Reason for Request Due to component design limitations the licensee was unable to obtain the ASME Code-required examination coverage for the components identified in its submittal, without extensive design modifications. The licensee stated that the subject welds were examined to the extent practical due to limited access. The licensee stated that its determination is based on actual demonstrated limitations experienced when attempting to comply with the code examination requirements.

The licensee explained that Item B1.30, reactor vessel shell-to-flange weld (1B13-AE), is a Class 1 pressure-retaining weld, and the examination is limited to a single-sided examination from the shell side due to the proximity of the reactor vessel flange and interference from the reactor vessel flange leak-off nozzle N17. The summary of the examination results is provided in Table 3.

The licensee also explained that Item B3.90, reactor vessel feedwater nozzle-to-vessel welds (1B13-N4A-KA through 1B13-N4F-KA), are Class 1 pressure-retaining welds and the examinations were limited due to the configuration of the nozzle forgings. The summary of the examination results is provided in Table 4.

3.3.3 NRC Staff Evaluation of Examination Category B-A and B-D Welds The NRC staff reviewed the licensees figures for the reactor vessel shell-to-flange weld (i.e., 1B13-AE) showing the location of the weld, showing the limitations of the examination from the shell side due to the proximity of the reactor vessel flange and interference from the reactor vessel flange leak-off nozzle N17, and the coverage plot for the single-sided scan. These figures detailed the areas for which examination coverage to this component was possible with the various scanner configurations (e.g., combination of 45, 60, 70 probes and T-scan and P-scan). Based on its review, the NRC staff finds that the redesign of the reactor vessel shell-to-flange weld (i.e., 1B13-AE) to obtain examination coverage of greater than 90 percent of the required Code examination volume or area is impractical due extensive effort of modifying the reactor pressure vessel. Thus, the NRC staff determined that the examinations identified by the licensee for the reactor vessel shell-to-flange weld (i.e., 1B13-AE) have been performed to the maximum extent possible and that it is impractical for the licensee to comply with the specified requirements without extensive design modifications.

Based on an evaluation of the licensees schematics and calculations, the NRC staff finds that the UT procedure and techniques used by the licensee for these examinations achieved the maximum coverage practical without burdensome and extensive alterations. In addition, the NRC staff noted that operational leakage from the reactor coolant system (RCS) within the drywell, which includes the reactor vessel shell-to-flange weld (i.e., 1B13-AE), is monitored per Technical Specification (TS) 3.4.5, RCS Operational Leakage, that will provide early detection of any RCS leakage within the drywell. Furthermore, the required visual (VT-2) examination in conjunction with the Class 1 system leakage test performed each refueling outage are capable of identifying leakage from these components. Thus, the staff finds that the licensees examination coverage of these components and the visual (VT-2) examination every refueling outage of the pressurizer provides reasonable assurance of structural integrity and leak tightness of the subject components.

The NRC staff reviewed the licensees figures for the feedwater nozzle-to-vessel welds (i.e., B13-N4A-KA though B13-N4F-KA), showing the examination limitations due to the configuration of the nozzle forgings, and the coverage plots both the radial and circumferential scans. These figures detailed the areas for which examination coverage to these components were possible with the various scanner configurations (e.g., combination of 45, 60, 70 probes and T-scan and P-scan, and IRS-Scan). Based on its review, the NRC staff finds that the redesign of the feedwater nozzle-to-vessel welds (i.e., B13-N4A-KA though B13-N4F-KA) to obtain examination coverage of greater than 90 percent of the required Code examination volume or area is impractical due extensive effort of modifying the reactor coolant pressure boundary. Thus, the NRC staff determined that the examinations identified by the licensee for feedwater nozzle-to-vessel welds (i.e., B13-N4A-KA though B13-N4F-KA) have been performed to the maximum extent possible and that is impractical for the licensee to comply with the specified requirements without extensive design modifications.

Based on an evaluation of the licensees schematics and calculations, the NRC finds that the UT procedure and techniques used by the licensee for these examinations achieved the maximum coverage practical without burdensome and extensive alterations. In addition, the NRC staff noted that operational leakage from the RCS within the drywell, which includes the feedwater nozzle-to-vessel welds (i.e., B13-N4A-KA though B13-N4F-KA), is monitored per TS 3.4.5, that will provide early detection of any RCS leakage within the drywell. Furthermore, the required visual (VT-2) examination in conjunction with the Class 1 system leakage test performed each refueling outage are capable of identifying leakage from these components.

Thus, the staff finds that the licensees examination coverage of these components and the visual (VT-2) examination every refueling outage of the pressurizer provides reasonable assurance of structural integrity and leak tightness of the subject components.

Based on its review of the subject Examination Category B-A and B-D welds at PNPP, the NRC staff finds that it is impractical to meet the ASME Code-required examination coverage for the subject welds due to the design configuration of the subject components. The NRC staff also determined that the examinations performed, despite the limited coverage obtained by the licensee, provide reasonable assurance of the structural integrity for the subject component welds. Furthermore, the continued performance of the periodic required VT-2 examinations through the system pressure tests provide additional assurance of structural integrity of the subject components. Hence, the NRC staff finds that the risk associated with granting the requested relief would be very low. Therefore, the NRC staff finds the licensees request acceptable.

4.0 CONCLUSION

As set forth above, the NRC staff has determined that granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest, given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

Furthermore, the NRC staff concluded that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject components. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Therefore, the NRC staff grants relief from the ASME Code examination requirements for the welds included in RR IR-062 for PNPP for the third 10-year ISI interval, which began on May 18, 2009, and ended on May 17, 2019.

All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

Principal Contributors: R. Kalikian O. Yee Date: September 18, 2020