ML25245A137
| ML25245A137 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 09/09/2025 |
| From: | Markley M Plant Licensing Branch II |
| To: | Coleman J Southern Nuclear Operating Co |
| Turner, Zachary | |
| References | |
| EPID L-2025-LLR-0048 | |
| Download: ML25245A137 (1) | |
Text
September 9, 2025 Jamie M. Coleman Regulatory Affairs Director Southern Nuclear Operating Company 3535 Colonnade Parkway Birmingham, AL 35243
SUBJECT:
JOSEPH M. FARLEY NUCLEAR PLANT, UNIT NO. 2 - RE: AUTHORIZATION OF PROPOSED ALTERNATIVE FNP-ISI-ALT-05-13 FOR REACTOR VESSEL BOTTOM HEAD INSPECTION (EPID L-2025-LLR-0048)
Dear Ms. Coleman:
By letter dated April 28, 2025, as supplemented by letter dated April 29, 2025, Southern Nuclear Operating Company (the licensee) submitted Relief Request FNP-ISI-ALT-05-13 (a proposed alternative) to the U.S. Nuclear Regulatory Commission (NRC) for the Joseph M. Farley Nuclear Plant (Farley), Unit 2. The proposed alternative requested relief from Subparagraph IWB-3142.2 of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code) related to supplemental examinations of reactor pressure vessel (RPV) bottom mounted instrument penetrations and instrument connections at Farley, Unit 2.
The licensee submitted the proposed alternative pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Section 50.55(a), Codes and standards, paragraph (z)(2) on the basis that the ASME BPV Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality of safety.
On April 30, 2025, the NRC staff verbally authorized the use of proposed alternative FNP-ISI-ALT-05-13 for Farley, Unit 2, until the completion of the 2R31 refueling outage scheduled for fall 2026. This letter provides the NRCs written safety evaluation for the proposed alternative.
All other ASME BPV Code,Section XI, requirements as incorporated by reference in the Code of Federal Regulations Section 50.55a for which relief or an alternative was not specifically requested, and granted or authorized (as appropriate), in the subject request remain applicable.
If you have any questions, please contact the project manager, Zach Turner, at 301-415-2258 or via email at Zachary.Turner@nrc.gov.
Sincerely, Michael Markley, Chief Plant Licensing Branch 2-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-364
Enclosure:
Safety Evaluation cc: Listserv MICHAEL MARKLEY Digitally signed by MICHAEL MARKLEY Date: 2025.09.09 08:32:41 -04'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ALTERNATIVE REQUEST FNP-ISI-ALT-05-13 FOR REACTOR VESSEL BOTTOM HEAD INSPECTION FIFTH INSERVICE TESTING PROGRAM INTERVAL SOUTHERN NUCLEAR OPERATING COMPANY JOSEPH M. FARLEY NUCLEAR PLANT, UNIT 2 DOCKET NUMBER 50-364 EPID: L-2025-LLR-0048
1.0 INTRODUCTION
By letter dated April 28, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25118A329), as supplemented by letter dated April 29, 2025 (ML25119A334), Southern Nuclear Operating Company (SNC, the licensee) requested authorization of Relief Request FNP-ISI-ALT-05-13 (a proposed alternative) from the U.S.
Nuclear Regulatory Commission (NRC) for the Joseph M. Farley Nuclear Plant (Farley), Unit 2.
The proposed alternative requested relief from Subparagraph IWB-3142.2 of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code) related to the supplemental examinations of reactor pressure vessel (RPV) bottom mounted instrument penetrations and instrument connections at Farley, Unit 2.
Specifically, pursuant to subparagraph (2) in paragraph (z), Alternatives to codes and standards requirements, of Section 55a, Codes and standards, in Part 50, Domestic Licensing of Production and Utilization Facilities, to Title 10 of the Code of Federal Regulations (10 CFR), the licensee requested an alternative to inspection items B15.80 and B15.100 examination requirements for specified RPV bottom mounted instrument penetrations and instrument connections, on the basis that compliance with certain ASME BPV Code requirements, at that time, would present an undue hardship without a compensating increase in the level of quality and safety.
On April 30, 2025, the NRC staff provided verbal authorization (ML25120A211) of Alternative Request FNP-ISI-ALT-05-13 for the proposed alternative of the Inservice Inspection (ISI) requirements at Farley, Unit 2, in accordance with 10 CFR 50.55a(z)(2). The NRC staff authorized the licensees proposed alternative until completion of the 2R31 refueling outage at Farley, Unit 2, scheduled for fall 2026. This safety evaluation documents the staffs review of the licensees Alternative Request FNP-ISI-ALT-05-13
2.0 REGULATORY EVALUATION
The NRC regulations in 10 CFR 50.55a(g)(4), Inservice inspection standards requirement for operating plants, state, in part, that ASME BPV Code Class 1, 2, and 3 components must meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in the ASME BPV Code,Section XI.
The NRC regulations in 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state that alternatives to the requirements of 10 CFR 50.55a(b) through (h) or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation. 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.
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 authorize the alternative requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1 Licensees Alternative Request Applicable ASME OM Code Edition The applicable Code of Record for the Fifth ISI Program interval at Farley, Unit 2, is the 2007 Edition through 2008 Addenda of ASME Code as incorporated by reference in 10 CFR 50.55a. The Fifth ISI Program interval at Farley, Unit 2, began on December 1, 2017, and is currently scheduled to end on November 30, 2027.
Applicable ASME Code Components The affected ASME Code components are ASME Code Case N-722-1, ASME Items B15.80 and B15.100 for RPV bottom mounted instrument penetrations and instrument connections.
Applicable ASME Code Requirements 10 CFR 50.55a(g)(6)(ii)(E), Augmented ISI requirements: Reactor coolant pressure boundary visual inspections, requires that all licensees of pressurized water reactors (PWR) must augment their ISI program by implementing ASME Code Case N-722-1, subject to the conditions specified in paragraphs (g)(6)(ii)(E)(2) through (4). Code Case N-722-1, Additional Examinations for PWR Pressure Retaining Welds in Class 1 Components Fabricated with Alloy 600/82/182 Section XI, Division 1, contains the requirements for the examination of RPV bottom mounted instrument penetrations and instrument connections. Specifically, Code Case N-722-1, Table 1, Examination Categories, delineate the specific examinations requirements for RPV bottom mounted instrument penetrations in IWB15.80 and instrument connections in IWB15.100. IWB15.80 requires that RPV bottom mounted instrument penetrations are examined visually every other refueling outage. IWB15.100 requires that RPV Instrument Connections are examined visually once per ISI interval.
Licensees Proposed Alternative:
In the Enclosure of the submittal dated April 28, 2025, the licensee stated:
SNC has completed cleaning of the bottom of the reactor vessel and all instrumentation connections above the insulation package to remove all boric acid residue. In addition, SNC performed a visual baseline examination of the cleaned areas to confirm no loss of material in the carbon steel annulus region during the current refueling outage.
Furthermore, SNC proposes to perform a visual examination of the bottom of the vessel above the insulation during the Class 1 system leakage test (at nominal operating pressure) to confirm that there is no active reactor vessel pressure boundary leakage occurring in this vicinity during this refueling outage. This will examine the accessible external exposed surfaces of pressure retaining components for evidence of leakage by a VT-2L qualified individual. It is important to note, that the ASME Code Case N-722-1 Item B15.100 welds are easily accessible for visual examination from above the insulation package, without complete removal of insulation. Additionally, SNC proposes to perform visual examinations of the bottom vessel (ASME Item 15.80 and 15.100) prior to reactor cavity flood up during 2R31 and will continue each refueling outage unit cavity seal leakage has been completely corrected.
Licensees Basis for Use:
The licensee performed several examinations and analyses regarding identifying the source of boric acid on RPV bottom mounted instrument penetrations and instrument connections, to include pre-flood-up visual inspections, correlating cavity seal leakage with the location of boric acid presence on affected ASME components, utilizing fleetwide operating experience to identify similarities and differences in leakage characteristics, trending radiation and leakage monitoring for insights on the source of leakage, as well as performing chemical analysis on the boric acid spots to identify source of radionuclides.
The licensee concluded that the examinations and analyses performed provided reasonable assurance that the boric acid observed is not a result of pressure boundary leakage. Additionally, the licensee stated that the proposed future examinations that would occur during refueling outage 2R30 would provide further reasonable assurance of structural integrity until refueling outage 2R31, where re-examination of the RPV bottom mounted instrument penetrations and instrument connection will occur in accordance with the requirements of ASME Code Case N-722-1 Licensees Reason for Request:
In the Enclosure of the submittal dated April 28, 2025, the licensee stated, in part, that:
Pursuant to 10 CFR 50.55a(z)(2), an alternative is being requested by Southern Nuclear Operating Company (SNC) for Farley Nuclear Plant (FNP) Unit 2 on the basis that a hardship and unusual difficulty exists in the supplemental examinations of the RPV bottom-mounted instrument penetrations and instrument connections as required by ASME Section XI IWB 3142.2. While performing the visual examinations required by ASME Code Case N-722-1, boric acid was present in the annulus areas at penetrations 1, 2, 5, 8, 12, 13, 17, 19, 20, 22, 23, 26, 28, 29, 36, 37, 39, 42, 43, and 46 for ASME Item B15.80. Additionally, boric acid was present on the alloy 600 tube to safe end welds at penetration locations 1-6, 8, 9, 10, 13, 17, 19, 20, 22, 26, 28, 29, 36, 37, 43, and 46 for ASME Item number B15.100 visual examinations. ASME Code Case N-722-1 required acceptance of this condition in accordance with IWB-3522. This is a relevant condition per IWB-3522; therefore, IWB-3142 and IWA-5250 are applicable.
Per IWB-3142, acceptance can be performed by four methods:
(1) IWB-3142.1 - Acceptance by Visual Examination (2) IWB-3142.2 - Acceptance by Supplemental Examination (3) IWB-3142.3 - Acceptance by Corrective Measures or Repair/Replacement Activity (4) IWB-3142.4 - Acceptance by Analytical Evaluation SNC continues to state that:
IWB-3142.1 is not possible due to the presence of boric acid in the annulus region and on the alloy 600 tube to safe end welds at the above noted locations.
IWB-3142.3, Corrective measures or repair/replacement activities are not applicable because there has been no physical flaw identified in any of the penetrations. IWB-3142.4, Acceptance by Analytical Evaluation, cannot be performed because there is no definitive method to determine if some boric acid was present due to inservice conditions prior to cavity seal leakage present following refueling cavity flood up to support refueling operations. Performance of IWB-3142.2 was considered to perform volumetric examinations of the subject penetrations; however, performance of supplemental examinations would result in a hardship without a compensating increase in the level of quality and safety.
To set proper conditions for the supplemental examinations it is necessary to disassemble the reactor vessel, offload the core, remove the upper and lower internals (core barrel) which results in high-risk tasks and substantial unplanned dose. High risk tasks include emergently lifting the reactor head, removal of the upper internals, fuel offload, removal of the lower internals, and returning all these components back into the vessel for start-up. All these tasks carry the risks of damaging components during the emergent evolution. Furthermore, the lower internals must be removed to perform supplemental exams on the reactor vessel bottom-mounted instrument penetrations and instrument connections from inside the reactor vessel. The supplemental examinations must be performed internally due to the orientation of the J-groove weld. The lower internals life will disrupt 2R30 outage projects during the lower internals lift due to the high dose of the component and potential exposure to employees on the 155 ft elevation (refueling floor) of containment. The estimated total dose for all the reactor vessel disassembly, the supplemental exams from the inner diameter, and the reactor vessel reassembly is 6.483 Person Rem if performed emergently during 2R30, this would be a 33% increase to total outage dose. If outer diameter (OD) volumetric examinations were performed on the impacted ASME Item number B15.100 exams alone due to their access from the OD, estimated dose for performance of this exam is 3.066 Person Rem. Therefore, the significant increase to personnel dose and safety risk to the plant that could result from performing the supplemental examinations required by ASME Section XI IWB-3142.2 represents a hardship.
Licensees Proposed Duration SNC requested approval of this alternative request by April 30, 2025 (within 48-hours of submittal), through the completion of the 2R31 refueling outage at Farley, Unit 2, scheduled for fall 2026.
3.2
NRC Staff Evaluation
The NRC staff reviewed the licensees hardship and determined the licensees estimation of radiological dose and industrial risk to perform the supplemental examinations, in accordance with IWB-3142.2, during the current outage, was consistent with estimates at other facilities.
The NRC staff finds that the licensees hardship justification meets the provisions of 10 CFR 50.55a(z)(2).
The NRC staff evaluated the level of quality and safety in the licensees proposed alternative in lieu of performing the supplemental examinations in accordance with IWB-3142.2. The NRC staff reviewed photographic evidence of the condition of the lower head at various times during the refueling outage. Follow-up communications with the licensees staff clarified the information in the photographs and location of the as found deposits. Further they assisted in clarifying the extent of the licensees identified a pre flood up visual inspection was completed of the vessel lower head with a qualified VT-2L examiner. While this inspection did not meet the requirements of ASME Code Case N-722-1 as required by 10 CFR 50.55a(g)(6)(ii)(E), the absence of boric acid deposits in examination results and photographic evidence were key factors in the NRC staffs evaluation.
The NRC staff review of the licensees ASME Code Case N-722-1 required examination found the extent of leakage from the cavity seals had masked the subject nozzles and safe end welds from reasonable review and prevented an effective examination. While evaluation and engineering judgement could be used to assume the postulated source of the significant deposits on the lower head, the masking deposits could prevent an examiner from identifying similar deposits to those found at the previous two plants to identify leaking bottom mounted nozzle penetrations. Therefore, the NRC staff notes the significance of the pre-flood-up visual inspection in evaluating the as found condition.
The NRC staff reviewed the additional steps taken by the licensee to evaluate the as found deposits, including chemical analysis, and found the licensees actions provided supporting information to confirm the deposits were from the cavity seal leakage and not a source of significant leakage from the bottom mounted nozzle penetrations or safe end welds. The NRC staff noted the licensees post cleaning examination provided additional confidence that no large active leakage was occurring. The NRC staff also considered the licensees leakage detection capabilities as a defense-in-depth measure to identify leakage prior to the growth of any hypothetically existing cracking to an extent to challenge the structural integrity of either the penetration nozzle, safe end welds or allow significant corrosion of the low alloy steel lower head itself. Finally, the NRC staff considered the proposed bare metal visual examination during the subsequent refueling outage in the pre-flood-up condition to verify no leakage. The NRC staff found the licensees proposed examination timing would address the leaking cavity seals masking effect for future examinations.
The NRC staffs evaluation found the quality and safety of the licensees proposed alternative versus the resultant hardship and value of the supplemental examinations was acceptable based on (1) the licensees analysis of the most probable source of the deposits was acceptable based on a pre-flood-up visual photographs, the light cleaning required for deposit removal, and the results of the chemical analysis from five deposit locations; (2) the licensees visual examinations at normal operating pressure will provide reasonable assurance of no significant active leakage prior to startup; (3) the licensees leak detection capability and action levels will ensure any potential leakage will be identified prior to the point of challenging the structural integrity of the subject locations; and (4) the visual examination prior to reactor cavity flood-up during 2R31 (and each subsequent outage until the cavity seal leakage has been completely corrected) will ensure reactor coolant pressure boundary integrity is maintained.
Therefore, the NRC staff finds that the licensees proposed alternative provides reasonable assurance of the structural integrity of the RPV lower head, subject penetration nozzles and safe end welds for the next operating cycle at Farley, Unit 2, without requiring the licensee to perform supplemental examinations during the current refueling outage.
4.0 CONCLUSION
As set forth above, the NRC staff determined that Alternative Request FNP-ISI-ALT-05-13 as described in the licensees submittal dated April 28, 2025, as supplemented by letter dated April 29, 2025, provides adequate justification that compliance with the applicable ASME BPV Code ISI requirements for the RPV bottom mounted instrument penetrations and instrument connections at Farley, Unit 2, would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Further, the licensees proposed alternative provides reasonable assurance of structural integrity of the RPV lower head, subject penetration nozzles and safe end welds. Accordingly, the NRC staff concludes that the licensee has adequately addressed all regulatory requirements set forth in 10 CFR 50.55a(z)(2).
Therefore, the NRC staff authorizes the use of Alternative Request FNP-ISI-ALT-05-13 (as supplemented) for the proposed extension until completion of the 2R31 refueling outage at Farley, Unit 2, scheduled for fall 2026.
All other requirements of ASME BPV Code and 10 CFR 50.55(a)(g)(6)(ii)(D) for which relief was not specifically requested and authorized by the NRC staff remains applicable, including the third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributors: O. Khan, NRR S. Cumblidge, NRR J. Collins, NRR Date: September 9, 2025
- via eConcurrence NRR-028 OFFICE NRR/DORL/LPL2-1/PM* NRR/DORL/LPL2-1/LA* NRR/DNRL/NPHP/BC NRR/DORL/LPL2-1/BC*
NAME ZTurner KZeleznock MMitchell MMarkley DATE 9/2/2025 9/4/2025 8/29/2025 9/9/2025