ML25212A064
| ML25212A064 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 08/11/2025 |
| From: | David Wrona Plant Licensing Branch II |
| To: | Erb D Tennessee Valley Authority |
| Green K | |
| References | |
| EPID L-2025-LLR-0050 | |
| Download: ML25212A064 (1) | |
Text
August 11, 2025 WATTS BAR NUCLEAR PLANT, UNIT 2 - AUTHORIZATION OF ALTERNATIVE REQUEST NO. WBN-2-ISI-03 (EPID L-2025-LLR-0050)
LICENSEE INFORMATION Recipients Name and Address:
Mr. Delson C. Erb Vice President, OPS Support Tennessee Valley Authority 1101 Market Street, LP 4A-C Chattanooga, TN 37402-2801 Licensee:
Tennessee Valley Authority (TVA)
Plant Name and Unit:
Watts Bar Nuclear Plant, Unit 2 Docket No.:
50-391 APPLICATION INFORMATION Submittal Date: April 29, 2025 Submittal Agencywide Documents Access and Management System (ADAMS) Accession No.: ML25119A203 Supplement Date(s): NA Supplement ADAMS Accession No(s).: NA Licensee Proposed Alternative No. or Identifier: WBN-2-ISI-03 Applicable Inservice Inspection (ISI) Program Interval and Interval Start/End Dates: The licensee will use Title 10 of the Code of Federal Regulations (10 CFR) paragraph 50.55a(y)(2) to apply this alternative to two successive ISI intervals. This alternative will therefore apply to the second ISI interval, currently scheduled to commence on March 1, 2026, and the third ISI interval.
Alternative Requested: TVA has requested an alternative to use the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) Case N-716-3, Alternative Classification and Examination Requirements,Section XI, Division 1, under 10 CFR 50.55a(z)(1), Acceptable level of quality and safety.
ISI Requirement: ASME Code Case N-716-3 provides an alternative to the requirements described in the 2019 Edition of ASME Code,Section XI, sections IWB-2420, IWB-2430, Table IWB-2500, Examination Categories B-F and B-J, sections IWC-2420, IWC-2430, and Table IWC-2500 (excluding Examination Categories C-C and C-H), for inservice inspection of Class 1 piping welds and Class 2 components, and sections IWB-2200 and IWC-2200 for preservice inspection of Class 1 piping welds and Class 2 components.
Applicable Code Edition and Addenda: 2019 Edition of ASME Code,Section XI.
Brief Description of the Proposed Alternative: The alternative is to use ASME Code Case N-716-3 to develop a risk-informed (RI) ISI program for the second and third ISI intervals.
For additional details on the licensees request, please refer to the document located at the ADAMS Accession No. ML25119A203 identified above.
REGULATORY EVALUATION Regulatory Basis:
Adherence to Section XI of the ASME Code is mandated by 10 CFR 50.55a(g)(4), which states, in part, that ASME BPV Code Class 1, 2, and 3 components will meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in Section XI of editions and addenda of the ASME BPV Code (or ASME OM Code for snubber examination and testing) that become effective subsequent to editions specified in paragraphs (g)(2) and (3) of this section and that are incorporated by reference in paragraph (a)(1)(ii) or (iv) for snubber examination and testing of this section, to the extent practical within the limitations of design, geometry, and materials of construction of the components.
Paragraph 10 CFR 50.55a(z) states, in part, that alternatives to the requirements of 10 CFR 50.55a(b)-(h) may be used, when authorized by the Director, Office of Nuclear Reactor Regulation, if (1) the proposed alternatives would provide an acceptable level of quality and safety or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The licensee has submitted this request on the basis that a proposed alternative would provide an acceptable level of quality and safety.
TECHNICAL EVALUATION The licensee is proposing to use ASME Code Case N-716-3 to develop an RI-ISI program at Watts Bar, Unit 2. ASME Code Case N-716-3 is conditionally approved for use, with the condition not allowing it to be used to develop RI-ISI programs for plants licensed after January 1, 2012. Watts Bar, Unit 2, received its full power license in 2015.
ASME Code Case N-716-1 was unconditionally approved for use and was added to Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1.
ASME Code Case N-716-1 provided requirements for developing RI-ISI programs for light-water reactors. Earlier RI-ISI programs were developed using analytical methods such as those described in Electric Power Research Institute (EPRI) Topical Report TR-112657, Revision B-A, Revised Risk-Informed Inservice Inspection Evaluation Procedure. These RI-ISI programs were developed using a detailed analysis of every piping segment to determine the consequences of the pipe segment failing. ASME Code Case N-716-1 was developed by looking at the piping segments that were commonly determined to be high safety significant by these analyses by analyzing the results from several boiling-water and pressurized-water reactors. ASME Code Case N-716-1 provided a simplified method of categorizing piping segments to provide similar results as a full analysis using EPRI TR-112657, Revision B-A with much lower effort.
As the requirements in N-716-1 were based on experience with developing and applying RI-ISI programs in the existing fleet, there was no given technical basis to apply these requirements to a new plant with an unknown design. Because of this lack of a technical basis for unknown designs, a provision in the Scope section of ASME Code Case N-716-1 was added to restrict the use of N-716-1 to plants licensed before the approval of the code case in 2012.
ASME Code Case N-716-3 removed the provision that restricted the use of the code case to plants licensed before 2012, but did not provide a basis for the removal of the prevision. The NRC approved the use of ASME Code Case N-716-3 with the condition that the code case could not be used for nuclear power plants licensed before 2012.
While Watts Bar, Unit 2, received its full power license in 2015, Watts Bar, Unit 2, received a construction permit on January 23, 1973, and is a similar design to Watts Bar, Unit 1. The technical concerns that motivated the restrictions in ASME Code Case N-716-1 and the NRC condition on the use of ASME Code Case N-716-3 are, therefore, not applicable to Watts Bar, Unit 2. The NRC staff finds that the use of ASME Code Case N-716-3 to develop an RI-ISI program would provide a similar level of safety for Watts Bar, Unit 2, as for a plant licensed before 2012. The proposed alternative would, therefore, provide reasonable assurance that an RI-ISI program developed with ASME Code Case N-716-3 would discover significant degradation before compromising plant safety.
CONCLUSION The NRC staff has determined that the proposed alternative in the licensees request referenced above would provide an acceptable level of quality and safety.
The NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1).
The NRC staff authorizes the use of proposed alternative WBN-2-ISI-03 at Watts Bar, Unit 2, for the second and third ISI intervals scheduled to commence on March 1, 2026.
All other ASME BPV Code,Section XI requirements for which an alternative was not specifically requested and authorized remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
David Wrona, Chief Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation cc: Listserv DAVID WRONA Digitally signed by DAVID WRONA Date: 2025.08.11 09:46:41 -04'00'
ML25212A064 via eConcurrence NRR-028 OFFICE NRR/DORL/LPLII-2/PM NRR/DORL/LPLII-2/LA NRR/DNRL/NPHP/BC NRR/DORL/LPLII-2/BC NAME KGreen ABaxter MMitchell DWrona DATE 7/31/2025 7/31/2025 7/17/2025 8/11/2025