CNL-25-060, American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI, Request for Alternative WBN-2-ISI-03
| ML25119A203 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 04/29/2025 |
| From: | Hulvey K Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| CNL-25-060 | |
| Download: ML25119A203 (1) | |
Text
1101 Market Street, Chattanooga, Tennessee 37402 CNL-25-060 April 29, 2025 10 CFR 50.55a ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391
Subject:
Watts Bar Nuclear Plant, Unit 2 - American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI, Request for Alternative WBN-2-ISI-03 Tennessee Valley Authority (TVA) hereby submits, for Nuclear Regulatory Commission (NRC) approval, the following inservice inspection (ISI) alternative request in support of the upcoming Watts Bar Nuclear (WBN), Unit 2 code of record interval. In accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(1), the enclosure to this submittal contains TVA alternative request WBN-2-ISI-03. This proposal requests an alternative to adopt American Society of Mechanical Engineers (ASME) Code Case N-716-3, "Alternative Piping Classification and Examination Requirements," for WBN Unit 2. No regulatory action is needed to adopt Code Case N-716-3 for WBN Unit 1.
WBN Unit 2 is in the first ISI interval. The applicable ASME Boiler and Pressure Vessel Code (BPV)Section XI, Division 1, code of record for the current WBN ISI interval is the 2007 Edition, 2008 Addenda for both units. TVA plans to adopt the 2019 Edition of the ASME BPV Section XI, Division 1, for the WBN Unit 2 upcoming code of record interval.
The current ISI interval for WBN Unit 2 expires on May 26, 2026. The proposed request supports the interval update now in development for WBN Unit 2. Therefore, TVA requests approval of this request no later than August 27, 2025.
There are no new regulatory commitments contained in this letter. Please address any questions regarding this request to Amber V. Aboulfaida, Senior Manager, Fleet Licensing, at avaboulfaida@tva.gov.
Respectfully, Kimberly D. Hulvey General Manager, Nuclear Regulatory Affairs & Emergency Preparedness Enclosure cc: See Page 2 Digitally signed by Edmondson, Carla Date: 2025.04.29 12:43:10
-04'00'
U.S. Nuclear Regulatory Commission CNL-25-060 Page 2 April 29, 2025
Enclosure:
Watts Bar Nuclear Plant Unit 2 American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI, Division 1 Request for Alternative WBN-2-ISI-03 cc:
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant
Enclosure CNL-25-060 E-1 of 3 Watts Bar Nuclear Plant Unit 2 American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI, Division 1 Request for Alternative WBN-2-ISI-03 I.
Proposed Alternative Request In accordance with Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a, Codes and standards, paragraph (z)(1), and the guidance provided in Revision 21 of Regulatory Guide (RG) 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1, Tennessee Valley Authority (TVA) requests Nuclear Regulatory Commission (NRC) approval to adopt Code Case N-716-3, "Alternative Piping Classification and Examination Requirements," for the Watts Bar Nuclear Plant (WBN), Unit 2.
WBN Units 1 and 2 have adopted N-716-1 and plan to adopt N-716-3 for the upcoming code of record interval. Code Case N-716-1 was previously adopted by the NRC in Revision 17 of Regulatory Guide (RG) 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1, with no conditions. However, in Table 2, Conditionally Acceptable Section XI Code Cases, of Revision 21 of RG 1.147, the NRC conditionally adopted Code Case N-716-3 as follows: Code Case N-716-3 is not approved for use by plants issued an operating license or combined license after January 1, 2012.
As noted in Reference 1, WBN Unit 2 received its operating license on October 22, 2015.
However, TVA believes that an NRC approved alternative for WBN Unit 2 to adopt Code Case N-716-3 in accordance with this request is warranted based on the below information.
II. Basis for proposed Alternative Request As noted in the Federal Register notice for the Final Rule adopting Revision 21 of RG 1.147 (Reference 2).
Code Case N-716 provides rules for alternative classification and examination requirements for piping welds and components. Revision 3 to Code Case N-716 would remove the provision for plants issued an operating license after January 1, 2012, to submit the application of this Code Case for regulatory approval. The NRC is cognizant of the committee's desire to eliminate the provision for newly constructed plants to submit first time applications of N-716 to the NRC. It was the Committee's intention to make this Code Case more generally applicable internationally. However, the NRC is of the opinion that the new designs may introduce additional variables, which in the absence of substantial operating experience with these new plants, may introduce uncertainty on the applicability of this Code Case to the new plants. Hence, the NRC has determined there is a need to review the initial proposals for new plants. The review would confirm the absence of new degradation mechanisms, evaluate with available operating experience, as well as the risk-related information for the new plants prior to the initial application of the Code Case to new plants. Therefore, the NRC is proposing a condition that this Code Case is not approved for use by plants issued an operating license or combined license after January 1, 2012. However, plants issued an operating license or combined license after January 1, 2012, may submit an alternative to use this Code Case in accordance with Sec.50.55a(z) for review and approval prior to implementation.
Enclosure CNL-25-060 E-2 of 3 Furthermore, in the Regulatory Analysis of the above Final Rule (Reference 3) NRC stated:
This condition affects two operating plants at one site (Vogtle) and will result in an alternative request, based on the staffs conservative assumption that the licensee will seek to use N-716-3. This Code Case concerns a risk-informed program for piping and components. The staff position is that operating experience is critical in the development of this program; hence, this condition is based on licensing date.
The new condition on N-716-3 would require the submittal of an alternative request to use the Code Case, as previously discussed, for plants licensed after the date in the condition. This condition would apply only to two units at one site (Vogtle Electric Generating Plant). Therefore, the staff conservatively assumed that one licensee would submit an alternative request in 2024 as a result of the condition, with the corresponding costs estimated as shown in Table 4.
The NRC did not take into consideration WBN Unit 2 when issuing the Final Rule adopting Revision 21 of RG 1.147 and the conditions imposed upon Code Case N-716-3.
WBN Unit 2 is of a similar design as WBN Unit 1. As noted in Section 1.1.1 of the WBN dual-unit Final Safety Analysis Report (UFSAR):
Unit 1 received the low power operating license (NPF-20) on November 9, 1995, and the full power operating license (NPF-90) on February 7, 1996. TVA declared commercial operation on May 25, 1996. Unit 2 received a construction permit on January 1, 1973, is a similar design, and was placed in deferred status by letter to NRC dated July 14, 2000.
By letter dated August 3, 2007, TVA notified the NRC of its plans to resume unrestricted construction activities, under the existing construction permit. Unit 2 received the full power operating license (NPF-96) on October 22, 2015.
Therefore, WBN Unit 2 is not a new design and does not introduce additional variables, which in the absence of substantial operating experience with these new plants, may introduce uncertainty on the applicability of this Code Case to the new plants. Therefore, the condition imposed upon Code Case N-716-3 from Revision 21 of RG 1.147 should not be applied to WBN Unit 2. Furthermore, WBN Unit 1 can apply N-716-3 with no regulatory relief needed; thus, it is reasonable that WBN Unit 2 should be able to adopt N-716-3 as both units are of a similar design.
Therefore, TVA is submitting this request for alternative in accordance with 10 CFR 50.55a(z)(1) to allow WBN Unit 2 to unconditionally adopt Code Case N-716-3 in that the proposed alternative would provide an acceptable level of quality and safety.
Enclosure CNL-25-060 E-3 of 3 III.
Duration of Proposed Alternative This alternative request is in support of the upcoming WBN Unit 2 code of record interval, scheduled to commence on March 1, 2026. WBN Unit 1 and 2 will be adopting the 2019 Edition of ASME Section XI, therefore the code of record interval is two consecutive inservice inspection intervals per 10CFR50.55a(y)(2).
IV.
Precedents None V.
References
- 1.
NRC letter to TVA, Issuance of Facility Operating License No. NPF-96, Watts Bar Nuclear Plant Unit 2, dated October 22, 2015 (ML15251A587)
- 2.
Federal Register Notice 89FR58045, Code Case N-716-3 [Supplement 5, 2019 Edition], dated July 17, 2024
- 3.
Regulatory Analysis for the Final Rule: American Society of Mechanical Engineers Code Cases and Update Frequency, dated March 1, 2024 (ML23291A333)