ML23060A478
| ML23060A478 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 03/01/2023 |
| From: | Sivaraman M Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| Download: ML23060A478 (1) | |
Text
Post Office Box 2000, Decatur, Alabama 35609-2000 March 1, 2023 10 CFR 50.4 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 3 Renewed Facility Operating License No. DPR-68 NRC Docket No. 50-296
Subject:
Boiling Water Reactor Vessel Internals Project (BWRVIP) - Notification of Deviation from BWRVIP-41, Revision 4-A, BWR Jet Pump Assembly Inspection and Flaw Evaluation Guidelines
Reference:
Letter from Boiling Water Reactor Vessel and Internals Project (BWRVIP) to the Nuclear Regulatory Commission dated October 30, 1997, BWRVIP Utility Commitments to the BWRVIP The Tennessee Valley Authority (TVA) is providing notification that the Browns Ferry Nuclear Plant (BFN) Unit 3 will not fully implement the subject guidance of BWRVIP-41, Revision 4-A, BWR Jet Pump Assembly Inspection and Flaw Evaluation Guidelines. In accordance with a prior agreement with the NRC and BWR utilities that are part of the Boiling Water Reactor Vessel and Internals Project (BWRVIP), participating licensees are required to provide timely notification to the NRC of a decision, by the licensee, to not fully implement the applicable BWRVIP product.
A deviation disposition (DD) has been prepared, reviewed, and approved in accordance with BWRVIP-94NP, Revision 4, BWR Vessel and Internals Project Program Implementation Guide, and TVA internal procedures. This DD provides assurance that there are no safety implications or reliability concerns with the deviation.
The BFN Unit 3 deviation concerns one item. BFN Unit 3 is not meeting the requirement for an EVT-1 visual examination of the riser brace to yoke welds (Welds RB-2a, b, c, d) for Jet Pumps 5/6 stipulated by BWRVIP-41, Revision 4-A, in Section 3.2.6, Table 3-1. During the In-Vessel Visual Inspection of Unit 3 performed in 1992 in preparation for restart, crack indications were identified at the two attachment welds of the riser brace to the riser pipe (RS-8 and RS-9) adjacent to Jet Pump Number 5 at reactor vessel 90° azimuth. A solution was required to provide for a method of securing the riser pipe to the existing riser brace. The solution decided upon was to design and install a positive locking mechanism (repair clamp) between the riser brace yoke and the riser pipe to capture the riser brace and perform the function of the deficient
U.S. Nuclear Regulatory Commission Page 2 March 1, 2023 weld attachment. The repair clamp was also designed so as to allow future inspections of the existing cracks. (NOTE: The repair clamp was installed prior to Unit 3 Restart in November 1995, which was roughly two years before the initial issue of BWRVIP-41 in October 1997.) However, it was discovered during the initial baseline inspection (Unit 3 Refueling Outage 8 (U3R8) in Fall 1998) of this jet pump assembly that the repair clamp obstructed inspection of the riser brace to yoke (RB-2) welds.
The RB-2 welds are categorized as a medium priority location. A baseline inspection of the RB-2 welds has been conducted (excluding the four welds in question) for all three units at BFN, and no indications have been observed at this location. For BFN Unit 3, since R07 in March of 1997, a total of sixty two subsequent EVT-1 RB-2 examinations have been performed on neighboring Jet Pumps with no relevant indications reported. Through that same time period the riser brace clamp has also been examined 8 times with no signs of degradation observed.
Moreover, The BWR Vessel Internals program continually evaluates industry-wide examination results from required inspection guidance, and as a result has relaxed the examination frequency of the RB-2 welds by half as documented in the release of BWRVIP-41, Revision 4-A.
This guidance document now allows for a maximum of 48 years (24 years previously) between examinations of a particular RB-2 weld, thus further indicating that little probability of failure concerning this component exists within the BWR community. Also of note is the data compiled in BWRVIP-266, Technical Bases for Revision of the BWRVIP-41 Jet Pump Inspection Program, which lists 1160 confirmed RB-2 exams performed throughout the industry with zero flaws recorded. This provides a reasonable level of assurance that the RB-2 welds associated with Jet Pumps 5/6 are intact. Therefore, BFN will permanently defer the RB-2a, b, c, d weld examinations for Unit 3 Jet Pumps 5/6 ONLY. The vendor-recommended inspection will continue to be performed every other refueling outage to ensure that the repair clamp is performing its function as designed. This inspection will provide us with information as to whether any signs of increased flow-induced vibration are present, which would be indicative of failure of the RB-2 welds.
The next scheduled inspection to ensure that the repair clamps functional integrity is satisfactory will be performed during Unit 3 Refueling Outage 22 (U3R22) in 2026 and each 2 cycle period after that. These examinations will continue to serve as Best Effort interrogations of the RB-2 welds in lieu of the BWRVIP-41 mandated inspections for this location.
This deviation is considered permanent and will remain in effect throughout the life of the plant.
This notification is being transmitted for information only. TVA is not requesting any specific action from the NRC.
U.S. Nuclear Regulatory Commission Page 3 March 1, 2023 There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact Christopher L. Vaughn, Nuclear Site Licensing Manager, at (256) 729-2636.
Respectfully, Manu Sivaraman BFN Site Vice President cc:
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant M
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