ML21095A042
| ML21095A042 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 04/02/2021 |
| From: | Kimberly Green NRC/NRR/DORL/LPL2-2 |
| To: | Wells R Tennessee Valley Authority |
| References | |
| L-2021-LLA-0026 | |
| Download: ML21095A042 (2) | |
Text
From:
Green, Kimberly Sent:
Friday, April 2, 2021 9:25 AM To:
Wells, Russell Douglas
Subject:
Added Clarification to RAI 2 for Thot LAR (EPID L-2021-LLA-0026)
- Russ, Below is the revision to RAI 1b to add temperature, and proposed:
The Westinghouse report, LTR-CDMP-21-4 NP-Attachment, Enclosure 3 to the LAR, states that Changing Thot at any point would affect the calculation of the temperature adjustment factor which would consequently affect the operating interval calculations. The proposed UFSAR revision states, in part, when operating temperature differences exist from cycle-to-cycle, could be interpreted as one temperature adjustment per cycle. Please confirm if this should be interpreted as only one temperature difference will be applied during Cycle 4a (and possibly a second single temperature difference in Cycle 4b). If multiple temperatures are intended within an operating cycle, please discuss if the proposed UFSAR wording should be revised. In addition, please provide any supporting data (e.g., plant or laboratory) for Alloy 600 that provides the effect of temperature cycling on stress corrosion crack growth.
Below is the proposed clarification to draft RAI 2 to acknowledge that subsequent operation can be up to the uprated power level of 3459 MWt:
- 2. The proposed UFSAR Section 5.5.2.4 language states that, This same temperature adjustment methodology will be used to modify the average growth rate used to determine the upper voltage repair limits. The justification for applying the temperature adjustment to the upper voltage repair limit is not clear to the NRC staff. Generic Letter 95-05, Section 2.a.2, Determination of the Upper Voltage Repair Limit for [Tube Support Plate] TSP Intersections, notes that the method for determining the flaw growth allowance is discussed in Section 2.b.2(2) and should be a plant-specific average growth rate or 30 percent per effective full power year, whichever is larger. Section 2.b.2(2) states, in part, that, If both of the two previous inspections employed similar guidelines, the most limiting of the two previous growth rate indications should be used to estimate the voltage growth for the next inspection cycle. In addition, it is not clear to the staff that applying a temperature-reduced growth to the upper voltage repair criteria would be conservative if subsequent plant operation returned to the Cycle 3 occurs above the current reduced power Thot value. Justify why it is appropriate to apply the temperature adjustment to the upper voltage repair limit.
Please let me know if TVA understands the revised wording.
- Thanks, Kim
Hearing Identifier:
NRR_DRMA Email Number:
1102 Mail Envelope Properties (MN2PR09MB573995E3B2A35B381A4B7AB58F7A9)
Subject:
Added Clarification to RAI 2 for Thot LAR (EPID L-2021-LLA-0026)
Sent Date:
4/2/2021 9:25:17 AM Received Date:
4/2/2021 9:25:17 AM From:
Green, Kimberly Created By:
Kimberly.Green@nrc.gov Recipients:
"Wells, Russell Douglas" <rdwells0@tva.gov>
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