ML25350A003
| ML25350A003 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 12/16/2025 |
| From: | Southern Nuclear Company |
| To: | NRC/NRR/DORL/LPL2-1 |
| Turner Z, NRR/DORL/LPL2-1 | |
| References | |
| EPID L-2025-LLA-0100 | |
| Download: ML25350A003 (0) | |
Text
SNC Proposed Alternatives for Containment Unbonded Post-Tensioning System lnservice Inspection Requirements Public Meeting Discussion December 16, 2025
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Southern Nuclear
Meeting Purpose and Agenda The purpose of this meeting is to discuss SNC Proposed Alternatives for Farley CTMT Post-Tensioning System This meeting will cover the following topics:
- Hydrogen Stress Cracking (1985, 2012, and 2017)
- Anchor Heads properties and locations
- Water Presence and location
- Augmented Exams for 2012, 2017, and 2021
- ASME Code Section IWL 2521 Requirements We appreciate your participation and feedback 2'
SNC Alternative for Farley CTMT Post-Tensioning System ASME Code Requirements ASME Boiler and Pressure Vessel Code,Section XI, 2007 Edition with 2008 Addenda
- IWL-2500
- Requires inspections for affected components each Section XI inspection interval
- Affected components: Farley Unit 1 and 2 J
SNC Alternative for Farley CTMT Post-Tensioning S stem Hydrogen Stress Cracking:
What were the causing of events of 1985, 2012, and 2017?
- The cause of the 1985 anchor head failures was attributed to hydrogen stress corrosion cracking. Reference LER 85-005-01 for more details.
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SNC Alternative for Farley CTMT Post-Tensioning S stem Hydrogen Stress Cracking:
What were the causing of events of 1985, 2012, and 2017?
- The cause of 2012 and 2017 anchor head failures were attributed to hydrogen stress corrosion cracking. Specifically, the 2011 and 2017 failures were tied to higher than specified hardness limits which would lend the heads more susceptible to hydrogen stress corrosion cracking when in the presence of moisture.
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SNC Alternative for Farley CTMT Post-Tensioning System
- Discuss the actions taken by SNC to detect widespread degradation beyond sampled components. NRC notes high number of replaced or repaired anchor heads compared to samples inspected.
- SNC has replaced all anchor heads from the lot that was identified as having high hardness. A sampling of other lots was performed with no results of high hardness. SNC performed visual exams on a sampling of anchor heads with a stamp FN to ensure no cracking was present. SNC has additionally inspected the grease in tendons to verify the moisture content. SNC also has installed automatic sump pumps in the tendon access gallery to ensure no standing water is in the area of the tendon access.
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SNC Alternative for Farley CTMT Post-Tensioning System
- Drawing or Diagram for material for anchor heads, unreplaced anchor head with potential high hardness
- Drawing or Diagram for locations with water presence
- Factors contributing to low CPM base numbers and locations
- All anchor heads in lot found with high hardness have been replaced.
- To be provided during presentation as separate file.
- Original P1 or P2 grease, how the samples were previously taken, and from where the sample was taken can affect the numbers.
Historically Samples have been taken from multiple location for tendons to verify the CPM numbers are correct.
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SNC Alternative for Farley CTMT Post-Tensioning S stem Locations affected by high hardness, water, and low CPM base numbers 2017/2019 Replaced anchor heads per SNC1000660 H1 CA, H29CA, H31 CA, H9AB, H15AB, H1BC,H3BC,H5BC,H7BC,H37AB,H13BC,andH15BC Anchor Head De-tensioned H11 BC All replaced anchor heads were from Lot 10114 except H-37 AB 2012 CAR Replacements: Unit 1: H25AC, H27 AC, H30AC, H7 AB(failed), H29AB, H33AB, H35AB, H41 AB, H44AB, H28BC and D322. Unit 2: H5DE, V60, D220, and D231.
THE LOCATIONS ABOVE CAN BE FOUND IN DIFFERENT CAR AND DESIGN WORK ORDERS.
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SNC Alternative for Farley CTMT Post-Tensioning System Tendon Selections in 2012, 2017, and 2021 examinations:
- For each of the exam periods the selections were completed through calculations. The program randomly selects tendons from each group (Hoop, Vertical, or Dome) all tendons that have not previously been inspected, outside of the common tendon, which is required to be selected for each inspection.
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SNC Alternative for Farley CTMT Post-Tensioning System
- Examination Results and resolutions of non-conformances for initial inspection and subsequent inservice inspections for tendons requiring AUG exams Per IWL-2512-2
- Present distribution of replaced or re-tensioned hoop tendon locations and demonstrate whether balanced effects of prestressing tendon system is maintained for structural integrity of the CTMT structure
- To be provided during presentation as separate file.
- To be provided during presentation as separate file.
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SNC Alternative for Farley CTMT Post-Tensioning System
- Present tendon force trends for the replaced/re-tensioned tendons during 2012 and 2017 events UNIT t HOOfl' lENDCttlAUGMENl'iOCltOUP 1 AVERAGE FORCE 1REJ<<)
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What Feedback Do You Have?
Any feedback or Questions
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