ML24029A174
| ML24029A174 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs, Dresden, Peach Bottom, Nine Mile Point, Byron, Braidwood, Limerick, Ginna, Clinton, Quad Cities, FitzPatrick, LaSalle  |
| Issue date: | 01/30/2024 |
| From: | Constellation Energy Generation |
| To: | Scott Wall NRC/NRR/DORL/LPL3 |
| Wall, SP | |
| References | |
| EPID L-2023-LRM-0111 | |
| Download: ML24029A174 (7) | |
Text
Proposed Alternative to Utilize Code Case N-932, Alternative Requirements for Acceptance of Containment Base Metal Corrosion or Erosion
- January 30, 2024
- Table IWE-2500-1, Examination Category E-A, Containment Surfaces, requires VT-3 examination of 100%
of the Wetted Surfaces of Submerged Areas once per inspection interval.
- For BWRs, this examination requires the use of divers in the torus or suppression pool which comes with significant personnel risk, dose, and cost.
Current ASME XI Requirements (2013 Edition) 1
- VT-3 Acceptance Standards, IWE-3513, require any corrosion or erosion of the torus shell greater than 10% of the nominal wall thickness to be repaired or evaluated.
- Acceptance by Engineering Evaluation, IWE-3122.3, requires successive inspections in accordance with IWE-2420(b) which requires inspection during the next inspection period in accordance with Table IWE-2500-1, Examination Category E-C.
Current ASME XI Requirements (2013 Edition) 2
- Table IWE-2500-1, Examination Category E-C, Containment Surfaces Requiring Augmented Examination, requires VT-1 examination of identified surfaces each inspection period until the areas of degradation remain essentially unchanged.
- Examination of wetted surfaces often identifies limited areas of corrosion exceeding 10% nominal wall thickness.
These areas are evaluated for structural integrity and recoated to prevent further wall loss.
- Reexamination of these limited areas also requires the use of divers and comes with the same personnel risk, dose, and cost.
- ASME XI Code Case N-932, allows for an alternative acceptance of areas with corrosion exceeding 10%
nominal wall thickness without the need for augmented examinations in future outages.
Current ASME XI Requirements (2013 Edition) 3
- Code Case N-932 (Record 21-1713) was approved by ASME in June of 2023.
Approved by Working Group Containment and Subgroup Water Cooled Systems with no negatives.
Approved by Section XI Standards Committee with only 1 negative, NRC voted in favor of the action.
- Code Case N-932 was published in Code Cases: Nuclear Components, 2023 Supplement 1 ASME Section XI Code Case N-932 4
- Provides an analytical option to demonstrate structural integrity of the torus shell or suppression pool liner with corrosion greater than 10% nominal wall thickness
- Requires the Owner to demonstrate continued structural integrity, with margin, until the next required inspection
- Avoids the risks, dose, and cost associated with diving in the torus or suppression pool to visually inspect a limited number of areas
- The approach in Code Case N-932 is consistent with previously approved versions of ASME XI which allowed for Owner established limits.
From 2001 Edition/2003 Addenda Benefits of Proposed Alternative based on Code Case N-932 5
- Submit Constellation Fleet Relief Request to Utilize Code Case N-932
- Submit one Relief Request for Constellation stations most in need of the alternative
- Submit Relief Requests separately for each Constellation station in need of the alternative
- Any issues or concerns with technical approach of Code Case N-932
- Any issues with duration of proposed acceptance by Code Case N-932 Allow for entire interval?
Allow for limited time until diving is required for other programs or commitments?
Options for Proposed Alternative 6
Feedback, Questions, Concerns?