ML20345A352
| ML20345A352 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/10/2020 |
| From: | NRC |
| To: | NRC/NRR/DNRL |
| References | |
| Download: ML20345A352 (16) | |
Text
From:
Gleaves, Billy Sent:
Thursday, December 10, 2020 7:03 AM To:
Vogtle PEmails Cc:
Schiller, Alina
Subject:
FW: Slides for Presubmittal Meeting Tomorrow Attachments:
VEGP 34 Code Alternative for Weldolets - Presentation for Dec 10 Pre-Submittal Meeting.pdf This email is being sent to ADAMS for public release of the 12.10.2020 meeting. This was received the night before at 6:19pm EST.
Billy William (Billy) Gleaves Senior Project Manager NRR/Vogtle Project Office US Nuclear Regulatory Commission The contents of this message may be sensitive. If this message has been received in error, please delete it without reading it. Your receipt of this message is not intended to waive any applicable privilege. Do not disseminate this message without the permission of the author. Communications by this author do not represent NRC policy and are not binding on the Commission.
From: Leighty, Steven <sleighty@southernco.COM>
Sent: Wednesday, December 9, 2020 6:19 PM To: Gleaves, Billy <Bill.Gleaves@nrc.gov>; Schiller, Alina <Alina.Schiller@nrc.gov>
Cc: Roberts, Kelli Anne <KROBERTS@southernco.com>; Chapman, Nathan B.
<NBCHAPMA@SOUTHERNCO.COM>; Arafeh, Yasmeen N. <YNARAFEH@southernco.com>
Subject:
[External_Sender] Slides for Presubmittal Meeting Tomorrow Billy/Alina, Attached are slides we put together to aid in the presubmittal meeting tomorrow morning. The slides are non-proprietary. The intent of these slides is to help address the feedback the staff has provided ahead of the meeting tomorrow.
We appreciate all the feedback we have received from the staff so far and look forward to our discussion tomorrow morning.
- Thanks, Steve Leighty l Southern Nuclear Licensing Supervisor l Vogtle 3&4 706.848.6790 l sleighty@southernco.com
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DM6PR09MB5880.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 1624 12/10/2020 7:03:06 AM VEGP 34 Code Alternative for Weldolets - Presentation for Dec 10 Pre-Submittal Meeting.pdf 332066 Options Priority:
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December 10, 2020 Alternative Request to ASME Section XI Code Examination Requirements for Weldolets Pre-submittal Meeting Plant Vogtle Units 3&4
2 Background
- Challenges have been identified with volumetric Section XI examination requirements for Weldolet ASME Class 1 Branch Connections in the Reactor Coolant System (RCS) Pressure Boundary
- Four applicable weldolets total [two in each Unit (3&4)]
- Located on branch connection lines within Automatic Depressurization System (ADS) Stage 1 piping
- Examination Volume not achievable for subject weldolets due to the geometry of the welds
- Challenges with these configurations are typical, and are frequently captured in relief requests
3 Reason for Request
- NPS >= 4, 100 percent surface and volumetric examinations for branch connection welds (B9.31)
- NPS < 4, Surface examinations only
- ASME Code Class 1, 2, and 3 components must be designed for inspectability
- The proposed best effort examinations, along with a flaw tolerance evaluation conducted showing acceptable structural integrity margin for the weldolet to pipe location, meets the intent of the code requirements
4 Proposed Alternative
- Best Effort Volumetric Examination
- Conducted to the maximum extent practical
- Single-side PDI-UT-2 examinations were performed
>> Maximum axial coverages of 72.9% and circumferential coverages of 55.4%
were achieved for each of the two Unit 3 weldolets
- Surface Examination
- Coverage of 100% was achieved using a liquid penetrant method
- Acceptance Criteria
- No indications that exceed the acceptance criteria were recorded
- In accordance with IWB-3000 for Class 1 systems
5 PDI-UT-2 Examination Coverage The following figures display the extent of coverage obtained during the PDI-UT-2 examinations
6 PDI-UT-2 Examination Coverage
7 PDI-UT-2 Examination Coverage
8 PDI-UT-2 Examination Coverage
9 PDI-UT-2 Examination Coverage
10 October Pre-Submittal Meeting
- Pre-submittal Meeting was held on October 15, 2020
- NRC Staff Provided Feedback on the Alternative Draft
- Review ALT-06 scope
- Reference precedents
- Include details of exams performed
- Minor editorial suggestions
11 Additional Information Flaw Tolerance Evaluation
- Conducted by Westinghouse
- Similar to evaluation conducted for code alternative request ALT-06 (ML1908A143)
- Demonstrates postulated flaws will not grow to maximum end-of-evaluation flaw size for 60-year design life of the plant
- Acceptable structural integrity margin for the weldolet to pipe location
12 Additional Information Flaw Tolerance Evaluation
- Guidance per 2007/2008 ASME Section XI Appendix C-5000
- Stainless steel material, weld process is GTAW
- AP1000 Plant-specific, location specific geometry, loadings, operating conditions, and transients and cycles were used
- Levels A, B, test, C, D conditions were considered
- Section II material properties
- Axial and circumferential inside flaw were postulated in the missed coverage, bounds embedded and outside surface flaws.
- Maximum allowable end-of-evaluation period flaw sizes
- Highly Flaw tolerant
- Axial Flaw Depth = 71% of the wall thickness is acceptable
- Circumferential flaw depth = 75% of the wall thickness is acceptable
13 Flaw Tolerance
- Fatigue Crack Growth Amount per ALT-06 (1% growth, design life)
- Design transient, cycles, loading combinations are same because weldolet and pipe weld location in ALT-06 are on the same piping lines
- Difference in the wall thickness between weldolet and ALT-06 location
- Note that the cumulative usage factor at the ALT-06 pipe location was
>0.8, while the weldolet location the CUF is less than 0.04.
- Therefore, the range in stresses and fatigue crack will be much less at the weldolet
- Initial Axial and circumferential flaw of 33% of the wall thickness
- Final flaw size after 60 years = 34% of the wall thickness
14 Summary
- 100% Volumetric Section XI Examination Requirements of Subject Weldolets is Not Achievable
- SNC Requests Alternative to ASME Section XI Requirements
- Best effort volumetric examinations
- Surface examinations
- Flaw Tolerance Evaluation Conducted by Westinghouse
- Precedent for Approval in Industry