ML20125A092
"Draft Meeting" is not in the list (Request, Draft Request, Supplement, Acceptance Review, Meeting, Withholding Request, Withholding Request Acceptance, RAI, Draft RAI, Draft Response to RAI, ...) of allowed values for the "Project stage" property.
| ML20125A092 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 05/04/2020 |
| From: | NRC/NRR/DNRL |
| To: | Technical Specifications Task Force |
| Honcharik M | |
| References | |
| Download: ML20125A092 (8) | |
Text
NRC Staff Comments Draft TSTF-577 Pre-Submittal Review NRR/DNRL/NCSG Public Meeting May 4, 2020
Background:
- The Steam Generator Task Force (SGTF) initially discussed modifying steam generator (SG) Technical Specifications (TS) during February 2019 and June 2019 public meetings
- Public meetings related to draft TSTF-577:
- November 2019
- February 2020 2
Background:
SG TS History
- Original SG TS
- Prescriptive surveillance requirements
- Mill-annealed (MA) Alloy 600 degradation -
inspections beyond TS requirements to maintain tube integrity
- TSTF-449 (2005)
- Performance based TS framework
- Changed regulatory focus to tube integrity
- TSTF-510 (2011)
- Extended inspection periods and eliminated mid-point requirements 3
NRC Staff Perspective
- The existing licensee SG programs and NRC regulatory framework are effective - good operating experience
- No cracking in thermally-treated (TT) Alloy 690 tubing
- Alloy 600TT tubing performance shows improvement compared to Alloy 600MA
-Not clear to NRC staff if cracking susceptibility will be limited to a small percentage of tubes 4
Staff Discussion - Alloy 600TT
- The proposed maximum 72 Effective Full Power Months (EFPM) between inspections:
- Recent cracking in non-high stress Alloy 600TT tubes at two plants Fall 2019 - Top of tube support plate (TSP) (deposits)
Spring 2020 - Upper TSP (dent locations)
- Consistent operating experience or indicative of a larger susceptible population size?
5
Staff Discussion - Alloy 600TT
- The proposed maximum 72 EFPM between inspections:
- Staff needs to improve understanding of how Alloy 600TT operating experience was used to develop the crack initiation/growth technical basis presented in February 24, 2020, SGTF slides
- For example, which cracks were used in the trending and details of flaw comparisons 6
Staff Discussion - Inspection
- The TSTF proposes longer times between inspections for Alloys 600TT and 690TT
- If plants were permitted to go beyond current TS maximum intervals between inspections:
- Robust inspection with advanced probes needed for improved probability of detection
- A requirement for minimum advanced probe inspections in the EPRI Guidelines seems appropriate to NRC staff 7
Staff Comments on Draft TSTF-577 (Pre-submittal Review)
- Higher-level comments in this presentation
- Additional NRC staff comments will be provided in writing to TSTF 8