ML15341A018
| ML15341A018 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 12/16/2015 |
| From: | Mahesh Chawla Plant Licensing Branch III |
| To: | |
| Chawla M | |
| References | |
| CAC MF7001 | |
| Download: ML15341A018 (5) | |
Text
LICENSEE: NEXTERA ENERGY POINT BEACH FACILITY: POINT BEACH NUCLEAR PLANT, UNIT 1
SUBJECT:
SUMMARY
OF NOVEMBER 12, 2015, CLOSED PRE-APPLICATION TELECONFERENCE WITH NEXTERA ENERGY POINT BEACH REGARDING STEAM GENERATORS H* LICENSE AMENDMENT REQUEST (CAC NO.
MF7001)
On November 12, 2015, a closed pre-application teleconference was held between the U.S.
Nuclear Regulatory Commission (NRC) and representatives of NextEra Energy Point Beach.
The purpose of the meeting was to discuss the NRC staff's review of proprietary documents at a Westinghouse facility, related to the H* (pronounced "H star") license amendment request, which the licensee plans to submit in the future. The meeting notice and agenda, dated November 2, 2015, are available in the Agencywide Documents Access and Management System (ADAMS) at Accession No. ML15302A170. The meeting notice was initially issued for both units of Point Beach Nuclear Plant. The licensee clarified later that the amendment will be submitted only for Unit 1. This meeting was noticed as a closed public meeting due to the proprietary nature of the discussions. The licensee did not provide any documents for the teleconference. A list of attendees is provided as Enclosure 1.
The NRC staff had previously read a report at the Westinghouse office in Rockville, MD, that described changes made to the structural and leakage models used to establish the behavior of steam generator (SG) tube-to-tubesheet joints, in preparation for Next Era Energy Point Beach submitting a license amendment request for the H* alternate plugging criteria. The purpose of the teleconference was for the NRC staff to confirm their understanding of changes made to the models and identify potential concerns the NRC staff had in various areas of the report.
The following summarizes the information discussed during the meeting and the accompanying comments and observations that resulted.
- Industry presented a brief summary of the H* technical basis that was previously approved for other plants, and discussed why specific conditions at Point Beach Unit 1 did not allow it to use the same technical basis. Specifically, the H* depth associated with a steam line break accident was greater than the thickness of the tubesheet for about 900 tubes in each steam generator.
- The licensee then discussed changes that were made to the structural and leakage models and how these changes affected the feasibility of applying the H* technical basis to Point Beach Unit 1. The major change to the methodology was the use of a three-dimensional (3D) sub-model rather than a two-dimensional (2D) model for determining the contact pressures between the tube and the tubesheet. The major change to the analysis integrates the 3D model of the lower steam generator complex and the 3D sub-model "couples the slices" used in the 2D model. The 3D sub-model extends the tube above the top of the tubesheet, accounts for the Poisson contraction of
the tubes directly, and uses the displacement analysis results from the lower SG complex, which includes a functional divider plate. These are all changes from the current licensing basis using the 20 model. The licensee indicated that including the functional divider plate in the 30 model H* analysis was conservative whereas it was not conservative in the 20 model (partially because of the assumed conditions in the Point Beach steam line break design basis accident).
- The next outage for Point Beach Unit 1 is scheduled for the spring of 2016. The licensee stated that they expected to submit the H* license amendment request in the spring of 2016, with a planned implementation date in fall of 2017.
The NRC staff provided the following observations to the industry:
- The calculated H* distance was found to be longer when the functional divider plate was included in the 30 model of the lower SG complex , which is a different result from all previous 20 H* analyses. The NRC staff expects any license amendment request (LAR) will explain why taking credit for the divider plate increases the H* distance, and will provide any supporting calculations that confirm the approach and results. We also anticipate any future license amendment will address why the 30 sub-model result is valid, in light of the previous 20 model results.
- The NRC staff noted that the tube-to-tubesheet contact pressures during the steam line break accident analysis were not always higher than the contact pressures during normal operation. This result was only encountered by one other H* plant and will be an area of the LAR that receives scrutiny from the staff.
- The leakage factor proposed in the report reviewed by the NRC staff was not the highest leakage factor result to come from the new analysis. It appears the selection of the proposed value required some judgement. The NRC staff anticipates this portion of the LAR to be an area of focus for the review. Any technical information to support the determination of the leakage factor may assist the staff in its review.
- In the 30 sub model, the tube was extended outside the thickness of the tubesheet. The importance of this assumption was not clear. We would expect any future license amendment will address the importance of this assumption and assumptions about the clearances at any tube support plates (including whether a locked/blocked tube support plate opening has any effect). In addition, the submittal should address where the expansion transition was modeled and how sensitive the results were to this assumption (i.e., was the expansion transition at the top of the tubesheet or one inch below the top of the tubesheet).
- There appear to be some different trends in the contact pressure data between the 20 and 30 sub-model results and in going from normal operating to steam line break conditions. We assume the trends in Tables 4.1 and 4.2 will be explained (the trends going from the 20 to 30 sub-model, from the inside to outside radius of the steam generator, and in going from the normal operating to steam line break conditions).
- If a license amendment request is submitted, we would highly encourage highlighting all differences from what was previously approved. This will allow the NRC staff to focus its review. A clear, definitive statement would be beneficial.
Due to the proprietary nature of the discussions, members of the public were not in attendance.
Public Meeting Feedback forms were offered, but were not requested by any of the attendees.
Please direct any inquiries to me at 301-415-8371, or Mahesh.chawla@nrc.gov.
Mahesh Chawla, Project Manager Plant Licensing Branch 3-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-266
Enclosure:
List of Attendees cc w/encl: Distribution via Listserv
LIST OF ATTENDEES NOVEMBER 12, 2015, MEETING WITH NEXTERA ENERGY POINT BEACH POINT BEACH NUCLEAR PLANT UNIT 1 CLOSED PRE-APPLICATION TELECONFERENCE REGARDING STEAM GENERATORS H* LICENSE AMENDMENT REQUEST NextEra Energy, Inc. Westinghouse William A. Cross Daniel Merkovsky Michael Macleod Gary W Whiteman Edward Kowkowski Hermann 0. Lagally David P. Lytle Nicholas D. Yurko William R. LaMantia Samuel P. Cline Enclosure
- If a license amendment request is submitted, we would highly encourage highlighting all differences from what was previously approved. This will allow the NRC staff to focus its review. A clear, definitive statement would be beneficial.
Due to the proprietary nature of the discussions, members of the public were not in attendance.
Public Meeting Feedback forms were offered, but were not requested by any of the attendees.
Please direct any inquiries to me at 301-415-8371, or Mahesh.chawla@nrc.gov.
IRA/
Mahesh Chawla, Project Manager Plant Licensing Branch 3-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-266
Enclosure:
List of Attendees cc w/encl: Distribution via Listserv DISTRIBUTION:
PUBLIC Branch Reading RidsACRS_MailCTR Resource RidsNrrDorllpl3-1 Resource RidsNrrMChawla Resource RidsNrrMHenderson Resource RidsRgn3MailCenter Resource TWertz, NRR KKarwoski, NRR AJohnson, NRR AObodoako, NRR Janelle Jessie, EDO Region 3 ADAM Accession Nos.: M eetmg Not1ce:
s . ML15302A170 Meetmg s ummary: ML 15341AO 18 OFFICE DORL/LPLlll-1/PM DORL/LPLI 11-1 /LA DE/ESGB/BC DORL/LPLlll-1/BC DORL/LP LI 11-1 /PM NAME MChawla MHenderson (PK/ein for) GKulesa DPelton MChawla DATE 12/09/2015 12/10/2015 12/14/2015 12/16/2015 12/16/2015 OFFICIAL RECORD COPY