L-23-048, Response to Request for Additional Information Regarding Technical Specification 5.6.6 Steam Generator Tube Inspection 180-Day Report
| ML23060A077 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/01/2023 |
| From: | Tony Brown Energy Harbor Nuclear Corp |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-23-048, EPID L-2022-LRO-0115 | |
| Download: ML23060A077 (1) | |
Text
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harbor Terry J. Brown Site Vice President, Davis-Besse Nuclear March 1, 2023 L-23-048 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
SUBJECT:
Davis-Besse Nuclear Power Station, Unit No. 1 Docket No. 50-346, License No. NPF-3 Energy Harbor Nuclear Corp.
Davis-Besse Nuclear Power Station 5501 N. State Route 2 Oak Harbor, Ohio 43449 419-321-7676 Response to Request for Additional Information Regarding Technical Specification 5.6.6 Steam Generator Tube Inspection 180-Day Report (EPID L-2022-LRO-0115)
By letter dated September 29, 2022, (Agencywide Document Access Management System (ADAMS) Accession No. ML22272A497), Energy Harbor Nuclear Corp. submitted a report of steam generator tube inspections performed in accordance with Technical Specification (TS) 5.6.6, "Steam Generator Tube Inspection Report," pursuant to TS 5.5.8, "Steam Generator (SG) Program," for the Davis-Besse Nuclear Power Station, Unit No. 1 (DBNPS).
By electronic mail dated February 1, 2023, the NRC staff issued a request for additional information to complete its review. The Energy Harbor Nuclear Corp. response is attached.
There are no regulatory commitments contained in this submittal. If there are any questions, or if additional information is required, please contact Mr. Phil H. Lashley, Manager - Fleet Licensing, at (330) 696-7208.
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Attachment Request for Additional Information Regarding the DBNPS 180-Day Steam Generator Tube Inspection Report cc:
NRC Region Ill Administrator NRC Resident Inspector NRR Project Manager Utility Radiological Safety Board
Attachment L-23-048 Request for Additional Information Regarding the DBNPS 180-Day Steam Generator Tube Inspection Report Page 1 of 3 By letter dated September 29, 2022, (Agencywide Document Access Management System (ADAMS) Accession No. ML22272A497), Energy Harbor Nuclear Corp.,
submitted a report of steam generator tube inspections performed in accordance with Technical Specification (TS) 5.6.6, "Steam Generator Tube Inspection Report," pursuant to TS 5.5.8, "Steam Generator (SG) Program," for the Davis-Besse Nuclear Power Station, Unit No. 1 (DBNPS).
By electronic mail dated February 1, 2023, the NRC staff issued a request for additional information to complete its review. The Energy Harbor Nuclear Corp. response is presented below.
Request for Additional Information
- 1. Please clarify the number of tubes plugged to date and causes of tube plugging in each SG following refueling outage 22 (1 R22). As shown in the table below, the sum of tubes plugged following 1 R21 (ML20260H057), and tubes reported plugged during 1 R22, did not equal the total number of tubes reported plugged following 1 R22.
Tube pluooing description SG2A SG1B Total 1
Tubes plugged to date following 1 R21 105 69 174 (Section 6 of ML20260H057}
2 Tubes plugged during 1 R22 14 1
15 (Section 5 of ML22272A497) 3 Tubes plugged to date following 1 R22 119 70 189 (based on sum of Row 1 and Row 2, above) 4 Tubes plugged to date following 1 R22 135 82 217 (Section 6 of ML22272A497) 5 Discrepancy in the number of tubes plugged to 16 12 28 date following 1 R22 (Row 4 minus Row 3}
Response
As required by TS 5.6.6.e, "Number of Tubes Plugged During the Inspection Outage for Each Degradation Mechanism," during 1 R22, 15 tubes were plugged for degradation mechanisms and documented in Section 5 of Energy Harbor Nuclear Corp.'s submittal (ML22272A497). In addition to the 15 tubes that were plugged and reported as required per TS 5.6.6.e, an additional 28 tubes were preventatively plugged during 1 R22 due to proximity indications between the lower tubesheet and first tube support plate detected with the bobbin probe. There was no detected pressure boundary degradation associated with these proximity indications. These additional 28 plugs (16 in SG2A and 12 in SG1 B) account for line 5 in the table above.
Attachment L-23-048 Page 2 of 3
- 2. For wear at drilled TSPs listed in the table in Section 4 of the report (page 86 of 89), the values of circumferential extent and percent degraded area (PDA) decreased compared to the 1 R21 inspection report in almost all cases for the five indications included in both reports. This was in despite of the axial extent values increasing in all cases and the maximum depth values increasing or decreasing only slightly. Please explain the reason for the change, if known, such as a change in the flaw sizing methodology or PDA calculation. If there was a change, please describe the change and how it was benchmarked.
Response
For wear at drilled TSPs in the 1 R22 inspection report (ML22272A497) page 86 of 89, the values for the circumferential extent decreased in tubes 2A-36-1, 2A-147-12, 1 B 114, 1 B-38-115, and 1 B-48-123 from the values reported in the 1 R21 inspection report (ML20260H057) page 75 of 78. Also decreasing in value was the PDA in tubes 2A-147-12, 1B-37-114, 1B-38-115, and 1B-48-123.
The depth reported in both the 1 R21 and 1 R22 inspection reports is per the bobbin Electric Power Research Institute ETSS 1-96042.1, Revision 4, while the axial and circumferential extents are sized using the Array ETSS 1-11956.3, Revision 3 and 1-11956.4 Revision 3, each with different sizing uncertainties.
Specific to the array probe techniques utilized for both the 1 R21 and 1 R22 examinations, the resolution of the circumferential measurement is 0.07 inches, or approximately 12.85 degrees. These techniques are for tapered wear and the selection of either end of the indication compounds this resolution uncertainty. To address this uncertainty in both 1 R21 and 1 R22, a uniform sizing was utilized, which conservatively assumed the maximum depth over the entire circumferential extent when calculating PDA. This technique can vary the values reported, but the results remain conservative for these types of structurally insignificant indications.
If the indications were to become structurally significant, an enhanced profile sizing would be performed to undertake "line-by-line" sizing of depth at each data point over the axial and circumferential extent of the indication to more precisely calculate PDA.
This would then be screened against structural and leakage integrity criteria and then further screened for in-situ pressure testing, if necessary.
- 3. Please provide the results of the channel head and installed plug inspections for each SG in 1 R22.
Response
No evidence of channel head degradation or installed plug leakage were observed in either SG 2A or SG 1 B in 1 R22.
Attachment L-23-048 Page 3 of 3
- 4. Please provide the scope and results of any secondary side inspection and maintenance activities performed, if any, in each SG during 1 R22.
Response
There were no secondary side visual examinations or maintenance performed in 1 R22 for SG 2A or SG1 B; however, all bobbin probes were run through a deposit standard to allow for deposit mapping analysis of the entire SG bundle. Additionally, a select group of tubes were inspected full length with the array probe for historical deposit tracking.