L-25-757, Response to Request for Additional Information (RAI) for 180-Day Steam Generator Tube Inspection Report
| ML25280A037 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 10/07/2025 |
| From: | Blair B FirstEnergy Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| EPID L-2025-LRO-0026, L-25-757 | |
| Download: ML25280A037 (1) | |
Text
UIfff}JL Beaver Valley Power $tation Barry N. Blair
$ite Vice President P.O. Box 4 200 State Route 3016
$hippingport, PA 15077 724-682-5234 L-25-757 October 7,20?S ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Beaver Valley Power Station, Unit No. 2 Docket No. 50-412, License No. NPF-73 Resrronse.to Bgguest for Additional Information {RAI-} for 180-D.4v Steam Generator Tube l4ispeglion Rerrort
{EPID L2025-LRO-0026)
By letter dated May L,2A?S (Agencywide Documents Access and ManagementSystem (ADAMS) Accession No. ML25121A190), Vistra Operations Company LLC submitted the steam generator tube inspection results obtained during inspections conducted in the fall 2024 refueling outage (2R24) for Beaver Valley Power Station, Unit No. 2 (BvPs2).
By electronic mail dated August 8,2025, the Nuclear Regulatory Commission (NRC) staff iderrtified that additirmal information was required for the staff to complete its review. A response to the RAI is attached.
There are no regulatory commitments contained in this submittal. If there are any questions, or if additional information is required, please contact ]ack Hicks, Seniol Manager, Licensing at (25a) 897'6725 or jack,hicks@vistracorp.com.
Attachment:
Resporlse to Request for Additional Information
\
NRC ltegion I Administrator NRC Resident Inspector NRC Project Manager Director BRP/DEP Site BRP/DEP Representative O:r
Attachment L-25-157 Response to Request for Additional Information Page 1 of 4 By electronic mail dated August 8, 2025, the NRC identified that additional information was required for the staff to complete its review of the 180-Day Steam Generator Tube Inspection Report for Beaver Valley Power Station, Unit No. 2 (BVPS-2). The steam generator (SG) tube inspections were performed during refueling outage 24 (2R24).
The request for additional information (RAI) is provided in bold font, followed by the Vistra Operations Company LLC (Vistra) response.
Question 1:
In the description of the tubes plugged or repaired during 2R24, the table for SG21A (page 15 of 29) lists one tube plugged due to parent tube degradation behind the sleeve nickel band. Appendix B (F* report) of the 90-day reports for 2R24 (ML25307A134) explains that this indication could not be evaluated for a change in the eddy current signal because of insufficient data during the 2R23 sleeve baseline inspection. Please explain why this data insufficiency was not identified during the sleeve baseline inspection. In addition, please discuss the potential effects of this inspection issue on other inservice sleeves.
Response
During the 2R24 inspection, all previously installed Alloy 800 nickel banded mechanical tubesheet sleeves were inspected at the lower joint with the Ghent Version 2 probe. In these inspections, an axial signal was reported in the parent tube ID behind the nickel band at the lower tubesheet joint in SG 21A Tube R31C58. This sleeve was installed at the prior 2R23 outage. As per the disposition protocol for sleeve signals, the 2R23 sleeve baseline inspection data was reviewed to determine whether the signal had exhibited change. It was discovered that in the baseline inspection, the probe did not have a smooth entry into the sleeve, and the probe had snapped through or hangs on the leading edge of the sleeve and skipped the rolled joint. At the location of the axial signal, the baseline data was insufficient to make a reliable comparison to show that the signal had changed or not changed.
Although the axial signal was similar to other confirmed benign signals, the axial signal was conservatively dispositioned as a repairable indication due to the inability to determine signal change from the baseline inspection. Since the tube with the subject indication was dispositioned for flaws and plugged during 2R24, there is no need to perform a line-by-line comparison to the baseline sleeve exam at the location of the axial signal in the parent tube.
In response to this question, the eddy current test (ECT) data from both the baseline sleeve exam from 2R23 (Figure 1) and the most recent sleeve exam from 2R24 (Figure 2) were reviewed to highlight the artifact in the baseline exam that hindered the capability to identify a change in signal between the two exams in this location.
The location of the axial signal detected during 2R24 is identified with an arrow in the ECT graphic (Figure 2).
This is located at the intersection between the nickel band and the Microlok of the sleeve rolled joint. The same location at the tubesheet sleeve lower joint is identified in the Figure 1 graphic with an arrow as well.
The Electric Power Research Institute (EPRI) Pressurized Water Reactor (PWR) SG Examination Guidelines (Reference 3) requires a pre-service inspection of a newly installed sleeve be performed over its full length before the SG is returned to service to ensure that the sleeve installation process was performed as intended. The 2R23 ECT data from the sleeve baseline exam is of sufficient quality to determine that the sleeve was installed properly and no damage was incurred in the process. However, the data is not clear enough in this region between the nickel band and Microlok to perform a line-by-line comparison against future inspections with the intention of identifying any changes in the eddy current signal. The data is sufficient for comparison both above and below the transition region between the bands, but as identified in Figure 1, there is a gap in the line-by-line data most likely because of the probe skipping through the rolled joint as discussed previously. As a means to provide a comprehensive level of documentation of the occurrence and the acceptability of the exam result, a Westinghouse corrective action report has been initiated.
Attachment L-25-157 Page 2 of 4 The eddy current data analysis process is robust, and the subject exam was the only instance in the 2R24 mechanical tubesheet sleeve exam scope where a flaw-like signal was identified in the parent tube behind the sleeve lower joint. Additional reviews of 2R23 tubesheet sleeve baseline exams are not considered to be required since these sleeves have all had a subsequent exam performed during 2R24 as part of the 2R24 base scope inspection program (100% Ghent Version 2 probe of sleeve nickel band region in lower tubesheet sleeve joints).
Information associated with the Alloy 800 sleeve inspections performed using the Ghent / +POINT combo probe at Beaver Valley Unit 2 is documented in site-specific examination technique specification sheets (ETSS). For the tubesheet sleeve lower joint exam, this ETSS is in accordance with approved detection techniques; the Ghent Version 2 probe is used for detection of degradation in the parent tube behind the nickel band (Reference 5) and
+POINT probe is used for detection of degradation in the remainder of sleeve and parent tube as specified in Reference 4. As a means of aiming to prevent reoccurrence of a similar issue in future examinations, a clarification regarding the sleeve lower joint exam is planned to be included in a supplemental training document.
Additional training will be provided to analysts reviewing tubesheet sleeve exam data to ensure data quality is maintained throughout the full extent of the sleeve inspection. Should any data quality concerns be identified, the sleeve will be retested using a new probe head or motor unit. This will provide confidence that beyond the intended purpose of the exam to ensure the sleeve was installed properly, the ECT data throughout the full extent of the sleeve boundary will be reliable for performing line-by-line comparisons to future exam data. This planned action is to improve reliability of future line-by-line comparisons between tubesheet sleeve inservice and baseline ECT exams over the full length of the test extent. It does not suggest that additional exams or reviews were required during 2R24 to satisfy ECT requirements.
Figure 1: 2R23 Baseline Alloy 800 Sleeve Exam at SG-A Tube R31C58
Attachment L-25-157 Page 3 of 4 Figure 2: 2R24 Alloy 0800 Sleeve Exam at SG-A Tube R31C58 Question 2:
In the description of the tubes plugged or repaired during 2R24, the table notes for SG21B (page 16 of 29) state that two tubes were de-plugged and returned to service without sleeving based on no degradation detected. Please explain why the tubes were previously plugged.
Response
During 2R24, a tube recovery program was implemented in SG 21A and SG 21B to return previously plugged tubes to service primarily through means of sleeving. Two of the tubes de-plugged and returned to service in SG 21B were found to contain no detectable degradation that would require sleeve installation from the 2R24 inspection scope. Both tubes were repaired during prior inspections due to volumetric indications reported as SVIs (single volumetric indication) in the STMax eddy current database.
Both SG 21B Row 10 Column 22 (plugged in 2005) and SG 21B Row 15 Column 41 (plugged in 2000) tubes were preventatively repaired due to SVIs detected at the top of tubesheet hot leg side (TSH) by the rotating pancake coil (RPC). These volumetric indications were, at the time of repair, attributed to being most likely the result of manufacturing artifacts (such as OD gouges during tube installation), or prior foreign object wear with the wear-initiating part no longer being present. However, volumetric indications detected by RPC at the top of the tubesheet were targeted for repair upon detection during these inspections.
Both tubes were targeted for de-plugging and tube recovery during 2R24. No degradation was detected during the full-length bobbin exam of these tubes. The 2R24 RPC exam for these tubes at the top of tubesheet location displayed no change in the ECT signals for which the tubes were initially plugged. This provides confidence that the artifact for which the tubes were originally plugged have not exhibited any growth over a substantial period of operation. The prior SVI signals for both tubes were recorded as indications not reportable for the RPC exam result in the 2R24 STMax database. As a result, both tubes were able to be returned to service without further repairs or sleeves being required.
Attachment L-25-157 Page 4 of 4 Question 3:
Please clarify the use of the notes for the tables of tubes plugged or repaired in item 4 of the report (pages 15-16 of 29). For example, the table for SG21B uses Note (4) four times within the table, but only one instance seems to match the text of Note (4) below the table. The tables for SG21A and SG21C have notes below the table, but no numbers referring to those notes within the table.
Response
The notes applicable to each table in this section of the report are used to provide general information regarding the sleeving and plug removal efforts for each table. Because these notes apply to the entire table, no Note numbers are needed within the tables themselves. However, Note (4) was specifically used within table 2RCS-SG21B to try to eliminate potential confusion regarding the summation of total number of plugs and total number of repairs.
For example - per table 2RCS-SG21B, 8 indications required plugging for circumferential ODSCC at TSH and Sludge Pile, 1 indication required plugging for Mixed Mode ODSCC at TSH, and 2 indications required plugging for AVB Wear. The number of indications that required plugging is 11 (8 + 1 + 2). However, the table lists that only 10 tubes were plugged. That is because 1 tube contained both AVB wear and circumferential ODSCC at TSH and Sludge Pile. Thus, plugging 1 tube was able to mitigate both an AVB wear and circumferential ODSCC indication.
Note (4) attempts to explain why that discrepancy exists. The same logic applies to the total column. Therefore, Note (4) was used within the table to indicate the numbers impacted by this clarification note.
References:
- 1. Vistra Letter L-25-072, Beaver Valley Power Station, Unit 2 Docket No. 50-412, License No. NPF-73, 180-Day Steam Generator Tube Inspection Report, May 1, 2025. (ADAMS Accession No. ML25121A190).
- 2. Nuclear Regulatory Commission Request for Additional Information, Beaver Valley, Unit 2 - Steam Generator Tube Inspection Report (Fall 2024 Refueling Outage (2R24)), August 8, 2025.
- 3. Steam Generator Management Program: PWR Steam Generator Examination Guidelines: Revision 8, EPRI, Pal Alto, CA: 2016. 3002007572.
- 4. USNRC Letter, Beaver Valley Power Station Unit No. 2 - Issuance of Amendment RE: The Use of Westinghouse Leak-Limiting Alloy 800 Sleeves for Steam Generator Tubes Repair, September 2009.
(ADAMS Accession No. ML092590189).
- 5. NRC Safety Evaluation Report, Beaver Valley Power Station, Unit No. 2 - Issuance of Amendment 201 RE: Revision of Technical Specifications Related to Steam Generator Tube and Repair Methods (EPID L-2020-LLA-0140), June 2021. (ADAMS Accession No. ML20285A266).