W3F1-2024-0041, Reply to a Notice of Violation, EA-24-052
| ML24263A158 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 09/19/2024 |
| From: | Sullivan J Entergy Operations |
| To: | Office of Nuclear Reactor Regulation, NRC Region 4, Document Control Desk |
| References | |
| W3F1-2024-0041, EA-24-052, IR 2024013 | |
| Download: ML24263A158 (1) | |
Text
- } entergy W3F1-2024-0041 September 19, 2024 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Reply to a Notice of Violation, EA-24-052 Waterford Steam Electric Station, Unit 3 Docket No. 50-382 Renewed Facility Operating License No. NPF-38
Reference:
NRC letter to Entergy, "Waterford Steam Electric Station, Unit 3 -
Joseph C. Sullivan Site Vice President Waterford Steam Electric Station. Unit 3 504-739-6660 10 CFR 2.201 Notice Of Violation; NRC Inspection Report 05000382/2024013" (ADAMS Accession No. ML24228A261), dated August 20, 2024 In accordance with 1 O CFR 2.201, Entergy Operations, Inc. (Entergy) hereby submits the Reply to a Notice of Violation, EA-24-052, for Waterford Steam Electric Station, Unit 3 (Waterford 3).
As requested, the Enclosure contains the following:
- 1. The reason for the violation
- 2. The corrective steps that have been taken and the results achieved
- 3. The corrective steps that will be taken
- 4. The date when full compliance will be achieved In addition to the required reply, as requested in the referenced letter, the Enclosure contains the following :
- 1. Entergy's determination as to the cause(s) of the ongoing tube wear mechanism in the replacement steam generators
- 2. A summary of corrective actions taken or planned to address these causes
- 3. Entergy's basis for determining the length of the interval before the next steam generator tube inspection is scheduled
- 4. Actions taken or planned to ensure the technical basis for current or future operational assessments is technically sound There are no new commitments contained in this submittal.
W3F 1-2024-0041 Page 2 of 2 If there are any questions concerning this letter, or additional information is required, please contact John Twarog at 504-739-6747.
Respectfully, Joseph C. Sullivan JCS/jac
Enclosure:
Reply to a Notice of Violation; EA-24-052 cc: NRC Region IV Regional Administrator NRC Senior Resident Inspector -Waterford Steam Electric Station Unit 3 NRC Project Manager Louisiana Department of Environmental Quality R4Enforcement@nrc.gov
Enclosure W3F1 2024-0041 Reply to a Notice of Violation; EA-24-052
W3F 1-2024-0041 Enclosure Page 1 of 4 Entergy Operations, Inc.
Reply to a Notice of Violation, EA-24-052 In the U.S. Nuclear Regulatory Commission (NRG) letter to Entergy Operations, Inc. (Entergy),
"Waterford Steam Electric Station, Unit 3 - Notice of Violation; NRG Inspection Report 05000382/2024013," (ADAMS Accession No. ML24228A261), dated August 20, 2024, the NRG issued a Notice of Violation to Entergy's Waterford Steam Electric Station, Unit 3 (Waterford 3) as restated below:
During an NRG inspection conducted from February 1 through August 9, 2024, a violation of NRG requirements was identified. In accordance with the NRG Enforcement Policy, the violation is listed below:
Technical Specification 6. 5. 9.b. 1 requires, in part, that all in-service steam generator tubes shall retain structural integrity over the full range of normal operating conditions, all anticipated transients included in the design specification, and design basis accidents by retaining a safety factor of 3. 0 against burst under normal steady state full power operation primary to secondary pressure differential.
Contrary to the above, on November 5, 2023, the licensee failed to ensure that all in-service steam generator tubes retained structural integrity over the full range of normal operating conditions, all anticipated transients included in the design specification, and design basis accidents by retaining a safety factor of 3. 0 against burst under normal steady state full power operation primary to secondary pressure differential. Specifically, in steam generator 31, tubes R1 C4 and R2 G35 failed to retain a safety factor of 3.0 against burst under normal steady state full power operation primary to secondary pressure differential.
During in-situ testing, both tubes failed to meet the 5500-psi pressure test 2-minute hold period.
This violation is associated with a Green Significance Determination Process finding.
Pursuant to the provisions of 1 O CFR 2.201, this enclosure provides Entergy's Reply to a Notice of Violation.
W3F 1-2024-0041 Enclosure Page 2 of 4 Reply to a Notice of Violation
- 1. The reason for the violation:
The steam generator (SG) tubes failed to retain structural integrity over the full range of normal operating conditions, all anticipated transients included in the design specification, and design basis accidents due to the operational assessment (OA) prepared in February 2022 not adequately predicting the tube wear through the end of operating cycle 25 (Fall 2023). The OA allowed an operating interval longer than appropriate to maintain tube integrity.
- 2. The corrective steps that have been taken and the results achieved:
To address the identified condition, the following actions have been taken:
Plugging and Stabilization:
o The tubes that failed structural integrity were plugged and stabilized before the plant returned to power.
Independent Third-Party Assessments:
o An independent third-party operational assessment for operating cycles 21 through 25 was conducted using historical data from Refueling Outage (RF) 21 and previous inspection outages as part of the causal investigation.
o An independent third-party operational assessment was performed using RF25 data to validate the acceptable operating interval between inspections that was determined by the inspection vendor's OA. Both OAs were reviewed in accordance with the Electric Power Research Institute (EPRI) Steam Generator Management Program (SGMP) guidelines and under an owner's acceptance review.
Procedure Reviews:
o Procedure reviews were completed to identify any needed revisions to incorporate the findings of the potential non-conservative factors identified during the causal analysis.
There were no immediate changes required as the EPRI SGMP, referenced by site procedures, discusses the non-conservative assumptions identified during the Adverse Condition Analysis (ACA). However, enhancements to the Steam Generator Assessment procedure were identified to incorporate Operating Experience (OE) learned from this event. These enhancements will be processed with the OEM wear depth error OE.
Changes expected to be incorporated by November 21, 2024 under Corrective Action (CA) process.
Industry Sharing:
o This operating experience was shared with the industry through EPRI SGMP meetings.
o The information was also shared with executives at the EPRI Nuclear Power Council meetings.
- 3. The corrective steps that will be taken:
Planned corrective actions include having an independent operational assessment completed following the next SG inspections and determining whether third party OAs are necessary for
W3F 1-2024-0041 Enclosure Page 3 of 4 future inspections. In addition, Entergy is reviewing the original equipment manufacturer's (OEM) evaluation of a flaw sizing discrepancy communicated to Entergy in June 2024. This evaluation will be incorporated into the causal analysis and, if necessary, additional corrective actions will be issued to ensure sizing errors are identified by Entergy's oversight process during SG inspections. Entergy is also part of the industry group that has been formed to review the SGMP Integrity Assessment Guidelines to determine if additional guidance regarding performance or review of OAs needs to be developed and implemented.
- 4. The date when full compliance will be achieved:
Full compliance was achieved on November 11, 2023 once the SG tubes that exceeded the structural integrity criteria were plugged.
Additional Requested Information In addition to the required reply, as requested in the NRC's letter, the following information is provided:
- 1. Entergy's determination as to the cause(s) of the ongoing tube wear mechanism in the replacement steam generators:
Steam Generator tube-to-tube-support plate wear is a known and expected wear mechanism and is monitored through eddy current inspections and evaluated in the OA. The tube-to-tube support plate wear within the low row tubes is occurring at a higher rate than other tube locations due to local high velocity flow conditions and the level of support provided to the tubes by the tube support plates. This wear mechanism was acknowledged by the OEM. Data retrieved during RF25 indicates that the wear rates are attenuating and the Tube Support Plates (TSP) wear rates over time are similar to typical observed TSP wear.
- 2. A summary of any corrective actions taken or planned to address these causes:
While actions have been identified to address the OA not accurately predicting wear, no corrective actions are planned to address the direct cause of the tube-to-tube support plate wear itself at this time. Monitoring and evaluation of tube wear, as well as tube repairs, will continue to be conducted in accordance with Waterford 3 Technical Specifications 6.5.9 "Steam Generator (SG) Program," the EPRI Steam Generator Guidelines, and Entergy procedures.
- 3.
Entergy's basis for determining the length of the interval before the next steam generator tube inspection is scheduled:
Two independent OAs from two separate vendors were performed utilizing RF25 eddy current results, operating history and previous steam generator inspection results. In addition to EPRI guideline requirements, the potential non-conservatives identified during the cause analysis (sub-population of wear in rows 1-3, bobbin under sizing, and tapered vs. flat wear morphology) were considered and incorporated as appropriate into both OAs. Both OAs provided reasonable assurance that performance criteria will be met over the next two operating cycles (26-27).
W3F 1-2024-0041 Enclosure Page 4 of 4 The OEM is currently investigating under sizing of flaws detected in RF21 and the impact this had on the 2022 OA that allowed for four (4) cycles of operation between steam generator inspections. A similar sizing discrepancy in RF21 was identified by both vendors who independently completed the post-RF25 OAs described above. Sizing corrections were used in these OAS.
Preliminary feedback from the OEM regarding the RF21 revised OA and failed in-situ pressure testing includes the following:
The sizing error is the main cause of the under sizing of flaws that failed in-situ pressure testing during the RF25 outage.
With the corrected TSP wear sizing values, the wear patterns were predictable utilizing EPRl's SG Integrity Assessment Guidelines, Rev.5. A 4-cycle operational interval would not have been permitted based on these findings. While the deposit loading is still considered to be a contributor to wear, it is not the main contributor, and the wear remains predictable by analysis utilizing EPRl's SG Integrity Assessment Guidelines.
Entergy expects to receive a summary of the overall findings from the OEM by September 30, 2024.
Entergy is currently considering a two operating cycle interval before the next SG tube inspection based on the close agreement in results of the independently performed OAs and also on the knowledge that the suspected under sizing occurred in RF21. A final decision on the length of the next inspection interval will not be made until after the OEM completes its review of the RF25 data and provides a recommendation for inspection frequency, which is expected to be completed by the second week of October 2024.
- 4. Actions taken or planned to ensure the technical basis for current or future operational assessments is technically sound:
An independent third party operational assessment was obtained for the RF25 OA. This was completed in order to validate the results of the inspection vendor's OA. Entergy participation in the scheduled EPRI Integrity Assessment training in February 2025 is planned to allow steam generator program personnel to obtain more knowledge on OA preparation and review. Steam generator program procedures were reviewed. Enhancements to the Steam Generator Assessment procedure were identified to include additional guidance when reviewing OAs, specifically addressing the potential non-conservative assumptions, and will include any necessary discussion derived from OEM report regarding wear depth error. Changes will be incorporated after review of OEM wear depth error report is received. Incorporation is expected by November 21, 2024.