05000259/LER-2022-002-01, High Pressure Coolant Injection System Declared Inoperable Due to a Corroded Actuator
| ML23285A192 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 10/12/2023 |
| From: | Sivaraman M Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| LER 2022-002-01 | |
| Download: ML23285A192 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2592022002R01 - NRC Website | |
text
Post Office Box 2000, Decatur, Alabama 35609-2000 October 12, 2023 10 CFR 50.73 10 CFR 50.4(a)
ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 1 Renewed Facility Operating License No. DPR-33 NRC Docket No. 50-259
Subject:
Licensee Event Report 50-259/2022-002 High Pressure Coolant Injection System Declared Inoperable Due to a Corroded Actuator
Reference:
- 1. Non-Emergency Event Notification 55992 - High Pressure Coolant Injection Inoperable
- 2. TVA letter to NRC, Licensee Event Report 50-259/2022-002 High Pressure Coolant Injection System Declared Inoperable Due to a Corroded Actuator, dated September 12, 2022 (ML22255A227)
In the reference letter, Tennessee Valley Authority (TVA) submitted the subject Licensee Event Report (LER), which provided details of the inoperability of the Browns Ferry Nuclear Plant (BFN), Unit 1, High Pressure Coolant Injection (HPCI) System due to a corroded actuator.
TVA submitted this report in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.73(a)(2)(v)(D), as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. As noted in the referenced letter, TVA planned to supplement this LER to provide additional time to complete the root cause evaluation.
Accordingly, enclosed is a supplement to the subject LER (i.e., LER 50-259/2022-002-01),
which provides additional detail into the causal factors of the event and includes additional corrective actions to prevent recurrence.
U.S. Nuclear Regulatory Commission Page 2 October 12, 2023 There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact David Renn, Site Licensing Manager, at (256) 729-2636.
Respectfully, Manu Sivaraman Site Vice President Enclosure: Licensee Event Report 50-259/2022-002 High Pressure Coolant Injection System Declared Inoperable Due to a Corroded Actuator cc (w/ Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant NRC Project Manager - Browns Ferry Nuclear Plant
Abstract
On July 12, 2022, during a routine surveillance test, the Browns Ferry Nuclear Plant (BFN), Unit 1, high pressure coolant injection (HPCI) turbine control (governor) valve did not open as expected. Upon investigation, it was discovered that the electro-governor remote hydraulic actuator (EGR) had internal corrosion, which resulted in binding of the pilot plunger and associated pilot bushing and a subsequent failure to supply the hydraulic oil needed to open the governor valve.
The resulting inoperability of the single-train HPCI system would have prevented HPCI from fulfilling its safety function to mitigate the consequences of an accident if demanded.
The event was caused by inadequate procedural guidance which led to failing to identify corrosion which led to the valve failure. Additionally, BFNs maintenance strategy was not aligned with industry best practices and was insufficient for making risk-based decisions related to the reliability of the U1 HPCI EGR. The EGR and remote servo were promptly replaced. As corrective actions to prevent recurrence, BFN revised maintenance procedures to include enhanced acceptance criteria (both wording and images) and now requires photographing inspection results. HPCI / Reactor Core Isolation Cooling (RCIC) moisture content limits, action levels and recovery actions were revised to reflect the new recommended levels. The HPCI Auxiliary Lube Oil Pump is now placed in service on a biweekly basis to recoat the EGR internals and provide real-time validation of anticipated governor valve response.
Page 8 of 8 was declared operable following post-maintenance testing approximately 3 days later, on July 15, 2022. The BFN, Unit 1, HPCI system was inoperable for approximately 48 days.
VI.
Corrective Actions
Corrective Actions are being managed by the TVAs corrective action program under CRs 1789217 1827759, and 1829973.
A. Immediate Corrective Actions
The EGR and remote servo were promptly replaced.
B. Corrective Actions to Prevent Recurrence or to reduce the probability of similar events occurring in the future As corrective actions to prevent recurrence, BFN has:
x Revised the section of MPI-0-073-TRB001, High Pressure Coolant Injection (HPCI)
Turbine Preventive Maintenance applicable to the EGR visual inspection. The revised procedure now includes enhanced acceptance criteria (both wording and images) to remove the task performer from knowledge-based performance and ensure that the task will be performed in rule-based performance during future inspections. The new inspection instructions will require CR initiation and photographing the inspection results.
x Revised 0-TI-230L, Lubrication Oil Analysis & Monitoring Program, to include HPCI /
RCIC moisture content limits, action levels and recovery actions to reflect the new recommended moisture limits and CAPR requirements.
x Established a new Preventive Maintenance Activity to place the HPCI Auxiliary Lube Oil Pump in service on a biweekly basis to recoat the EGR internals and provide a real-time validation of anticipated governor valve response.
VII. Previous Similar Events at the Same Site
A search of LERs from BFN, Units 1, 2, and 3 over the last five years identified no similar events.
VIII. Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments.