05000412/LER-2025-001, Automatic Reactor Trip and Automatic Actuation of the Auxiliary Feedwater System Due to Loose Feedback Linkage on Feedwater Regulating Valve
| ML25092A162 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 04/01/2025 |
| From: | Blair B Vistra Operations Company |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-25-075 LER 2025-001-00 | |
| Download: ML25092A162 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B)(1) 10 CFR 50.73(a)(2)(iv)(B)(6) |
| 4122025001R00 - NRC Website | |
text
L-25-075 April 1, 2025 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 LER 2025-001-00 Beaver Valley Power Station Barry N. Blair Site Vice President P.O. Box4 Shippingport, PA 15077 10CFR50.73 Enclosed is Licensee Event Report (LER) 2025-001-00, "Unit 2 Automatic Reactor Trip and Automatic Actuation of the Auxiliary Feedwater System due to Loose Feedback Linkage on Feedwater Regulating Valve." This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A).
There are no regulatory commitments contained in this submittal. If there are any questions or if additional information is required, please contact Ms. Hope Gilliam, Manager, Regulatory Compliance, at 724-682-4224.
Barry N. Blair Enclosure: Beaver Valley Power Station, Unit No. 2 LER 2025-001-00 cc:
NRC Region I Administrator NRC Senior Resident Inspector NRC Project Manager INPO Records Center (via INPO Industry Reporting and Information System) BRP /DEP 555 5,1: RA DR VE RVIN6 T£:
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Enclosure L-25-075 Beaver Valley Power Station, Unit No. 2 LER 2025-001-00 6555 SIERRA DRIVE IRVING. TEXAS 75039 o 214-812-4600 VISTRACORP.COM
Abstract
At 1002 on February 5, 2025, with Unit 2 in Mode 1 at 100 percent power, the reactor automatically tripped due to low-low level in the "B" steam generator. The "B" steam generator experienced a level transient when the main feedwater regulating valve went closed while displaying a position of 62 percent. This was due to the positioner feedback linkage coming loose, preventing the positioner from receiving feedback on the valve position. Corrective actions include applying thread locker on the coupling screw, tightening the linkage and a future upgraded feedback lever arm.
This is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in automatic actuation of the Reactor Protection System per 10 CFR 50.73(a)(2)(iv)(B)(1) and an automatic actuation of the Auxiliary Feedwater System per 10 CFR 50.73(a)(2)(iv)(B)(6).
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NARRATIVE Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
DESCRIPTION OF EVENT
At 1002 on February 5, 2025, with Beaver Valley Power Station, Unit No. 2 (BVPS-2) in Mode 1 at 100 percent power, operators took the B main feedwater regulating valve (MFRV) 2FWS-FCV488 [SJ-FCV] to manual control as part of routine maintenance to calibrate the main steam flow loop [SB]. Immediately after taking the valve to manual control, the operator observed from the level indicator that the level in the steam generator [SG] began to rise quickly. The operator in control of the valve began to lower demand. The flow rate had a sharp drop and the steam generator level rapidly lowered. BVPS-2 automatically tripped due to low-low level in the "B" Steam Generator and the Auxiliary Feedwater System [BA] automatically started in response to the trip. Initial investigation found that the valve positioner digital display indicated the position was at 62 percent when the valve was in the full closed position. Further inspections found the screw holding the feedback lever arm to the magnet assembly had backed out and the positioner was not getting any feedback. There was no equipment inoperable at the start of the event that contributed to the event.
CAUSE OF EVENT
The direct cause was determined to be the feedback to the positioner was lost when the lever arm coupling screw backed out due to an inadequate design. A contributing cause was the industry operating experience evaluation was not robust enough to address potential future changing conditions of the valve. An additional contributing cause was not verifying the tightness of the feedback arm screw while performing maintenance on the valve.
ANALYSIS OF EVENT
This is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in automatic actuation of the Reactor Protection System per 10 CFR 50.73(a)(2)(iv)(B)(1) and an automatic actuation of the Auxiliary Feedwater System per 10 CFR 50.73(a)(2)(iv)(B)(6). The actuation of the Auxiliary Feedwater System is an expected response and therefore not a complicated trip of BVPS-2.
The plant risk associated with the BVPS-2 failure of the main feedwater regulating valve and subsequent reactor trip is considered to be very low. This is based on the change in average core damage frequency and average large early release frequency. Therefore, this event had very low safety significance.
CORRECTIVE ACTIONS
Completed Actions:
The valve positioner feedback lever arm was reattached with the use of thread locker on the coupling screw. The positioner was recalibrated and diagnostic testing was performed satisfactorily. As an extent of condition, the other two main feedwater regulating valves had the lever arm screw backed out to apply thread locker and retightened. The other four positioners of the same type installed in the plant were inspected and verified to have an upgraded design and were visually inspected to be tight.
Planned Actions:
- 1. Upgrade the feedback lever arm on all three main feedwater regulating valves and apply thread locker to the screws.
- 2. Apply thread locker to all the lever arm screws on the four similar positioners installed in the plant.
- 3. Review all air operated valve procedures to ensure explicit steps to check tightness of feedback arm.
PREVIOUS SIMILAR EVENTS
A review of the previous three years identified one similar LER.
LER-2024-004: on May 19, 2024, during startup from the 29th refueling outage (1R29) with Beaver Valley Power Station, Unit No. 1 (BVPS-1) at approximately 14 percent reactor power, operators initiated a manual reactor trip on low steam generator (SG) water level after multiple attempts to establish control of the "A" SG water level. The cause was excessive air leakage on the actuator for the "A" train bypass feedwater regulating valve. Corrective actions included repair of the leak prior to restart and a full actuator overhaul planned for prior to the next refueling outage.
Although the event of May 19, 2024 shares some similarities, the corrective actions for the 2024 event would not have been expected to prevent this current event on February 5th 2025. Page 3
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