05000260/LER-2021-001, Inoperability of a TS-required Main Steam Isolation Valve
| ML21172A305 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 06/21/2021 |
| From: | Rasmussen M Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 2021-001-00 | |
| Download: ML21172A305 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| 2602021001R00 - NRC Website | |
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ENCLOSURE Browns Ferry Nuclear Plant Unit 2 Licensee Event Report 50-260/2021-001-00 Inoperability of a TS-required Main Stream Isolation Valve See Enclosed
Abstract
On June 5, 2021, Control Room Operators closed the Main Steam Line C Valves to support the installation of a Temporary Modification. However, the C Inboard Main Steam Isolation Valve (MSIV)
[FCV; JM] unexpectedly re-opened after closure. This condition prevented the C Inboard MSIV from closing on a valid PCIS signal and it was declared inoperable. Troubleshooting identified a ground on the C Inboard MSIVs DC solenoid/wiring which caused the DC solenoid to remain energized. The valve was subsequently declared operable.
An in-progress Past Operability Evaluation (POE) initially identified a potential for an earlier time-of-failure on April 22, 2021, when an Assistant Unit Operator identified a -150 VDC ground on Battery Board [BYBD] 3 [EI] during one of their rounds.
The root, apparent, and contributing causes of this event, and the corrective actions to prevent or preclude their recurrence, have not been determined and will be explained in a supplementary report.
Additional reporting criteria will be evaluated upon completion of the POE.
A. Immediate Corrective Actions
The DC solenoid input wires were lifted and a tagout/clearance was placed to maintain the solenoid in a de-energized state, so that the MSIV C Inboard Isolation Valve would close on demand.
B. Corrective Actions to Prevent Recurrence or to reduce the probability of similar events occurring in the future The Corrective Actions to prevent or preclude the recurrence of this event have not been determined, and will be explained in a supplementary report.
VII. Previous Similar Events at the Same Site
A search of BFN LERs and CRs found no previous examples of similar events.
VIII. Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments.