05000390/LER-2025-001, Loss of the Control Room Emerency Air Temperature Control System Due to Chiller Oil Migration
| ML25062A082 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 03/03/2025 |
| From: | Reneau W Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| WBL-25-007 LER 2025-001-00 | |
| Download: ML25062A082 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3902025001R00 - NRC Website | |
text
WA TENNESSEE VALLEY AUTHORITY Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 WBL-25-007 March 3, 2025 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 10 CFR 50.73
Subject:
Watts Bar Nuclear Plant, Units 1 and 2 Facility Operating License No. NPF-96 NRC Docket No. 50-390, 50-391 Licensee Event Report 390/2025-001-00, Loss of The Control Room Emergency Air Temperature Control System Due to Chiller Oil Migration Pursuant to the reporting requirements of 10 CFR 50. 73, attached is the subject Licensee Event Report concerning the Loss of The Control Room Emergency Air Temperature Control System Due to Chiller Oil Migration for Watts Bar Nuclear Plant, Unit 1, which occurred on January 4, 2025.
There are no new regulatory commitments contained in this letter. Please direct any questions concerning this matter to Jonathan Johnson, WBN Licensing Manager, at jtjohnsonO@tva.gov.
William C. Rene u Site Vice Presiden Watts Bar Nuclear Plant
U.S. Nuclear Regulatory Commission WBL-25-007 Page 2 March 3, 2025 Enclosure: LER 390/2025-001-00, Loss of The Control Room Emergency Air Temperature Control System Due to Chiller Oil Migration cc (w/Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Region II
WBL-25-007 E1 of 1 ENCLOSURE Tennessee Valley Authority Watts Bar Nuclear Plant Unit 1 LER 390/2025-001-00, Loss of The Control Room Emergency Air Temperature Control System Due to Chiller Oil Migration
Abstract
On January 4, 2025 at 0855 EST, with Unit 1 and Unit 2 at 100% rated thermal power, both trains of the Control Room Emergency Air Temperature Control System (CREATCS) were simultaneously inoperable. This condition occurred when the A-A Main Control Room (MCR) chiller experienced an oil migration event and tripped on oil failure while the B train of CREATCS had been previously declared inoperable for a B-B MCR chiller maintenance outage. The A train of CREATCS was later restored at 1408 EST on January 4, 2025 following the addition of MCR chiller oil, adjustment of the chillers temperature control valve (TCV) and subsequent observation of stable chiller parameters. Applicable technical specification (TS) limiting conditions for operability (LCO) were entered for less than six hours as a result.
This condition is being reported in accordance with 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident.
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VII. Previous Similar Events at the Same Site
WBN LER 391-2025-001-00 documented a loss of both trains of CREATCS on November 22, 2024 due to a MCR Chiller TCV malfunction.
VIII. Additional Information
None.
IX.
Commitments
None.