05000391/LER-2023-001, Unanalyzed Condition Related to Loss of the 2A Emergency Diesel Generator During a Postulated Appendix R Fire
| ML23201A109 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 07/20/2023 |
| From: | Anthony Williams Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| WBL-23-031 LER 2023-001-00 | |
| Download: ML23201A109 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| 3912023001R00 - NRC Website | |
text
l\\'4 TENNESSEE VALLEY AUTHORITY Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 WBL-23-031 July 20, 2023 ATTN : Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391 10 CFR 50.73
Subject:
Licensee Event Report 391/2023-001-00, Unanalyzed Condition Related to.
Loss of the 2A Emergency Diesel Generator During a Postulated Appendix R Fire This submittal provides Licensee Event Report (LER) 391/2023-001-00. This LER provides details where an Appendix R fire in the Auxiliary Building could lead to a loss of 480V Diesel Generator Auxiliary Boards 2A 1-A and 2A2-2 and the loss of Diesel Generator 2A. This represents an unanalyzed condition, which is reportable in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50. 73(a)(2)(ii)(B).
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.
Anthony L. Williams IV Site Vice President Watts Bar Nuclear Plant
U.S. Nuclear Regulatory Commission WBL-23-031 Page 2 July 20, 2023
Enclosure:
LER 391/2023-001-00, Unanalyzed Condition Related to Loss of the 2A Emergency Diesel Generator During a Postulated Appendix R Fire cc (w/Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Region II
ENCLOSURE Tennessee Valley Authority Watts Bar Nuclear Plant Unit 2 LER 391/2023-001-00, Unanalyzed Condition Related to Loss of the 2A Emergency Diesel Generator During a Postulated Appendix R Fire
Abstract
On May 25, 2023 at 1345 Eastern Daylight Time (EDT), operations personnel were verbally notified that a fire barrier for area 737-A1B was not installed, and would render the 2A Emergency Diesel Generator (EDG) not operable in the event of a fire on the Unit 2 side of elevation 737 in the Auxiliary Building. The 2A EDG is the credited power source for fire safe shutdown for a fire located in this area. Without the credited source of power, this placed Watts Bar Nuclear Plant (WBN) Unit 2 in an unanalyzed condition. A fire watch was established in the area until the issue was resolved.
The cause is a legacy design issue which failed to recognize the Normal and Alternate Feeders share the same breaker on the associated 480V shutdown board (2-BD-212-A1-A and 2-BD-212-A2-A). Permanent corrective action by implementation of a design change was completed on June 10, 2023.The design change disconnected the Alternate Feeder Cable for the Diesel Auxiliary Boards from the associated 480V Shutdown Board. Therefore, a fire in fire area 737-A1B would no longer trip the common breaker and the 2A EDG would remain operable.
Page 5 of 5 VI.
Corrective Actions
This event was entered into the TVA Corrective Action Program and is being tracked under Condition Report 1858921.
A. Immediate Corrective Actions
Immediate corrective actions were to institute a fire watch until the identified issue was corrected.
B. Corrective Actions to Prevent Recurrence or to reduce the probability of similar events occurring in the future Design change WBN-23-034 was implemented by Work Order (WO) 123783604 on June 10, 2023. The design change disconnected the Alternate Feeder Cable for the Diesel Auxiliary Boards from the associated 480V Shutdown Board. Therefore, a fire in fire area 737-A1B would no longer trip the common breaker. The normal feeder remains protected in this area.
VII. Previous Similar Events at the Same Site
Multiple Licensee Event Reports (LERs 390-2013-005-00, 390-2014-004-02, 390-2015-002-01, and 390-2015-004-01) were submitted to NRC in 2014 and 2015 for Unit 1 related to unanalyzed conditions associated with Appendix R. These issues were identified during the licensing of WBN Unit 2. This LER is the first item identified for WBN Unit 2.
VIII. Additional Information
None.
IX.
Commitments
None.