05000277/LER-2025-002, Uncoordinated DC Circuits Cause Unanalyzed Condition
| ML25281A104 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 10/08/2025 |
| From: | Stiltner R Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| CCN 25-86, ENS 57899 LER 2025-002-00 | |
| Download: ML25281A104 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 2772025002R00 - NRC Website | |
text
10 CFR 50.73 CCN: 25-86 October 8, 2025 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station (PBAPS) Units 2 and 3 Subsequent Renewed Facility Operating License No. DPR-44, DPR-56 NRC Docket No. 50-277, 50-278
Subject:
Licensee Event Report (LER) 2025-002-00 Uncoordinated DC Circuits Cause Unanalyzed Condition
Reference:
ENS 57899 The subject report is being submitted in accordance with 50.73(a)(2)(ii)(B) for being in an unanalyzed condition that significantly degraded plant safety, due to uncoordinated DC circuits that result in being outside the bounds of the 10CFR50 Appendix R Fire Safe Shutdown Analysis.
There are no commitments contained in this letter. If you have any questions, please contact the Peach Bottom Regulatory Assurance Manager, Mr. Brian Woodard at (257) 533-7430.
Respectfully, Ryan C. Stiltner Plant Manager Peach Bottom Atomic Power Station Enclosure cc:
USNRC, Administrator, Region I USNRC, Senior Resident Inspector W. DeHaas, Commonwealth of Pennsylvania S. Seaman, State of Maryland B. Watkins, PSE&G, Financial Controls and Co-Owner Affairs Stiltner, Ryan C
Digitally signed by Stiltner, Ryan C Date: 2025.10.08 11:54:47
- - 04'00'
Abstract
On 09/04/2025, an analysis was completed which confirmed that six cables associated with direct current circuits (EIIS:EI) at PBAPS Units 2 and 3 were non-compliant with 10CFR50 Appendix R, Section III.G.1, Fire protection of safe shutdown capability. It was determined that the circuits were uncoordinated due to inadequate fuse sizing, meaning that during a postulated fire, the circuits fuse may not act to protect the circuit from a fire-induced hot short. Without adequate overcurrent protection for these circuits, a fire-induced short could lead to excessive current through the circuits. This could lead to secondary damage in another fire area where the circuits are routed, challenging the ability to achieve and maintain safe shutdown. Compensatory measures have been implemented and will remain until the identified non-compliant conditions are resolved.
This event is reported under 10CFR50.73(a)(2)(ii)(B) as an unanalyzed condition because a fire that affects multiple fire areas is outside the bounds of the 10CFR50 Appendix R Fire Safe Shutdown Analysis.
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) Page 2 of 2
Plant Operating Conditions Before the Event
Prior to the event, Peach Bottom Atomic Power Station (PBAPS), Unit 2 was operating at approximately 100%
power in MODE 1. PBAPS, Unit 3 was operating at approximately 96% power in MODE 1. There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.
Event Description
On 09/04/2025, an analysis was completed which confirmed that six cables associated with direct current circuits (EIIS:EI) at PBAPS, Units 2 and 3 were non-compliant with 10 CFR 50 Appendix R, Section III.G.2,Fire protection of safe shutdown capability. It was determined that the circuits were uncoordinated due to inadequate fuse sizing, meaning that during a postulated fire, the circuits fuse may not act to protect the circuit from a fire-induced hot short. Without adequate overcurrent protection for these circuits, a fire-induced short could lead to excessive current through the circuits. This could lead to secondary damage in another fire area where the circuits are routed, challenging the ability to achieve and maintain safe shutdown.
Compensatory actions were implemented immediately for the affected fire areas in accordance with procedural requirements. Compensatory actions will remain in place until the identified non-compliant conditions are resolved.
The circuits for PBAPS,Units 2 and 3 noted above were reported under ENS 57899 per 10CFR50.72(b)(3)(ii)(B) as an unanalyzed condition because a fire that affects multiple fire areas is outside the bounds of the 10CFR50 Appendix R Fire Safe Shutdown Analysis.
Safety Consequences
There were no actual consequences caused by this condition. The potential consequence of a hot short condition is for fire damage in one fire area to occur which subsequently damages cables in a second fire area.
This chain of events could cause a loss of safe shutdown capability outside the bounds of the Fire Safe Shutdown Analysis. However, the risk of fire damage is limited by the use of fire retardant cabling, divisional separation, and fire protection features such as automatic suppression and detection, where required.
Additionally, the station Fire Brigade is trained and will readily respond to all fire conditions.
Cause and Corrective Actions
The cause is an inadequate design dating back to original construction. Fire Protection Program compensatory measures were implemented as immediate actions to mitigate the risk of the affected circuits.
Corrective Actions will include modification of the affected circuits to ensure they are properly coordinated.
Previous Similar Events
Peach Bottom LER 2-18-001, dated 05/18/2018, reported an unanalyzed condition due to valve cables not being protected from spurious operation during a postulated fire.
Peach Bottom LER 2-14-001, dated 07/17/2014, reported an unanalyzed condition due to broken wires in breakers credited in the Appendix R Post-Fire Safe Shutdown Analysis.
Peach Bottom LER 3-11-04, dated 01/13/2012, reported an unanalyzed condition due to an error in cable routing which affected the Post-Fire Safe Shutdown Analysis.