05000277/LER-2024-002, Uncoordinated DC Circuits Cause Unanalyzed Condition

Uncoordinated DC Circuits Cause Unanalyzed Condition

ML24099A001
Person / Time
Site:	Peach Bottom
Issue date:	04/08/2024
From:	Stiltner R Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
24-17 LER 2024-002-00
Download: ML24099A001 (1)

LER-2024-002, Uncoordinated DC Circuits Cause Unanalyzed Condition

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
2772024002R00 - NRC Website

text

10 CFR 50.73 CCN: 24-17 April 8, 2024 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) 2024-002-00 Uncoordinated DC Circuits Cause Unanalyzed Condition

Reference:

ENS 56957 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. Wade Scott at (717) 456-3047.

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: 2024.04.05 14:39:13

- 04'00'

Abstract

On 02/09/2024, an analysis was completed which confirmed that a direct current (DC) circuit (EIIS:EI) within Unit 2 caused a non-compliant condition with 10CFR50 Appendix R Fire Safe Shutdown. It was determined that the circuit was 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. Extent of condition review revealed several additional circuits, including circuits within Unit 3. Compensatory measures have been implemented and will remain until the identified conditions are resolved.

These events are 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 3 of 3 reported under 10CFR50.73(a)(2)(ii)(B) in this report 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

As described above, this condition is considered non-compliant because it is outside the bounds of the Appendix R analysis.

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 could damage cables in a second fire area. This may cause a loss of safe shutdown capability outside the bounds of the Fire Safe Shutdown Analysis. 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. The station Fire Brigade is trained and can readily respond to all fire conditions.

Cause and Corrective Actions

The cause is an inadequate design dating back to original construction. Immediate actions were implemented as compensatory measures 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 May 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 July 17, 2014, reported an unanalyzed condition due to broken wires in breakers used for Appendix R Post-Fire Safe Shutdown.

Peach Bottom LER 3-11-04, dated January 13, 2012, reported an unanalyzed condition an error in cable routing which affected the Post-Fire Safe Shutdown analysis.