NL-24-0123, for Manual Reactor Trip Due to Loss of Power to the 2A 125 Volt DC Distribution Panel

for Manual Reactor Trip Due to Loss of Power to the 2A 125 Volt DC Distribution Panel

ML24106A162
Person / Time
Site:	Farley
Issue date:	04/15/2024
From:	Dean E Southern Nuclear Operating Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
NL-24-0123 LER 2024-002-00
Download: ML24106A162 (1)

Text

A Southern Nuclear Edwin Dean Ill Joseph M. Farley Nuclear Plant Vice President - Farley 7388 North State Hwy 95 Columbia. Alabama 36319 334.661.2100 tel 334.661.2512 fax

EDDEANll@southemco.com

April 15, 2024

Docket No.: 50-364 NL-24-0123

U.S. Nuclear Regulatory Commission A TIN: Document Control Desk Washington, D. C. 20555-0001

Joseph M. Farley Nuclear Plant - Unit 2 Licensee Event Report 2024-002-00 Manual Reactor Trip due to Loss of Power to the 2A 125 Volt DC Distribution Panel

Ladies and Gentlemen:

In accordance with the requirements of 10 CFR 21.2(c) and 10 CFR 50.73(a)(2)(iv)(A),

Southern Nuclear Company is submitting the enclosed Licensee Event Report for Unit 2.

This letter contains no NRC commitments. If you have any questions regarding this submittal, please contact Gene Surber, Licensing Manager, at (334) 661-2265.

Respectfully submitted,

Vice President - Farley

ED/rgs/cbg

Enclosure:

Unit 2 Licensee Event Report 2024-002-00

Cc: Regional Administrator, Region II NRR Project Manager - Farley Nuclear Plant Senior Resident Inspector-Farley Nuclear Plant RTYPE: CFA04.054 Joseph M. Farley Nuclear Plant - Unit 2 Licensee Event Report 2024-002-00 Manual Reactor Trip due to Loss of Power to the 2A 125 Volt DC Distribution Panel

Enclosure

Unit 2 Licensee Event Report 2024-002-00 NRCFORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2024 (10-01-2023) Es1inaled burden per response to c:cmply wllh lhls mandatory collecllon request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons I""......, loamed are ina,rpc181ed into Iha licensing process and lad back to industry. Sand c:cmmants regarding blJrden

,~... LICENSEE EVENT REPORT (LER) estimate to the FOIA, l.iJrary, and lnfonnation Collactions Branch (T-6 A10M), U. S. Nuclear Regulatory i 1 (See Page 2 for required number of digits/characters for each block) aComrrission, Washington, DC 20555-0001, or by email to lnfocollects.Resource@nrc.gov, end Iha 0MB......_

\\ I..... (See NUREG-1022, R.3 for Instruction and t. 0MB Office of lnfonnalion and Regulatory Affairs, (3150--0104), Attn: Desk Officer for Iha Nuclear Regulatory guidance for completing this form Comrrission, 725 171h S~aet NW, Washington, DC 20503; amail: oira submjssjon@omb eop goy. Toa NRC may bllp *I/Www ors. gowr1111dlog-((IJldoc-coll11ctlans/01J[!lg:W,lllfflll[]Q22/Ql) not conduct or sponsor, end a person Is not required to respond lo, a c:ollection of lnformatloo unless Iha document requesllng or reqliring Iha collec:Uon displays a aurently valid 0MB contml numbet

1. Faclllty Name 050 2. Docket Number 3. Page Joseph M. Farley Nuclear Plant, Unit 2 052 364 1 OF 3 ~

4. Title Manual Reactor Trip due to Loss of Power to the 2A 125 Volt DC Distribution Panel

5. Event Date 6. LER Number 7. Report Date 8. Other Facllltles Involved

Month Day Year Year Sequenllal Revision Month Day Year Faclllty Name Docket Number Number No. 050

02 16 2024 2024 - 002 - 00 04 15 2024 Faclllty Name 052 Docket Number

9. Operating Mode 110. Power Level 1 100

11. This Report Is Submitted Pursuant to the Requirements of 1 0 CFR §: (Check all that apply) 10 CFR Part 20 20.2203(a)(2)(vl) 10 CFR Part 50 50.73(a)(2)(11)(A) 50. 73(a)(2)(viii)(A) 73.1200(a)

20.2201(b) 20.2203(a)(3)(I) 50.36(c)(1)(I)(A) 50.73{a)(2)(11)(B) 50. 73(a)(2)(vlii)(B) 73.1200(b) 20.2201(d) 20.2203(a)(3)(1i) 50.36(c)(1)(11)(A) 50.73(a)(2)(111) 50.73(a)(2)(Ix)(A) 73.1200(c) 20.2203(a)(1) 20.2203(8)(4) 50.36(c)(2) ~ 50. 73(a)(2)(Iv)(A) 50.73(a)(2)(x) 73.1200(d) 20.2203(a)(2)(I) 10 CFR Part 21 50.46(a)(3)(ii) 50. 73(a)(2)(v)(A) 10 CFR Part 73 73.1200(e) 20.2203(8)(2)(11) ~ 21.2(c) 50.69(g) 50.73(a)(2)(v)(B) 73.77(a)(1) 73.1200(f) 20.2203(a)(2)(iii) 50.73(a)(2)(I){A) 50. 73(a)(2)(v)(C) 73. 77(a)(2)(i) 73.1200(g) 20.2203(a)(2)(Iv) 50.73(a)(2)(I)(B) 50.73(a)(2)(v)(D) 73. 77(a)(2)(11) 73.1200(h) 20.2203(a)(2)(v) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii)

OTHER (Spec ify here, in abstract, or NRC 366A).

12. Licensee Contactfor this LER

Licensee Contact Phone Number (Include area code)

Gene Surber. Farlev Licensina Manaaer 3346612265

13. Complete One Line for each Component Failure Described in this Report

Cause System Component Manufacturer Reportable to IRIS Cause System Component Manufacturer Reportable to IRIS B EJ BKR S188 y

14. Supplemental Report Expected Month Day Year

15. Expected Submission Date

~ No Yes (If yes, complete 15. Expected Submission Date)

16. Abstract (Li mit to 1326 spaces, I.e., approximately 13 single-spaced typewritten lines)

On February 16, 2024, at 00:48 CDT while in Mode 1 and at 100% power, Farley Nuclear Plant (FNP) operators manually tripped Unit 2 following a loss of control of critical air-operated valves due to a partial loss of A-train DC power. LA08-2, the feeder breaker to the 2A 125VDC Distribution Panel, was found tripped open. This event resulted in a loss of letdown and the reactor makeup system. With volume control tank (VCT) makeup capability lost, operators made the decision to trip the reactor prior to charging pump suction rollover to the refueling water storage tank (RWST).

The cause of the breaker opening was due to a short between wires on the A phase current transformer (CT) / sensor wiring harness in breaker LA08-2 because of poor workmanship. Immediate corrective action included replacing breaker LA08-2 with a spare breaker to restore plant equipment to operation and stabilize the plant.

This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) due to the automatic actuation of multiple systems listed in 10 CFR 50.73(a)(2)(iv)(B). FNP Unit 1 was not affected during this event.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2024 (10-01 -2023) Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to Industry. Send comments LICENSEE EVENT REPORT (LER) regarding burden estimate to the FOIA, Library, and Information Collections Branch (T-6 A10M), U.S.

Nuclear Regulatory Commission, Washington, DC 2~01, or by email to CONTINUATION SHEET lnfocollects.Resource@nrc.gov, and the 0MB reviewer at: 0MB Office of Information and Regulatory Affairs, (3150-0104), Attn: Desk Officer for the Nuclear Regulatory Commission, 725 17th Street NW, (See NUREG-1022, R.3 for instruction and guidance for completing this form Washington, DC 20503; email: aha :rubiIJjsslon@omb eoo gov. The NRC may not conduct or sponsor, and a person is not required to respond to, a collection of information unless the document http*/lwww.nrc gov/reading-rm/doc-collect!ons/nuregs/staff/sr1022/r3O requesting or requiring the collection displays a currently valid 0MB control number.

1. FACILITY NAME 050 2. DOCKET NUMBER 3. LER NUMBER YEAR SEQUENTIAL REV Joseph M. Farley Nuclear Plant, Unit 2 364 NUMBER NO.

052 I I -1 002 1-0 NARRATIVE EVENT DESCRIPTION:

On February 16, 2024, at 00:48 CDT, with reactor power at 100% and in Mode 1, Farley Nuclear Plant (FNP) operators manually tripped Unit 2 following a partial loss of A-train 125V DC power which affected critical air-operated valves.

Breaker LA08-2 [EIIS: EJ/BKR] the supply breaker to the 2A 125VDC Distribution Panel, was found tripped open. Loss of power to the 2A 125VDC Distribution Panel resulted in a loss of letdown and the reactor makeup system. With the volume control tank (VCT) [EIIS: CB / TK] makeup capability lost operators made the decision to trip the reactor prior to the charging pump suction rollover to the refueling water storage tank (RWST).

Operating events and actions occurred in the following timeline on February 16, 2024:

00:35 Multiple Main Control Room Alarms are received.

00:35 Breaker LA08-02 Tripped (Entry into TS 3.8.9) 00:35 Entry into Abnormal Operating Procedure for CVCS Malfunction 00:36 Entry into Abnormal Operating Procedure of Loss of Instrument Air 00:36 Letdown confirmed isolated and loss of makeup capability.

00:48 Operators Manually Trip Reactor based on VCT level.

01 :42 Reactor Coolant Pump 2B secured due to low seal leak off.

01 :45 Pressurizer (PZR) level rises to Technical Specification {TS) high value of 63.5%. (Entry into TS 3.4.9) 02:09 Instrument Air realigned to Containment.

03:08 Commenced Reactor Coolant System (RCS) Cooldown 04:20 Following troubleshooting and breaker replacement, closed Breaker LA08-02 and restored Letdown (Exit TS 3.8.9) 04:34 NRC notified per 10 CFR 50. 72 (EN# 56971) 04:54 PZR level restored (Exit TS 3.4.9)

Following the reactor trip, main feedwater [EIIS: JB] continued to be available. An actuation of the Auxiliary Feedwater System [EIIS: BA] occurred following the manual reactor trip as designed due to low level in the steam generators [EIIS:

SB/SG].

BASIS FOR REPORTABILITY AND SAFETY ASSESSMENT:

The safety consequences of this event were low. Although the component failure had downstream interrelation system effects on letdown and makeup, the operating crew appropriately mitigated the transient with abnormal and emergency operating procedures. Additionally, all TS required actions were met and parameters restored well within required action times. The operating crew responded appropriately to the event. This event was within the analysis of the UFSAR Chapter

15. This event is reportable per 10 CFR 50. 73(a)(2)(iv)(A) due to the automatic actuation of the Reactor Protection System

[EIIS: AA] and AFW system as listed in 10 CFR 50.73(a)(2)(iv)(B). FNP Unit 1 was not affected during this event.

CAUSE:

The 125 Volt DC AKW breaker was built by Siemens and equipped with SIGMATRIP DC Analog Trip Unit built by SURE-TRIP. Framatome was the vendor used to qualify the safety related breakers and trip units. The analysis determined that the vendor QA/QC program was not sufficient to identify poor practices when interfacing with third party products. It was determined that during installation of the SIGMATRIP DC Analog Trip Unit that the stranded wires that were terminated in the harness protruded in such a manner they were able to short to an adjacent wire in the harness. The short occurred in breaker LA08-2 (Serial Number R-300950258102B-001) on the A phase current transformer {CT)/sensor harness. For the SIGMA TRIP DC Analog Trip Unit, Siemens and Framatome do not currently have a verification step/QA/QC check or any instruction for inspecting the wires connected in the wiring harnesses mounted to the CTs/sensors or the trip unit/logic box.

NRC FORM 366A (10-01-2023) Page 2 of 3 NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2024 (1(H)1-2023) Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are Incorporated into the licensing process and fed back to Industry. Send comments LICENSEE EVENT REPORT (LER) regarding burden estimate to the FOIA. Library, and Information Col ections Branch (T-6 A10M), U. S.

Nuclear Regulatory Commission, Washington, DC 2055>0001, or by email to CONTINUATION SHEET lnfocollects.Resource@nrc.gov, and the 0MB reviewer at: 0MB Office of Information and Regulatory Affairs, (3150-0104), Attn: Desk Officer for the Nudear Regulatory Commission, 725 17th Street NW, (See NUREG-1022, R.3 for instruction and guidance for completing this form Washington, DC 20503: email: oira submlsrJon@omb eop goy. The NRC may not conduct or sponsor, and a person is not required to respond to, a collection of information unless the document http:/lwww.nrc.gov/readlng-rm/doc-coUectionslnureaslfilaffM022lQll requesting or requiring the collection displays a currently valid 0MB control number.

,--~;;;.;..;,..;..,;,,;,;_,;;_;;.:,;__1. FACILITY NAME _________ ~ 2. DOCKET NUMBER 3. LER NUMBER Joseph M. Farley Nuclear Plant, Unit 2 050 364 YEAR SEQUENTIAL REV NUMBER NO.

052 I I -1 002 1-0 NARRATIVE CORRECTIVE ACTIONS:

The associated breaker was immediately replaced by a spare breaker during the event. A systematic plan has been developed to inspect all AKW Series breakers which are installed or will be installed in the plant. Additionally, site actions have been created to monitor the changes by SURE-TRIP, Siemens, and Framatome associated with wire stripping, installation, inspection, and QC/QA checks.

Additionally, Framatome has notified SNC by letter dated March 26, 2024 (L TR24010) that their evaluation has determined that this results in a Part 21 Deviation because the potential failure to inadvertently trip Siemens Low Voltage {LV) AKW circuit breakers is a departure from the technical requirements included in the Procurement Document.

Farley has begun a substantial safety hazard evaluation to determine if the deviation could constitute a defect in this application or if the deviation exists on other breakers delivered under affected Purchase Orders but notes that per 10 CFR 21.2{c) {and Information Notice 2011-19), evaluation and appropriate reporting under 10 CFR 50.73 {as completed herein) satisfies Farley's evaluation, notification, and reporting obligation to report defects under 10 CFR Part 21 for this particular application.

Basic Component: Siemens Low Voltage AKW Circuit Breaker

Serial Number: R-300950258102B-001

Supplying/Dedicating Entity: Framatome Inc.

PREVIOUS SIMILAR EVENTS:

No similar events or failure of AKW breakers were identified.

NRC FORM 366A (1<H>1-2023) Page 3 of 3