05200026/LER-2024-001, Manual Reactor Protection System Actuation Due to Procedure Not Optimally Sequenced to Reset the Rapid Power Reduction Signal

Manual Reactor Protection System Actuation Due to Procedure Not Optimally Sequenced to Reset the Rapid Power Reduction Signal

ML24218A260
Person / Time
Site:	Vogtle
Issue date:	08/06/2024
From:	Martino P Southern Nuclear Operating Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
NL-24-0307 LER 2024-001-00
Download: ML24218A260 (1)

LER-2024-001, Manual Reactor Protection System Actuation Due to Procedure Not Optimally Sequenced to Reset the Rapid Power Reduction Signal

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat
0262024001R00 - NRC Website

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Southern Nuclear August 05, 2024 Patrick Martino Site Vice President, Vogtle Units 3 & 4 7825 River Road Waynesboro, Georgia 30830 (706) 848-6602 tel NL-24-0307 10 CFR 50.73(a)(2)(iv)(A)

Docket No.:

52-026 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Southern Nuclear Operating Company Vogtle Electric Generating Plant (VEGP) - Unit 4 Licensee Event Report 2024-001-00 Manual Reactor Protection System Actuation Due to Procedure Not Optimally Sequenced to Reset the Rapid Power Reduction Signal Ladies and Gentlemen:

In accordance with the requirements of 10 CFR 50.73(a)(2)(iv)(A), Southern Nuclear Operating Company is submitting the enclosed Licensee Event Report for VEGP Unit 4.

This letter contains no regulatory commitments. If you have questions regarding the enclosed information, please contact Will Garrett at (706) 848-7154.

Respectfully submitted, kZ~~

Patrick A. Martino Site Vice President Vogtle Units 3 & 4 PAM/KMS/cbg

Enclosure:

Unit 4 Licensee Event Report 2024-001-00 CC:

Regional Administrator, Region II VPO Project Manager Senior Resident Inspector-Vogtle Units 3 & 4 Director, Environmental Protection Division - State of Georgia

Vogtle Electric Generating Plant - Unit 4 Licensee Event Report 2024-001-00 Manual Reactor Protection System Actuation Due to Procedure Not Optimally Sequenced to Reset the Rapid Power Reduction Signal Enclosure Unit 4 Licensee Event Report 2024-001-00

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 04/30/2027 (D4*02*2024)

Estinaled burden pe, response to canply wflh !his mandatory colection n,quest 80 houri. Repc,ttd lessens

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LICENSEE EVENT REPORT (LER) learned 11111 lnccrporaled Into Ille llalllSing process and fed bad< lo IIQl>by. Send COIIWIMlllts Ngalding bunion

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Commisai0<1, Washington, DC 20565--0001, a, by emal lo ln!ooollecb.Resource@m:.IIOV, and lhe 0MB mi-al: 0MB Offia o/ lnlormalion and Reg1At<<y Allain, (3151HJ104), Ann: Desk Officer !or tho Nude"' Regulatory (See NUREG-1022. R.3 for limtrucllon and guidance for completing this form Commissioo, 725 17th SlJNl NW. Waslllngton, DC 20503. The NRC may nolconwct or sponsor, and a pe'10II is http lfwww nrc.govlreading-rm/doc-collections/nuregs/slafflsr1022/r31) not n,quiAld to rasporld to. I ~

ol lnlonnalion unless the clocumenl n,quemg Of requiring the colection displays

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1. Facility Name 050

2. Docket Number

3. Page Vogtle Electric Generating Plant, Unit 4

~ 052 00026 1 OF 2

4 Title Manual Reactor Protection System Actuation Due to Procedure Not Optimally Sequenced to Reset the Rapid Power Reduction Signal

5. event Date

6. LER Number

7. Report Date

8. Other Facllltles Involved Month D1y Year Year Sequential Revision Month Day Yaar Faclllty Name Docket Number Number No.

050 06 05 2024 2024 -

001 -

00 08 05 2024 FacllltyNme Docket Numbtr 052

9. Operating Mode 110. Power Level 1

035

11. This Report Is Submitted Pursuant to the Requirements of 10 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)(vlii)(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)(vltl)(B) 73.1200(b) 20.2201(d) 20.2203(a)(3)(11) 50.36(c)(1)(11)(A)

50. 73(a)(21(111)

50. 73(a)(2)(Ix)(A) 73.1200{c) 20.2203(a)(1) 20.2203(a)(4) 50.36(c)(2)

~ 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 73.1200(d) 20.2203(a)(2)(I)

II 10 CFR Part 21 50.46(a}(3)(11) 50.73(a)(2)(v){A) 10 CFR Part 73*

73.1200(e) 20.2203(a)(2)(ti) 21.2(c) 50.69(g) 50.73(a)(2)(v)(B) 73.77(a)(1) 73.1200(f) 20.2203(a)(2)(111)

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)(vli)

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

12. Licensee Contact for this LER Licensee Contact Phone Number (Include area coda)

Will Garrett. VEGP 3&4 Licensina Manaaer 7068487154 Cause System Component Manufacturer Reportable to IRIS

Cause

System Component Manufacturer Reportable to IRIS

14. Supplemental Report Expected Month Day Year

15. Expected Submission Date

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

16. Abstrac:t (limit to 1326 spaces, i.e, approximately 13 single-spaced typewritten lines)

On June 05, 2024, at 1648 EDT with Vogtle Electric Generating Plant (VEGP) Unit 4 in Mode 1 at 35 percent power, the reactor was manually tripped due to the reactor coolant system (RCS) temperature deviation after the rapid power reduction system (RPR) actuated. The initiating event was a trip of the Main Feedwater Pump ~c" that occurred while the unit was at 100 percent reactor power. The unit was stabilized in Mode 3, with decay heat removed through the steam dumps to the condenser and main feedwater supplying the steam generators. The cause of the event was procedure 4-AOP-207, Loss of Turbine Load, not optimally sequenced to reset the RPR signal to re-enable control rod movement for RCS temperature control. The loss of turbine load response procedure was revised to establish the appropriate time to reset the RPR logic.

This event is reportable under 10 CFR 50. 73(a)(2)(iv)(A) due to the manual actuation of the Reactor Protection System (RPS).

VEGP Units 1, 2 and 3 were unaffected by this event.

EVENT DESCRIPTION

I

2. DOCKET NUMBER

3. LER NUMBER I YEAR SEQUENTIAL REV 00026 NUMBER NO.

[2024[ -l 001 1-0 On June 05, 2024, at 1648 EDT with Vogtle Electric Generating Plant (VEGP) Unit 4 in Mode 1 at 35 percent power the reactor protection system (RPS) [EIIS: JC] was manually actuated. Earlier, while at 100% power, the initiating event was a main feedwater pump (MFP) [EIIS: SJ/P) motor stator winding high temperature signal [EIIS: SJ/TT] that tripped the MFP.

This resulted in a turbine runback and rapid power reduction (RPR) [EIIS: JD] logic actuation. As the reactor coolant system (RCS) temperature continued to lower, the RPR logic remained active, which inhibited the control rod function by preventing more than one control rod M-Bank [EIIS: AA] from withdrawing for temperature control. The procedure's sequence was not optimal to efficiently reset the RPR logic and restore control to multiple control rod banks. Three turbine runbacks were initiated by the RPR system to raise the RCS temperature, the temperature deviation continued to diverge.

Operators manually activated the RPS due to the diverging RCS temperature trend.

EVENT ANALYSIS

The cause of the event was the Loss of Turbine Load procedure not being sequenced to reset the RPR signal at the optimal time to re-enable multiple control rod movement for RCS temperature control.

SAFETY ASSESSMENT AND REPORTABILITY

There were no safety consequences as a result of this event because the RPS maintained the plant in a safe condition.

The operators responded timely by ensuring plant stability. Decay heat was removed by discharging steam to the main condenser [EIIS: SG / COND] using the steam dump valves [EIIS: SB / PCV}, and the steam generators [EIIS: SB / SG]

were supplied by main feedwater [EIIS: SJ/ PJ.

There were no safety-related structures, systems, or components that were inoperable at the beginning of the event that contributed to the event. This event is reportable per 10 CFR 50.73(a)(2)(iv)(A) due to manual actuation of the RPS. All safety systems functioned as expected as a result of the event. VEGP Units 1, 2, and 3 were unaffected by this event.

CORRRECTIVE ACTIONS

• The Loss of Turbine Load procedure was revised to re-sequence resetting of the RPR signal.

PREVIOUS SIMILAR EVENTS

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