NL-23-0915, Manual Reactor Trip Due to Loss of Feedwater

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Manual Reactor Trip Due to Loss of Feedwater
ML23353A109
Person / Time
Site: Hatch Southern Nuclear icon.png
Issue date: 12/19/2023
From: Busch M
Southern Nuclear Operating Co
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
NL-23-0915
Download: ML23353A109 (1)
v • d • e


Text

>-,. Southern Nuclear Matt Busch Vice President - Plant Hatch December 19, 2023 Hatch Nuclear Plant 11028 Hatch Parkway North Baxley, GA 31513 912 537 5859 tel 912 366 2077 fax Docket No.: 50-366 NL-23-0915 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant - Unit 2 Licensee Event Report 2023-003-00 Unit 2 Manual Reactor Trip due to Loss of Feedwater Ladies and Gentlemen:

In accordance with the requirements of 10 CFR 50.73(a)(2)(iv)(A), Southern Nuclear Operating Company hereby submits the enclosed Licensee Event Report.

This letter contains no NRC commitments. If you have any questions, please contact the Plant Hatch Licensing Manager, Jimmy Collins, at 912-453-2342.

Respectfully submitted,

~

M.S. Busch Vice President - Hatch MSB/CJC

Enclosure:

LER 2023-003-00 Cc: NRC Regional Administrator, Region II NRR Project Manager-Plant Hatch NRC Senior Resident Inspector - Plant Hatch RTYPE: CHA02.004

Edwin I. Hatch Nuclear Plant - Unit 2 Licensee Event Report 2023-003-00 Unit 2 Manual Reactor Trip due to Loss of Feedwater Enclosure LER 2023-003-00

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 315CMl104 EXPIRES: 03/31/2024 (10-01-2023)

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It 0MB Ofict of lnlonnllllon and Rllg"8lory Affalra, (315CM>104), Alln: Deak Olllcer for lhe Nuda-Ragutllary (Saa NUREG-1022, R.3 for Instruction and guidance for completing this form ComniSlion, 725 17'1 ~

'fit, WllllinalDn. DC 20503: email: oira subi,mo.,Oonlb..ip.gov. The NRC may lll!Jl;b'W.WWJl[!;,aov/m11!1la~d~llilffilt!!llslB!1111/11r1!!22{Q[)

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1. Faclllty Name

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2. Docket Number
3. Paga Edwin I. Hatch, Unit 2 052 00366 1 OF 2
4. Title Manual Reactor Trip Due To Loss of Feedwater
5. Evant Data I. LER Number
7. Report Data
8. Other FacllltlH Involved Month Day Year y..,

llequenllal Revision Month Day y..,

Faclllly Name Dockal Number Number No.

050 11 01 2023 2023 -

003 -

00 12 19 2023 Faclllly Nam*

Dockal Number 052

9. Operating Mode r
0. Po-r Laval 1

056

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)(vlll)(A) 73.1200(8) 20.2201(b) 20.2203(8)(3)(1) 50.36(c)(1 )(l)(A)
50. 73(8)(2)(11)(8) 50.73(a)(2)(vlll)(B) 73.1200(b) 20.2201(d) 20.2203(8)(3)(11) 50.36(c)(1 )(ll)(A)
50. 73(8)(2)(111)
50. 73(a)(2)(Ix)(A) 73.1200(c) 20.2203(8)(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(8)(3)(11)

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(8)(1) 73.1200(f) 20.2203(8)(2)(111) 50.73(a)(2)(I)(A)
50. 73(8)(2)(v)(C)
73. 77(8)(2)(1) 73.1200(g) 20.2203(a)(2)(Iv)
50. 73(8)(2)(1)(8)
50. 73(8)(2)(v)(D)
73. n(a)(2)(11) 73.1200(h) 20.2203(a)(2)(v) 50.73(a)(2)(I)(C)
50. 73(a)(2)(vll)

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

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

Jimmv Collins - Licensina Manaaer 9124532342

13. Complete One Line for each Component Failure Described In this Report Caua System Component Manufacturer Reportable to IRIS Cause System Component Manufacturer Reportable to IRIS X

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8580 y

14. Supplemental Report Expected Month Day Year

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15. Expected SubmlAlon Data No Yes (If yes, complete 15. Expected Submission Date)
11. Abatract (Limit to 1326 spaces, i.e., approximalely 13 single-spaced typewritten lines)

On November 1, 2023, reactor power was being lowered on Unit 2 to support removal of the 'A' Reactor Feed Pump (RFP} from service due to a suction pipe drain line leak. The 'A' RFP was removed from service and isolated at 0642 EDT. During this evolution, water from the leak on the drain line of the 'A' RFP entered various electrical cabinets and components related to the

'B' RFP, causing the 'B' RFP to trip at 0648 EDT. The trip of the 'B' RFP resulted in a loss of feedwater and lowering of reactor water level. Due to the lowering reactor water level, operators manually inserted a reactor trip in anticipation of water level dropping to the automatic reactor protection system (RPS} trip setpoint. The Reactor Core Isolation Cooling (RCIC) and High Pressure Coolant Injection (HPCI) pumps were used to restore reactor water level. All safety system responded as required.

The cause of the leak from the 'A' RFP suction drain line was a pipe shear due to excessive stresses from thermal cycling and flow induced vibration. This was corrected by implementing a design change that cut and capped that portion of piping. The cause of the 'B' RFP trip was electrical grounding due to water intrusion from the 'A' RFP leak resulting in an invalid low suction pressure trip on the 'B' RFP.

NRC FORM 388A (10-01-2023)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2024 LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET (See NUREG-1022, R.3 for Instruction and guidance for completing this fonn htto*/fwww.nrc.gov/reading-rm/doe:collections/nuregs/staff/s.l1022lQLl

1. FACILITY NAME IEdwin I. Halch, Unit 2 050 052 NARRATIVE EVENT DESCRIPTION Ellllmatad burden per l8Sp0IIS8 to comply with this mandaby collection requell: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned ara lncorporatad Into the lk:enslng process and fed back to lnduatly. Send comments regardng burden estimate to the FOIA, Library, and lnfonnallon Collections Bnlnch (T-8 A10M), U. S.

Nuclear Regulatory Commlulon,

Watlqton, DC 20566-0001, or by email to lnfoc:alledl.Resoun:e@nre.gov, and the 0MB r9¥1eMr at 0MB Offlce of Information and Regulaloly AffallB, (3150-0104), Altn: Delk Officer for the Nuclear Regufaby Commlalion, 725 17th Slreel NW, Washington, DC 20503; ernall: oira submlssicn@omb 80J) gov. The NRC may not conduct or sponsor, and a pe!S011 la not required to respond to, a c:olledion of lnfonnatlon unless the d0a1ment requesting or requiring the c:ollection displays a cum,ntly valid 0MB control number.
2. DOCKET NUMBER
3. LER NUMBER 00366 I

YEAR SEQUENTIAL REV NUMBER NO.

_t5-I 003 1-0 On November 1, 2023, reactor power was being lowered on Unit 2 to support removal of the 'A' Reactor Feed Pump (RFP)

[EIIS Code: SJ] from service due to a leak on a drain line connected to the suction piping of the pump. At 0642 EDT with the reactor at approximately 56% rated thermal power, the 'A' RFP was removed from service and isolated. While removing the 'A' RFP from service, water from the leak on the drain line of the 'A' RFP entered various electrical cabinets and components related to the 'B' RFP, causing the 'B' RFP to trip at 0648 EDT. The trip of the 'B' RFP resulted in a loss of feedwater and reactor water level lowering. Due to the lowering reactor water level, operators manually inserted a reactor trip in anticipation of water level dropping to the automatic trip setpoint. The Reactor Core Isolation Cooling (RCIC) [EIIS Code: BN] and High Pressure Coolant Injection (HPCI) [EIIS Code: BJ] pumps automatically started and were used to restore reactor water level. Secondary containment isolated and Standby Gas Treatment (SBGT) [EIIS Code: BH]

autostarted, and Group 2 and Group 5 primary containment isolation valves [EIIS Code: JM] isolated as expected when their setpoints were reached. There was no safety related equipment inoperable at this time and no other nonfunctional, non-safety equipment that contributed to this event.

This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in manual actuation of the reactor protection system and automatic actuation of general containment isolation signals affecting containment isolation valves in more than one system. Additionally, HPCI and RCIC automatically started when their reactor water level setpoints were reached.

EVENT CAUSE ANALYSIS A root cause analysis was performed and determined that the direct cause of the leak from the 'A' RFP suction drain line was a pipe shear due to excessive stresses from thermal cycling and flow induced vibration. The cause of the 'B' RFP trip was electrical grounding due to water intrusion from the 'A' RFP leak resulting in an Invalid low suction pressure trip on the

'B'RFP.

SAFETY ASSESSMENT There were no safety consequences as a result of this event. All safety related systems functioned as designed during this event. The operating crew responded correctly to the event. The applicable abnormal/emergency operating procedures were entered. The event was within the analysis of the Updated Final Safety Analysis Report (UFSAR) Chapter 15.

No radiological release occurred due to this event.

CORRECTIVE ACTION The leak from the 'A' RFP suction piping drain line was corrected by implementing a design change that cut and capped that portion of piping. The cause of the 'B' RFP trip was electrical grounding due to water intrusion from the 'A' RFP leak resulting in an invalid low suction pressure trip on the 'B' RFP. All electrical components related to the 'B' RFP were investigated. Impacted components were dried out or replaced as required.

PREVIOUS SIMILAR EVENTS None.

NRC FORM 386A (1~1-2023)

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