05000458/LER-2023-001, Ultimate Heat Sink Inoperable Due to Boundary Valve Leakage

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Ultimate Heat Sink Inoperable Due to Boundary Valve Leakage
ML23143A276
Person / Time
Site: River Bend Entergy icon.png
Issue date: 05/23/2023
From: Hansett P
Entergy Nuclear Operations
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
RBG-48236 LER 2023-001-00
Download: ML23143A276 (1)
v • d • e


LER-2023-001, Ultimate Heat Sink Inoperable Due to Boundary Valve Leakage
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)
10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor
10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat
10 CFR 50.73(a)(2)(v), Loss of Safety Function
10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
4582023001R00 - NRC Website
v • d • e

text

)entergy RBG-48236 Philip Hansett Site Vice President 225-381-4374 10 CFR 50.73 May 23, 2023 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Licensee Event Report 50-458 / 2023-001-00, Ultimate Heat Sink Inoperable due to Boundary Valve Leakage River Bend Station - Unit 1 NRC Docket Nos. 50-458 Renewed Facility Operating License No. NPF-47 In accordance with 10 CFR 50.73, enclosed is the subject Licensee Event Report.

This document contains no commitments.

Should you have any questions, please contact Mr. Randy Crawford, Regulatory Assurance Manager, at 225-381-4177.

Respectfully, l:A/.. *r---

PH/dmw

Enclosure:

cc:

NRC Region IV Regional Administrator - Region IV NRC Senior Resident Inspector - River Bend Station Entergy Nuclear Operations, Inc., River Bend Station, 5485 LJ_S Highway 61, St Francisville, LA 70775

Enclosure RBG-48236 Licensee Event Report 50-458 / 2023-001-00, Ultimate Heat Sink Inoperable due to Boundary Valve Leakage

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08131/2023 (03-14-2023)

Estlmelad bunion per response lo comply with Ns marda1o<y cclledlon rvCJ18S1: 80 houls. Repor1ed lessons

<W.*,

LICENSEE EVENT REPORT (LER) leamed 1111 Into the lcenslng process and fed back to Industry. Send comments raganlng burden estimate to the FOIA, Library, and Information Cdlections Branch (T -6 A10M), U. S. Nucleat Rep,tory (See Page 2 for rwqulred number of dlgltslcharactens for each block)

Comnisslon, Wasling!Dn, DC 20555-0001, or by emal to lnlocotlads.R.......,@nro.gov, and the OM8 11'1iawer al: 0MB Olla! ol ll1fonnallon 81-.1 Regulalory A!laln, (3150-0104), Attn: Oest Officer fm the llueleat -

(See NUREG-1022, R.3 for instruction and guidance for completing this fonn Corrvrisslon, 725 171h Slleat NW, Waslllngton, DC 20503; emal: tlra su?flisslon@omb oop.ooy. The NRC may

!:J.ljp://www.nrc.gov/rea,ging,rm/doc-colleclions/nurezs/staff/sr10221r3/)

not conduct m sponsor, and a person Is no1 requred to respond ID, a cotlecbon of information unless the document requestingorrell"lringthe coffec:tlon dlSJllays a Qlffently vald 0MB conlrol number.

1. FaclUty Name 050
2. Docket Number
3. Page River Bend Station, Unit 1 052 458 1 OF 3
4. Title Ultimate Heat Sink Inoperable due to Boundary Valve Leakage
5. Event Date
6. LER Number
7. Report Date B. other Facllltles Involved Montll Day Year Year Sequential Revision
Monti, Day Year Faculty Name Dockal Number Number No.

N/A 050 N/A 03 24 2023 2023 -

001 -

00 05 23 2023 Faculty Name Docket Number N/A 052 N/A

9. Operating Mode r

O. Powar Level 4

0%

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(a)(3)(I) 50.36(c)(1 )(l)(A) 50. 73(a)(2)(11)(B) 50. 73(a)(2)(vlll)(B) 73.1200(b) 20.2201(d) 20.2203(a)(3)(11) 50.36(c)(1 )(ll)(A) 50.73(a)(2)(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)(1v)(A) 50. 73(a)(2)(x) 73.1200(d) 20.2203(a)(2)(I) 10 CFR Part 21 50.46(a)(3)(11) 50.73(a)(2)(v)(A) 10 CFR Part 73 73.1200(8) 20.2203(a)(2)(11) 21.2(c) 50.69(9) 0 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(9) 20.2203(a)(2)(1v)

§ 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)(vll)

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

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

Randy Crawford 225-381-4177 Cause System Component Manufacturer Reportable to IRIS

Cause

System Component Manufacturer Reportable to IRIS X

BS ISV J010 y

X BS ISV J010 y

14. Supplemental Report Expected Month Day Year 0
15. Expected Submission Date No Yes (If yes, complete 15. Expected Submission Date) 07 24 2023 16, Abstract (Limit to 1326 spaces, i.e., approximately 13 single-spaced typewritten lines)

On March 24, 2023, River Bend Station was in Mode 4 during Refuel Outage 22 when testing revealed leakage rates from Division 1 of the Standby Service Water system that could have previously rendered the Ultimate Heat Sink inoperable. On May 6, 2023, testing on Division 2 of the Standby Service Water system also resulted in leakage rates that could have previously rendered the Ultimate Heat Sink inoperable. These discoveries were made when River Bend Station was not in a required Mode of Applicability for the Ultimate Heat Sink. Corrective actions to restore compliance with the allowed design basis leakage were completed for both of the conditions described above prior to the completion of the refuel outage.

These events are being reported in accordance with 10 CFR 50.73(a)(2)(v)(B) as an event that could have prevented fulfillment of the safety function provided by the Ultimate Heat Sink and 10 CFR 50. 73(a)(2)(i)(B) as an operation or condition prohibited by Technical Specifications. The events are being reported in a single Licensee Event Report per guidance contained in NUREG-1022, Revision 3.

EVENT DESCRIPTION

I

2. DOCKET NUMBER 3..1.... NIIMB--*

I YEAR SEQUENTIAL REV NUMBER NO.

458 2023 -I 001 I -I 00 On March 24, 2023, River Bend Station (RBS) was in Mode 4 during Refuel Outage 22 (RF22) when testing revealed eakage from the Standby Service Water (SSW) [Bl] system that could have previously rendered the Ultimate Heat Sink (UHS) [BS] in-operable. The condition was discovered when a seat leakage test of SWP-MOV57A [ISV], Service Water Normal Supply Header A Inlet Isolation Valve resulted in a leak rate of approximately 30 gallons per minute (gpm). On May 6, 2023, while RBS was still in Mode 4 during RF22, a seat leakage test performed on SWP-MOV57B [ISV], Service Water Normal Supply Header B Inlet Isolation Valve resulted in a leak rate of 15.5 gpm. Design Basis calculations only allow a leakage rate of 6.9 gpm.

SSW and the UHS are required by Technical Specification (TS) 3.7.1 to be operable in Modes 1, 2, and 3. The UHS consists of one 200% cooling tower and one 100% capacity water storage basin. The UHS basin capacity is required by Reg Guide 1.27 and Updated Safety Analysis Report (USAR) 9.2.5 to maintain a minimum 30-day inventory to mitigate the consequences of a Design Basis Accident (DBA) without replenishment.

¨WP-MOV57 A was repaired by replacing the valve seat seals and adjusting the closing torque. SWP-MOV57B was repaired by adjusting the closing torque. Satisfactory post maintenance testing was completed for both valves.

rrhis event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(B) as an event that could have prevented fulfillment

©f the safety function provided by the Ultimate Heat Sink because the amount of leakage through SWP-MOV57 A and ISWP-MOV57B would not allow the UHS to fulfill the required 30-day mission time. The event is also being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as an operation or condition prohibited by Technical Specifications based on the past-operability review. Although this was a first-time performance of the SWP-MOV57A and SWP-MOV57B seat leakage est, the assumption is that the leakage existed prior to RF22 and TS 3.7.1 would have been applicable.

EVENT CAUSE

The direct cause of this event was excessive seat leakage past SWP-MOV57 A and SWP-MOV57B. A supplement to this LER is expected following completion of a Root Cause Evaluation which is underway.

SAFETY ASSESSMENT

'A risk assessment was completed using assumptions of the worst-case ambient temperature and minimum initial water level

  • n the UHS. The assessment concluded that although the UHS would not require replenishment until at least 22 days into an event, there is negligible severe accident risk associated with total leakage of 45.5 gpm (both trains combined) past SWP-MOV57 A and SWP-MOV57B since the UHS would require replenishment prior to the 30 day mission time. Additionally, risk would be further reduced by consideration of actual annual temperature cycles which would significantly reduce vaporative loss from the UHS as well as proceduralized replenishment capabilities.

rThere were no actual Nuclear or Radiological safety consequences due to this event since the OBA did not occur. This

<<vent was of minimal significance to the health and safety of the public.

CORRECTIVE ACTIONS

1. Replace valve seat seals on SWP-MOV57 A - COMPLETE I
2. DOCKET NUMBER

'.l. LER NUMBE

19-,

SEQUENTIAL REV NUMBER NO.

458 001 1-1 00

2. Adjust closing torque on SWP-MOV57 A and SWP-MOV57B - COMPLETE
3. Root Cause Evaluation - Due on June 24, 2023 PREVIOUS SIMILAR OCCURRENCES This information will be provided in the Supplemental LER following completion of Root Cause Evaluation. Page 3

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