05000373/LER-2022-003-01, Main Control Room and Auxiliary Electric Room HVAC Declared Inoperable Due to Multiple Component Failures

Main Control Room and Auxiliary Electric Room HVAC Declared Inoperable Due to Multiple Component Failures

ML22266A056
Person / Time
Site:	LaSalle
Issue date:	09/23/2022
From:	Van Fleet J Constellation Energy Generation
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA22-034 LER 2022-003-01
Download: ML22266A056 (5)

LER-2022-003, Main Control Room and Auxiliary Electric Room HVAC Declared Inoperable Due to Multiple Component Failures

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(x) 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)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(ix)(A)
3732022003R01 - NRC Website

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LaSalle County Station 2601 North 21 " Road Constellation ~ Marseilles, IL 61341 815-415-2000 Telephone

10 CFR 50.73

RA22-034

September 23, 2022

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

LaSalle County Station, Units 1 and 2 Renewed Facility Operating License No. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374

Subject: Licensee Event Report 2022-003-01, Supplement to Main Control Room and Auxiliary Electric Room HVAC Declared Inoperable Due to Multiple

Component Failures

In accordance with 10 CFR 50.73(a)(2)(v)(D), Exelon Generation Company, LLC (EGC) is submitting Licensee Event Report (LER) Number 2022-003-01 for LaSalle County Station, Units 1 and 2.

There are no regulatory commitments in this letter. Should you have any questions concerning this report, please contact Mr. Dan Mearhoff, Regulatory Assurance Manager, at (815) 415-2800.

Respectfully,

John Van Fleet Jr Plant Manager LaSalle County Station

Enclosure: Licensee Event Report

cc : Regional Administrator - NRC Region Ill NRC Senior Resident Inspector - LaSalle County Station NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB : NO. 3150-0104 EXPIRES: 08/31/2023 (08-2020 )

LaSalle County Station, Unit 1 05000 -373 1 OF 4

4. Title Main Control Room and Auxiliary Electric Room HVAC Declared Inoperable Due to Multiple Component Failures.

5. Event Date 6. LER Number 7. Report Date 8. Other Facilities Involved Month Day Year Year Month Day Year Sequent ial Rev ision Fac ility Name Docket Number Number No. LaSalle County Station, Unit 2 05000-374 05 20 2022 2022 003 01 09 23 2022 Facility - - NA NA Name Docket Number

9. Operating Mode 1 110. Power Level 100 percent

11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)

I* 10 CFR Pal!t1't> D 20.2203(a)(2)(vi) D 50.36(c)(2) D 50.73(a)(2)(1v)(A) D 50.73(a)(2)(x) 20.2201(b) D 20.2203(a)(3)(i) D 50.46(a)(3)(ii) D 50.73(a)(2)(v)(A) 10 CFR Part 13 20.2201(d) D 20.2203(a)(3)(ii) 50.69(g) D 50.73(a)(2)(v)(B) D 73.71(a)(4)

D 20.2203(a)(1) D 20.2203(a)(4) 50. 73(a)(2)(1)(A) D 50.73(a)(2)(v)(C) D 73.71(a)(5) 0 20.2203(a)(2)(1) 110 'CFR Part 21 50.73(a)(2)(i)(B) ~ 50.73(a)(2)(v)(D) D 73.77(a)(1)(i) 0 20.2203(a)(2)(ii) D 21.2(c) 50. 73(a)(2)(1)(C) D 50.73(a)(2)(vii) D 73.77(a)(2)(i)

D 20.2203(a)(2)(iii) 1'0 CFR Part 50 ' 50.73(a)(2)(ii){A) D 50.73(a)(2)(vlii)(A) D 73.77(a)(2)(ii) 0 20.2203(a)(2)(iv) 50.36(c)(1)(1)(A) 50.73(a)(2)(11)(B) D 50.73(a)(2)(vlii)(B) 0 20.2203(a)(2)(v) 50.36(c)(1)(il)(A) D 50.73(a)(2)(iil) D 50.73(a)(2)(ix)(A) 0 OTHER (S pec ify here, in abstract, or NRC 366A).

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

CJ Smith, Operations Director (815) 415-2200

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 D VI FAN C147 y

14. Supplemental Report Expected Month Day Year 15. Expected Submission Date

[8J No I D Yes (If yes, complete 15. Expected Subm ission Date)

6. Abstract (Limit to 1560 spaces, i.e.. approximately 15 single-spaced typewritten lines)

On May 20, 2022, both Units 1 and 2 were in Mode 1 and at 100% power. The B train of the Main Control Room Ventilation (VC) and Auxiliary Electric Room Ventilation (VE) was inoperable due to a planned maintenance window. The Main Control Room ventilation envelope consists of both the Main Control Room and the Auxiliary Electric Equipment Room. Both trains of VC and VE were required to be operable at the time of these events.

On 5/20/22 at 0905 and again on 5/23/22 at 1256, various equipment on the A VCNE train tripped following train swaps to support ongoing maintenance activities. This resulted in the A VCNE train be ing declared inoperable.

With both the A and B trains being simultaneously inoperable, the system was in a condition that could have prevented fulfillment of a safety function.

The probable cause of the events was determined to be inadequate isolation between the A and B VCNE trains.

This allowed the VE return fan to spin backwards resulting in locked rotor amps when the breaker was closed.

Plant and System Identification

LaSalle Country Station Unit 1 and 2 is a General Electric Boiling Water Reactor with 3546 Megawatts Thermal Rated Core Power. The affected system was the Main Control Room Area Ventilation system (VC) and the Auxiliary Equipment Room Ventilation System (VE).

Condition Prior to Event

Unit(s) : 1/2 Date : May 20, 2022 Time : 0905 CDT Reactor Mode(s) : 1/1 Mode(s) Name: Power Operation Power Level: 100%1100%

Description

On May 20, 2022 the station was executing a 8 VCNE work window and in the following TS actions: 3.7.4 A.1,

restore 8 train to operable status (expires 5/23/22 at 0500) and 3.7.5 A.1, restore 8 train to operable (expires 6/15/2022 at 0300). The station began procedures to swap to the A train to allow repairs identified dur ing post maintenance testing on the 8 train. After swapping to A VCNE, the A VE return fan tripped and immediately tripped after a second attempt to start.

At 0905, the A train was declared inoperable for both TS 3.7.4 (CRAF) and 3.7.5 (MCR ventilation). With both trains of VCNE inoperable, the Station entered TS 3.7.4 RA E.1 be in mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, TS 3.7.5 RA 8.1 to verify control room area temperature less than 90 degrees once per four hours, and RA 8.2 to restore one control room area ventilation air conditioning subsystem to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

The Electrical Ma intenance department performed bas ic troub leshoot ing. The fan was restarted and following sufficient run time of the A VE return fan, the A VCNE train was declared operable at 1200. TS actions 3. 7.5 E. 1 and 3.7.4 8. 1 and 8.2 were exited.

On 5/23/2022 the station began act ivities to swap to A VCNE to allow for system restoration on 8 VCNE. After swapping to A VCNE, the A VE return fan tripped at 1256. Operations reset the breaker and restarted the fan.

The A VCNE train was declared inoperable for CRAF (3.7.4) and MCR ventilation (3.7.5). The station entered the following time c locks : 3. 7.4 A.1, restore A train to operable status within 7 days, 3. 7.5 RA 8.1 to verify control room area temperature less than 90 degrees once per four hours, and RA 8.2 to restore one control room area ventilation air conditioning subsystem to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. (Note : The 8 train was declared operable for CRAF on 5/20/22 at 1841 fo llowing repa irs, but the 8 train remained in the 3.7.5 MCR ventilation LCO for continued maintenance activities from the previous week that resulted in the condition discussed above on 5/23.)

The 8 train was fully restored to operable status at 1755 on 5/23/22. TS action 3.7.5 8.1/8.2 were exited. The station declared the A train operable on 5/24/22 at 2230 after completion of an Operability evaluation and subsequent run time.

Cause

The probab le cause of the return fan trips was determined to be inadequate isolation between the A and 8 VCNE trains. Th is a llowed the VE return fan to spin backwards resulting in locked rotor amps when the breaker was c losed.

A contributing cause was identified as inadequate work instructions and procedural guidance in the Maintenance work packages during periodic maintenance of Hydra-motors.

Reportability and Safety Analysis

The A and B VCNE trains of the simultaneous inoperability is reportable under 10 CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented the fulfillment of the safety function of the structures or systems that are needed to mitigate the consequences of an accident. Two ENS reports were made to the NRC at 1639 CDT on May 20, 2022 (EN 55905) and at 1815 CDT on May 23, 2022 (EN 55908). Both reports were pursuant to 10 CFR 50. 72(b)(3)(v)(D).

The safety significance of this event was minimal. For approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> on 5/20/22, both VCNE trains were inoperable for CRAF and HVAC (TS 3.7.4 and TS 3.7.5). For approximately 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> on 5/23/22, both trains were inoperable for HVAC only (TS 3.7.5). Main Control temperature did not exceed 90 degrees and online risk remained Green throughout the event.

Corrective Actions

Corrective actions taken in response to the conditions were :

• Basic troubleshooting was performed.

• Operability evaluation was performed prior to declaring VCNE operable after failure of the VC return fan.

• Perform inspections and testing of the A and B VCNE trains. Based on testing results perform repairs and changes to the station PM program as required.

• Update Hydra-motor replacement procedures and work packages.

Previous Occurrences

LER 373-2014-004

On August 28, 2014, both Units 1 and 2 were in Mode 1 at 100% power. The ' B' train of Auxiliary Electric Equipment Room ventilation (VE) was inoperable due to a planned repair of an oil leak. At 1227 hours0.0142 days <br />0.341 hours <br />0.00203 weeks <br />4.668735e-4 months <br /> CDT, the A VE compressor was not found to be cycling on and off resulting in the 'A' train of VCNE being declared inoperable. With both trains of VCNE inoperable, this resulted in an event or condition that could have prevented the fulfillment of a safety function. The cause of the event was a shorted wire on liquid line solenoid valve 0RG053A that caused the solenoid valve to close, resulting in the compressor shutting down on low suction pressure. The corrective action was to repair the wiring problem and return the compressor to service.

LER 373-2013-008

On November 22, 2013, both Units 1 and 2 were in Mode 1 at 100% power. The 'A ' train of Main Control Room ventilation (VC) was inoperable due to an emergent repair of a Freon leak. At 1920 hours0.0222 days <br />0.533 hours <br />0.00317 weeks <br />7.3056e-4 months <br /> CST, the ' B' AEER Cooler Condenser Fan tripped. An acrid smell was detected coming from the fan motor breaker compartment. The 'B' train of VC and VE was declared inoperable. With both trains of VCNE inoperable, this resulted in an event or condition that could have prevented the fulfillment of a safety function. The cause of the event was a winding failure of the 'B' AEER Cooler Condenser fan motor. Corrective actions included replacing the failed fan motor and performing a failure analysis to determine the cause of the winding failure.

Component Failure Data

Manufacturer : Carrier Corp.

Device: A AEER HVAC Return Van (Model: 5H66-607)

Component ID: 0VE02CA (CAT ID : 32349)