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LER-2022-003, Submittal of Class 1E Electrical Air Conditioning System Thermal Expansion Valve Failure Resulted in Condition Prohibited by Technical Specifications
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation; 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)(A), Completion of TS Shutdown; 10 CFR 50.73(a)(2)(v), Loss of Safety Function; 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications; 10 CFR 50.73(a)(2)(i); 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded; 10 CFR 50.73(a)(2)(viii)(A); 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition; 10 CFR 50.73(a)(2)(viii)(B); 10 CFR 50.73(a)(2)(iii); 10 CFR 50.73(a)(2)(ix)(A)
	4832022003R00 - NRC Website
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Submittal of Class 1E Electrical Air Conditioning System Thermal Expansion Valve Failure Resulted in Condition Prohibited by Technical Specifications
	ML22355A440
Person / Time
Site:	Callaway
Issue date:	12/21/2022
From:	; Ameren Missouri, Union Electric Co
To:	; Office of Nuclear Reactor Regulation
Shared Package
ML22355A438	List: 05000483/LER-2022-003, Submittal of Class 1E Electrical Air Conditioning System Thermal Expansion Valve Failure Resulted in Condition Prohibited by Technical Specifications;
References
	ULNRC-06790 LER 2022-003-00
	Download: ML22355A440 (1)
	v • d • e

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023 (08-2020)

(See NUREG-1O22, R.3 for instruction and guidance forcompleting this form

Affairs, (3150-0104),

Attn:

Desk ail: oira submission@omb.eo.pov.

The NRC may not conduct or sponsor, and a person is not required to respond to, a collection of intormation unless the document 1. Facility Name

2. Docket Number I. Page Callaway Plant Unit 1 05000483 I

1 OF 4

4. Title Class 1 E Electrical Air Conditioning System Thermal Expansion Valve Failure Resulted in Condition Prohibited by Technical Specifications

5. Event Date

6. LER Number

7. Report Date

8. Other Facilities Involved Sequential R

Facility Name Docket Number Month Day Year Year Number evision Month Day Year 05000 Facility Name Docket Number 10 25 2022 2022

- 003-00 12 21 2022

9. Operaling Mode

10. Power Level 100 1 1. This Report is Submitted Pursuantto the Requirements of 10 CFR §:

(Check all that apply) 10 CFR Part 20 LI 20.2203(a)(2)(vi) 50.36(c)(2)

LI 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

D 20.2201(b)

D 20.2203(a)(3)(i)

D 50.46(a)(3)(ii) 50.73(a)(2)(v)(A) 10 CFR Part 73 D

20.2201 (U)

LI 20.2203(a)(3)(ii)

LI 50.69(g)

LI 50.73(a)(2)(v)(B)

D 73.71 (a)(4)

LI 20.2203(a)(1 )

LI 20.2203(a)(4)

El 50.73(a)(2)(i)(A)

D 50.73(a)(2)(v)(C)

LI 7371 (a)(5)

LI 20.2203(a)(2)(i) 10 CFR Part 21 50.73(a)(2)(i)(B)

D 50.73(a)(2)(v)(D)

El 73.77(a)(1)(i)

LI 202203(a)(2)(ii)

LI 21.2(c)

LI 50.73(a)(2)(i)(c)

D 5073(a)(2)(vii)

D 73.77(a)(2)(i)

LI 20.2203(a)(2)(iii) 10 CFR Part 50 D

50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 73.77(a)(2)(ii)

LI 20.2203(a)(2)(iv)

D 50.36(c)(1)(i)(A) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B)

Li 20.2203(a)(2)(v)

El 50.36(c)(1)(ii)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)

LI Other (Specify here, in Abstract, or in NRC 366A).

12. Licensee Contact for this LER Licensee Contact Phone Number (Include Area Code) rB. Elwood, Supervising Engineer, Regulatory Affairs and Licensing 314-225-1905

13. Complete One lineforeach Comgonent Failure Described in this Report

Cause

System Componej Manufacturer fReportable To IRIS

Cause

System f Component Manufacturer Reportable To IRIS B

VI V

ME34 Y

14. Supplemental Report Expected Month Day Year

15. ExpectedSubmissionDate

- 02 23 2023 El No Yes (If yes, complete 15. Expected Submission Date) 1 6. Abstract (Limit to 1 560 spaces, i.e., approximately 15 single-spaced typewritten lines) t 1 530 on 1 0/25/22, a condition was identified for one of the two Class 1 E Electrical Equipment Air Conditioning (Class 1 E JC) trains. Specifically, frost and condensation were observed on the equalizing line for the #1 thermal expansion valve (TXV) associated with the compressor on the A trains refrigeration unit, SGKO5A [EIIS system: VI, component: ACUJ. At hat time, the unit was considered Operable but degraded. At 0947 on 1 0/27/22, however, SGKO5A was discovered to be ripped due to high compressor exhaust temperature. The A Class 1 E NC train was declared inoperable.

Upon further review, it was determined that the condition observed on 1 0/25/22 was firm evidence of a malfunctioning TXV

(#1 ), which caused inadequate refrigerant flow to the compressor.

It was thus determined that SGKO5A became inoperable at that time.

Nith one Class 1 E NC train inoperable, Required Action A.1 of TS 3.7.20, Class 1 E Electrical Equipment Air Conditioning (NC) System, requires immediately taking action to implement mitigating actions. With Required Action A.1 not met, the plant must be in Mode 3 within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months per Required Action B.1

. Since SGKO5A was not considered to be inoperable on 1 0/25/22, these Required Actions and Completion Times were not met, thus resulting in a condition prohibited by TS 3.7.20.

rxV #i was replaced, and SGKO5A was declared OPERABLE on 1 0/30/22 at 1 420. Investigation of this event is in

)rOgress. A supplement to this LER is expected to provide additional information.

1. DESCRIPTION OF STRUCTURE(S), SYSTEM(S), AND COMPONENT(S)

rhe Class 1 E electrical equipment air conditioning (Class 1 E NC) trains provide a suitable environment for the Class 1 E electrical equipment trains. The Class 1 E NC system {EIIS system: VI] consists of two independent trains such that each rain provides cooling of recirculated air in the rooms normally dedicated to that train. Each train consists of a prefilter, self-contained refrigeration unit (SGKO5NB) fEllS system: VI, component: ACU] using normal service water or essential service water (ESW) [ElIS system: BIJ as a heat sink, centrifugal fans, instrumentation, and controls to provide for electrical equipment room temperature control.

rhe Class 1 E NC trains have emergency operation functions and also operate during normal unit operation. Each train is normally aligned to cool only the equipment associated with its emergency load group. The Class 1 E NC trains are operated in a continuous recirculation mode to maintain the ESF switchgear [EIIS systems: EB, ED, and EJ, component

$WGRJ rooms, the battery [EIIS system: EJ, component: BTRYJ rooms, and the DC switchboard [ElIS system: EJJ rooms 0 a temperature of less than or equal to 90 degrees F.

\\dditional recirculation capability is provided via the supplemental cooling system, which consists of two trains of standby ans and dampers that may be actuated via operator action. With a Class 1 E A/C train inoperable, the additional recirculation capability (either train) may be utilized in conjunction with the remaining Class 1 E NC train to provide adequate area cooling for both trains of Class 1 E electrical equipment during normal and accident conditions.

Requirements for the Class 1 E NC trains are specified in Technical Specification (TS) 3.7.20, Class 1 E Electrical Equipment Air Conditioning (A/C) System. Limiting Condition for Operation (LCO) 3.7.20 specifies that two Class 1 E electrical equipment A/C trains shall be Operable during Modes 1, 2, 3 and 4. With one Class 1 E electrical equipment NC rain inoperable, Condition A and its three Required Actions under LCO 3.7.20 apply. Required Action A.1 requires Immediately initiating action to implement mitigating Actions; Required Action A.2 requires verifying room area

emperatures less than or equal to 90 degrees F within 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months and once per 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months thereafter; Required Action A.3 requires restoring the inoperable Class 1 E electrical equipment NC train to Operable status within 30 days. With the Required Action(s) and Completion Time(s) not met, Condition B and its Required Actions under LCO 3.7.20 apply.

Specifically, Required Actions B.1 and B.2 require the plant to be in Mode 3 (Hot Shutdown) within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and in Mode 5 (Cold Shutdown) within 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months , respectively.

2. INITIAL PLANT CONDITIONS

Callaway Plant was in MODE 1 at approximately 1 00% rated thermal power at the time of discovery of this event. For the period of time during which it was determined that the affected Class 1 E NC train had been inoperable, the plant remained in Mode 1

. No other contributing inoperable SSCs were identified during this event.

3. EVENT DESCRIPTION

Dn 1 0/25/22 at 1 530, frosting and condensation were observed on the equalizing line from the thermal expansion valve (TXV) #1 for the compressor on the A Class 1 E A/C unit, SGKO5A. TXV #1 is the first of four thermal expansion valves (for each NC unit) that sequentially operate to regulate refrigerant flow to the units compressor. The identified frosting nd condensation indicated that TXV #1 could be impeding refrigerant flow to the compressor. An Immediate Operability Determination (IOD) was per[ormed, which concluded that SGKO5A was Operable but degraded, as the associated ESF 5witchgear room temperature was still being maintained at approximately 67 degrees (i.e., within its normal day-to-day range), thus providing evidence that the A/C unit was providing adequate cooling at that time.PageofU.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3750-0104 EXPIRES: 08/31/2023 (08-2020)

1. FACILITY NAME

2. DOCKET NUMBER

3. LER NUMBER YEAR SEQUENTIAL REV Callaway Plant Unit 1 05000-483 NUMBER NO.

2022

- 003

- 00 on 1 0/27/22 at approximately 0947, electricians investigating an elevated compressor head temperature on SGKO5A noticed that the compressor was not running upon arrival. The thermostat was adjusted (downward) to attempt to start the compressor; however, SGKO5A failed to start and was declared inoperable. The unit had tripped due to high compressor exhaust temperature and was thus declared inoperable. Plant operators logged entry into the applicable Condition and completed the Required Actions of TS LCO 3.7.20.

Nith a Class YE NC unit inoperable, LCO 3.7.20 Required Action A.1 requires starting a supplemental cooling train to provide additional recirculation capability. (As explained in the Bases for TS 3.7.20, starting and running the supplemental cooling train is the primary mitigating Action required for fulfilling Required Action A.Y.) This action was implemented at 1 035 on 7 0/27/22. LCO 3.7.20 Required Action A.2 requires verifying room area temperature is less than 90 degrees iithin 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months and at least once per 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months thereafter. This action was initially performed at 1 030 on 10/27/22.

Based on subsequent investigation into this event, and as further described in the Cause of Event section of this LER, it has been determined that the period of SGKO5A inoperability began when the frosting and condensation were first observed on TXV #1

, which as stated above, was at 1 530 on 1 0/25/22. Since the IOD determined SGKO5A was DPERABLE at that time, the supplemental cooling system was not immediately inititated per TS LCO 3.7.20 Required ction A.1, and room temperatures were not verified per station procedures to be less then 90 degrees within the required ime(s) for compliance with Required Action A.2. Thus, retrospectively, the Required Actions of TS LCO 3.7.20 were not Bntered and met when SGKO5A actually became inoperable.

SGKO5A was declared OPERABLE on 10/30/22 at 1420 after replacement of TXV #1 and completion of post-maintenance esting.

. ASSESSMENT OF SAFETY CONSEQUENCES:

There were no actual nuclear, radiological, or personnel safety impacts associated with this event. The potential impact as on nuclear safety with respect to ensuring adequate area cooling for the potentially affected Class 1 E electrical equipment. The temperature limit for the ESF switchgear rooms, the battery rooms, and the DC switchboard rooms is 87 degrees F. The room temperatures are constantly monitored, and control room annunciator 1 9F is designed to alarm if the room temperature reaches 83 degrees F. No control room log entries were made for this annunciator coming in during the

imeframe of this event. All temperatures recorded locally in this timeframe were between 72.5 and 77.5 degrees F. This provides reasonable assurance that the Class 1 E electrical equipment in the ESF switchgear rooms, battery rooms and DC switchboard rooms was not affected by the identified condition. However, there is not reasonable assurance that SGKO5A itself would have been capable of perForming its required cooling function for the entirety of its 30-day mission ime in the event of a DBA during the noted timeframe.

During the timeframe of this event (1 0/25/22 at 1 530 until 1 0/30/22 at 1 420), the second train (i.e., the B train) of Class 1 E NC was OPERABLE and able to fulfill its mission time of 30 days. With a supplemental cooling system train capable of being placed into service and one train of Class 1 E electrical equipment air conditioning OPERABLE, the capability to cool both trains of Class 1 E electrical equipment was maintained.

5. REPORTING REQUIREMENTS

rhis LER is submitted pursuant to 10 CFR 50.73(a)(2)(i)(B) to report a condition prohibited by the Technical Specifications.

As described above, it has been determined, retrospectively, that the SGKO5A unit actually became inoperable at 1 530 on 10/25/22. At that point, Required Action A.1 of TS 3.7.20 should have been entered such that action should have beenPage of 4U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023 (08-2020)

7. FACILITY NAME

2. DOCKET NUMBER

3. LER NUMBER YEAR SEQUENTIAL REV Callaway Plant Unit 1 05000-483 NUMBER NO.

2022

- 003

- 00 immediately taken to implement mitigating actions (i.e., to start the supplemential cooling train). With that Hequired

\\ction not met, the plant should have then been placed in Mode 3 within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months per Required Action B.1 of IS 3.7.20.

ft!ith these Required Actions and their Completion Times not met (due to the unknown inoperability at the time), a ondition prohibited by TS 3.7.20 occurred. That is, with the plant in Mode 1 throughout the time of the noted condition, he affected Class 1 E A/C train was inoperable for a period of time longer than allowed by the Technical Specifications.

6. CAUSE OF THE EVENT

rhe cause of this event was malfunctioning of thermal expansion valve (TXV) #1

. Investigation has determined that the valve was not properly regulating flow when the valve was operating at or near its closed position, thus resulting in inadequate refrigerant flow to the compressor on SGKO5A. This caused the compressor to run at an elevated

emperature, as evidenced by the compressors high head temperature, and subsequent trip of the unit.

Results from further investigation into the cause(s) of this event will be included in a supplement to this LER.

7. CORRECTIVE ACTIONS

Upon declaring the SGKO5A unit inoperable, the TXV valve was replaced, post-maintenance testing was completed, and he unit was restored to Operable status.

s noted above, evaluation of this event is still in progress. Additional information concerning the cause and other Dorrective actions will be provided in a supplement to this LER.

B. PREVIOUS SIMILAR EVENTS

Failure of the SGKO5A/B units was previously reported in LER 2013-001-00, as submitted to the NRC on February 15, 013.

In that case, the failure was due to refrigerant leakage. Compared to the currently reported event, the Technical 3pecification compliance aspect of the LER 201 3-001 -00 event was different because Technical Specification 3.7.20 was iot incorporated into the Callaway Technical Specifications until 2019.Page4of

05000483/LER-2022-003, Submittal of Class 1E Electrical Air Conditioning System Thermal Expansion Valve Failure Resulted in Condition Prohibited by Technical Specifications

Contents

text

Cause

Cause

1. DESCRIPTION OF STRUCTURE(S), SYSTEM(S), AND COMPONENT(S)

2. INITIAL PLANT CONDITIONS

3. EVENT DESCRIPTION

5. REPORTING REQUIREMENTS

6. CAUSE OF THE EVENT

7. CORRECTIVE ACTIONS

B. PREVIOUS SIMILAR EVENTS

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05000483/LER-2022-003, Submittal of Class 1E Electrical Air Conditioning System Thermal Expansion Valve Failure Resulted in Condition Prohibited by Technical Specifications

text

Cause

Cause

1. DESCRIPTION OF STRUCTURE(S), SYSTEM(S), AND COMPONENT(S)

2. INITIAL PLANT CONDITIONS

3. EVENT DESCRIPTION

5. REPORTING REQUIREMENTS

6. CAUSE OF THE EVENT

7. CORRECTIVE ACTIONS

B. PREVIOUS SIMILAR EVENTS

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