05000483/LER-2013-001, Re Violation of Technical Specification 3.0.3 Due to Class 1E Electrical Equipment AC Unit Inoperability

Re Violation of Technical Specification 3.0.3 Due to Class 1E Electrical Equipment AC Unit Inoperability

ML13050A216
Person / Time
Site:	Callaway
Issue date:	02/15/2013
From:	Diya F Ameren Missouri, Union Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC-05958 LER 13-001-00
Download: ML13050A216 (9)

LER-2013-001, Re Violation of Technical Specification 3.0.3 Due to Class 1E Electrical Equipment AC Unit Inoperability

Event date:
Report date:
Reporting criterion:	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)(vii), Common Cause Inoperability 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) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function
4832013001R00 - NRC Website

text

~~

WAmeren MISSOURI Fadi M. Diya Vice President Nuclear Operations Ameren Missouri Callaway Plant T 573.676.6411 F 573.676.4056 February 15, 2013 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 ULNRC-05958 10 CFR 50. 73(a)(2)(i)(B)

Ladies and Gentlemen:

DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.

FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2013-001-00 VIOLATION OF TECHNICAL SPECIFICATION 3.0.3 DUE TO A CLASS 1E ELECTRICAL EQUIPMENT A/C UNIT INOPERABILITY The enclosed licensee event report is submitted in accordance with 1 OCFR50.73(a)(2)(i)(B) to report a violation of Technical Specification 3.0.3 due to 'B' Class IE Electrical Equipment A/C Unit Inoperabili ty.

This letter does not contain new commitments.

Enclosure: LER 2013-001-00 Fadi M. Diya Vice President Nuclear Operations Junction CC & Hwy 0 PO Box 620, MC CA-460 Fulton, MO 65251 AmerenMissouri.com

ULNRC-05958 February 15, 2013 Page 2 cc:

Mr. Elmo E. Collins Regional Administrator U.S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Fred Lyon Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-8B 1 Washington, DC 20555-2738

ULNRC-05958 February 15, 2013 Page 3 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 4150 International Plaza Suite 820 Fort Worth, TX 76109 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)

Electronic distribution for the following can be made via LER ULNRC Distribution:

A. C. Heflin F. M. Diya C. 0. Reasoner III L. H. Graessle D. W. Neterer S. A. Maglio R. Holmes-Bobo Corporate Oversight NSRB Secretary T. B. Elwood Performance Improvement Coordinator Resident Inspectors (NRC)

B. D. Brooks (WCNOC)

Mr. Mike Westman (WCNOC)

Mr. Tim Hope (Luminant Power)

Mr. Ron Barnes (APS)

Mr. Tom Baldwin (PG&E)

Mr. Mike Murray (STPNOC)

Mr. Mark Morgan (SCE)

Mr. John O'Neill (Pillsbury Winthrop Shaw Pittman LLP)

Missouri Public Service Commission Records Center (INPO)

NRC FORM366 (10-2010)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 LICENSEE EVENT REPORT (LER)

(See reverse for required number of digits/characters for each block)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME Callaway Plant Unit 1

2. DOCKET NUMBER 05000483

13. PAGE I

1 OF 6

4. TITLE Violation of Technical Specification 3.0.3 Due To A Class 1 E Electrical Equipment A/C Unit lnoperability

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV MONTH NUMBER NO.

YEAR FACILITY NAME DOCKET NUMBER MONTH DAY YEAR DAY FACILITY NAME DOCKET NUMBER 12 17 2012 2013 001 -

00 02 15 2013

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)

D 2o.22o1(b)

D 20.2203(a)(3Hi>

D 50.73(a)(2)(i)(C>

D 50.73(a)(2)(vii) 1 D 20.2201 (d)

D 20.2203(a)(3)(ii)

D 50. 73(a)(2)(ii)(A)

D 50. 73(a)(2)(viii)(A)

D 20.2203(a)(1)

D 20.2203(a)(4)

D 50.73(a)(2)(ii)(B)

D 50.73(a)(2)(viii)(B) 1---------tD 20.2203(a)(2)(i)

D 50.36(c)(1)(i)(A)

D 50.73(a)(2)(iii)

D 50.73(a)(2)(ix)(A)

10. POWER LEVEL 100 D 20.2203(a)(2)(ii)

D 50.36(c)(1 )(ii)(A)

D 50. 73(a)(2)(iv)(A)

D 50. 73(a)(2)(x)

D 20.2203(a)(2)(iii)

D 50.36(c)(2)

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

D 73.71(a)(4)

D 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii)

D 50. 73(a)(2)(v)(B)

D 73.71 (a)(5)

D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

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

D OTHER D 20.2203(a)(2)(vi)

[8] 50.73(a)(2)(i)(B)

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

Specify in Abstract below or in LICENSEE EVENT REPORT (LER) u.s. NUCLEAR REGULATORY COMMISSION CONTINUATION SHEET

2. DOCKET 05000483 YEAR 2013

6. LER NUMBER I

SEQUENTIAL I NUMBER 001 REV NO.

00 3

3. PAGE OF 6

conjunction with several other compensatory measures). A practice has thus been established at Callaway such that in the event of inoperability of one C 1 EEEAC unit, operability of the Class 1 E electrical equipment (both trains) can be supported by the remaining operable C 1 EEEAC unit once the noted compensatory actions (including opening the electrical equipment room doors) have been completed.

In accordance with the above-described practice, when a C 1 EEEAC unit/train is declared inoperable during power operation, the applicable Conditions and Required Actions ofTS 3.8.4, TS 3.8.7, and TS 3.8.9 are entered due to declaring the supported train of Class 1E electrical equipment inoperable. Since there are two inverters in each train of Class 1 E electrical equipment, but the Conditions and Required Actions under TS 3.8.7 only address inoperability of a single inverter, declaring one train of supported Class 1 E electrical equipment inoperable also requires entry into TS LCO 3.0.3. After entering LCO 3.0.3 and the Conditions and Required Actions ofTS 3.8.4, TS 3.8.7, and TS 3.8.9 upon declaring a C1EEEAC train/unit inoperable, these Conditions and Required Actions (and LCO 3.0.3) may be exited once supported equipment operability is restored by completion of the noted compensatory actions. Even with the compensatory actions completed, however, the inoperable C1EEEAC unit/train must be restored within seven days per Callaway's requirements.

2.

INITIAL PLANT CONDITIONS

The plant was in MODE 1 at 100 percent power at the time when a Freon leak was first discovered in the B Class 1E AC Unit on December 17,2012.

3.

EVENT DESCRIPTION

On 12/17/2012, during performance of a quarterly leak check on SGK05B, a small amount of refrigerant was identified to be leaking from the compressor suction and discharge pressure-sensing lines by use of a halide detector. The leakage was the result of the two 118-inch copper sensing lines rubbing together. The identified leakage and inability to quantify leakage rates caused SGK05B to be declared inoperable at 10:45. LCO 3.0.3 and the Applicable Conditions and Required Actions ofTS 3.8.4, TS 3.8.7, and TS 3.8.9 were entered with the intent of completing the necessary compensatory actions for restoring Operability of the affected Class 1 E electrical equipment. Steps were taken to perform plant procedure, "Control Room and Class 1 E Air Conditioning Unit Charging," which is used to check the unit for adequate refrigerant charge. Prior to the completion of the refrigerant charge check on SGK05B, an inspection was performed on SGK05A. This inspection identified visible leakage on the unit's low oil pressure and compressor discharge sensing lines. As a result of the inability to quantify the identified leakage, SGK05A was declared inoperable at 14:35. This placed the plant in LCO 3.0.3 (without the ability to implement compensatory measures for the supported Class 1 E electrical equipment, assuming both C 1 EEEAC units inoperable). Steps were immediately taken to also perform a refrigerant charge check on the SGK05A unit.

Upon completion of the refrigerant charge check on SGK05B, it was identified that no refrigerant addition was necessary. It was thus confirmed that SGK05B had in fact remained Operable throughout this time. At I6:00 on I2/I7/20I2 SGK05B was declared operable. LCO 3.0.3 was exited at I6:I2 (as the necessary compensatory actions had been completed to ensure cooling to both Class IE electrical equipment trains via the operable CIEEEAC unit, SGK05B). The charge check for SGK05A, however, identified that 9 lbs. 3 oz. of refrigerant needed to be added to the system. Based on the reduced Freon charge, it was apparent that the leak rate would challenge the unit's capability to meet its required mission time.

In order to isolate the leaking sensing lines, a Temporary Modification was installed. This modification disconnected the two I/8-inch sensing lines and capped their termination ports on the compressor body. {The functions of the sensing lines are not essential to the safety function performed by the CIEEEAC unit, except for being an extension of the Freon pressure boundary).

Following implementation of this modification, SGK05A was restored to an operable status at II:08 on I2/I8/20I2. SGK05A was inoperable for approximately twenty hours and 30 minutes.

4.

ASSESSMENT OF SAFETY CONSEQUENCES

The Class IE Air Conditioning units, SGK05A and B, are not explicitly modeled in the Callaway Probabilistic Risk Assessment (PRA) model. Analysis supporting the PRA model demonstrates that safety systems supported by the SGK05 units are capable of meeting a 24-hour PRA mission following loss of a single SGK05 unit. As such, the Class IE electrical equipment air-conditioning units are below the truncation significance level for inclusion in the PRA model.

Further, as previously noted, with one SGK05 unit inoperable the remaining operable unit can be utilized to support both trains of Class IE electrical equipment with the appropriate compensatory actions completed. Although both units had been declared inoperable, it was soon confirmed that the leak condition identified for SGK05B was not sufficient for actually rendering the unit inoperable. Thus, SGK05B remained operable, and as such it was capable of providing cooling to both trains of supported Class IE electrical equipment.

5.

REPORTING REQUIREMENTS

This LER is submitted pursuant to IO CFR 50.73(a)(2)(i)(B) to report a condition or operation prohibited by the plant's Technical Specifications.

A condition or operation prohibited by the plant Technical Specifications was determined to have occurred due to the leakage condition identified for SGK05A. As explained previously, when a CIEEEAC unit/train is declared inoperable, LCO 3.0.3 is required to be entered due to the impact on the supported Class IE inverters. Upon declaring a CIEEEAC unit inoperable (i.e., when it is known to be inoperable), compensatory actions can be taken to restore operability of the inverters (and the other supported Class IE equipment) via the remaining operable CIEEEAC unit, thus allowing LCO 3.0.3 to be exited. If the compensatory actions are not (or cannot be) taken, LCO 3.0.3 remains in effect such that per the requirements of that TS, action must be taken within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to place the plant in Mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />, in Mode 4 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />, and in Mode 5 within 3 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. Thus, with a C 1 EEEAC unit inoperable and no compensatory actions taken, the plant must be in Mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> (and so on) to comply with the plant's Technical Specifications (i.e., LCO 3.0.3).

When the tubing leak was identified for SGK05A on 12/17/2012, it was declared inoperable on the basis that the leak condition would not have enabled the unit to fulfill its 30-day post-accident mission time from that point in time. Although it is not certain when the leak began, it was concluded that the leakage had existed for a period of time prior to the discovery of the leak such that the period of SGK05A inoperability exceeded the time allowed by the Technical Specifications (i.e., longer than the 7-hour period of plant operation allowed by LCO 3.0.3 with no compensatory measures in place).

6.

CAUSE OF THE EVENT

The Direct Cause of the leak condition identified for each of the SGK05 units was determined to be the seismically qualified design of the skid-mounted unit which exposes some sub-components to excessive vibration during unit operation. The leakage was the result of two sensing lines rubbing together. The Root Cause was determined to be an inadequate scope of previously conducted equipment reliability evaluations on the Control Building HV AC System. These evaluations should have identified the long-term trends in equipment failure that led to the event in this LER.

7.

CORRECTIVE ACTIONS

As noted in the Event Description section of this LER, a temporary modification was installed to disconnect two 1/8-inch sensing lines and cap their termination ports on the compressor body.

The direct cause is addressed by an increase in preventative maintenance and monitoring of vibration susceptible sub-components and piping on the Class 1 E electrical equipment air-conditioning units.

In order to identify other latent, long-term trending issues, Engineering will document a review of the history of the safety-related Control Building HVAC system Air Conditioning units. As part of the review, an analysis of historical data, including subcomponent failure data, will be performed.

Engineering will then revise or implement new Preventative Maintenance Tasks to address any failure mechanisms that are identified.

8.

PREVIOUS SIMILAR EVENTS

On March 31,2011, Callaway submitted LER 2010-010-00 about a violation of Technical Specification 3.0.3 due to inoperability of the B Class IE electrical equipment air conditioning unit.

The air conditioning unit was out-of-service for a timeframe longer than permitted by the Technical Specifications; however, it was for a cause other than a Freon leak.

An internal operating experience search for vibration-induced leakage from copper tubing during the last three years was completed using Callaway's corrective action program and the Equipment Out of Service Logs (EOSLs ). This review identified multiple examples of Freon leakage from similar air conditioning units.

On 12/17/2012: Corrective Action Program document, SGK05B Freon Leaks on sensing line, was written on the same day as the SGK05A leak was identified. This documents nearly identical leakage due to vibration induced wear on sensing lines.

On 9/18/2011: Corrective Action Program document, Hazardous Environment developed in A CRA C Room, documents Freon leakage on hot gas piping due to mechanical fatigue leading to a though wall crack.

On 5/15/2011: Corrective Action Program document, Small Freon Leak on SGK05A, documents small refrigerant leak due to an incomplete solenoid joint.

On 3/8/2011: Corrective Action Program document, Oil Leak on SGK04A, documents oil leaking from an oil pressure sensing line. The leak occurred where a sensing line was bent at a sharp angle. This was determined to be the result of work in area contributing to the failure.

On 2/27/2011: Corrective Action Program document, SGK05A 'A' Train Class JE AIC Unit declared inoperable, identifies leakage discovered coming from the high side of the piping about a foot from the compressors high side isolation valve. The failure was attributed to wear from the edge of the installed fabric insulation on the compressor discharge piping which was vibrated by the compressor.

From the internal examples, only the 3/8/2011 Oil Leak on SGK04A event, deals with leakage on small diameter copper sensing lines. Corrective actions from this event only repaired the leak.

This event was determined to be a maintenance preventable functional failure with the basic cause being that work in the area contributed to failure.