05000483/LER-1917-001, Regarding Violation of Technical Specification 3.7.9 Due to Ultimate Heat Sink (UHS) Cooling Tower Train Inoperability

Regarding Violation of Technical Specification 3.7.9 Due to Ultimate Heat Sink (UHS) Cooling Tower Train Inoperability

ML17227A129
Person / Time
Site:	Callaway
Issue date:	08/15/2017
From:	Cox B Ameren Missouri, Union Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC-06386 LER 17-001-00
Download: ML17227A129 (7)

LER-1917-001, Regarding Violation of Technical Specification 3.7.9 Due to Ultimate Heat Sink (UHS) Cooling Tower Train 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)(ii) 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)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
4831917001R00 - NRC Website

text

Ameren MISSOURI August 15, 2017 Callaway Plant U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Ladies and Gentlemen:

ULNRC-063 $6 10 CFR 50.73(a)(2)(i)(B)

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

RENEWED FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2017-001-00 VIOLATION OF TECHNICAL SPECIFICATION 3.7.9 DUE TO ULTIMATE HEAT SINK (UHS) COOLING TOWER TRAIN INOPERABILITY The enclosed Licensee Event Report (LER) is submitted in accordance with 10 CfR 50.73(a)(2)(i)(B) to report a violation of Technical Specification 3.7.9, Ultimate Heat Sink, due to the inoperability of the A UHS Cooling Tower Train for a duration of 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> and 23 minutes with the plant operating in Mode

1. As indicated in the LER, a supplemental report is expected to be submitted in November 2017.

This letter does not contain new commitments.

If you have any questions concerning this LER, please contact Tom Elwood, Supervising Engineer. Regulatory Affairs and Licensing at (314) 225-1905.

Enclosure:

LER 2017-001-00 Director, Nuclear Operations P.O. Box 620 Fulton, MO 65251 AmerenMisseuri.corn

ULNRC-063 $6 August 15, 2017 Page 2 cc:

Mr. Scott A. Morris Acting Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Cal laway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. L. John Kios Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 081-14 Washington. DC 20555-0001

ULNRC-063 $6 August 15, 2017 Page 3 Index and send hardcopy to QA File A160M761 Hardcopy:

Certrec Corporation 6100 Western Place, Suite 1 050 Fort Worth, TX 76107 (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:

F. M. Diya B. L. Cox T. E. Herrmann S. P. Banker R. C. Wink T. B. Fiwood K. A. Mills D. Turley R. J. Herman G. J. Reinhard R. C. Dismang Corporate Oversight Corporate Communications NSRB Secretary Performance Improvement Coordinator Resident Inspectors (NRC)

STARS Regulatory Affairs Mr. Jay Silberg (Pillsbury Winthrop Shaw Pittman LLP)

Missouri Public Service Commission

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 0313112020 104-2017)

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and to the Desk

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3. PAGE Callaway Plant Unit 1 05000483 1 of 4

4. TITLE Violation of Technical Spçcification 3.7.9 Due to Ultimate Heat Sink (UHS) Cooling Tower Train lnoperability

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MONT DAY YEAR YEAR SEQUENTiAL jMONTH FACILITY NAME 06 16 2017 2017

- 001

- 00 08 15 2017 FACIUTYNAME OCKETNUMBER

N/A N/A

9. OPERA71NG MODE

11. THIS REPORT IS SUBMflTED PURSUANT TO THE REQUIREMENTS OF ID CFR §: (Check all that apply) i:i 20.2201(b)

LI 20.2203(a)(3)O)

LI 50.73(a)(2)(ii)fA)

LI 50.73(a)(2)(viii)(A)

Mode 1 U 20.2201(d)

LI 20.2203(a)(3)(ii)

LI 50.73(a)(2)(ii)(B)

LI 50.73(a)(2)(viii)(B)

LI 20.2203fa)f 1)

LI 20.2203(a)(4)

LI 50.73(a)(2)(iii)

LI 50.73fa)(2)(ix)fA)

LI 20.2203(a)(2)(i)

LI 50.36(c)(l)(i)fA)

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

LI 50.73(a)(2)(x)

10. POWER LEVEL LI 20.2203(a)f2)(ii)

LI 50.36(c)(l )(ii)(A)

LI 50.73(a)f2)(v)(A)

LI 73.71 (a)(4)

LI 20.2203(a)f2)(iii)

LI 50.36(c)(2)

LI 50.73(a)(2)(v)fB)

LI 73.71(a)(5) 100%

LI 20.2203(a)(2)(iv)

LI 50.46(a)(3)(ii)

LI 50.73(a)(2)(v)(C)

LI 73.77fa)f1)

LI 20.2203(a)(2)(v)

LI 50.73(a)(2)(i)(A)

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

LI 73.77(a)(2)(i)

LI 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B)

LI 50.73(a)(2)(vii)

LI 73.77fa)(2)(ii)

LI 50.73(a)(2)(i)(C)

LI OTHER Specify in Abstract below or in NRC Form 366A

12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (include Area Code)

TB. Elwooc Supervising Engineer, Regulatory Affairs and. Liçensin P14-225-1905

13. COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT

CAUSE

SYSTEM COMPONENT FACTURER TOEPIX MANU-REPORTAB_1jUsE SYSTEM COMPONENT MANU-REPORTABLE Cutler-Y B

BS RLYj FACTURER TOEPIX 15 EX

14. SUPPLEMENTAL REPORT EXPECTED PECTED I

YES (If yes, complete 75. E)(PECTED SUBMISSION DATE) j SUBMISSION MONTH DAY YEAR DATE 11 30 2017 kBSTRACT (Limit to 7400 spaces, i.e., approximately 15 single-spaced typewritten fines)

On June 16, 2017, with the plant in Mode 1 and 100% reactor power, the A Ultimate Heat Sink (UHS) Cooling Tower Fan vas operating in fast-speed to cool the UHS retention pond. The fan spuriously tripped after 44 minutes of operation. The most probable cause of the spurious trip was a defective fast-speed thermal overload relay that had been installed as a replacement during recent preventative maintenance activities.

In Mode 1, Technical Specifications require each of two redundant UHS cooling tower trains to be capable of dissipating the heat contained in the Essential Service Water (ESW) system. An inoperable UHS cooling tower fan renders its UHS cooling tower train inoperable. Review determined that the fan was inoperable from the start of the preventative maintenance task, and existed for a duration of 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> and 23 minutes while the plant was in Mode 1. Consequently, it was concluded that the A UHS Cooling Tower Train had been inoperable for a period of time longer than allowed by the plants Technical Specifications.

Failure analysis is being performed by a vendor which will provide insight into the nature of the defective fast speed thermal Dverload relay. Maintenance procedures will be revised to include additional pre-installation testing of similar thermal Dverload relays to ensure that defects similar to the one that caused the reported failure are detected prior to installation in he plant.

NRC FORM 366 (04-2017)

1.

DESCRIPTION OF STRUCTURE(S), SYSTEM(S) AND COMPONENT(S):

Ultimate Heat Sink (UHS) System Description; The UHS [EIIS system: BSJ consists of a seismic Category I mechanical draft cooling tower and a seismic Category I

source of makeup water (retention pond) for the tower. The UHS cooling tower provides heat dissipation from the Essential Service Water (ESW) system [EllS system: BI] for safe shutdown of the plant following an accident. The UHS cooling tower is divided into two trains each with two cells having one fan assembly (fan, gear reducer, and motor) per cell. A single train with two cells is required for safe shutdown. Supply headers and spray pipes for each train are separated by interior walls.

Per Technical Specification 3.7.9, Ultimate Heat Sink, two UHS cooling tower trains are required to dissipate the heat contained in the ESW system during Modes 1, 2, 3, and 4. An inoperable UHS cooling tower fan renders its UHS cooling tower train inoperable.

If one cooling tower train is inoperable, action must be taken to restore the inoperable cooling tower train to Operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

If the cooling tower train cannot be restored to Operable status within the associated Completion Time, the plant must be placed in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

Thermal Overload Relay:

Thermal overload relays function to protect motors, motor control apparatus and motor-branch circuit conductors against excessive heating due to motor overloads and failure to start.

2.

INITIAL PLANT CONDITIONS

The plant was in Mode 1, Power Operation, at 100% reactor power at the time of this event. Besides the noted defective fast-speed thermal overload relay, there were no structures, systems, or components inoperable that contributed to the event.

3.

EVENT DESCRIPTION

On June 13, 2017, at approximately 0730, the A Train of the UHS Cooling Tower was rendered inoperable when a maintenance activity to clean and inspect starter NGO7SAF1 was authorized to start. During this maintenance activity, the fast-speed thermal overload relay was replaced. The A train of the UHS Cooling Tower was declared operable upon completion of the maintenance activity and the associated post-maintenance testing on June 14, 2017 at 1340.

On June 16, 2017 at 0732, an unexpected ESW Engineered Safety Feature Actuation Signal (ESFAS) alarm was received in the Control Room. At the time, the A Train of the UHS Cooling Tower (Fans A and C) was operating in fast speed to cool the UHS retention pond.

Upon investigation, it was determined that the A fan was not running and that the fast-speed thermal overload relay (on starter NGO7SAF1) was tripped. The A Train of the UHS Cooling Tower was declared inoperable as a result of the failure to run the A UHS Cooling Tower Fan, CEFO1A. Operability was restored when post maintenance testing was satisfactorily completed on June 17, 2017 at 0753.

The duration of the A UHS Cooling Tower Fan (CEFO1A) inoperability was 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> and 23 minutes, beginning with the maintenance activity (and associated thermal overload relay replacement). The inoperability existed while the plant was in Model.(04-2017)

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1. FACILITY NAME

- 2.DOCKETNUMBER 3LERNUMBER_______

YEAR i

SEQUENTtAC REV Callaway Plant Unit 1 05000-483 NUMBER NO i°1fl_-001

- 00 4.

ASSESSMENT OF SAFETY CONSEQUENCES

The UHS provides a source of water for use by the ESW system. The UHS retention pond and cooling tower are designed to work together to meet temperature and inventory requirements for up to a 30-day (post-accident) mission time. The inoperable condition associated with the A UHS Cooling Tower Fan (CEFO1A) would have prevented the A UHS Cooling Tower Train from performing its specified safety functions. The protected B UHS Cooling Tower Train remained Operable during this event. Due to established procedural guidance to secure the inoperable train, a loss of UHS safety function would not have occurred. The B Train of the UHS Cooling Tower would have been able to maintain UHS retention pond temperature limits and adequate UHS retention pond inventory for the required 30-day UHS mission time.

Partial train failures of the UHS cooling tower are specifically analyzed in the licensing basis analyses of record for Callaway. Sensitivities using the GOTHIC model developed for the licensing basis UHS thermal hydraulic analysis of record show that an unmitigated failure of the A UHS Cooling Tower Fan, CEFO1A, would have resulted in no adverse impact on water inventory in the UHS retention pond, but would have resulted in post-Design Basis Accident (DBA) UHS retention pond temperatures in excess of the analyzed limit discussed in the Callaway FSAR. However, specific procedural guidance exists for the Operators to diagnose and mitigate failure of a UHS Cooling Tower fan during post-accident conditions. This guidance is incorporated into the Callaway Emergency Operating Procedure (EOP) network.

Licensed operators receive training on FOPs.

The specific operator actions required to diagnose and mitigate a partial train failure in the UHS cooling tower are included in Callaways Significant Operator Response Timing program. This provides assurance of the ongoing validity of the operator response times credited in the Callaway analysis of record. Crediting manual operator actions to diagnose and mitigate partial train failures or failure of an entire train of the UHS Cooling Tower was submitted for and received NRC approval as a part of License Amendment 208. Based on the Operability of the B UHS Cooling Tower Train, and the ability of Callaway operators to diagnose and mitigate a partial failure of the A UHS Cooling Tower Train, it can be concluded that the event described in this LER did not prevent the fulfillment of any safety function or significantly degrade plant safety.

5.

REPORTING REQUIREMENTS

This LER is submitted pursuant to 10 CFR 50.73(a)(2)(i)(B) to report an operation or condition prohibited by Technical Specifications.

Technical Specification 3.7.9 requires the UHS to be Operable in Modes 1, 2, 3, and 4. With one UHS Cooling Tower train inoperable, Condition A applies such that Required Action A.1 must be entered. Required Action A.1 requires the inoperable train to be restored within a specified Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. With Required Action A.1 and its associated Completion Time not met, Condition B applies such that Required Action B.1 and B.2 must be entered. These actions direct the plant to be in Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />, respectively.

The A Train of the UHS Cooling Tower was inoperable for a duration of approximately 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> and 23 minutes, with the plant operating in Mode 1. This was a violation of TS 3.7.9, and consequently, this event is required to be reported as a condition or operation prohibited by the plants Technical Specifications, pursuant to 10 CFR 50.73(a)(2)(i)(B).Page 3 of 4U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3131/2020 104-2017)

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1._FACILITY NAME

2. DOCKET NUMBER

3. LER NUMBER Callaway Plant Unit 1

SAL I

2017

- 001

- 00 6.

CAUSE OF THE EVENT

The most probable root cause was determined to be a defective fast-speed thermal overload relay (Cutlet-Hammer Freedom Series C306) based on additional bench testing of the relay. The failure of the relay resulted in a trip of the A UHS Cooling Tower Fan. Pre-installation testing and setup of the relay was performed in accordance with Callaway procedures and work instructions. The pre-installation testing and setup confirmed that the relay would provide fan motor protection by tripping under overload conditions.

However, the testing did not confirm that the relay would not spuriously trip during extended operation in elevated ambient temperatures representative of the installed location.

Failure analysis is being performed by an offsite vendor which will provide better insight into the nature of the defective thermal overload relay and establish if a potential manufacturing defect exists.

Once vendor testing results are received, a supplemental report will be submitted to clarify root cause and/or corrective actions.

7.

CORRECTIVE ACTIONS

Maintenance procedures will be revised to include an elevated temperature hold-in test prior to installation of Cutler-Hammer Freedom Series 0306 thermal overload relays in the plant. This will prevent installation of relays that are defective in the manner that caused this event. Subjecting the overload relays to temperatures that are likely to occur in the plant rather than just room temperature will indicate which relays are defective in regards to ambient temperature compensation.

8.

PREVIOUS SIMILAR EVENTS

A review of Callaway LERs for the past three years did not identify any other examples of defective thermal overload relays that caused a component to fail to run in a manner that resulted in a condition or operation prohibited by Technical Specifications. Two corrective action documents were identified in which thermal overloads were involved with UHS Cooling Tower Fan start failures. Those two documents, i.e. CAR 200704421 and CAR 201703163 (written in 2007 and 2017, respectively) are included as internal Operating Experience in the Root Cause Analysis for the current event.

These two events document start failures, not failures of the fan to run subsequent to a successful start.Page 4 of 4