05000423/LER-2019-001

LER 2019-001-00 for Millstone Power Station Unit 3 Regarding Plant Shutdown Required by Technical Specifications, Emergency Diesel Generator Exceeded Allowed Outage Time

ML20055D320
Person / Time
Site:	Millstone
Issue date:	02/13/2020
From:	Daugherty J Dominion Energy Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
20-002 LER 2019-001-00
Download: ML20055D320 (6)

LER-2019-001,

Event date:
Report date:
4232019001R00 - NRC Website

text

Dominion Energy Nuclear Connecticut, Inc.

~ Dominion Rt 156, Rope Ferry Road, Waterford, CT 06385 Dominion Energy.com P' Energy U. S. Nuclear Regulatory Commission Serial No.20-002

• Attention: Document Control Desk MPS Lie/DCB RO Washington, DC 20555 Docket No. 50-423 License No. NPF-49 FEB 1 3 2020 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 LICENSEE EVENT REPORT 2019-001-00 PLANT SHUTDOWN REQUIRED BY TECHNICAL SPECIFICATIONS, EMERGENCY DIESEL GENERATOR EXCEEDED ALLOWABLE OUTAGE TIME This letter forwards Licensee Event Report (LER) 2019-001-00 documenting a condition at Millstone Power Station Unit 3, on December 18, 2019. This LER is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(A), the completion of any plant shutdown required by the plant's Technical Specifications.

If you have any questions or require additional information, please contact Mr. Jeffry A.

Langan at (860) 444-5544.

Sincerely, Jo Sir 1.::ce Daugherty President - Millstone Attachments: 1 Commitments made in this letter: None

Serial No.20-002 Docket No. 50-423 Licensee Event Report 2019-001-00 Page 2 of 2 cc: U.S. Nuclear Regulatory Commission Region 1.

2100 Renaissance Blvd.

Suite 100 King of Prussia, PA 19406-2713 RV. Guzman NRG Senior Project Manager Millstone Units 2 and 3 U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 C-2 Rockville, MD 20852-2738 NRG Senior Resident Inspector Millstone Power Station

Serial No.20-002 Docket No. 50-423 Licensee Event Report 2019-001-00 ATTACHMENT LICENSEE EVENT REPORT 2019-001-00 PLANT SHUTDOWN REQUIRED BY TECHNICAL SPECIFICATIONS, EMERGENCY DIESEL GENERATOR EXCEEDED ALLOWABLE OUTAGE TIME MILLSTONE POWER STATION UNIT 3 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

NRG FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018) Estimated burden per response to comply with this mandatorY collection request: 80

.::,C..,J.t-flREGt,(.,_. hours. Reported lessons learned are incorporated into the licensing process and fed g~ \ back to industrY. Send comments regarding burden estimate to the Information Services

'. J LICENSEE EVENT REPORT (LER) Branch (T-2 F43), U.S. Nuclear RegulatorY Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of

~-s-., ~of

....... ,,.. Information and RegulatorY Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information (See NUREG-1022, R.3 for instruction and guidance for completing this form collection does not display a currently valid 0MB control number, the NRG may not http://www.nrc.gov/readinq-rm/doc-collections/nureqs/staff/sr1022/r3/l conduct or sponsor, and a person is not required to respond to, the information collection.

1. Facility Name 2. Docket Number 3.Page Millstone Power Station Unit 3 05000423 1 OF 3

4. Title Plant Shutdown Required by Technical Specifications, Emergency Diesel Generator Exceeded Allowed Outage Time

5. Event Date 6. LER Number 7. Report Date 8. Other Facilities Involved I I Sequential Rev Facility Name Docket Number Month Day Year Year Month Day Year Number No. 05000 Docket Number 12 18 2019 2019 - 001 - 00 02 13 2020 05000

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

D 20.2201(b)

D 20.2203(a)(3)(i)

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

D 50.73(a)(2)(viii)(A) 1 D 20.2201(d)

D 20.2203(a)(3)(ii)

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

D 50.73(a)(2)(viii)(B)

D 20.2203(a)(1)

D 20.2203(a)(4)

D 50.73(a)(2)(iii)

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

D 20.2203(a)(2)(i)

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

D 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

10. Power Level D 20.2203(a)(2)(ii)

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

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

D 73.71 (a)(4)

D 20.2203(a)(2)(iii)

D 50.36(c)(2)

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

D 73.71(a)(5)

D 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii)

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

D 73.77(a)(1) 100 D 20.2203(a)(2)(v) 5a 50.73(a)(2)(i}(A) D 50.73(a)(2)(v)(D)

D 73.77(a)(2)(i)

D 20.2203(a)(2)(vi)

D 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 73.77(a)(2)(ii)

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

D Other (Specify in Abstract below or in NRC Form 366A)

12. Licensee Contact for this LER Licensee Contact Telephone Number (Include Area Code)

Jeffry A Langan, Manager Nuclear Station Licensing (860) 444-5544

13. Complete One Line for each Component Failure Described in this Report Cause System I Manufacturer Reportable to ICES Cause System Component I I I Component I

Manufacturer ~eportable to ICES B EK DUCT

14. Supplemental Report Expected N

I B EK SIT Month Day Year

15. Expected Submission Date D Yes (If yes, complete 15. Expected Submission Date)

Abstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)

On December 17, 2019 at 1936 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.36648e-4 months <br />, while operating in Mode 1, at 100% power, Millstone Power Station Unit 3 (MPS3) operators commenced an orderly shutdown of MPS3 when it was determined that the 'A' Emergency Diesel Generator (EOG) maintenance, modifications and testing would not be completed within the allowed outage time by Technical Specification Action Statement (TSAS) 3.8.1.1 action b.5. The TSAS required that the plant be placed in Hot Standby (HSBY) within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Cold Shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. The plant entered Hot Standby on December 18, 2019 at 0117 hours0.00135 days <br />0.0325 hours <br />1.934524e-4 weeks <br />4.45185e-5 months <br /> and entered Cold Shutdown on December 18, 2019 at 1948 hours0.0225 days <br />0.541 hours <br />0.00322 weeks <br />7.41214e-4 months <br />.

During the post maintenance testing activities, the EOG first experienced unexpected EOG load reductions and then turbocharger surging. The load reductions were caused by an intermittent speed signal change (while paralleled to the grid). This was resolved by implementing a design change to utilize a magnetic pick up speed signal. The primary resolution for turbocharger surging was the replacement of the newly installed spread exhaust system with the original exhaust system, which was removed during the plant maintenance activities. Resolving these two unrelated issues required more than the TSAS Allowed Outage Time to correct.

This condition is being reported pursuant to 10 CFR 50.73(a)(2)(i)(A) - The completion of any nuclear plant shutdown required by the plant's technical specifications.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BYOMB: N0.3150-0104 EXPIRES: 03/31/2020 (04-2018)

Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Information LICENSEE EVENT REPORT Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer,

{LER) CONTINUATION SHEET Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an (See NUREG-1022, R.3 for instruction and guidance for completing this form information collection does not display a currently valid 0MB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the http://www. nrc.qov/readinq-rm/doc-collections/nureqs/staff/sr1022/r3D information collection.

1.FACILITYNAME 2. DOCKET 3. LER NUMBER YEAR SEQUENTIAL REV Millstone Power Station Unit 3 05000423 NUMBER NO.

2019 001 00 NARRATIVE

1. EVENT DESCRIPTION On December 17, 2019 at 1936 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.36648e-4 months <br />, while operating in Mode 1, at 100 percent power, Millstone Power Station Unit 3 (MPS3) operators commenced an orderly shutdown of MPS3 when it was determined that the 'A' Emergency Diesel Generator (EOG) would not be restored to operable status before the expiration of the Technical Specification Action Statement (TSAS) 3.8.1.1 action b.5. The TSAS required that the plant be placed in Hot Standby (HSBY) within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The plant entered Hot Standby on December 18, 2019 at 0117 hours0.00135 days <br />0.0325 hours <br />1.934524e-4 weeks <br />4.45185e-5 months <br /> and entered Cold Shutdown on December 18, 2019 at 1948 hours0.0225 days <br />0.541 hours <br />0.00322 weeks <br />7.41214e-4 months <br />.

The Unit 3 'A' EOG was removed from service and TSAS 3.8.1.1 action b was entered on December 3, 2019 at 2005 hours0.0232 days <br />0.557 hours <br />0.00332 weeks <br />7.629025e-4 months <br /> for planned maintenance activities. The maintenance activities included replacement of the exhaust system with a new Spread Exhaust system and completion of scheduled preventative maintenance activities.

MPS3 Technical Specification (TS) 3.8.1.1.b requires that two separate and independent diesel generators be operable in modes 1, 2, 3 and 4. TSAS 3.8.1.1 Action b.5 requires if one EOG is inoperable to restore the inoperable EOG to operable status within 14 days (if the required Unit 2 EDGs are operable and the Unit 3 Station Blackout (SBO) diesel generator is available within one hour prior to or after entering this condition, and at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter) or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. Included in the planned maintenance activities was the implementation of a design change to replace the EOG exhaust system with an upgraded spread exhaust system. During the post maintenance testing activities, the EOG experienced unexpected load reductions. The load reductions were caused by an intermittent reduction in speed signal, while operating in parallel mode, that was resolved by implementing a design change to utilize a magnetic pick up speed signal. This troubleshooting and correction impacted the schedule by approximately 2.5 days. During subsequent post maintenance testing activities, the EOG experienced unexpected turbocharger surging at or above full diesel load. The station spent approximately 5.5 days investigating the cause, including; multiple engine balancing runs, replacement of combustion air inlet filters, inspection of the inlet silencer, and mechanical governor/actuator replacement. The turbocharger surging was not corrected prior to the expiration of the TSAS.

Following the unit shutdown, the primary resolution of the turbocharger surging was replacement of the spread exhaust system with the original exhaust system. The 'A' EOG was then retested and satisfactorily passed the TS surveillance tests required to restore its operability. The 'A' EOG was declared operable on December 21, 2019 at 1508 hours0.0175 days <br />0.419 hours <br />0.00249 weeks <br />5.73794e-4 months <br />.

This condition is being reported pursuant to 10 CFR 50. 73(a)(2)(i)(A) - The completion of any nuclear plant shutdown required by the plant's technical specifications.

2 CAUSE The direct cause of the shutdown of MPS3 was the inability to identify and correct the turbocharger surging noted during post maintenance testing within the TSAS Allowed Outage Time.

NRC FORM 366A (04-2018) Page 2 of 3

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BYOMB: N0.3150-0104 EXPIRES: 03/31/2020 (04-2018)

Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Information LICENSEE EVENT REPORT Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Jnfocollects.Resource@nrc.gov, and to the Desk Officer, (LER) CONTINUATION SHEET Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid 0MB control number, the (See NUREG-1022, R.3 for instruction and guidance for completing this form NRG may not conduct or sponsor, and a person is not required to respond to, the http://www.nrc.gov/readinq-rm/doc-collections/nureqs/staff/sr1022/r3/) information collection.

1. FACILITY NAME 2. DOCKET 3. LER NUMBER YEAR SEQUENTIAL REV Millstone Power Station Unit 3 05000423 NUMBER NO.

2019 001 00 NARRATIVE

3. ASSESSMENT OF SAFETY CONSEQUENCES All requirements of Technical Specifications were met while the 'A' EOG was out of service. The risk profile was managed in accordance with 10 CFR 50 .65(a)(4). The shutdown of MPS3 in accordance with TSAS 3.8.1.1 action b was conducted in an orderly and controlled manner. No other risk significant equipment was out of service during the time that the 'A' EOG was out of service or during the controlled shutdown evolution. The safety consequences of this condition were low. No safety systems actuated. Although the 'A' EOG was out of service, MPS3 was in a normal electrical configuration. All equipment powered from offsite sources and the 'B' EOG, the steam-driven auxiliary feedwater pump, the Unit 3 SBO diesel generator and the two Unit 2 EDGs remained operable throughout. There was no loss of decay heat removal capability, because main and auxiliary feedwater pumps remained operable and available to feed the steam generators.

4. CORRECTIVE ACTION The signal generator for the speed input to the 'A'EOG tachometer relay was replaced with a magnetic pick up speed signal. The spread exhaust system modification was removed, and the original exhaust system was re-installed. The EOG was balanced and retested in accordance with its post maintenance test plan and satisfactorily passed the required TS surveillance tests to return the EOG to operability.

Extent of condition was evaluated and addressed for the 'B' EOG.

Additional corrective actions are being taken in accordance with the station's corrective acUon program.

5. PREVIOUS OCCURRENCES No previous similar events were identified in the last three years in which the condition of an EOG resulted in a plant shutdown required by Technical Specifications.

6. Energy Industry Identification System (EIIS) codes

• EK, Emergency Diesel Generator NRG FORM 366A (04-2018) Page 3 of 3