05000423/LER-2011-003, Regarding Reactor Trip Due to Loss of Condenser Vacuum

Regarding Reactor Trip Due to Loss of Condenser Vacuum

ML12039A105
Person / Time
Site:	Millstone
Issue date:	01/27/2012
From:	Scace S Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
12-001A LER 11-003-00
Download: ML12039A105 (5)

LER-2011-003, Regarding Reactor Trip Due to Loss of Condenser Vacuum

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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) 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)(iv)(B), System Actuation
4232011003R00 - NRC Website

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wk Dominion Nuclear Connecticut, Inc.

Millstone Power Station Rope Ferry Road Waterford, CT 06385 JAN 2 7 2012 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.

MPS Lic/GJC Docket No.

License No.

12-001A RO 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 LICENSEE EVENT REPORT 2011-003-01 REACTOR TRIP DUE TO LOSS OF CONDENSER VACUUM Licensee Event Report (LER) 2011-003-00, documenting an event that occurred at Millstone Power Station Unit 3 on November 20, 2011 was inadvertently sent on January 18, 2012 without the report date entered on the LER form. This letter forwards a corrected copy of the LER that includes the report date.

If you have any questions or require additional information, please contact Mr. William D. Bartron at (860) 444-4301.

Sincerely,

/

tepnen E. Scace Site Vice President - Millstone Attachments: 1 Commitments made in this letter:

None jj~9~

Serial No. 12-001A Docket No. 50-423 Licensee Event Report 2011-003-00 Page 2 of 2 cc:

U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 C. J. Sanders Project Manager - Millstone Power Station U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08B3 Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No. 12-001A Docket No. 50-423 Licensee Event Report 2011-003-00 ATTACHMENT LICENSEE EVENT REPORT 2011-003-00 MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10/2010)

, the NRC may not conduct or sponsor, digits/characters for each block) and a person is not required to respond to, the information collection.

3. PAGE Millstone Power Station - Unit 3 05000423 1 OF 2

4. TITLE Reactor Trip Due to Loss of Condenser Vacuum

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER SEQUENTIAL REV MONTH DAY YEAR 05000 MONTH DAY YEAR YEAR NUMBER NO.

FACILITY NAME DOCKET NUMBER 11 20 2011 2011 -003-00 01 18 2012 05000

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR'.heck all that apply)

9. OPERATING MODE 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 2 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B)

__20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A)

X 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)

10. POWER LEVEL 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71 (a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 002 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)

OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)

Specify in Abstract below or in

1.

EVENT DESCRIPTION

At approximately 1750 hours0.0203 days <br />0.486 hours <br />0.00289 weeks <br />6.65875e-4 months <br /> on November 20, 2011, during power ascension with the unit in Mode 2, at 1.7 % reactor power, a report from the field informed the control room that the auxiliary boilers [SA, BLR]

had tripped. The operators promptly attempted to restart the auxiliary boilers. The condenser air ejectors [SG, COND, EJR] were already in service, and the 'A' turbine driven main feedwater pump [SJ, P] was running and being placed in service. Steam generator feedwater was being supplied by the emergency feedwater system [BA] as is normal for this power level. Before the auxiliary boilers could be restarted a gland seal supply header alarm was received. Gland sealing steam [TC] was being supplied by auxiliary steam from the auxiliary boilers. The crew referred to the appropriate alarm response procedure (ARP) for required actions. Gland seal pressure was monitored in the control room. This monitoring indicated a decreasing trend in gland seal pressure. The guidance in the ARP directed the operators to trip the main turbine and break condenser vacuum to minimize damage to the turbine gland seals. Once condenser vacuum was broken abnormal operating procedure (AOP) 3559 directed a manual reactor trip if condenser vacuum is less than or equal to 7.5 inches of Hg absolute. At 1758 hours0.0203 days <br />0.488 hours <br />0.00291 weeks <br />6.68919e-4 months <br /> the operators initiated a manual reactor trip.

All control rods fully inserted into the reactor and all emergency systems functioned as designed. There were no radiological challenges as a result of the event. There were no detrimental effects to station equipment. No limiting safety system settings were exceeded. The operators responded properly to the loss of condenser vacuum and there were no deviations from the procedure guidance in effect.

This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in manual or automatic actuation of systems listed in 10 CFR 50.73(a)(2)(iv)(B).

2.

CAUSE

As directed by plant procedure (AOP 3559) a reactor manual trip is required after a loss of condenser vacuum. Condenser vacuum was lost due to a reduction in auxiliary steam pressure after the loss of both auxiliary boilers. The auxiliary boiler shutdown was caused by a loss of boiler feed due to cavitation of the dearator feed pumps.

3.

ASSESSMENT OF SAFETY CONSEQUENCES

The operating crew responded to the loss of the auxiliary boilers and the resultant loss of gland sealing steam and ultimately the loss of main condenser vacuum as directed by approved procedures. The reactor was at 1.7% power. All control rods fully inserted into the reactor and all emergency systems functioned as designed. There were no radiological challenges as a result of the event. There were no detrimental effects to station equipment. No limiting safety system settings were exceeded. The operator actions and plant mitigating equipment responded as expected with no safety system failures.

There were no challenges to any fission product barrier. Therefore, there were no safety consequences as the result of the reactor trip.

4.

CORRECTIVE ACTION

The auxiliary boilers were restarted, auxiliary steam, gland sealing steam, and main condenser vacuum were re-established, unit start-up recommenced and the unit placed in service. Additional corrective actions are being taken in accordance with the station's corrective action program.

5.

PREVIOUS OCCURRENCES

No previous similar events/conditions were identified.

Energy Industry Identification System (EIIS) codes are identified in the text as [XX].

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