05000423/LER-2008-003, Automatic Reactor Trip During Shutdown for Refueling Outage 3R12

Automatic Reactor Trip During Shutdown for Refueling Outage 3R12

ML083570152
Person / Time
Site:	Millstone
Issue date:	12/10/2008
From:	Morris L Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
08-0726 LER 08-003-00
Download: ML083570152 (5)

LER-2008-003, Automatic Reactor Trip During Shutdown for Refueling Outage 3R12

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), System Actuation
4232008003R00 - NRC Website

text

I'il Dominion Nuclear Connecticut, Inc.

Millstone Power Station Rope Ferry Road, Waterford, CT 06385 DEC 1 0 2008 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.

MPS Lic/GJC Docket No.

License No.

08-0726 RO 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 LICENSEE EVENT REPORT 2008-003-00 AUTOMATIC REACTOR TRIP DURING SHUTDOWN FOR REFUELING OUTAGE 3R12 This letter forwards Licensee Event Report (LER) 2008-003-00 documenting a condition discovered at Millstone Power Station Unit 3 on October 11, 2008. This LER is being submitted pursuant to 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).

If you have any questions or require additional information, please contact Mr. William D.

Bartron at (860) 444-4301.

Sincerely, Linwood L. Morris Plant Manager - Nuclear Attachments: 1 Commitments made in this letter: None

/

Serial No. 08-0726 Docket No. 50-423 Licensee Event Report 2008-003-00 Page 2 of 2 cc:

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

Serial No. 08-0726 Docket No. 50-423 Licensee Event Report 2008-003-00 ATTACHMENT LICENSEE EVENT REPORT 2008-003-00 AUTOMATIC REACTOR TRIP DURING SHUTDOWN FOR REFUELING OUTAGE 3R12 MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.

Abstract

On October 11, 2008, while in MODE 1 at approximately 30% power an automatic reactor trip occurred, as Millstone Power Station Unit 3 was reducing power in preparation for the 12th refueling outage. Prior to the reactor trip the plant was experiencing Steam Generator (SIG) level oscillations as the result of removing feedwater system components from service. The operators took manual control of the feedwater.system, however, the oscillations increased and the 'A' S/G reached its 'high-high' set point resulting in an automatic turbine trip and feedwater isolation. A reactor trip on 'low-low' S/G level followed. All safety systems operated normally including the automatic start of the auxiliary feedwater pump, and the reactor shut down safely. All secondary systems operated normally.

The cause was determined to be the operating crew on shift failed to effectively use the tools necessary to enable an event free shutdown of the plant. The organization with respect to monitoring and measuring crew performance was not effective in implementing programs designed to manage the challenges to the operators.

Prior to start up from the refueling outage, training on low power feed station operations for on shift and active licensed operators was conducted. Additionally proper operation of the SIG water level control system and the feedwater regulating valves was verified. Additional corrective actions will be entered into the station's corrective action program.

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

NRC FORM 366 (9-2007)

(If more space is required, use additional copies of NRC Form 366A) (17)

1.

EVENT DESCRIPTION

On October 11, 2008, while in MODE 1 at approximately 30% power an automatic reactor [AB] [RCT] trip occurred, as Millstone Power Station Unit 3 (MPS3) was reducing power in preparation for the 12th refueling outage. Prior to the reactor trip the plant was experiencing Steam Generator (S/G) [SB] [SG] level oscillations as the result of removing feedwater system [SJ] components from service. In an effort to control the S/G level oscillations, the operators took manual control of the feedwater system; however, the oscillations increased to the point that the 'A' S/G reached its 'high-high' set point resulting in an automatic turbine [TRB] trip and feedwater isolation. Once the turbine tripped, the 'C' S/G level quickly shrank to its 'low-low' S/G level set point resulting in a reactor trip. All safety systems operated normally including the automatic start of the auxiliary feedwater (AFW) pump [BA] [P], and the reactor shut down safely. All secondary systems operated normally.

2.

CAUSE

The cause was determined to be the operating crew on shift failed to effectively use the tools necessary to enable an event free shutdown of the plant. The organization with respect to monitoring and measuring crew performance was not effective in implementing programs designed to manage the challenges to the operators.

3.

ASSESSMENT OF SAFETY CONSEQUENCES

With MPS3 at approximately 30% power during the down-power evolution, the S/G levels began to oscillate over a wider and wider range. The S/G oscillations increased to the point that the 'A' S/G reached its 'high-high' set point resulting in an automatic turbine trip and feed water isolation. Once the turbine tripped, the 'C' S/G quickly shrank to its 'low-low' S/G level set point resulting in a reactor trip. All safety systems operated normally and the reactor shut down safely.

As the result of the reactor trip, the AFW pump automatically started in accordance with plant design and the system operated as designed. No other mitigating systems were challenged.

The integrity of the fuel, reactor coolant system, or containment was not challenged or degraded as the result of this event.

There were no challenges to public or occupational radiation safety, or personnel safety as the result of this event.

4.

CORRECTIVE ACTION

Prior to start up from the refueling outage, training on low power feed station operations for on shift and active licensed operators was conducted. Additionally proper operation of the S/G water level control system and the feedwater regulating valves [FCV] was verified. Additional corrective actions will be entered into the station's corrective action program.

5.

PREVIOUS OCCURRENCES

LER 2005-005-00 documents an automatic reactor trip of Millstone Unit 3 due to 'low-low' steam generator level.

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

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