United States Nuclear Regulatory Commission - Protecting People and the Environment

Event Notification Report for November 30, 2011

U.S. Nuclear Regulatory Commission
Operations Center

Event Reports For
11/29/2011 - 11/30/2011

** EVENT NUMBERS **


47485 47488 47489

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Power Reactor Event Number: 47485
Facility: SOUTH TEXAS
Region: 4 State: TX
Unit: [ ] [2] [ ]
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: ROBERT BRINKLEY
HQ OPS Officer: HOWIE CROUCH
Notification Date: 11/29/2011
Notification Time: 06:55 [ET]
Event Date: 11/29/2011
Event Time: 03:29 [CST]
Last Update Date: 11/29/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Person (Organization):
THOMAS FARNHOLTZ (R4DO)

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
2 A/R Y 100 Power Operation 0 Hot Standby

Event Text

AUTOMATIC REACTOR TRIP DUE TO TURBINE TRIP ON GENERATOR LOCKOUT

"At 0329 CST on 11/29/2011, Unit 2 experienced an automatic Reactor Trip while the plant was stable at 100% power in Mode 1. All systems actuated as designed. The reactor trip was caused by Generator Lockout.

"All ESF systems actuated as designed. The following systems actuated: Auxiliary Feedwater [AFW] and Feedwater Isolation.

"All control rods fully inserted. Steam Dump system valve FV 7485 failed open and was manually isolated. This caused a letdown isolation that was restored. No primary/secondary relief valves lifted. There were no electrical bus transfer problems. Normal operating temperature and pressure [of] 567 degrees F and 2235 psig [is being maintained]. There were no significant TS LCOs entered."

The electrical grid is stable and is supplying power to the plant via a normal shutdown electrical line-up. Decay heat is being removed via steam dumps to the condenser with AFW supplying the steam generators. There was no effect on Unit 1.

The licensee has notified the NRC Resident Inspector.

* * * UPDATE ON 11/29/11 AT 1312 EST FROM BRINKLY TO HUFFMAN * * *

The licensee has issued a press release concerning this event. The NRC Resident Inspector will be notified. R4DO (Farnholtz) informed.

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Part 21 Event Number: 47488
Rep Org: FLOWSERVE
Licensee: FLOWSERVE
Region: 1
City: LYNCHBURG State: VA
County:
License #:
Agreement: Y
Docket:
NRC Notified By: JEFF McCONKEY
HQ OPS Officer: BILL HUFFMAN
Notification Date: 11/29/2011
Notification Time: 17:25 [ET]
Event Date: 08/02/2011
Event Time: [EST]
Last Update Date: 11/29/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
21.21 - UNSPECIFIED PARAGRAPH
Person (Organization):
WAYNE SCHMIDT (R1DO)
BINOY DESAI (R2DO)
KENNETH RIEMER (R3DO)
THOMAS FARNHOLTZ (R4DO)
PT 21 GRP (E-MAIL) ()

Event Text

PART 21 NOTIFICATION ON LIMITORQUE SMB-5T ACTUATOR CLUTCH LUG FAILURE

The following is a summary of information was received from Limitorque via facsimile:

"On August 2, 2011, Flowserve-Limitorque was notified by Browns Ferry Nuclear (BFN) Generating Station that a Limitorque SMB-5T valve actuator (1-MVOP-074-052) had failed to run open automatically during the performance of a stroke test. Electrical maintenance personnel working at the valve reported an abnormal mechanical noise. Upon disassembly, it was found that the driving lugs on both the sliding clutch gear and the flexible clutch were seriously worn with a significant amount of deformation. Further investigation by BFN showed that the declutch mechanism would not allow full engagement of the drive lugs on the sliding clutch and flexible clutch. These lugs must be engaged for motor operation to take place. The declutch mechanism required adjustment to allow full drive lug engagement.

"Following reassembly of the SMB-5T on 1-MVOP-074-052, an inspection was performed of the SMB-5T on valve 1-MVOP-074-066 which was manufactured and supplied to TVA at the same time. This actuator was functioning normally at the time of the inspection. Disassembly of the clutch compartment revealed evidence of deformation of the clutch drive lugs. To better evaluate the operation of the clutch components, the grease was cleaned out of the compartment and a boroscope used so that the action of the clutch could be seen. Boroscope examination of several declutching and re-clutching tests showed that the clutch lugs would not engage fully. The major contributing factor in this issue was found to be the external declutch lever stop screw adjustment. Adjustment of the lever stop screw significantly improved the lug engagement. Subsequently, BFN personnel inspected four additional SMB-5T actuators. The declutch components were found to be adjusted correctly and no indications of abnormal clutch lug wear were found.

"The potential for this issue is limited to SMB-5 and SMB-5T actuators only. Other sizes of SMB/SB/SBD actuators are not affected. This issue, when it occurs can affect the safety related function of the actuator by preventing proper motorized operation. Indications of the issue can include failure to complete valve stroke, failure to remain in motorized operation, intermittent motorized operation resulting in longer than expected stroke time, and/or abnormal noise in the clutch compartment.

"Limitorque performed an investigation per the guidelines of 10 CFR Part 21. The failure of 1-MVOP-074-052 to operate was due to damage to the drive lug interface between the sliding clutch and the flexible clutch which resulted in the actuator disengaging from electric motor operation in mid-stroke of the valve. This lug damage occurred over time during normal operation of the actuator and is directly attributable to an assembly set-up error resulting in partial lug engagement. The actuators which were investigated at BFN Unit 1 were of relatively recent manufacture, having been shipped from the Limitorque factory in 2004. Limitorque's review of existing SMB-5/5T assembly procedures followed by interviews with assembly personnel led to the conclusion that the root cause of this event was that the Limitorque factory assembly procedure documents for the SMB-5/5T lack adequate detail to ensure reliable long term functionality of the clutching mechanism.

"Limitorque's review of previous industry operating experience did not show any history of problems related to drive lug engagement and/or declutch components in SMB-5/5T actuators. However to address the potential issue of insufficient drive lug engagement, Limitorque will issue a Maintenance Update to the MOV Users Group for distribution to the utilities (on or before January 15, 2012) containing recommendations for site inspection of the SMB-5/5T clutch mechanism as well as detailed instructions for set-up, adjustment and verification of proper clutch operation. As part of our internal corrective action, Limitorque will develop enhanced assembly and service procedures for the SMB-5/5T to include sufficient detail to ensure the proper set-up and function of the clutching mechanism. Limitorque assembly, field service, and QC personnel will be trained in the enhanced procedures."

Technical contacts:
John Thilking 434-522-9862
Jeff McConkey 434-845-9738

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Power Reactor Event Number: 47489
Facility: CLINTON
Region: 3 State: IL
Unit: [1] [ ] [ ]
RX Type: [1] GE-6
NRC Notified By: KEN LEFFEL
HQ OPS Officer: STEVE SANDIN
Notification Date: 11/29/2011
Notification Time: 21:47 [ET]
Event Date: 11/29/2011
Event Time: 17:28 [CST]
Last Update Date: 11/29/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
Person (Organization):
KENNETH RIEMER (R3DO)

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 A/R Y 16 Power Operation 0 Hot Shutdown

Event Text

UNIT EXPERIENCED AN AUTOMATIC REACTOR SCRAM DURING A PLANNED SHUTDOWN

"During a planned shutdown in preparation for refueling outage C1R13, shortly after tripping the main turbine, an automatic reactor scram occurred due to high reactor steam dome pressure. Preliminarily, per the plant process computer, the reactor pressure was observed to reach approximately 1074 psig approximately 26 seconds after main steam bypass valves unexpectedly closed. An investigation will be conducted to determine the cause of the bypass valve closure and reactor scram. No safety relief valves lifted as a result of the pressure increase.

"This event is being reported under 10 CFR 50.72(b)(2)(iv)(B) as an event or condition that results in actuation of the reactor protection system when the reactor was critical."

The licensee is manually controlling the steam bypass valves to remove decay heat via the main condenser. All control rods fully inserted. The Unit is in a normal shutdown electrical lineup.

The licensee informed the NRC Resident Inspector.

Page Last Reviewed/Updated Wednesday, November 30, 2011
Wednesday, November 30, 2011