05000336/LER-2009-001, For Millstone Power Station Re Reactor Trip Due to High Pressurizer Pressure
| ML092390049 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 08/19/2009 |
| From: | Jordan A Dominion, Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 09-467, FOIA/PA-2011-0115 LER 09-001-00 | |
| Download: ML092390049 (6) | |
| 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 |
| 3362009001R00 - NRC Website | |
text
~Dominion-Dominion Nuclear Connecticut, Inc.
Millstone Power Station Rope Ferry Road Waterford, CT 06385 AUG 1 9 2009 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 Serial No.
MPS Lic/MAE Docket No.
License No.09-467 RO 50-336 DPR-65 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 2 LICENSEE EVENT REPORT 2009-001-00, REACTOR TRIP DUE TO HIGH PRESSURIZER PRESSURE This letter forwards Licensee Event Report (LER) 2009-001-00 documenting an event which occurred at Millstone Power Station Unit 2 on July 3, 2009. 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, A. J. J r an Sifte lVic President - Millstone
Serial No.09-467 Docket No. 50-336 Licensee Event Report 2009-001-00 Page 2 of 2 Attachment (1):
Licensee event report 2009-001-00, Reactor Trip Due To High Pressurizer Pressure Commitments made in this letter:
- 1. None 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 One White Flint North 11555 Rockville Pike Mail Stop 08B3 Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station
0 Attachment I LICENSEE EVENT REPORT 2009-001-00.
REACTOR TRIP DUE TO HIGH PRESSURIZER PRESSURE Millstone Power Station Unit 2 Dominion Nuclear Connecticut, Inc. (DNC)
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Abstract
At 1304 on July 3, 2009, with the Millstone Power Station Unit 2 at 100% power in Mode 1, the reactor automatically tripped due to a high pressurizer pressure reactor trip signal. There was a grid disturbance coincident with the time of the trip. Approximately 5 seconds prior to the trip, the four.main turbine stop valves and four intermediate stop valves went fully closed. With the main turbine stop valves closed, the reactor coolant system (RCS) pressure increased to the high trip setpoint. The reactor automatically tripped and both pressurizer power operated relief valves (PORVs) lifted to relieve pressure as designed. The reactor trip generated a turbine trip signal.
The most probable cause of this event is that the 24VDC power supply to the electro-hydraulic control (EHC) of the turbine valves did not tolerate the July 3, 2009 grid disturbance. As a result of the grid disturbance, the master trip solenoid valves (MTSVs) provided fluctuating emergency trip system (ETS) hydraulic pressure to the turbine valves. This fluctuating hydraulic pressure caused the turbine stop and intermediate stop valves to close unexpectedly.
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 fisted in 10 CFR 50.73(a)(2)(iv)(B).
NRC FORM 366 (9-2007)
(If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
- 5.
Previous Occurrences
LER 2008-003-00, Failed Pilot Wire Causes Reactor Trip:
On May 22, 2008 at 1359 with the Millstone Power Station Unit 2 at 100% power in Mode 1, the reactor automatically shutdown following a loss of load and subsequent turbine trip. Investigation determined that a lightning strike on a transmission line created an over current condition to which the unit responded. The direct cause of the switchyard breakers opening and remaining open was a mechanical failure of a connecting wire lug in the pilot wire circuitry causing an open circuit.
LER 2008-005-00, Feedwater Heater Level Oscillation and Manual Reactor Trip:
On June 28, 2008, at 1146 with the Millstone Power Station Unit 2 in Mode 1 at 100% power, operators manually tripped the reactor when both main feedwater pumps tripped. Main turbine combined intercept valve (CIV) testing was in progress. The testing of the #3 CIV had just been completed when the 2A feedwater heater level began oscillating. The perturbations in the feedwater heater levels caused a feedwater pump suction pressure to decrease to the pump trip setpoint tripping both pumps. The operators manually tripped the reactor prior to reaching the steam generator low level automatic trip setpoint. Ineffective configuration control of parts allowed parts to be installed in a feedwater level control valve causing it to operate incorrectly which caused divergent feedwater heater level oscillations and the main feedwater pumps to trip.
The May 22, 2008 event and the July 3, 2009 event were initiated by grid disturbances. However, the most probable causes for the reactor trips were different. There are no prior corrective actions from the May 22, 2008 event that could have prevented occurrence of the July 3, 2009 event.
The June 28, 2008 event showed anomalies related to the VR-1 1 power supply. Power to VR-1 1 was lost momentarily (approximately 3 seconds) subsequent to the reactor trip during fast transfer from the normal station service transformer (NSST) [XFMR], to the reserve station service transformer (RSST). Corrective actions are in place to implement a design change to install a UPS to VR-1 1. The implementation of this design change may have prevented occurrence of the July 3, 2009 event. Design and implementation efforts were originally targeted for a 2011 implementation date. The targeted implementation date has been changed to June 30, 2010 and efforts continue to improve on that target date.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].