05000498/LER-2003-002, Manual Reactor Trip Due to Reduced Deaerator Level
| ML031250392 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 04/30/2003 |
| From: | Halpin E South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-03001503 LER 03-002-00 | |
| Download: ML031250392 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| 4982003002R00 - NRC Website | |
text
Nuclear Operating Company South TCSuhJ'rcd Eledrlc GencratinrStation PO Box 2891 PdAvrth.
ro 77483 A AA Apri1l 30, 2003 NOC-AE-03001503 File No.: G25 1 OCFR50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 South Texas Project Unit 1 Docket No. STN 50-498 Licensee Event Report 03-002 Manual Reactor Trip Due to Reduced Deaerator Level Pursuant to 10CFR50.73, the South Texas Project submits the attached Unit 1 Licensee Event Report 03-002 regarding a manual reactor trip that occurred on March 1, 2003, due to a reduction in the deaerator water level following loss of condensate flow. This event did not have an adverse effect on the health and safety of the public.
Commitments are listed in the Corrective Actions section of the attached report.
If there are any questions on this submittal, please contact S. M. Head at (361) 972-7136 or me at (361) 972-7849.
E. D. Halpin Plant General Manager p1w Attachment: LER 03-002 (South Texas, Unit 1)
NOC-AE-03001 503 Page 2 of 2 cc:
(paper copy)
(electronic copy)
Ellis W. Merschoff Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 Richard A. Ratliff Bureau of Radiation Control Texas Department of Health 1100 West 49th Street Austin, TX 78756-3189 Cornelius F. O'Keefe U. S. Nuclear Regulatory Commission P.O. Box 289, Mail Code: MN116 Wadsworth, TX 77483 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP L. D. Blaylock City Public Service Mohan C. Thadani U. S. Nuclear Regulatory Commission R. L. Balcom Texas Genco, LP A. Ramirez City of Austin C. A. Johnson/A. C. Bakken IlIl AEP - Central Power and Light Company Jon C. Wood Matthews & Branscomb C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704
Abstract
At 0149 on March 1, 2003, a 24-volt DC (VDC) power supply in the Unit 1 Condensate Polishing System failed. This failure caused the Condensate Polishing service vessel outlet valves to close, as well as failure of the system bypass valve to open on high Condensate System differential pressure.
The pressure transmitter signal that is required for opening the bypass valve was also not available due to the failed power supply. With all Condensate Polishing service vessel outlet valves closed and the system bypass valve closed, condensate flow to the deaerator was isolated. The Unit 1 reactor was manually tripped because of the ensuing decrease in deaerator level.
The cause was a design characteristic in which loss of one power supply disabled the differential pressure signal required to open the system bypass valve and the signal required to maintain the output valves open for the normal system flow path. The power supply was determined to have failed due to age-related degradation.
The affected power supply units have been replaced. A lock-up feature will be incorporated to ensure the Condensate Polishing Service Vessel outlet valves are locked in place in the event of a power supply failure.
A fault tolerant power circuit will be developed and installed to prevent recurrence.
This event resulted in no personnel injuries, offsite radiological releases, or damage to safety-related equipment. There were no challenges to plant safety.
NRC FORM 366 (7-2001)
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
Make-up Demineralizer Building Panel ZLP140 (9Q210ZLP140)
Plant Yard Water System Control Panel ZLP139 (9Q210ZLP139).
There are no significant plant effects from loss of the power supplies in the Make-Up Demineralizer and Yard Water Systems. The Unit 1 and Unit 2 Condensate Polishing Control Panel applications are addressed under Corrective Actions 2 and 4.
Additional Information
There have been no previous plant trips at the South Texas Project caused by loss of flow through the CP System and failure of the Condensate Polishing System Bypass MOV to open.
A review of industry operating experience found no other failures of this model power supply unit.