05000498/LER-2003-001, From South Texas Regarding Partial Loss of Offsite Power to Units 1 & 2 Resulting in Engineered Safety Feature Actuations
| ML030840662 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/20/2003 |
| From: | Halpin E South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| G25, NOC-AE-03001493, STI:31577599 LER 03-001-00 | |
| Download: ML030840662 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4982003001R00 - NRC Website | |
text
Nuclear Operating Company South ToasPocctdctnc Grnerating Station PO. Box 2 MYadsmvrth Teas 77483 March 20, 2003 NOC-AE-03001493 File No.: G25 10CFR50.73 STI: 31577599 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 50498 Licensee Event Report 03-001 Partial Loss of Offsite Power in Units 1 and 2 resulting in Engineered Safety Feature Actuation Pursuant to 10CFR50.73(a)(2)(iv)(A), the South Texas Project submits the attached Unit I Licensee Event Report 03-001 concerning the partial Loss of Offsite Power (LOOP) in Units 1 and 2 and actuation of Engineered Safety Feature Standby Diesel Generators for Units I and 2. The cause of the partial Loss Of Offsite Power was the de-energizing of the switchyard North bus due to a malfunctioning motor operated circuit switcher.
This event did not have an adverse effect on the health and safety of the public.
Corrective actions number 1, 2 and 3 are the only commitments contained in this event report.
If there are any questions on this submittal, please contact W. R. Bealefield, Jr. at (361) 972-7696 or me at (361) 972-7849.
E. D. Halpin Plant General Manager Attachment: LER 03-001 (South Texas, Unit 1)
NOC-AE-03001493 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. 0. Box 289, Mail Code: MN116 Wadsworth, TX 77483 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP L. D. Blaylock/W. C. Gunst 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 AEP Texas Central Company Jon C. Wood Matthews & Branscomb C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704
Abstract
On January 19, 2003 at 1255, Unit 1 was in Mode 1 at 100% power and Unit 2 was in Mode 3 with the 2A and 2D Reactor Coolant Pumps running. While placing the North Bus Shunt Reactor in the switchyard in service, Unit 1 Standby Transformer received a lockout due to an over-current condition on the neutral of the Shunt Reactor. This caused the North Bus to clear and isolate the North Bus Shunt Reactor.
Unit 1 experienced a partial Loss of Offsite Power (LOOP) to Standby Bus 1 G and 1 H which supply power to Engineered Safety Feature (ESF) Trains 1 B and 1 C. The Train 1 B and Train 1 C Emergency Diesel Generators (EDG) started as a result of the ESF Actuation - LOOP. The Train 1 C components automatically loaded per design. The Train 1 B Sequencer did not automatically load resulting in the manual loading of the Train 1 B components by the Reactor Operators.
Unit 2 experienced a partial LOOP due to the loss of the Unit 1 Standby Transformer which was supplying power to Auxiliary Busses 2F, 2J and Standby Bus 2F, which supplies ESF Train 2A. The Train 2A Emergency Diesel Generator automatically started and loaded as expected.
The cause of the loss of Unit 1 Standby Transformer was de-energizing the switchyard North Bus, which provides power, to the Standby Transformer, due to a malfunctioning motor operated circuit switcher.
There was no impact to radiological safety, safety of the public or safety of station personnel.
Corrective actions include changing the protective relay scheme for the Shunt Reactor.
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 (If more space is required, use additional copies of NRC Form 366A) (17)
The cause of the Unit 2 PORV lifting when the 2A RCP was started is as follows:
Prior to the pump start, the Reactor Coolant System (RCS) was about 16 degrees cooler than the Steam Generators (SG) due to low decay heat and isolation of the SGs. The SGs acted like a heat source instead of a heat sink. This resulted in a moderate RCS heatup and pressurizer (PZR) insurge when RCP 2A was started, PZR level increased approximately 4 percent which rapidly increased pressure. The PZR pressure control system responded to open both spray valves. RCP 2A was the only RCP started during this event. Previous events have revealed that the use of only RCP 2A does not create enough differential pressure across the PZR to drive adequate spray flow, especially with both spray valves open. In this condition the PZR spray water from RCP 2A likely short-cycled through the 2D spray valve to bypass spray flow that would otherwise travel to the PZR spray nozzle.
With little to no spray flow, pressure continued to drift up to the PORV open setpoint of 87.5 percent.
Plant procedures have been revised to ensure operators verify the delta temperature between RCS and SG secondary side is less than ten degrees before starting a RCP when primary temperature is greater than 350 degrees. Procedures previously allowed the temperature verification to be omitted.
In addition, for starting the first RCP, guidance has been provided to direct placing the spray valve for the RCP not being started in manual to prevent bypassing spray flow from the PZR.