05000327/LER-2004-001, Regarding Automatic Reactor Trip with Main Feedwater Isolation and Auxiliary Feedwater Start as a Result of a Main Generator Trip from Inadvertent Protective Relay Operation on a Main Transformer
| ML041340386 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 05/13/2004 |
| From: | Salas P Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 04-001-00 | |
| Download: ML041340386 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3272004001R00 - NRC Website | |
text
May 13, 2004 U.S. Nuclear Regulatory Commission 10 CFR 50.73 ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:
TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 -
DOCKET NO. 50-327 - FACILITY OPERATING LICENSE DPR LICENSEE EVENT REPORT (LER) 50-327/2004-001-00 The enclosed LER provides details concerning an automatic reactor trip and engineered safety feature (ESF) actuation (auxiliary feedwater start and main feedwater isolation).
The automatic reactor trip occurred as a result of a main generator trip from inadvertent protective relay operation on a main transformer. This event is being reported, in accordance with 10 CFR 50.73(a)(2)(iv)(A), as an event that resulted in a automatic actuation of the reactor protection system and ESF actuation.
Sincerely, Original signed by:
Pedro Salas Licensing and Industry Affairs Manager Enclosure cc: See page 2
U.S. Nuclear Regulatory Commission Page 2 May 13, 2004 cc (Enclosure):
Mr. Michael Marshall, Senior Project Manager U.S. Nuclear Regulatory Commission MS 0-8G9 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2739 INPO Records Center Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, Georgia 30339-5957
Abstract
On March 15, 2004, at approximately 1517 Eastern standard time, automatic turbine and reactor trips occurred. The trips were the result of a main generator trip. The generator trip occurred because of inadvertent protection relay actuation. Relay actuation occurred as a result of a ground loop (a positive side and negative side ground) on the non-safety related 250 Volt direct current (Vdc) Battery Board 2 system. Following the reactor trip, reactor coolant system (RCS) temperature decreased below 550 degrees Fahrenheit (F). Based on this RCS temperature coincident with a reactor trip, a main feedwater isolation occurred as expected. As designed, auxiliary feedwater was automatically initiated on steam generator low-low level following the reactor trip. The immediate cause of the event was inadvertent actuation of the Unit 1 generator main bank transformer protective relay. The root cause of the event was that a negative ground was created by an improperly abandoned cable. Contrary to the design change, only one end of the cable was lifted and insulated during design change implementation in 1999 by TVAs Transmission Group. Since completion of the design change in 1999, TVA has taken steps to improve work standards in its Transmission Group by documenting management observations of work activities and implementation of the Substation and Switchyard Construction Standards Manual.
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 (If more space is required, use additional copies of NRC Form 366A) (17) accomplished during performance of outage work activities. The corrective actions taken for that event, counseling of involved individuals and providing lessons learned to site personnel, would not have prevented the event described in this LER since the error described in this LER occurred in 1999 by non-station personnel.
C.
Additional Information
The corrective action documents associated with this event contains actions to:
Perform a visual inspection of remaining site transformers for improperly abandoned cables.
Perform a visual inspection of selected breakers for improperly abandoned cables that could impact the 250Vdc system.
Develop new guidance for responding to and initiating work documents to locate grounds.
Perform an industry review to determine if ground locating equipment is available which will locate high impedance grounds.
D.
Safety System Functional Failure:
This event did not result in a safety system functional failure in accordance with 10 CFR 50.73(a)(2)(v).
E.
Loss of Normal Heat Removal Consideration This event did not result in a loss of normal heat sink because main steam isolation and steam dump valves were available.
VIII.
COMMITMENTS
None.