05000286/LER-2007-002, Regarding Automatic Reactor Trip Due to a Turbine-Generator Trip Caused by a Fault on the 31 Main Transformer Phase B High Voltage Bushing
| ML071620122 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 06/05/2007 |
| From: | Dacimo F Entergy Nuclear Indian Point 3 |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-07-053 LER 07-002-00 | |
| Download: ML071620122 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2862007002R00 - NRC Website | |
text
Indian Point Energy Center 450 Broadway, GSB P.O. Box 249 fBuchanan, N.Y. 10511-0249 Entf--,-
Tel (914) 734-6700 Fred Dacimo Site Vice President June 5, 2007 Indian Point 3 Docket No. 50-286 NL-07-053 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop O-Pl-17 Washington, D.C. 20555-0001
Subject:
Licensee Event Report # 2007-002-00, "Automatic Reactor Trip Due to a Turbine-Generator Trip Caused by a Fault on the 31 Main Transformer Phase B High Voltage Bushing"
Dear Sir or Madam:
Pursuant to 10 CFR 50.73(a)(1), Entergy Nuclear Operations Inc. (ENO) hereby provides Licensee Event Report (LER) 2007-002-00. The attached LER identifies an event where the reactor automatically tripped while critical, which is reportable under 10 CFR 50.73(a)(2)(iv)(A).
This condition has been recorded in the Entergy Corrective Action Program as Condition Report CR-IP3-2007-01834.
There are no new commitments identified in this letter. Should you have any questions regarding this submittal, please contact Mr. T. R. Jones, Manager, Licensing at (914) 734-6670.
Sincerely, Fred R. Dacimo Site Vice President Indian Point Energy Center cc:
Mr. Samuel J Collins, Regional Administrator, NRC Region I NRC Resident Inspector's Office, Indian Point 3 Mr. Paul Eddy, New York State Public Service Commission INPO Record Center
Abstract
On April 6, 2007, at 1109 hours0.0128 days <br />0.308 hours <br />0.00183 weeks <br />4.219745e-4 months <br />, an automatic reactor trip (RT) occurred due to a turbine-generator trip as a result of a fault on the 31 main transformer.
All control rods fully inserted and all required safety systems functioned properly.
The plant was stabilized in hot standby with decay heat being removed by the main condenser.
There was no radiation release.
The Emergency Diesel Generators did not start as adequate offsite power remained available.
Two of three 138 kV offsite power substation feeders tripped as a result of the event.
The Auxiliary Feedwater System automatically started as expected due to Steam Generator low level from shrink effect.
Control Room (CR) operators were notified of a fire at the 31 main transformer with the fire protection deluge system actuated.
The plant fire brigade responded to the fire and applied foam.
The fire brigade leader reported to the CR the fire was extinguished at 1121 hours0.013 days <br />0.311 hours <br />0.00185 weeks <br />4.265405e-4 months <br />.
The CR was notified at approximately 1140 hours0.0132 days <br />0.317 hours <br />0.00188 weeks <br />4.3377e-4 months <br /> that a visible explosion had previously occurred.
Based on the report of an explosion, the CR declared a Notice of Unusual Event (NUE) in accordance with the emergency plan which was terminated at 1254 hours0.0145 days <br />0.348 hours <br />0.00207 weeks <br />4.77147e-4 months <br />.
The direct cause of the RT was due to the actuation of the 86P and 86BU relays that sensed a fault from the failure of 31 main transformer 345 kV phase B bushing.
The most probable cause was a design weakness associated with the type bushing used in the Phase B bushing. Significant corrective actions included replacement of 31 main transformer, and inspection, repair and replacement of damaged components as required associated with the 32 main transformer, the unit auxiliary transformer, and high voltage components.
The event'had no effect on public health and safety.
(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)
PAST SIMILAR EVENTS A review of the past two years of Licensee Event Reports (LERs) for events that involved a RT from a failure of the high voltage electric power system identified no applicable LERs.
Safety Significance
This event had no effect on the health and safety of the public.
There were no actual safety consequences for the event because the event was an uncomplicated RT with no other transients or accidents.
Required primary safety systems performed as designed when the RT was initiated.
There were no risk related components out of service at the time of the RT.
The AFWS actuation was an expected reaction as a result of low SG water level due to SG void fraction (shrink), which occurs after automatic RT from full load.
The AFWS actuated and provided required FW flow to the SGs.
The AFWS capacity is sufficient to provide the minimum required FW flow to the SGs.
There were no significant potential safety consequences of this event under reasonable and credible alternative conditions.
This event was bounded by the analyzed event described in FSAR Section 14.1.8, "Loss of External Electrical Load."
RCS pressure remained below the set point for pressurizer PORV or code safety valve operation and above the set point for automatic safety injection actuation.
Following the RT, the plant was stabilized in hot standby.