05000272/LER-2014-003
| Salem Generating Station - Unit 1 | |
| Event date: | 04-13-2014 |
|---|---|
| Report date: | 06-04-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2722014003R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
Westinghouse - Pressurized Water Reactor (PWR/4) Main Generator {ELI-}
IDENTIFICATION OF OCCURRENCE
Event Date: April 13, 2014 Discovery Date: April 13, 2014
CONDITIONS PRIOR TO OCCURRENCE
Salem Unit 1 was in operational Mode 1, operating at 100 percent rated thermal power. No additional structures, systems or components were inoperable at the time of discovery that contributed to this event.
DESCRIPTION OF OCCURRENCE
On April 13, 2014 at 2113, Salem Unit 1 experienced a reactor trip due to actuation of the main generator lockout protection circuitry. Generator protection lockout circuitry tripped the generator and turbine which tripped the reactor. The direct cause of the reactor trip was a generator lockout resulting from a main generator transformer overall differential relay trip.
All control rods fully inserted on the trip. All three AFW pumps started as expected in response to low SG levels and decay heat was removed by the steam dumps to the main condenser. Operators entered the emergency procedures for the plant trip and stabilized the plant in Mode 3 (HOT STANDBY).
CAUSE OF OCCURRENCE
A failed wiring termination on the C phase neutral generator current transformer caused the Generator Overall Differential Trip to occur.
PREVIOUS OCCURRENCES
A review of Licensee Event Reports at Salem Station identified one other similar event in 2001.
Transformer Field Wiring" describes a degraded termination associated with field wiring to the "A" Phase Main Generator Neutral Current Transformer as well as degradation of the current transformer itself. The current transformer was abandoned in place.
SAFETY CONSEQUENCES AND IMPLICATIONS
There were no safety consequences associated with this event. Operators appropriately responded to the reactor trip to stabilize the plant. All plant safety systems operated as required.
A review of this event determined that a Safety System Functional Failure (SSFF) as defined in Nuclear Energy Institute (NEI) 99-02, Regulatory Assessment Performance Indicator Guideline, did not occur.
CORRECTIVE ACTIONS
1. The failed wiring termination on the C phase neutral generator current transformer was repaired.
2. All generator current transformer junction boxes were inspected for visible degradations. Degraded wire insulations were identified and contained using high heat insulating tape. Two additional terminations were repaired.
3. Final testing was performed on all main and neutral current transformers. The current transformers were meggered from phase to ground and from phase to phase. Turns-Ratio testing was also performed on all main and neutral current transformers. All testing results were satisfactory.
4. A root cause evaluation is in progress to evaluate design specifications, previous corrective actions, and current maintenance inspection procedures for wiring terminations in the generator current transformer protection circuitry.
COMMITMENTS
No commitments are made in this LER