05000425/LER-2013-002

LER-2013-002, Automatic Unit 2 Reactor Trip due loss of Generator Excitation

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
4252013002R00 - NRC Website

A. REQUIREMENT FOR REPORT

This report is required per 10 CFR 50.73(a)(2)(iv)(A) as there was an unplanned automatic actuation of the Reactor Protection System (RPS) and an automatic actuation of the Auxiliary Feedwater System (AFW).

B. UNIT STATUS AT TIME OF EVENT

Mode 1 , 1 00% power

C. DESCRIPTION OF EVENT

While operating at 1 00% power with no abnormal indications, Unit 2 experienced a loss of generator excitation which tripped the Main Generator. This resulted in a Reactor Protection System (RPS) actuation due to a Turbine Trip above the P9 setpoint of 40% which shut down the reactor. The Auxiliary Feedwater System (AFW) actuated as Main Feedwater isolated when the RPS actuated. All rods inserted and the plant was stabilized in Mode 3 and no complications were experienced during the trip as all systems responded as designed.

D. CAUSE OF EVENT

The probable cause of the event was an intermittent fault in the Main Generator de-excitation control circuitry.

E. SAFETY ASSESSMENT

When the reactor tripped, all rods fully inserted. As a result of the reactor trip, the Feedwater System isolated and the Auxiliary Feedwater System actuated as designed. The unit was stabilized in Mode 3 at the applicable temperature and pressure. Because the plant responded as designed and there were no complications with the plant shutdown, there was no adverse effect on plant safety or the safety and health of the public.

F. CORRECTIVE ACTION

Following the failure of the de-excitation control circuitry of the EX21 00 generator excitation system, three controller cards and a breaker were replaced within the de-excitation system at the recommendation General Electric.

G. ADDITIONAL INFORMATION

1) Failed Components:

2013 I - 02 - 00 General Electric EX-21 00 generator de-excitation control circuitry.

2) Previous Similar Events:

ICES 235585 Bruce 6 Turbine Trips Due to Loss of Excitation 3) Energy Industry Identification System Code:

[TL] - Main Generator Excitation System [JC]- Reactor Protection System [BA] - Auxiliary Feedwater System 4) Other Systems Affected:

None 5) Commitment Information:

This report does not create any commitments.