05000244/LER-2013-002

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LER-2013-002, Reactor Trip Due to Generator Trip During Main Generator Reactive Power Testing
R.E. Ginna Nuclear Power Plant
Event date: 07-24-2013
Report date: 09-17-2013
2442013002R00 - NRC Website

I. DESCRIPTION OF EVENT

A. PRE-EVENT PLANT CONDITIONS:

The reactor was in Operational Mode 1 at 100% power, 2235 psig and 574 degrees F.

B. EVENT:

On July 24, 2013 at

1419 hours
0.0164 days
0.394 hours
0.00235 weeks
5.399295e-4 months

R.E. Ginna experienced a Turbine and Reactor Trip, caused by a Generator Trip. The Reactor Trip was caused by a RPS actuation signal from a Turbine Trip, which was caused by a Generator Trip. All Control Rods inserted on the trip, and Auxiliary Feedwater auto started as expected. The Generator Trip was caused by generator protective relays that were incorrectly configured in the Ginna 2012 refueling outage. The protective relays' outputs were configured incorrectly to trip at the alarm setpoint

C. INOPERABLE STRUCTURES, COMPONENTS OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:

None.

D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES:

06/2011 Installation of Multifunction Relays with Trip functions disabled 11/2012 Trip functions of Multifunction Relays Enabled 11/2012 Plant Startup from Refueling Outage 07/24/2013 Plant trip during Reactive Power testing

E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

None.

F. METHOD OF DISCOVERY:

Plant Trip

G. MAJOR OPERATOR ACTION:

Operations entered plant procedures for a reactor trip and stabilized the plant in Mode 3.

H. SAFETY SYSTEM RESPONSES:

The reactor protection system operated as expected as a result of the Turbine Trip. Motor Driven and Turbine Driven auxiliary feedwater pumps started on the Anticipated Transient Without Scram (ATWS) mitigation system signal. All systems operated as expected.

II. CAUSE OF EVENT:

The cause of the shutdown was determined to be an inadequate guidance for enabling the trip output of the generator protection relays while implementing a modification during the 2012 refueling outage. An alarm was expected while raising voltage during reactive power testing, but due to the incorrect configuration of the relays' outputs, a trip signal was received along with an alarm.

This event was entered into the site corrective action program with CR-2013-004461.

III. ANALYSIS OF THE EVENT:

This event is reportable in accordance with 10 CFR50.73, "Licensee Events Report System," under paragraph (a)(2)(iv)(A) based on actuation of the the following systems listed in paragraph (a)(2)(iv)(B): (1) Reactor Protection System (RPS), and (6) PWR Auxiliary Feedwater System.

An assessment was performed considering both the safety consequences and implications of this event with the following conclusions:

Reactor trip breakers opened as required and control rods inserted as designed. Heatup and pressurization of the Reactor Coolant System (RCS) presented no significant challenge to RCS pressure control systems and no Power Operated Relief Valve (PORV) or safety valve actuation occurred. Maximum steam generator secondary side pressures were well below the atmospheric relief valve pressure setpoint. Automatic actuation of the Motor Driven and Turbine Driven Auxiliary Feedwater pumps occurred as expected due to the ATWS mitigation system on low feedwater flow signal. All Auxiliary Feedwater pumps performed as expected and met required flow rates.

The plant transient response is bounded by the Loss of External Electrical Load transient analyzed as part of the licensing basis described in the UFSAR. Based on the above considerations, the nuclear safety consequences of this event are very low.

This event impacted NRC performance indicator 1E01, Unplanned Scrams per 7000 Critical Hours. This value changed from 0 to 0.9.

Ginna returned to Mode 1 on July 28, 2013.

IV. CORRECTIVE ACTIONS:

A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

The trip function of the digital relays were removed and post maintenance testing completed.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE

A review of the digital relays associated with offsite power has been completed to ensure they have been configured correctly.

Procedures for relay calibration and trip testing have been quarantined until a procedure upgrade is complete.

V. ADDITIONAL INFORMATION:

A. FAILED COMPONENT

None.

B. PREVIOUS LERS ON SIMILAR EVENTS

None.