Information Notice 2010-23, IN: Malfunctions of Emergency Diesel Generator Speed Switch Circuits

IN: Malfunctions of Emergency Diesel Generator Speed Switch Circuits

ML102420002
Person / Time
Issue date:	11/01/2010
Revision:	0
From:	McGinty T J Division of Policy and Rulemaking
To:
Beaulieu, D P, NRR/DPR, 415-3243
References
IN-10-023
Download: ML102420002 (3)

ML102420002 November 1, 2010 NRC INFORMATION NOTICE 2010-23: MALFUNCTIONS OF EMERGENCY DIESEL GENERATOR SPEED SWITCH CIRCUITS

ADDRESSEES

All holders of an operating license or construction permit for a nuclear power reactor issued under Title 10 of the Code of Federal Regulations, Part 50, "Domestic Licensing of Production and Utilization Facilities," except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vesse

PURPOSE

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform addressees about recent examples of malfunctions of emergency diesel generator (EDG) speed switch circuit The NRC expects that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problem Suggestions contained in this IN are not NRC requirements; therefore, no specific action or written response is require DESCRIPTION OF CIRCUMSTANCES Wolf Creek Generating Station On October 22, 2009, with the Wolf Creek Generating Station in a refueling outage, the control room annunciator for the "A" EDG actuate The licensee took the "A" EDG out of service for troubleshootin The cause of the event was the actuation of the speed switch in the starting circuit of the "A" EDG because of high alternating current (ac) noise on the direct current (dc) supply circuit of the speed switc The source of this electrical noise was traced to the annunciator power supply within the EDG gauge board pane The noise was more than the filtering capacity of the capacitor installed on the dc feed to the speed switc The licensee replaced the annunciator power supply and the speed switc It also established a preventive maintenance activity to have the ac ripple voltage measured at the dc supply circui Additional information appears in Wolf Creek Generating Station Licensee Event Report 50-482/2009-005, dated December 21, 2009, on the NRC's public Web site in the Agencywide Documents Access and Management System (ADAMS) under Accession No. ML09364004 San Onofre Nuclear Generating Station On December 12, 2009, at San Onofre Nuclear Generating Station Unit 3, during the performance of a test required by the technical specifications, the train "A" EDG failed to start because a capacitor failed in one of the two dc-dc converter power supplies for the local panel IN 2010-23