United States Nuclear Regulatory Commission - Protecting People and the Environment

Morning Report for April 11, 2005

Headquarters Daily Report

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REGION II

Heat-damaged Cables in Containment Cause Potential Inoperability of Pressurizer Level Channels

Licensee/Facility:

FLORIDA POWER & LIGHT CO.
Turkey Point 3
MIAMI, Florida
Dockets: 05000250
[3] W-3-LP
License No:
Notification:

MR Number: H-2005-0012
Date: 02/01/2005

Letter

Discussion:

In October 2004, Turkey Point Unit 3 was shutdown for a refueling outage when abnormal pressurizer pressure indications were observed. Troubleshooting revealed that the instrument cable associated with pressurizer pressure transmitter PT-3-445 had shorted conductors, which resulted in the spurious pressurizer pressure signal. Further investigations revealed additional degraded cables contained in conduits located above the reactor coolant system (RCS) hot legs. The licensee determined that two affected level transmitters LT-3-460 and LT-3-461, pressurizer level channels 2 and 3, respectively, were not assured to function after an accident.

The cause of cable degradation was conduits/cables routed in close proximity to RCS hot leg piping in areas with limited heat dissipation capability. This resulted in localized hot spots that subjected the cables to prolonged temperatures above the cable insulation design rating. Although the cables were rated for a 60 year service life, it was based on a much lower environmental temperature. Other contributing factors included closed ventilation registers, gaps in RCS piping insulation and uninsulated RCS pipe stubs.

Among other corrective actions, the licensee replaced all the degraded cables and installed temperature monitoring equipment on conduits in close proximity above the RCS hot legs.

The licensee event report (LER) regarding this condition is available in ADAMS, accession number ML050460212.

Accession Numbers:

Accession No Accession Date
ML050460212 02/01/2005

Contacts:

Name Office Abbrev Phone No E-Mail
TABATABAI, OMID NRR (301) 415-6616 OTY@nrc.gov
Page Last Reviewed/Updated Thursday, March 29, 2012