United States Nuclear Regulatory Commission - Protecting People and the Environment

Morning Report for December 3, 1999

                       Headquarters Daily Report

                         DECEMBER 03, 1999

***************************************************************************
                    REPORT             NEGATIVE            NO INPUT
                    ATTACHED           INPUT RECEIVED      RECEIVED

HEADQUARTERS        X
REGION I                               X
REGION II                              X
REGION III          X
REGION IV                              X
PRIORITY ATTENTION REQUIRED  MORNING REPORT - HEADQUARTERS DEC. 03, 1999

Licensee/Facility:                     Notification:

Firstenergy                            MR Number: H-99-0104
Davis-Besse 1                          Date: 12/03/99
Oak Harbor,Ohio
Dockets: 50000346

Subject: FAILURE OF 5KV CABLE IN UNDERGROUND CONDUIT

Discussion:

On October 2, 1999, the #2 component cooling water (CCW) pump tripped at
the Davis-Besse Nuclear Generating Station. The supply breaker tripped as
a result of a phase-to-ground fault on a 3-phase power cable. The
safety-related Okonite cable consists of three twisted 2/0 single
conductors with a bare #4 copper ground. The insulation on each 2/0 cable
consists of ethylene- propylene- rubber (EPR) insulation, a wrapped
semiconductor tape, a tinned copper tape shield, and a neoprene jacket
(which is painted to identify the phases as black, red, and white). The
cable was installed in a 4-inch pvc conduit that runs partially
underground from the switchgear room in the turbine building to the CCW
pump room, and had been in service for about 23 years.

The licensee removed the cable and sent it to the corporate laboratory
for a root cause analysis. Part of the laboratory evaluation was observed
by a vendor representative from Okonite and NRC staff. The appearance of
the cable showed severe corrosion of the bare copper ground conductor and
cracking of the neoprene outer jacket, particularly in the areas where
the cable laid in the low point of the conduit run and would be most
susceptible to standing ground water. Although a conclusive root cause
has not been determined, it appears that the most likely degradation
mechanism is intrusion of ground water into the cable over a period of
time. Although this cable is water resistant, it is not water proof, and
over time water can permeate through the EPR insulation by the process of
osmosis.

The licensee plans on performing as-found Doble power factor testing and
partial discharge testing of the CCW Pump 1 and CCW Pump 3 cables in
January, 2000, before replacing them. Those cables will then be inspected
to determine if similar degradation has taken place. If similar
degradation has occurred on those cables, the licensee may inspect and
test other safety-related cables that are installed in underground
conduits.

The NRC is interested in this cable failure because there are potential
generic implications for cable failures caused by aging at other nuclear
power plants. Three 5-kV cables and two 15-kV cables in underground
conduits experienced failures at Diablo Canyon between 1989 and 1993 (see
LER 50/275 93-005-01). The 15-kV cable failures were attributed to
chemical attack but no positive root cause for the 4-kV cable failures
could be determined. On January 16, 1996, Palisades experienced a
phase-to-phase fault on a 2400-V safeguards bus feeder cable in an
underground conduit (see LER 50/255 96-002-01). The cause was attributed
to water intrusion and contaminant treeing (microscopic voids in cable
insulation that resemble tree branches) in the EPR insulation.

The staff will review the results of the Davis-Besse testing and

HEADQUARTERS      MORNING REPORT     PAGE  2          DEC. 03, 1999
MR Number: H-99-0104 (cont.)

inspection that will be performed in January and determine whether
further action may be warranted to address the potential for cable
failure caused by intrusion of water vapor into cable insulation over a
long period of time.


Contacts:   Paul Shemanski, NRR/DE/EEIB     Jitendra Vora, RES/DET/MEB
            301-415-1377                    301-415-5833
            E-mail: pcs@nrc.gov             E-mail: jpv@nrc.gov

            Dave Skeen, NRR/DRIP/REXB
            301-415-1174
            E-mail: dls@nrc.gov
_
REGION III  MORNING REPORT     PAGE  2          DECEMBER  3, 1999

Licensee/Facility:                     Notification:

Illinois Power Co.                     MR Number: 3-99-0098
Clinton 1                              Date: 12/02/99
Clinton,Illinois                       via telephone
Dockets: 50-461
BWR/GE-6

Subject: MANAGEMENT CHANGES

Discussion:

The licensee announced that effective today Mr. Patrick Walsh will
succeed Mr. Bill Carsky as the Manager of the Nuclear Station Engineering
Department. Previously, Mr. Walsh was the Director of Equipment
Reliability at Three Mile Island. The licensee plans to reassign Mr.
Carsky to a position to be determined.

Regional Action:

For Information Only.

Contact:  T. Kozak                   (630)829-9866
_
Page Last Reviewed/Updated Thursday, March 29, 2012