ML20082L271

Special Rept:On 950308,Unit 2 Cathodic Protection Sys Was Declared Inoperable & Remained Inoperable Greater than 10 Days

ML20082L271
Person / Time
Site:	Catawba
Issue date:	04/17/1995
From:	Rehn D DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9504210081
Download: ML20082L271 (2)

Text

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ll l DukeIbwerCornpany D. L Rats

'4 Catauba Nuclear Generation Department Vicelhsident 4800 ConcordRoad (803)&113205 O!! ice Y- . York SC29745 (803)&114426 Fax i DUKEPOWER April 17,1995 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 ' j

Subject:

Catawba Nuclear Station, Unit 2

' Docket No. 50-413 and 50-414 Special Report '

Cathodic Protection System l

t Pursuant to Technical Specification 3.8.1.1 ACTION Statement "g" and 6.9.2, find attached a Special Report conceming the inoperability of the Unit 2 Cathodic Protection System. The system was declared inoperable on March 8,1995, and remained inoperable greater than 10 days.

Sincerely, DL Rehn KEN /SR041795. CAT Attachment xc: SD Ebneter, Region 11 RE Martin, ONRR RJ Freudenberger, SRI 01GOCO

/ I 9504210081 950417 3 f nam on w= m- DR ADOCK 0500 d l

'... . i SPECIAL REPORT l w CATAWBA NUCLEAR STATION I r . CATHODIC PROTECTION SYTEM INOPERABLE

. 50-413,50-414 On March 6,1995, Instrument and Electrical (IAE) technicians began the routine 60 day surveillance test on the Unit 1 and 2 Diesel Piping Cathodic Protection System. Unit 1 piping passed the acceptance criteria of IP/0/B/3550/01, Cathodic Protection Testing Procedure. However, Unit 2 had two Test Stations (TS 19 and 40) which did not meet  ;

the first acceptance criteria of the procedure which requires a reading of more negative )'

than .850 mV. Test Station 40 passed the second test, which is verification of a 300 mV shift when the rectifier is de-energized. Test Station 19 did not pass this second test criteria. At this time, it was identified that Test Sta. ion 19 had not pass its surveillance on l September 22, 1994 due to failure of Prepacl. aged Anode Well (PPAW) #1. The l Technicians were instructed to measure the cmrent being drawn by PPAW #1, which had  !

been installed on November 15, 1995. Measurement of the cable to PPAW #1 showed that no current was being drawn, therefore, indicating that this anode well had failed.  !

Work Order #95020480-01 was initiated for repair / replacement of the failed anode.

l Discussions took place with Electrical Systems and Equipment personnel in the General l Office and Harco Corporation, who is the manufacturer of the anode well, as to the cause  ;

of the premature failure of the anode well. Following installation of the replacement well i on November 15,1994, current was read and found to be at 2 amps. The anode well and )

cable was then buried. Test Station #19 read satisfactorily on the surveillances which were performed on November 16,1994 and January 10,1995, indicating that PPAW #1 was working at that time. According to Harco Corporation, the model of anode well that was installed has a maximum current rating of 2 amps. The life expectancy of that i particular model of anode is very short if operated at currents in excess of 2 amps. With l the constant changes in soil moisture and resitivity, it is diflicult to ensure that current  !

stays below that value. This is the most likely reason for the failure of the anode.

l Harco Corporation has recommended replacement of the original graphite type anode with

one of mixed metal oxide construction. This type of anode is capable of handling approximately 15 amps. The replacement anode will provide the same level of protection for the diesel generator piping in the area as did the original graphite anode. Minor modification CE-5074 has been initiated for the replacement and work will be performed  !

per Work Order #95023568-01. The new anode will be installed at the same location and depth as the failed anode. This work is currently on the schedule for May 1,1995.

Rectifier #3 remains on during this time period. The only section of the diesel generator piping which does not meet the acceptance criteria of the surveillance procedure is that piping which is in the small area of Test Station 19 and PPAW #1. Even though this area l is not presently meeting the acceptance criteria, some protection is still being given by other anode wells powered by Rectifier #3. Corrosion protection for the diesel generator piping is a long term process and poses no immediate concerns.

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