ML20042E125

Special Rept:On 900325,meteorologic Tower Declared Inoperable for More than 7 Days.Caused by Failure of Primary Delta Temp Channel

ML20042E125
Person / Time
Site:	San Onofre
Issue date:	04/04/1990
From:	Nandy F SOUTHERN CALIFORNIA EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9004200169
Download: ML20042E125 (1)

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Southem Califomia Ed/ son Company v;. 23 PARKEF $ s j<EET IRVINE. CALIFORNIA 92716 '

'F.R.NANDY 'T E'LE smoN E

, .cu orn or wuctsan t. ice...no 4 -April 4, 1990 ,,,,,..,...oo U. S. Nuclear Regulatory Commission

'E  : Occument Control Desk Washington, D.C. 20555 -

Subject:

. Docket Nos. 50-361 and 50-362

!.Special Report m i San Onofre Nuclear Generating Station, Units 2 and 3 This report is being submitted in accordance with Technical Specification (TS) 3.3.3.4, Action a, of d Facility Operating Licenses NpF 10 and NPF.15, San Onofre Units 2 and 3? The TS requires Southern .

California Edison (SCE) to submit a Special Report when the Meteorological Tower becomes inoperable ' q for more than 7 days. i i

On March 25,1990,' the Meteorological Tower (MT) was declared inoperable after a review of routme daily surveillance results showed that the prhnary 10/40 meter delta temperature readings had not:

changed in four surveillances. Further review concluded that the MT had been inoperable since the

' March 22,1990.

Two channels (primary and seconda y) provide delta-temperature monitoring for the 10/40 meter.

elevation.' Each channel is provided with two temperature sensors, one sensor at the 10-meter elevatien and the other at the 40-meter elevation. These-sensors provide input to the ' computer for deha-

temperature readings. '

-Our investigation determined that a shorted temperature sensor for the 40-meter elevation caused the -

failure of the primary delta. temperature channel.nThis is the' first known failure'of this type for the.  :

sensor. : The 40-meter sensor was replaced and the MT was returned to service on March 30,1990.. 1

.No further corrective action is planned.

if you require any additional information, please let me know.

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Very tmly yours, y

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cc: J. B. Martin'(Regional Administrator, NRC. Region V)

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' C. W. Caldwell (NRC Senior Resident inspector, Units 1, 2 and 3)  ;;

Institute of Nuclear Power Operations (INPO) .

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