ML20005F811

Special Rept:On 891219,differential Air Temp Instrumentation Inoperable for More than 7 Days.Caused by Problem in Temp Probe on Meteorological Tower.Tower Differential Temp Instrumentation Declared Operable on 891229

ML20005F811
Person / Time
Site:	Clinton
Issue date:	01/04/1990
From:	Holtzscher D ILLINOIS POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
U-601582, NUDOCS 9001170283
Download: ML20005F811 (2)

Text

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4 - U 601582 i V L30 90(01-04)-LP l 8E.110 1LLIN0/8 POWER 00MPANY IP CLI.4 ton POMR STATION, P.o. BOX 678. CLINToN. ILLINOIS 61727 January 4, 1990 10CFR50.36 Docket No. 50-461 Nuclear Regulatory Commission Document Control Desk Wash Sgton, D.C. 20555 Subj ect: Special Report: .Inoperability of the Differential Air Ig;nnerature Indleation at Clinton Power Station (CPS)

Dear Sir:

i CPS Technical Specification 3.3.7.3,: Action _"a", requires that I i

inoperabilities of meteorological monitoring instrumentation channels j for more than 7 days be: reported to the Commission within 10 days. '

pursuant to Technical Specification 6.9.2,'SPECTAL REPORTS. From 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on December 19, 1989 until 1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br /> on D6cember 29,~ 1989, the 10 l meter to 60 meter differential air temperature instrumentation was -

delared inoperable. This SPECIAL REPORT is being submitted in ]

l accordance with the CPS Technical' Specifications to provide.information j j regardirg the cause of the malfunction'and. plans for. restoring the

• instrumentation to OPERABLE status.

• Cause of Malfunction On December 19, 1989, while performing the daily channel check in accordance with Technical Specification Surveillance. Requirement l 4.3.7.3, Radiation Protection personnel noted that the differential i

!- temperature indicated by channel'7 did not agree with.the differential -l

{_ tempercure obtained by subtracting the 10 meter temperature indication l l-from the 60 meter temperature. indication. - Maintenance Work Request (MWR) D06162 was written and at 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br />, the differential temperature.

instrumentation was declared' inoperable.

Control and Instrumentation (C&I) personnel began troubleshooting on December 21, 1989 in accordance with MWR D06162. They determined that the differential temperature: instrumentation had: malfunctioned l

' because of a problem in one of the temperature probes:on the meteorological tower. Extremely cold ambient'and wind chill

temperatures'(-40 to1-50 degrees F), and ice formation on the meteorological towcr however, prevented C&I personnel from safely climbing the-tower that day to perform further troubleshooting.

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, On December 27, 1989, weather conditions had improved sufficiently to_ allow further troubleshooting to resume. On December 28, 1989, C&I peraonnel-determined that a thermistor network in the 60 meter temperature sensor required replacing. Each temperature sensor contains two temperature elements, each containing a thermistor network. One temperature element provides temperature indication, the other is used as input to the differential temperature indication (channel 7). The resistance of the two thermistor networks in the 60 meter temperature sensor differed by approximately 2000 ohms at.approximately 37 degrees l F. The 60 meter temperature sensor was replaced and a functional test i with an ice bath was successfully performed. .

Plans for Restoration ,

On December 29, 1989, further data was obtained in accordance with.

MWR D06162 to verify that the problem had been corrected. At 1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br />, the meteorological tower differential temperature instrumentation was declared operable.

Sincerely yours, >

% 2) ~ Lu D. L. Holtzscher Acting Manager -

Licensing and Safety DAS/ arm cc: NRC Region III Regional Administrator NRC Clinton Licensing Project Manager NRC Resident Office Illinois Department of Nuclear Safety I

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