ML19291A677

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Discusses Monitoring Capabilities of Reactor Incore Thermocouples.Fifty Operable Thermocouples May Be Defective or Have Insecure Head Connectors
ML19291A677
Person / Time
Site: Beaver Valley
Issue date: 05/16/1979
From: Carey J
DUQUESNE LIGHT CO.
To: Wigginton D
Office of Nuclear Reactor Regulation
References
NUDOCS 7905240583
Download: ML19291A677 (2)


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'Af um m-4rc 435 Sixth Avenue Pittsburgh, Pennsylvania 15212 May 16, 1979 United States Nuclear Regulatory Commission Attention: D. L. Wigginton EVPS Licensing Project Manager Washington, D. C. 20555

Reference:

Beaver k7 alley Power Station, Unit No. 1 Docket No. 50-334 License No. DPR-66 BVPS Reactor Incore Thermocouples

Dear Mr. Wigginton:

The following information is provided in response to your request to the station regarding reactor incore thermocouples.

The Beaver Valley Power Station, Unit No. 1 has fifty-one (51) reactor incere thermocouples (T/C). Each thermocouple is a Type K (nickel-chromium versus nickel-aluminum) thermocouple purchased from Westinghouse on Stone & Webster Purchasa Order No. BV-2 (Theruocouple Part Number 618F134H47, in accordance with Westinghouse Drawing No. 635J845G01).

The BVPS Unit 1 P250 Plant Computer is the main readout device for these thermocouples with the Control Room (double range, 100 - 400F and 400 - 700F)

Reactor Incore Temperature Indicator (Honeywell Model Y15618836) as backup. The P250 Computer Software Data Base (analog format) is set up to monitor each point every eight (8) seconds with an input range of 1 20 MV. These thermocouples are designated as points T0001A to T0051A. The computer's analog-to-digital converter system is designed to handle up to 1 200% of full scale of the input signal range.

This allows computer monitoring and conversion for thermocouple inputs up to 1 40 MV (Type K thermocouple at + 40 MV is about 1774 degrees F).

Presently, however, we are limitea to monitoring up te about 913 degrees F.

This is because the software data base high out-of-range index is set for 101%

(101% of 20 MV is 20.20 MV, or about 913 degrees F for the Type K thermocouple) and the computer flags that point as unreliable at that temperature. If the high out-of-range index is set to zero (computer does not flag point as unreliable for higher temperatures), then we can monitor up to about 1700 degrees F with 1 0.13%

accuracy (this is accuracy above 1 20 MV range; below t 20 MV range, accuracy is 1 0.065%).

Df

$ I(}l 99052405/t '

Beaver Valley Power Station, Unit No. 1 BVPS Reactor Incore Thermocouple Requested Data Bhy 16, 1979 Page 2 At this time, we have fifty (. ) operable thermocouples, reading about

+ 6 degrees F of each other (between 99 to 105 degress F). Point T0037A reads low out-of-range and we suspect that either the thermocouple itself is defective or its head connection is not secure.

If you have any questior_s concerning this response, please contact my office.

Very truly yours,

/

8N J. J. Carey Technical Assistant-Nuclear