ML20086S591

Ro:On 760322 & 23,temp Difference Across Station Exceeded 15 F.Caused by Rapid Drop in River Water Ambient Temp Making Prediction When Action Necessary to Avoid Temp Increase Difficult

ML20086S591
Person / Time
Site:	Surry
Issue date:	04/01/1976
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Rusche B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
References
959, NUDOCS 8403020459
Download: ML20086S591 (2)

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Mr. Benard C. Rusche Serial No. 959 Director of Nuclear Reactor Regulation P0&M/ALH:clw U.S. Nuclear Regulatory Comnission Washington, D. C. 20555 Docket Nos. 50-280 50-281 Attn: Mr. Robert W. Raid, Chief License Nos. DPR-32 Operating Reactor s Branch 4 DPR-37

Dear Mr. Rusche:

In accordance with Technical Specification 4.14.C.1 for Surry Power Station, this report describes two occurrences during which the difference between the river water ambient temperature measured at the station high level intake and cooling water at the discharge control structure exceeded 15 degrees F.

At the time of the first occurrence, both Unit Nos. 1 and 2 were operating at 100 per cent power. On March 22, 1976 at approximately 0015 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> the temperature difference (AT) across the station exceeded 15 degrees F. A power reduction was initiated on Unit No. 2 at 0015 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> and on Unit No. I at 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> to reduce and maintain the temperature difference across the station with-in 15 degrees F. At no time did AT exceed 15.7 degrees F.

At the time of the second occurrence both Unit Nos. I and 2 were operating at 100 per cent power. On March 23, 1976 at approximately 1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br /> the temperature difference (AT) across the station exceeded 15 degrees F. The duration of operation with the station AT in ercess of 15 degrees F was approx-imately 30 minutes. The maximum station AT during this period was 16 degrees F.

The temperature increase during both occurrences was caused by a rapid drop in the river water ambient temperature. This rapid cooling was the result of river tidal action and the natural cooling of river water that occurs during the afternoon and evening hours.

Radical temperature fluctuations in river water ambient temperature such as those encountered in these instances make it extremely difficult to predict when action is necessary to avoid the 15 degree F increase across the station.

8403020459 760401 .

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VssoistA EtscTute. Axo Powza CowrANY To Mr. Benard C. Rusche ..,Page 2 There was no evidence of any adverse environmental impacts resulting from these occurrences.

Very truly yours, m

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C. M. Stallings Vice President-Power Supply and Production Operations 4

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