ML20005B383

RO NP-09-81-01:on 810526,max Discharge Temp Differential, Above Ambient Lake Temp,Was Slightly Exceeded.Caused by Difficulty in Maintaining Balance Between Operating to Prevent Exceeding Limit & to Prevent Cooling Tower Damage

ML20005B383
Person / Time
Site:	Davis Besse
Issue date:	06/25/1981
From:	Murray T TOLEDO EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
L81-590, RO-NP-09-81-01, RO-NP-9-81-1, NUDOCS 8107080158
Download: ML20005B383 (3)

Text

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e TOLEDO EDISON June 25, 1981 L81-590 FILE: RR 2 (NP-09-81-01)

Dccket No. 50-346 License No. NPF-3 Mr. James G. Keppler Regional Director, Region III Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 799 Roosevelt Road .

Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

Enclosed are two copies of Reportable Occurrence NP-09-81-01, which are being submitted to you in accordance with Technical Specificatica 6.9 to provide 30 day written notification of this occurrence.

Yours truly,

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Terry D. Murray Station Superintendent Davis-Besse Nuclear Power Station TDM/1jk Enclosure cc: Mr. Norman Haller, Director Office of Management Program Analysis Enc 1: 2 Ohio Environmental Protection Agency Northwest District Office ys Ig g'/ g f -

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'8107080158 810625 PDR ADOCK 050003461 S PDR ;M 2 91981 THE TOLEOO EDISON COMPANY EDISON PLAZA 300 MADISON AVENUE TOLEDO, OHIO 43G52 1

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• TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE REPORTABLE OCCURRENCE NP-09-81-01 DATE OF EVENT: May 26, 1981 EACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Discharge temperature for station liquid effluents slightly exceeded 20 F limit above lake temperature Conditions Prior to Occurrence: The unit was in Mode I with Power (MWT) = 1525 and Load (Gross NWE) = 495 Description of Occurrence: On May 26, 1981, the station learned that on December 20, 1980 at 1200 and 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> and on December 21, 1980 at 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />, the maximum discharge temperature differential, above ambient lake temperature, was slightly exceeded. In all cases, the limit was exceeded by only 01 to 40F, and the differ-ential was restored to within limits within one hour. Environmental Technical Specification 2.1.1 lLaits the maximum discharge temperature for station liquid effluents to 20 F above lake temperature. When the temperature is exceeded, dilu-tion water shall be supplied from the dilution pump to the collection box to keep the discharge temperature difference within the limits specified. Tihe dilution pump was on during these times but the limit was still slightly exceeded.

Designation of Apparent Cause of Occurrence: The cause of the occurrence is the difficulty in maintaining a balance between operating to prevent exceeding the 20 F discharge differential limit and operating to prevent damage to the cooling tower internals. During very cold weather conditions, ice will form in the cooling tower if the circulating water is not hot enough before it is sprayed into the tower To avoid ice buildup and the related damage, a bypass mode of operation is used when the circulating water temperature is less than 85 F. This diverts water directly into the basin. When the temperature of the water recovers, it is then re-directed back into the cooling tower. However, while in bypass operation, the basin tempera-ture increases which increases the blowdown temperature. This in turn will cause the discharge temperature to increase, even with the dilution pump on, to the point where the limit is slightly exceeded. This is most likely to occur on very cold

, winter days during a plant startup or low power operation.

Analysis of Occurrence: There.was no danger to the health and safety of the public or station personnel. The slight increase in temperature above the limit and its short duration should not cause environmental damage.

Corrective Action: In each occurrence the discharge temperature differential was restored to within limits within an hour when circulating water flow was re-directed through t'ie cooling tower when temperatures allowed. A facility change request has ocen initiated to modify the environmental technical specifications to eliminate non-radiological requirements.

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.: TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR P0b'ER STATION UNIT ONE '

I REPORTABLE OCCURRENCE NP-09-81-01 PAGE 2 Failure Data: Prior occurrences of the temperature limit being exceeded were ,

reported in reports NP-09-78-03 and NP-09-80-01.

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