ML19296A926

RO-NP-09-80-01:on 800116,during Normal Plant Startup,Temp Differential Limit Between Station Liquid Effluent Discharge & Lake Temp Was Exceeded.Caused by Operation of Plant W/ Cooling Tower in Bypass Mode

ML19296A926
Person / Time
Site:	Davis Besse
Issue date:	02/12/1980
From:	TOLEDO EDISON CO.
To:
Shared Package
ML19296A924	List: ML19296A923 ML19296A926
References
NUDOCS 8002190455
Download: ML19296A926 (2)

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M TOLEDO EDISON COMPANY DAVIS-BESSE MUCLEAR POWER STATION UNIT ONE REPORTABLE OCCURRENCE NP-09-80-01 DATE OF EVENT: January 16, 1980 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Discharge temperature for station liquid effluents exceeded 20"F limit above lake tenperature Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MRT) = 166, and Load (Gross MWE) = 0.

0 Description of Occurrence: On January 6, 1980 during normal plant startup, the 20 F temperature dif f erential limit between station liquid effluent discharge and lake temperature was exceeded.

Environmental Technical Specification (ETS) 2.1.1 specifies that the maximum discharge lake temperature for station liquid ef fluents shall not exceed 20 F above ambient water temperature. When the limit is exceeded, dilution water is to be supplied by the dilution pump to keep the discharge temperature differential within the limit.

the The 20 F temperature differential lim'it was observed to have been exceeded at following times: 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br /> and 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> on January 6, 1980; 0000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />, 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br />, On January 16, and 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> on January 7, 1980; and 0600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br /> on January 8, 1980.

1980 at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br />, the unit was operating at 100% pcwer and the 20 F temperature differential limit was exceeded again. During each of the occurrences the tempera-ture differential limit was exceeded by approximately 1 F to 5 F.

The dilution pump was operating during each of the occurrences but failed to maintain the liquid effluent temperature within the 20 F limit.

Designation of Apparent Cause of Occurrence: The apparent cause of the occurrence -

was procedural deficiency. On January 6, 7, and 8, 1980, the plant was operating with the cooling tower in bypass mode causing the cooling tower basin temperature to be elevated above normal operating temperature during startup, thus producing a high station liquid effluent temperature.

The combination of high station liquid effluent temperature and low lake temperature caused the tenperature differential limit to be exceeded. The dilution pump was operating per SP 1104.09, Circulating Water System and Cooling Tower Operatian, but was unable to provide the adequate cooling effect and prevent exceeding the 200F temperature differential limit.

On January 16, 1980 the unit was operating at 100% power with all circulating water pumps operating. High station liquid ef fluent tenperature was caused by the combina-tion of unseasonably warm weather and reduced cooling tower efficiency due to both control flume isolation valves being inoperable. The combination of high station liquid effluent temperature and low lake temperature caused the temperature differ-ential limit to be exceeded. Again the dilution pump was operating per SP 1104.09 but was unable to prevent exceeding the 20 F temperature differential limit.

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TOLEDO EDISON COMPXiY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE PAGE 2 REPORTABLE OCCURRENCE NP-09-80-01 SP 1104.09, Circulating Water System and Cooling Tower Operation Procedure, was deficient of adequate guidelines to maintain station liquid effluent t emperature within the 20 F limit beyond just verifying the dilution pump being on.

Analvsis of Occurrence: There was no danger to the health and safety of the public or to station personnel. It is believed that the slight increase in temperature above the discharge limit did not cause environmental damage.

Corrective Action: On January 6, 7, and 8, 1980, the station liquid effluent temperature returned to within the 200F limit when the circulating water flow was transferred from the normal startup bypass mode of operation and directed through the cooling tower.

On January 16, 1980, the service water discharge was diverted from the forebay to the collection box which reduced station liquid effluent temperature to with-in the 20 F limit.

SP 1104.09, Circulating Water System and Cooling Tower Operation Procedure, will be modified to provide additional guidelines to the operators to assist in main-taining station liquid effluent temperature within Itaits.

Failure Data: A prior occurrence of the temperature limit being exceeded was reported in Licensee Event Report NP-09-78-03.

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