ML19347B629

Environ RO 50-259/8073:on 800928 & 29,temp Rise of Wheeler Reservoir Between Upstream & Downstream Thermal Monitors Exceeded Tech Specs.Caused by Extensive Rainfall & Lower than Normal Ambient Temp,Adding to Errors in Prediction

ML19347B629
Person / Time
Site:	Browns Ferry
Issue date:	10/08/1980
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
RO-8073, NUDOCS 8010150463
Download: ML19347B629 (5)

Text

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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374ot 400 Chestnut Street Tower II October 8,1980 Mr.JamesP.O'Reiliy, Director .

I U.S. Nuclear Regulatory Commission Region II - Suite /3100 101 Marietta Stre'et, NW Atlanta, Georgia 30303 -

se i Dear Mr. O'Reillyt i

TENNESSEE VALLEY AUTHORITY - BR0iiNS FERRY NUCLEAR PLANT, j UNITS 1, 2, AND 3 - DOCKET NOS. 50-259, 50-260, AND 50-296 - ,

FACILITY OPERATING LICENSES DPR-33, DPR-52, AND DPR l ENVIRONMENTAL REPORTABLE OCCURRENCE - BFRO-50-259/8073 The enclosed report is submitted in aacordance with Browns Ferry's environmental technical specification 5.6.3b. This report supple-ments our report by telecopy to you on September 29, 1980, from i H. L. Abercrombie, Power Plant Superintendent, Browns Ferry Nuclear Plant, l and provides details concerning the violation of the reservoir water maximus temperature rise specification of 5 degrees Fahrenheit on September 28 and 29, 1980.

The predicted computer temperature rise was incorrectly reported as 3.8 degrees Fahrenheit for September 28, 1980, and is corrected in the enclosed report.

Very truly yours, TENNESSEE VALLEY AUTHORITY J '

, .M1 4 ,

I

. M. Mills, Man ger Nuclear Regulation and Safety j

Enclosure cc: See page 2 l

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An Ecual Opportunity Employer 801015 0YG 3 S . . -

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-2 Mr. James P. O'Reilly, Director October 8,1980 cc (Enclosura):

Director Division of Oferating Reactors U.S. Nuclear Regulatory Commission -

Washington, DC 20555 Director (3)

Office of Management Ir. formation ~

and Program Control U.S. Nuclear Regulatory Co= mission Washington, DC 20555 Director (40)

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 1

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I a e LCO VIOLATION REPORT Browns Ferry Nuclear Plant- ~

l Report No.  : BFR0 5'0-259-8073 Report Date  : October 8,1980 Occurrence Date  : September 28 and 29, 1980 i Facility  : Browns Ferry Nuclear Plant -

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Conditions Prior to Occurrence On September 28, 1980, unit I was operating at 1,070 MWe; unit 2 was shut j down for refueling; and unit 3 was operating at 1,082 MWe.

j On September 29,1980, unit 1 was operating at 905 MWe; unit 2 was shut  ;

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! down for refueling; and unit 3 was operating at 1,087 MWe.

i i Descriotion of Violation i

The temperature rise of Wheeler Reservoir measured between upstream and

] downstream thermal monitors exceeded the maximum allowable temperature rise limitation of 5 0 degrees Fahrenheit from 2000 through 2115 CDT and i

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from 0615 througn 0645 CDT on September 23 and 29, 1980, respectively.

The maximum temperature rise which occurred during these violations was 5.1 degrees Fahrenheit. The maximum downstream temperatures during these periods were 78.2 and 77.5 degrees Fahrenheit, respectively.

Cause of Violation l Extensive rainfall throughout the Tennessee Valley combined with lower than normal ambient temperatures may have contributed to errors in predicted computer values.

The predictive computer program estimated the maximum temperature rise 4

during the periods of violation to be 2.8 degrees Fahrenheit on Septemoer 28 and 4.9 degrees Fahrenheit on September 29, 1980. As a result of these underestimations by the computer program and the rapid increases in the temperature rise, plant personnel could not react quickly enough to prevent the violation.

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Corrective Action On September 28, 1980, when predictive temperature data indicated a possible thermal limit violation, no mitigative actions were taken

'; because it was originally believed that the thermal monitors were in error and no real problem existod. After the violation had occurred, additional river flow was requested to preclude further violation. On September 29,1980, at 0415 CDT when a rapid increase in the temperature rise was noted, Unit No. 3 was placed on the cooling towers. However, i the thermal limit was again violated.

Analysis of Violation -

An analysis of all river water temperature data available before and after 4 the violations indicate that the Environmental Technical Specification limit regarding the maximum temperature rise was exceeded. The predicted and actual temperature rises are shown on the attached graph. Since the violations only lasted for 1.25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> on September 29 and 0.50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> on i September 29, and the limit was only exceeded by 0.1 degrees Fahrenheit in both cases, no significant adverse environmental impact was experienced in 'dheeler Reservoir due to plant-induced heating.

i Recommendations to Avoid Future Violations Hydrologic and thermal stud:.es of the river near the plant have been done, l l and a ' proposal to revise the thermal monitoring system to provide more '

accurate thermal data has been submitted to EPA. Design change requests ,

are being prepared as the first step in the installation of the revised l system. l t

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