ML20084H826
| ML20084H826 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/23/1974 |
| From: | Eric Thomas TENNESSEE VALLEY AUTHORITY |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| AO-BFAO-7419W, NUDOCS 8305060004 | |
| Download: ML20084H826 (13) | |
Text
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Mr. John F. O' Leary, Director Qhoqp?g / Directorate of Licensing 7 g g.7.,, t
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Dear Mr. O' Leary:
TENNESSEE VALIEY AUTHORITY - BROWNS FERRY NUCIEAR PL1NT UNIT 1 - DOCKET UO. 50-259 - FACILITY OPERATING LICENSE DPR AENORYAL OCCURRENCE REPORT BFFAO-7419N The enclosed report is to provide details concerning a river temperature-increase exceeding the t;nvironmental Tecnnical Specification. This event occurred on Browns Ferry Nuclear Plant unit 1 on April 29, 1974. This report is submitted in accordance with Appendix A to Regulatory Guide 1.16, Revision 1, October 1973 This letter supersedes a letter dated Fay 9,1974, in which the Abnormal Occurrence Report number was incorrectly given. Very truly yours, TENNESSEE VALLEY AUIHORITY E. F. Thorras Director of Power Production Enclosures CC(Enclosures): Mr. Iiorran C. Moseley, Director Region II Regulatcry Operations Office, USAEC #
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' . ABNo'Rl/AL oCCURREIE REPORT -
Report No.: BFEAo-74197 T,
' Report Date: Iray 9,1974 occurrence Date: April 29, 1974 Facility: Browns Ferry Nuclear Plant Unit 1 Identification of occurrence At 4 p.m. on April 29, 1974, Browns Ferry Nuclear Plant exceeded the Environmental Technical Specification limit of. 5.0 F.0 river temperature increase.
Conditions Prior to occurrence The reactor load increased steadily from 487 We at 9 a.m. to 773 We at 4 p.m. Riverflow was between 30,000 and 45,000 efs for the entire period and was about 40,000 cfs at the time of occurrence. The weather was clear and air tecperatures ranged from a low of 60 9 F. at 5 a.m. to a high of 81.1 0 F. at 4 p.m. Descriptien of occurrence The temperature difference between the upstream control thermistor at TRM 309 7 and the downstream thermistor at TRM 292.5, as displayed in the power plant centrol room, reached 5.3 0 F. at 4 p.m. The data printout from the monitoring staticns at 4 approxirately the same time showed this difference to be 5.1 F. Designation of Arcarent Cause of occurrence
. This situaticn was apparently caused by a natural difference in the temperature of. the water between the upstream and downstream monitors at the 5-foot depth. This difference is not the result of plant operation but is apparently caused by diurnal solar heating.
Analysis of occurrence The attached sketches show the variation of temperatures at the surface and at the 5-foot depth throughout the monitored reach of the river during the abnormal occurrence period. These sketches show a higher temperature rise between the two upstream thermistors than between any of the five thermistors in the immediate upstream and downstream vicinity of the plant. With riverflow between 30,000 and 45,000 cfs during the entire period, there is no doubt that positive flow was maintained past the plant at all times. This, together with the rapid air warming from 60 90 F. to 81.10 F. and the large river surface area dcwnstream from Decatur, indicates that most of the temperature rise was
. caused by natural conditicns rather than the plant discharge.
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t O O L i An analysis of the plant heat load and streamflow will also show that the plant dischar6e could not have been responsible for the entire temperature rise. The rise in temperature of the condenser circulating water ranged from 150 F. at 2 p.m. to 17.1 F. at 4 p.m. The circulating water ficw rate was between 1,400 and 1,425 cfs for this period. The plant effluent diffuser is designed to in: mediately mix this with at least 22 percent of the riverflow or 8,800 cfs. This immediate dilution is about 6 to 1 and therefore the maximum temperature rise caused by the plant effluent would have been 2 90 F. Freliminary results of a field investigation \ made on thy 4,.1974, indicate that the diffuser is operating as designed and is holding the temperature rise to 2 or 30 F. Corrective Action An immediate solutien to this problem is not available. We are analyzing the results of the field investigaticn and are developing a technique to interpret the data frcm the monitoring system to acccunt for the effects of solar heating and lateral wind-induced currents. This should provide a river temperature rise attributable only to the plant discharge. 8 4 I i i e r
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