ML19289C368
| ML19289C368 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/05/1979 |
| From: | TOLEDO EDISON CO. |
| To: | |
| Shared Package | |
| ML19289C366 | List: |
| References | |
| NUDOCS 7901120099 | |
| Download: ML19289C368 (2) | |
Text
.
TOLEDO EDISON COMPA'iY DAVIS-EESSE NUCLEAR POWER STATION UNIT ONE SUPPLEME';TAL INFORMATION FOR _LER NP-09-78-03 DATE OF EVENT: December 9 and 10, 1978 FACILITY: Davis-Besse Unit 1 Discharge Te=perature for Station Liquid Effluents IDENTIFICATI0" 0F OCCURRENCE:
Exceeded 200F Limit Above Lake Temperature The unit was in Mode 1, with Power (MWT) = 1358, Conditions Prior to Occurrence:
and Load (Grcss :m) = 420.
On December 9,1978, at 1700 hocrs, the Circulating Water Description of occurrence:
The combina-System had been operating in bypass mode; bypassing the cooling towe the cooling tower) and the 1cw lake temperature caused the indicated temperature dif ferential between the lake and ef fluent discharge to increase and exceed the 20cF limit.
1733 hours0.0201 days <br />0.481 hours <br />0.00287 weeks <br />6.594065e-4 months <br /> on December 9, 1978, indicating a Computer alarm T191 was received at 19 F temperature differential. Upon receiving the alarm, the operator diverted service 0
water from the cooling tcwcr =akeup to the collection box and reduced cooling tower blowdown flow in an effort to decrease the temperature differential.
The temperature differential reached approximately 210F at 1737 hours0.0201 days <br />0.483 hours <br />0.00287 weeks <br />6.609285e-4 months <br /> on December 9, The temperature differential decreased below the 1978, before starting to decreare.
20 F limit at 1755 hours0.0203 days <br />0.488 hours <br />0.0029 weeks <br />6.677775e-4 months <br /> on Dece=ber 9, 1978.
0 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br />, the circulating water flow had been operating in On December 10, 1978 at Again, the combination of the cooling tower Fvpass mode bypassing the cooling tower.
basin'tcaperature increasing and the low leke temperature caused the indicated tempera-tyre differential between the lake and effluent discharge to increase and exceed the 0
20 F IL=it.
10, 1978, indicating a Conputer alarm T191 was received at 0950 hours0.011 days <br />0.264 hours <br />0.00157 weeks <br />3.61475e-4 months <br /> on DecemberUpon receiving the 190F tecperature differential.
The tempera-cooling tower bicwdown ficw to reduce the effluent discharge te=perature.
The tempera-ture differential reached approximately 22 F before starting to decrease.
ture differential decreased below 200F at 3026 hours0.035 days <br />0.841 hours <br />0.005 weeks <br />0.00115 months <br /> on December 10, 1978.
The apparent cause of the occurrencc' was Desigt.ation of Anoarent Cause of Occurrence:
(1) There is a design deficiency in the system used to determine the station tbreefold.
The location of the resistance temperature effluent liquid discharge te=perature.
detector (RTD) wnich measures the statien effluent discharge temperature, TE2696, does is not respord accurate 1** to effluent discharce terocrature when the north sample pump in operation.
7901120039
e TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE PAGE 2-r SUPPLDIENTAL INFORMATION FOR LER NP-09-78-03 i
l (2) The co=bined effect of the high cooling tower basin temperature caused by operac-ing in bypass :tode and low leak temperature caused the 20 F limit to be exceeded.j the common suction line of the RE sample pu=ps is heat traced such that t
the indicated temperature differential could be higher than the actual tempera ure (3) Also, differential.
is believed this slight increase in temperature above It cause environmental damage.
Analysis of Occurrence:
the discharge limit f or the short period of time did not An investigation into the occurrence discovered a design defi-Corrective Action:
ciency in the system which measures the station liquid effluent di The RTD is located such that ture.
piping of the Radiation Monitor RE 8433 sample pumps.
the RTD.
If the north the south pump must be operating in order to obtain flow past the RTD reading doesn't accurately respond to the discharge te=pera-pump is running, ture.
Facility Change Request 78-020 was submitted to eliminate the existing design defi-tracing to eliminate ciency by relocating the therttoccuple TE 2696 and revise the heat the indicated temperature differential error.
An investigation is being made into cooling tower operation and blowdown rates to determine if guidelines for cooling tower blowdown rates need to be revised.
An additional temperature diffe.rential alarm is being added to provide the operators more time to take corrective action.
There have been nc previously reported incidents of discharge te=pera-Failure Data:
ture dif ferential limit being exceeded.
\\
O 4