



AUG01 AUG20 SEP09 SEP28 OCTIS N0V07 



aevan-yaar mean (1976-86) 



1987 values; », o-doys of survey and probe deployment 



21- 

 20- 

 19- 

 IB- 

 17- 

 16- 

 15- 





AUGl AUG20 SEP09 SEP28 0CT18 N0V07 



Deven-year mean (1976-86) 



1987 values: «, o-doys of survey ond probe deployment 



AUG01 AUG20 SEP09 SEP28 0CT18 N0V07 



Deven-year mean (1976-86) 



1987 values: », o-days of survey and probe deployment 



Fig. 2. Air and water temperature, and wind speed 

 recorded by the environmental data acquistion network 

 (EDAN), August through October, 1976 - 1986. Am- 

 bient water temperatures (°C) are averag.is of those 

 measured at 15-minute intervals at the MNPS Units 1 

 and 2 intakes. Air temperature and wind speed are 

 averages ormeasurments taken at 15-minute intervals, 

 10 m high on the meterological tower. 



TempMentors were deployed and water 

 tempertures were below the 11 -year mean. 



Dye concentration mapping was conducted un- 

 der nearly ideal weather conditions (26 August). 

 Seas were calm (less than 0.3 m), reducing thermal 

 plume mixing due to wave action to a minimum. 

 The light winds, averaging 2 m/s (Figs. 2, 3), 

 assured that the dispersal of the thermal plume 

 was due predominantly to tidal influences. Con- 

 ditions were good enough to allow surface expres- 

 sion of the plume boundaries during maximum 

 flood, high slack and maximum ebb stages of the 

 tide. A further benefit of the good conditions was 

 the development of the 1.5°F (0.83°C) isotherm. 

 Greater wind and wave action would have dimin- 

 ished the lateral extent of this isotherm. Thus, 

 error-free equipment operation combined with 

 excellent site conditions allowed for the clear def- 

 inition of this isotherm. 



Station operating conditions 



All three MNPS units normally operate at a 

 constant base load. Unit 1 resumed power pro- 

 duction on 19 August 1987 subsequent to the 

 completion of its refuel outage. Power production 

 reached 100 % capacity on 21 August 1988 (Fig. 

 4). During the background monitoring period, 

 the dye build-up period, and low slack and max 

 flood mapping periods (0900 on 26 August 1987) 

 all three units operated at full capacity and 

 pumped a total of 4,364 cfs ( 124 m /s) of cooling 

 water (Fig. 4). Between 0900 and 1400 hours on 

 26 August, Unit 1 power production was reduced. 

 Concurrently, Unit 1 cooling water usage was 

 reduced from 989 cfs (28 m"/s) to 521 cfs (15 

 m' /s) and the effluent water temperature dropped 

 about rC (Fig. 5). The Station, however, was 

 still using 94% of its maximum cooling water at 

 1200 hours, during the high slack mapping session, 

 and nearly 90% of its maximum at 1430 hours, 

 the start of the maximum ebb tide mapping ses- 

 sion. Considering the nearly ideal survey condi- 

 tions, these reductions in discharge volume should 

 not have greatly altered the patterns and magni- 

 tudes of the plume from those presented; adverse 

 wind and sea conditions could be expected to 



Hydrothermal Studies 331 



