806 POJE, GINN, AND O'CONNOR 



DISCUSSION 



The condenser-tube simulator represents an important develop- 

 ment in the field of entrainment research. This apparatus provides a 

 controlled experimental system that can test individual and com- 

 bined stresses encountered by biota entrained in power-plant 

 condensers. The split flow design permits simultaneous exposure of 

 test organisms to different concentrations of biocides and changes in 

 temperature at a variety of flow velocities. The research presented 

 here is preliminary in nature and seeks primarily to demonstrate the 

 fact that testing of condenser-related stresses is feasible in a 

 simulator. In addition, relevant data on synergistic stress phenomena 

 can be obtained with a controlled-variable testing device. The results 

 from these experiments are consistent with data from laboratory 

 studies with the same species and shed new light on power-plant 

 impact studies conducted in the field with conventional techniques. 



In experiments under conditions similar to those expected in 

 operating steam-electric stations (Coutant, 1970), the power-plant 

 condenser simulator confirms that short-term exposure to thermal 

 stresses in the range of ~10°C AT in the condensers is most likely 

 not the major cause of ichthyoplankton mortality at power stations. 

 Thermal-induced mortality of striped bass in the condenser simulator 

 was similar to that derived by Schubel, Koo, and Smith (1976) in a 

 model system and by Lauer et al. (1974) in static tests. 



The simulator tests verified the hypotheses of Marcy(1975) and 

 of Kedl and Coutant (1976) that mechanical damage to organisms in 

 the circulating water system of power plants was of significance in 

 entrainment impact. Fluid-induced stresses (see, e.g., Morgan et al., 

 1976) were identified as contributing to the mortality of striped bass 

 but not of carp. 



Synergism between temperature and fluid-induced stress was 

 identified in the simulator as contributing to collection mortality. 

 O'Connor and Schaffer (1977) suggested that the differential effects 

 of collection mortality may preclude valid impact assessment at 

 operating power stations. The condenser tube simulator has demon- 

 strated that collection mortality is affected by both flow velocity 

 and thermal exposure. O'Connor and Schaffer tested striped bass 

 collection mortality at different velocities but did not test the effect 

 of thermal or biocide shock. Our results demonstrate that true 

 estimates of cross-plant mortality may be most accurate under 

 near-lethal conditions for the species in question. Under moderate 

 conditions of AT, fluid-induced stress, and chlorination, such as 

 those seen at most operating stations, collection mortality may be as 



