The double integral 



A 



/ppc /• ppc 

 I sdAdt 







then represents the total activity, per unit of depth, which occurs in 

 the area having concentrations exceeding ppc values, times the time 

 interval during v/hich the concentration exceeds that critical value. 

 The area of "new" water available for dilution each time period T is 

 given by 



AT 



2 t 



'^ 1/2 



Hence the relationship 



2 N t 



1/2 



X2 



/ / 







A 



ppc 



sdAdt 



then defines a mean concentration for the total area A^ during the time 

 period T, resulting from N discharges, each having the same amount 

 of activity. This relationship serves to establish the criteria for eval- 

 uating the suitability of any particular marine area as a receiver of 

 radioactive wastes from nuclear-pow^ered ships. 



If the distribution of contaminated volumes within the area were 

 truly random at all times, and if the processes of biological concen- 

 tration of radioisotopes were instantly reversible, then a suitable cri- 

 terion for safe discharge to the marine environment would be the re- 

 quirement that the mean concentration defined by the above relationship 

 be less than the ppc value (here designated as Snnc ) ^°^ that environ- 

 ment. Unfortunately, marine organisms which take up radioisotopes 

 when in contact with sea water of a given concentration of activity, do 

 not reach a new equilibrium readily when exposed to water of much 

 lower activity. Also, it would be difficult to assure a completely uni- 

 form distribution of the contaminated volumes within the subject area. 

 Finally, and perhaps most important, the condition discussed in the 

 previous section entitled "Restrictions on the Application of ppc Values 

 in Seafood and in the Marine Environment" must be satisfied. There- 

 fore, the criterion employed here is that the mean concentration de- 

 fined by the above relationship be 1/ 100th of the ppc value for the en- 

 vironnnent; that is, the number of releases N in the area A during the 

 time period X must satisfy the relationship 



28 



