mix in the primary coolant. This weighted mean ppc value can then be 

 compared with the gross activity resulting from the mix of the signifi- 

 cant isotopes listed. In computing the weighted mean ppc value for 

 coastal waters, and the gross activity, which are included in Table 3 

 for the SAVANNAH primary coolant and in Table 5 for the NAUTILUS 

 primary coolant, only the isotopes listed in these Tables have been con- 

 sidered. Very short lived isotopes are not included in the calculation. 



BASIS FOR EVALUATING SAFE DISCHARGE RATES 



The partial permissible concentrations in the various subdivisions 

 of the marine environment given in Table Z, and utilized by this working 

 panel in the computations which follow, are based on long time exposure 

 of a selected segment of the population. After release of a given volume 

 of liquid wastes or of spent ion exchange resin to the sea water, proces- 

 ses of diffusion will continually reduce the concentration of activity in 

 the water. There will occur a certain period of time during which the 

 activity in a restricted volume of the sea water may possibly exceed the 

 environmental limits which are based on long term exposure. The pur- 

 pose of the following development is to provide criteria which would in- 

 sure that no significant volume of a given marine locale would have an 

 average activity exceeding the ppc value for that locale over a signifi- 

 cant period of time. 



Let A designate the area of a particular marine region within 

 which N discharges of radioactive materials are made during the time 

 period T. Further, designate by t2/2 the time interval required to re- 

 place 50% of the water in the area A with "new" water from an adjacent, 

 uncontaminated area. The area A must be chosen such that the H con- 

 taminated volumes are randomly distributed throughout the area, as a 

 result both of variations in the discharge site and of the movement of 

 the contaminated volumes by currents. The time period T_ must be short 

 compared to a man's lifetime, but long compared to the time required 

 for the maximum concentration of activity from a point source discharge 

 to be reduced by processes of dispersion to less than ppc values for the 

 environment. 



The concentration of activity at a given position and a given time 

 which results from a single discharge is designated by s^, and the incre- 

 ment of area within which the concentration varies from s - 1/2 ds to 

 to s + 1/ Z ds during the increment of time dt is designated by dA. 

 Further, let the total area within which the concentration at any time t_ 

 exceeds the ppc values for the environment be designated by App^ , and 

 let the time required to reduce the concentrations everywhere in the area 

 to less than ppc values be designated by tpp^.. 



27 



