3. Advection of the waste material away from the source region, 

 and simultaneous turbulent diffusion, which lead to reduced concentra- 

 tions of the radioactive components in the water. 



4. Uptake of the activity onto suspended silt and bottom sediments, 

 which removes some of the radioactive materials from the water, and 

 restricts further dispersion. In deep water such removal would be fa- 

 vorable since material incorporated with the bottom sediments there 

 would be unlikely to return to man's environment. In shallow coastal 

 areas containing bottom living shellfish and bottom feeding commercial 

 fin fish, concentration of radioactivity on the bottom may be unfavorable 

 since these detritus and filter feeders may further concentrate the ac- 

 tivity from the bottom material. 



5. Concentration of activity by various parts of the biota, includ- 

 ing shellfish and fin fish important to man as a source of food. Some 

 important fission products and corrosion products are concentrated by 

 marine organisms by factors of 100 to 10,000 over the concentrations 

 of these isotopes in the water. 



The evaluation of the suitability of any particular marine locality 

 as a receiver of nuclear wastes ideally involves the precise, step by 

 step consideration of all factors affecting the possible return of radio- 

 active material to man. The general procedure is the same whether the 

 evaluation concerns: (a) the selection of suitable disposal areas for 

 packaged wastes; (b) the selection of the position of an outfall discharg- 

 ing low level liquid effluent from a chemical processing plant; (c) the 

 consideration of the suitability of a given harbor or harbor approach to 

 receive low level liquid wastes from nuclear powered ships; or (d) the 

 determination of the suitability of the mixed layer of the open ocean to 

 receive wastes from the ion exchange resins on nuclear powered ships. 

 Understanding of many of the physical and biological processes involved 

 is, however, far from adequate, and further research is recommended 

 to provide a more adequate foundation for the determination of the ca- 

 pacity of any particular marine locale to receive nuclear waste mate- 

 rials without undue risks to man. 



Figure 1 presents in schematic form such a step by step procedure. 

 The solid arrows between blocks on the diagram indicate the route taken 

 by the radioactive material in returning to man, while the dashed arrows 

 indicate the reverse course taken in the evaluation. The starting point 

 in the evaluation is man . In order to make any evaluation of the problem 

 at all, some maximum permissible rate of exposure must be adopted. 

 The usual basis for the selection of such a maximum rate would be 

 national (or international) published statements of the maximum permis- 

 sible ingestion rate for the various isotopes, for the general population. 

 At the outset it should be recognized that such a maximum permissible 

 rate of exposure is not the most desirable rate. The latter, where tech- 

 nical and economic feasibility allow, should be as close to zero as pos- 

 sible. Thus in making this evaluation, some real, though admittedly 

 extremely slight, risk to the general public is assumed. 



