Nuclear-powered ships will spend a part of their time in areas 

 well removed from man, w^here perhaps the disposal of limited amounts 

 of w^astes w^ould not result in ready return to man through the food chain. 

 These ships will also spend part of their time in regions of high human 

 activity, such as harbors and harbor approaches. The release of even 

 very small amounts of radioactive materials in these latter environments 

 might result in the return to man, through the food chain, of undesirable 

 amounts of activity. For this reason even the relatively sraall amount of 

 activity present in the primary coolant is considered deserving of con- 

 sideration. 



PREDICTED NUMBER OF NUCLEAR-POWERED SHIPS 



In order to evaluate properly the capacity of the various parts of 

 the marine environment to receive radioactive wastes from nuclear- 

 powered ships, it is necessary to have a reasonably correct prediction 

 of the number of such ships which will be operating on the world oceans 

 w^ithin the next several decades. Efforts to obtain such an evaluation 

 have not resulted in consistent estimates, w^ithin even an order of mag- 

 nitude. For this reason the evaluation presented herein is based on an 

 arbitrary number of 300 nuclear-powered ships of the 60 MW class. 

 It is believed that this figure should safely apply to the next ten to fif- 

 teen years. Thus, adequate time is available to revise the conclusions 

 made here on the basis of more dependable estimates of the probable 

 number of nuclear-powered ships which will, in the foreseeable future, 

 operate on the world oceans. Undoubtedly, better information thaji is 

 now^ available on the allow^able exposure of man to radiation, and on the 

 processes of dispersion, uptake, and concentration in the marine envi- 

 ronment, will become available over the next ten years, making such a 

 re-evaluation desirable in any case. 



GENERAL APPROACH TO THE PROBLEM 



The fate of radioactive material introduced into the marine envi- 

 ronment is dependent upon the following considerations: 



1. The physical and chemical form in which the material occurs 

 at time of introduction, together v/ith any relatively rapid changes in the 

 physical and chemical character of the introduced material w^hich occur 

 v/hen it is brought into contact with sea water. The subsequent disper- 

 sion by physical processes and re-concentration by the biota and bottom 

 materials will be greatly affected by the physical and chemical form in 

 which the w^astes occur in sea w^ater. 



2. Initial mechanical dilution of the wastes by the receiving waters, 

 w^hich will depend upon the manner of introduction. Thus a liquid waste 

 w^ill be subject to greater initial mechanical dilution if introduced as a 

 strong jet into the body of the receiving waters, than if introduced as a 

 gently flowing stream on the surface. Large initicd mechanical dilution 



is important in reducing the density difference between the initial con- 

 taminated volume and the surrounding receiving waters. This reduction 

 in turn favors subsequent turbulent diffusion. 



