(d) The ocean is considered to be of uniform depth , equal to the depth 

 at the source and no flux of radioactivity is presumed to occur across the 

 upper or lower boundaries (however, the special case of infinite depth is 

 considered in part of the analysis). 



The assumption of Fickian diffusion implies that the decay of activity 

 concentration with distance from the source region is much slower than is 

 known to occur under actual conditions in the presence of turbulence [ Sutton 

 (1953), p. 279 ] . The assumption of no adsorption on the sea bed and no 

 natural radioactive decay obviously leads to an overestimate of activity con- 

 centrations within the sea water . 



The problem is treated from both a gross source standpoint and an indi- 

 vidual source point of view. In the gross source problem, we visualize that a 

 specified amount of radioactivity is deposited continuously within a certain 

 confined area of the sea bed per unit time and that this material is in a form 

 which is subject to dispersal from the source area by diffusion and currents. 

 Actually the material deposited is in the form of packages which may contain 

 the material long enough that natural decay renders it harmless . On the other 

 hand , the contents of packages may , conceivably , be subject to dispersal due 

 to destruction of the container by impact or errosion or to dispersal through 

 a continuous leaching action . This we presume occurs on the average at a rate 

 equal to the average rate of addition of the packages . In other words , we 

 visualize that the radioactive material is effectively flowing into the source 

 area on the sea bed in solution form at a steady uniform rate and dispersing 

 into the environment at the same rate. For all practical purposes the lateral 

 extent of the environment (hence its capacity) can be considered infinite , and 



