124 



Atomic Radiation and Oceanography and Fisheries 



provided by fallout, they have some mathemati- 

 cal simplicity. It would appear economical and 

 informative to drop two sources almost simul- 

 taneously, some distance apart — say one to ten 

 kilometers; this would permit large-scale ad- 

 vection also to be studied at little extra ship 

 cost. 



From the sources s and s' will grow a larger 

 more dilute patch of water finally ceasing to 

 penetrate rapidly downward at depth d. The 

 rate and lateral spread prior to this time as 

 functions of wind velocity are of special in- 

 terest. After further downward penetration is 

 retarded, the areas a and a' move and expand 

 to the larger areas A and A' conserving most 

 of the original radioactive material, and the 

 product of activity and area should be almost 

 constant after correction is made for the known 

 rates of decay of radioactive constituents. 



Dual ship operations 



Experience has shown that operations on the 

 scale of this sort can scarcely hope to be suc- 

 cessful unless more than one ship is used ; even 

 with the best facilities one ship may lose con- 

 tact with the invisible patch and waste valuable 

 time locating it. One ship, X, must stay in or 

 near the tagged mass while the other one, Y, 

 may survey the area in detail, inspecting sections 

 across the mass, studying the bottom for ref- 

 erence features, and chasing missing buoys if 

 necessary. 



Ultimate disposal of hazard in surface waters 



Reduction of activity to a level below that 

 of the natural activity of sea water is one cri- 

 terion which has been used for planning dis- 

 posals (Glueckoff 1955), and this is fairly 

 reassuring provided the specifically dangerous 

 and the long-lived activities are eliminated, for 

 example, after radiostrontium and radiocesium 

 are removed from raw fission wastes. Present 

 evidence permits the conclusion that in the 

 open ocean, when winds are above the critical 

 white-cap level and under circumstances where 

 mixing ceases at a depth of about 30 to 50 

 meters, as much as 1,000 curies would mix to 

 a safe dilution in less than 40 days. An ex- 

 ample of the dispersal rate in the open sea 

 will now be given. 



Brief outcome of an experimental tagging of 

 surface waters in the open sea 



Surface water made active by introducing fis- 

 sion products concentrated within a few square 

 kilometers was intercepted by a ship 36 days 

 after inoculation and traversed for 10 days. 

 After corrections were made for the drift of 

 the water during the survey, and for radioactive 

 decay, a synoptic picture could be drawn roughly 

 locating the contours of activity. This estimate 

 of radioactive distribution was referred to the 

 time of 40 days after the start of dispersal. 



The contamination had mixed significantly 

 only to about 30 to 60 meters, although the 

 thermocline lay nearer to 100 meters depth. 

 The following tabular description of this synop- 

 tic sketch can be made. 



TABLE 1 Approximate Distribution of Radio- 

 activity Found in the Surface Waters of the 

 Open Seas 40 Days After Being Introduced Sud- 

 denly AS A ""Point Source." (A Synoptic Picture 

 Computed from Measurements Made on 

 Several Different Days.) 



Concentration 

 Areas inside of radio- 

 Areas inside con- the contours activity (as 

 tours of equal as percentages per cent of 

 concentration of the area of the maximum 

 in square the maximum concentration 

 kilometers. contour. measured). 



40,000 (km^) 100% 10% 



24,000 65 20 



14,000 38 30 



8,000 22 40 



800 2 60 



490 1 80 



35 0.1 100 



At the end of 40 days, the center of gravity 

 of this distribution was about 120 miles from 

 the point of inoculation and the pattern was 

 about four times longer than broad. The wind 

 was 3 and 4 of Beaufort's scale for the first 

 20 days, but was much calmer for the last 20 

 days. 



If the average mixing depths are taken as 

 50 meters, then, 1,000 curies distributed over 

 40,000 square kilometers would result in an 

 average concentration of 1.5 X 10-^°/yu,c/ml. 

 This would certainly be safe sea water in most 

 senses; and even in the smaller areas where 

 much less than the average dispersal took place 

 the water should also be safe. In fact, the 

 experiment indicated that it is likely that after 

 40 days, following the introduction of 1,000 



