130 



Atomic Radiation and Oceanography and Fisheries 



oil-filled float F. Numerous accessories might 

 profitably ornament this sort of gear, but the 

 one which might prove most rewarding would 

 be a sound producer capable of reporting the 

 moment of contact with the tagged water mass ; 

 even a crude sonic signal sent from a transducer 

 on the float, F to the ship, A, via the towed 

 hydrophone, H, would suffice. Details of the 

 gamma signals need only be recorded so that 

 they might be inspected later on the recorder 

 chart, however, it would be important for the 

 navigator to recognize instantly when contact 

 was made so that he could maneuver the ship 

 economically. 



The operations proposed above are not un- 

 like those used successfully by cable ships when 

 retrieving submarine wires. Careful preliminary 

 surveys of the whole area, the selection of iden- 

 tifying landmarks, and the laying of the mark- 

 ing buoys also appear essential for success in 

 work of this type. 



The final results might have the general char- 

 acter of the hypothetical signals shown graphi- 

 cally at lower right in Figure 3. Change in 

 amplitude and displacement, and skewness of 

 the signal records should lead to estimates of 

 both velocity and rate of mixing. If each survey 

 included ten or more intersectings, and if each 

 contact brought separate gamma signals from 

 several detectors distributed along the hound's 

 vertical "tail," then the data of the sort needed 

 would accumulate quickly. 



Rough estimate of effectiveness of 1,000 curies 

 for tagging bottom waters 



It appears possible to distribute radioactivity 

 uniformly along the course of a device dragged 

 over the sea bottom, and it would appear pos- 

 sible also to deposit the material so gently that 

 it would come to rest within a few meters of 

 the precise course. If, for a rough evaluation, 

 we assume that local difl^usion sooner or later 

 produced a uniform distribution within a radius 

 of 10 meters, and that the total activity, M, was 

 1,000 curies, then the length of the water mass 

 which might be tagged can be stated 



0) 



/= 



C7rr2 



where C is the average concentration of activity 

 within the tagged mass. 



If now we assume that only 10 seconds can 

 be allotted for traversing 20 meters (that is the 



ship's speed is about 4 knots), then the equa- 

 tion (9) of Appendix A indicates that a single 

 detector like the 1955 SIO Geiger instrument 

 could detect, in the presence of a realistic deep- 

 water background of 15 cps, a limiting gamma 

 source concentration of 0.061 disintegrations/ 

 sec/ml, or C = 0.06l/3.7 x lO'^o curies/ml, and 

 the length of traverse which could be tagged 

 with 1,000 curies would be, under these as- 

 sumptions. 



/= 



1000 



1.65x10-12^(1000)2 



- = 1900 Km (2) 



It would appear feasible to locate and allocate 

 by ordinary navigational means a geographical 

 line in the deep sea floor of less than two kil- 

 ometer's length, so that the hypothetical ex- 

 ample just given suggests that 1,000 curies 

 could equally well be used to produce a very 

 concentrated streak of activity having a length 

 of two or three kilometers which might still be 

 detected with ease after it had difl^used, mixed, 

 or decayed to less than one percent of its initial 

 concentration. Thus it can be concluded that 

 1,000 curies, or even less activity, put into bot- 

 tom water would be quite adequate for tracing 

 movements on a scale large enough to contrib- 

 ute information useful in disposal planning. 



SUMMARY AND CONCLUSIONS 



1. Consideration has been given some of the 

 problems involved in tagging water masses in 

 the open ocean. 



2. The problems are different in the three 

 major strata; the surface layers, the thermocline, 

 and the deep water layer. 



3. It appears that under certain circumstances 

 water tagged with even moderate quantities of 

 activity can be followed for at least several 

 weeks; surface waters contaminated by large 

 activities such as result from fallout can cer- 

 tainly be followed for a year or more. 



4. Much field experience in radiological ocea- 

 nography has been gained already. A fairly clear 

 direction for development of instruments has 

 been indicated. 



5. The need is seen for attention to the perfec- 

 tion of navigational aids, for use of specialized 

 vessels and gear, and for the use of several ves- 

 sels simultaneously in oceanic surveys of this 

 sort. 



