(16) 
an auxiliary navigation system to determine the exact location. 
Anchor buoys will have to be spotted around to navigate from, 
especially during the early stages when the contaminated area is 
small and can be followed around with detectors. When the activity 
spreads out it will not be difficult to spot, but the activity read- 
ings will be close to the limits of detection. It will not be easy 
to determine relative concentrations and concentration areas at this 
baal” 
Radiation Measurement Difficulties in Bottom Waters: The 
practical design limit for a tracer experiment in the deep open ocean 
appears to be the ultimate sensitivity of the radiation measuring 
(27) ate (14) 
device. The readable level is about 10 megacuries per cc. 
Instantaneous reading of radioactivity may be obtained by sending down 
a sensing instrument. The limiting level for this technique is about 
(14) 
7 megacurie per cc. If a volume 100 kilometers (62.5 miles) 
107 
square by 100 meters thick received one megacurie, the activity would 
pemeetucedesi 107" x 1o-" = 10-4" 4 101° megaeuries per ec. -- weld 
below the direct or instantaneous readable level. Taking samples for 
concentration and subsequent reading introduces many difficulties. 
In such a case you would not know where to take the sample, nor would 
you know whether you had selected the right location for sampling until 
sometime later. If a smaller area was charged, direct readings might 
be feasible. The material would start diffusing the instant it was 
released and tracing it with a direct reading instrument should give 
information as to how fast diffusion takes place at the bottom. Nobody 
knows how fast it would be, although observations are available for 
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