FALL-OUT MEASUREMENTS IN AUSTRALIA 



The first weapon, Round 1, was mounted on a tower and fired on Sep- 

 tember 14, 1957. Marked directional variation with altitude of the upper 

 level winds resulted in the radio-active material being dispersed very widely 

 over the continent north of the test area. Rainfall during the period was 

 restricted to the south-eastern coastal areas. It did not coincide with the 

 fall-out material. 



Round 2, also mounted on a tower, was fired on December 25, 1957. 

 Both velocity and angular wind sheer caused the main cloud to be distri- 

 Inited widely to the north-east and the east of Maralinga. 



The third and last weapon of the scries was suspended above the desert 



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I Port Hedland 



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Figure 2. Fall-out sampling stations during a test series at Maralinga — stations 

 marked with an additional circle are continuing in operation 



by means of balloons. It was fired on October 9, 1957. As had been pre- 

 dicted, rain was restricted to southern New South Wales and Victoria, and 

 the main cloud of radio-active material moved eastward and then north- 

 eastward in its passage to the Queensland coast. Again, the material was 

 distributed very widely. The cloud trajectories for the three rounds are 

 indicated in Figure 1. 



Between September 10 and October 24, 85 stations continuously monitored 

 fall-out, using gummed films. Each film was exposed for 24 hours before 

 being forwarded to a central laboratory for analysis. Some of these stations 

 also sampled air and rainwater. The distribution of the sampling stations 

 is given in Figure 2. It will be noted that the network was chosen to have 



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