Based on stated assumptions, the ratio of potential external energy releases from fission products in “local” fallout compared to the cobalt-60 that may be produced can vary from a factor of 40, based on an exposure period from 1 hr to 1 month after a detonation, to 0.17 based on an exposure period from the twenty-fourth hour to 35 years. It is concluded that other factors, i.e. fission yields and position of firing, would be more critical in determining the external y-hazard than the added cobalt-60. One megaton (total yield) detonated in the air might create enough cobalt-60 to produce a theoretical total dose of 0.17 r in the most heavily contaminated band of the earth f 300-600 north latitude), with weathering and shielding effects reducing this by as much as a factor of 10. Decontamination measures could reduce this dose further. Other doses may be calculated as a linear function of the tonnage assumed. Thus, the estimated doses could be significant in long-term effects but not lethal in the sense of wiping out a worldwide population. Mathematically, one can go to ever higher and higher assumed tonnage and cobalt-60 production until a lethal range is reached.
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