product activity still in the atmosphere. The following table is presented to provide representative figures to use in calculations taking into account the factors listed above. Note that this table applies only to land surface bursts. TABLE 9 Gross Fall-out Local 60% Strontiw-90 . 30% 10% Extended Local 10% World-wide deposited 1% ym World-wide not deposited 29% 57% 100% 100% Within the limits of accuracy of this type of analysis, it may be said that about half of the strontium-90 produced during a surface burst attack on an area the size of the United States will de= posit within the country. The SUNSHINE model, modified as noted above, can be applied t: the calculation of the strontium-90 concentration possible in such a localized target area, assuming surface burst weapons: 6 3x 102 mi (area offu. U. Ss. ) x 100 = 1.54 2x10 sq mi (area of earth) Therefore: 1.5% of the area assumed available in the original model would receive 50% of the strontium-90 produced and 25,000 MI x .015 x 2 = 750 MI is the amount needed to bring such an area to the 1 microcurie bone. level, if the distribution over the area were assumed to be uniform. The wiform distribution assumption for local fall-out areas is NOT a valid one; in fact, roughly 10 times the yield figure stated, or 7500 MI, would have to be detonated on land surface in the United States to cover all of its area with at least the strontium-90 needed for 1 microcurie per man. It must be remembered that the SUNSHINE Model is 117