gic which are the residue of bomb elements and surface materials, soil and water, made redicactive by eccozmpanying radiatiosa fields. Debris is sucked high into the atzospvhere by efter winds of the explosion. Where this radioactive debris will fall is a mejor pre-shot consideration end pricerily invluences the decision to detonate a nuclear explosion at a certain tins. The area over which radioactive debris is spread end the intensity of fall-out on the ground are deterxined by the yield of the explosion as well as by wind pattern since the larger the yield, the more surface raterials ere sucked up into the cloud end the more fission fragments are availeble. The rela- tionship between yield and fall-out is kmowm only qualitatively. 4. PRE-SHOT INFOXMATION: The operational aspects of the BRAVO experience were plannea and conceived in the lisht of experience gained from previms operations. These factors were considered: ea. The dbasis for ferecasting where fallout will go is experience gained from overseas test operations CROSS20ADS, SaNDSTONS, GREENHOUSE and IVY and to a certain extent fron tests at the Neveda Proving Ground. Prior to the firing of BRaATO, only one megaton yield device (IVY-LIIK=) had been detamted. Although conscientious efforts were rade vo document the falout from LIKE, only adout 5% of the total debris could ever be eccoucted for. ‘ The technique used for forecasting fallout patterns is to consider the cloud as a small area source (adout a 15 mile radius); then add vectorially forecast winds fras the surface to approximately 100,000 feet. The next step is to outline an area on the ground where fallout is expected. Tiis area is computed by taking into consideration particle size, diffusion into the atmosphere, wind pattern, yield and source radius. Such patterns have been largely confirmed by erperience in Nevada as well as by the meager data available here. hw e a~oN - 6. The surface radex was plotted, with an insuresce factor edded, i.e., smaller particles than previous experiesce jndicated necessary were considered. This doubled distances from ground zerp wnere fallout was predicted to occur. &. The upwind intensity of radiation levels at vazri- ous distances was mnsidered to be of the sase order of cagnitude as for IVY-LUKe. Radietion versus distance lines were transposed to Bikini Atoll. — - qzanaT Baa?