i . one FALL-OUT FOLLOWING BRAVO EVs (Combined Analyses - Immediate and One week after BRAVO) 1. Genera}. The pattern of ultimate fall-out of radioactive sarticles has been established utilizing in the cases of the nost critical ares (1.0. bearing about 050° True, clockwise to 120° True from Ground Zero) the follows be Known ground readings taken at sone atolls (early and later) Ce Resultant wind pattern to establish best wind for period froa used with their time and intensity (actual observations) to get a feeling for the overall situation. . 43. a. Aerial survey by P2V employing NYOO-aSC survey equipment, with readings in ar/hr extrapolated to ground level. beet 8 ete —_a - ings an % oF XS SRN OF 0 sounding) together with the H minus 34 hours (Rongerik 030QR!f) to piece ssgether the wind pattern above the tropopause. @. Since the Rongerik (NYOO0-a2C) survey meter trace established initial time of arrival of fall-out, this tine was used in coordination with resultant wind at the cloud level which rassed over Rongerik. This level was 25,000 feet vector. Its average speed from Ground Zero calculated froa resultant wind plot was 10.4 miles/hr. At first, there was considerable difficulty in making fall-out arrive from the stem of the atomic cloud (355,000 feet-tropopause) at Rongerik in 8 hours. The 10.4 ailes/hr above would make cloud arrive at Rongerik at about © plus 12 hours. Zowever, she method of plotting the entire clond height (which is believed to de arcaz 100,000 feet) for which there were available winds to ¥5,000 feet, and with the assumptions listed below in constructing shadows (fall-out) of stem and mushroom, there are obtained 2 areas - elliptical in shape, generally east of Ground Zero and superimposed on each other (Appendix I). The suggeszed Zallout area (blue) for the stem is oriented about 070° True from point SB of Ground Zero, distant 35 miles and with a 200-nile major axis, 100-si-e x‘inor aris with a series of extremely hot elliptical envelopes ezansting froa Sround Zero out to about 110 niles. Superimposed on this area (red) is <he suggested wn oN mushroom fall-out pattern which is an ellipse oriented 080° True, 4) stiles from Ground Zero, major axis at least 180 ailes, xinor aris 45-90 nites. It is assumed thatthe cloud diateter in the sushroon for the period in suestian was at least 70«100 miles, This shows therefore, that che early ‘ai--<c=~ 8% Rongerik could ‘@eme easily fron the aushrooz - large pazzicles oy = pics & hours, and since’ the superimposed fall-outs °rcn stez and susszecs cress =e northern half of Rongelap Atoll, one would expect these islands <5 be exceesingly high with their radiation levels, This xight be likened to scavexzing of the hot stem aaterial by large particles Src= the cropopause asc afcve. However, the major hot fall-out elenent must coas fron <ne stea debris. The assunptions used in the rough constr-ction of the ellipse fcr =e whole cloud ares (LtCol Lulejian report on Pell-out - ARDC, SECaET, RD): Inclosure 6 1 per - 3 mims 1 hour (USS CURTISS Observation - BIXINI) to H plus 8 hours (Rengerik