ZRN PALL-OUT FOLLOWING BRAVO EVs (Combined Analyses = Immediate and One week after BRAVO) ‘* ry. 1. Generg}. The pattern of ultimate fall-out of radioactive rarticles has been established utilizing in the cases of the most critical area (1.6. bearing about 050° True, clockwise to 120° True from Ground Zero) the follove ings ae Aerial survey by P2ZV employing NYO0-a3C survey equipment, with readings in ar/hr extrapolated to ground level, . be Known ground readings taken at sone atolls (early end later) used with their time and intensity (actual observations) to get a feeling for the overall situation. Ce Resultant wind pattern to establish best wind for period froa 3 mims 1 hour (USS CURTISS Observation - BISINI) to 8 plus & hours (Reagerixz sounding) together with the 8 minus 3# hours (Rongerik 030Q!) to piece cogether the wind pattern above the tropopause. d. . Since the 3ongerik (NY00-aZC) survey meter trace established initial time of arrival of fall-out, this time 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 cousideradle difficulty in making fall-out arrive from the stem of the atomic cioud (555,000 feet-tropopause) at Rongerik in 8 hours. The 10.4 miles/hr above would meke cloud arrive at Rongerik at about = plus 12 hours. fowever, by <he method of plotting the entire cloud height (which is believed to be a5cu: 100,000 feet) for which there were available winds to 95,000 feet, and with the assumptions listed below in constructing shadows (fall-out) of steam and mushrooms, there are obtained 2 areas ~- elliptical inshape, generally east of Ground Zero and superimposed on each other (Appendix I). The suggeszed Zall- out area (blue) for the stem is oriented about 070° Trae from point SB of Ground Zero, distant 35 miles and with a 200-mile zajor axis, 100-a:1e =‘cor axis with a series of extremely hot elliptical envelopes ezanating froa Ground Zero out to about 110 miles. Superimposed on this area (red) is «he suggested mushroom fall-out pattern which is an ellipse oriented 080° True, 49 stiles from Ground Zero, aajor axis at least 180 niles, =incr aris 45-70 aices. It is assumed the#the cloud dieneter in the sushroom for the period ic suestioa was at least 7aet00 miles. This shows therefore, that che early fall-~<=. et on ‘\ easily fron the mushroom - large particles oy = pics 8 Rongerik could hours, and since’ the superimposed fall-outs frem stem and susarecn cross =e northern half of Rongelap Atoll, one would expect these islands +2 be exceece ingly high with their radiation levels, This sight be likened to scavenging of the hot stem material by large particles Src= the cropopause anc a>cve. However, the major hot fall-out elenent nust cons froa <ce stea debris. The assuaptions used in the rough constr-ction of the ellipse fer =e whole cloud ares (LtCol Lulejian report on Fell-out - ARDC, SECRET, RD)s tInclosure 6 1 Cee