isodose and isodose rate contour plots will be developed for the two types of explosions, surface~land and surface-water, taking into account the time of fallout. arrivel. Comparisons with other models and with nuclear data will be carried out and the cloud geometry factor exanined. we The centribution which these upper yield limit data make to the develor— ment of scaling relationships can then be fully evaluatec. Improvements of and seneralizations: on the experimental model are exnected te accompany the foregoing analyses. Use of the method as a tool for fforecastinzs primary fallout appears premising and will be explored, ' Additional development and evaluation of data on gamma field decey will te carried out. Ideelization of the decay curve from 5 to £00 hr post detonation is expectcd to produce a simplified appro:dmation suit= able for military planning and field use. This approximation may reduce to two straicnt line functions on a logarithmic plot, one covering the period from 5 to 50 hr, and the other, 50 to 5CU hr. Later decay is assumed to follow the normal fission product function. 7.3 SPECIFIC CONCLUSIONS The following conclusions present evaluation of data on primary fellout at CASTLE: (a) Gamna fields fron fallout decayed at rates differing from the (bo) Fallout from the surface land detonations was in the fora of t~1-2 approximation common to fission weapons. The extent of tnis dif ference is militarily important over certain time periods. irregular solid particulates. The geometric mean particle diameter de~ creesed with distance from the shot points; for Shot 1 the geometric mean varied from 112 H at Eikini Atoll to45 » at Utirik Atoll. (c) Of the solid particulates studied, approximately 25 per cent were inective with their mean particle size smaller than the active. (a) 236 g/eu (e) The average density of the solid particles from Shot 1 was CMe Little data were obtained on the nature of the fallout from over~water shots. There was some indirect evidence that the fallout 50 nautical miles from Shot 2 arrived as a fine mist or aerosol. (f) Time and rate of arrival of fallout were documented only with- in the atolls by Project 2.5a. tlowever, limited results on more distant islanis were obtained for Snot 1. Arrival was characterized by a rapid rise to a peak followed by a decline which, in the measurement of ga™ma dose-rate, merged imperceptibly with radioactive decay. ‘iaterial first arrived at approximately 1/2 hr after detonation and continued for 1-1/2 to 2 hr. (¢) A contimous 100 hr unshielded exposure after the detonation of a 15+'f device on land will result in a minimum free field total dose of 190 r over an area as large as 25,000 sq mi. , (nh) The development of an experimental model has provided a means of recoistructing fallout patterns using limited gamma field data end a conprenensive analysis of the .cteorolozical situation as applicd to particle trajectories. Conclusions as to the usefulness of free-floating buoy stations for 102