. ‘” KrLLOds (continued) down te the ground in the first few hours, First of we knew that if sand gets inte the cloud under the right cone tiong = we'll specify what these are later - that it may cosbine|with the radioactive material and may then bring the radicactive gaterial down to the ground, due to the fact that sand, at least in Nevada, is large enough te fall, and from the height of the mshiocm7, reach the ground myrvhere from an hour to four hours after sho§ time, Ancther inportant aschanism which is universally recognised es a way for bringing down radioactive material, is rain. Homever, we don't have very many well documented cases where rain hag trought radioactive material down to the ground, ao we can't rely on the recults from the test sitcs in order to establish how thiB siprht occur, and we have gone into the mechenisasg whereby rain pan ecavenre debris in a good deal cf detail, and X'l) tell yim about thore in a minute. The snall radioactive dust particles which are less than 20 or 50 microns are so sasll that their rate of fall 4s negligible, and we can consider that cravity will not bridg these down to the gourd in the first few hours, or even days, look for other mechaniazs to bring those dom. as & possible wey to bring theze down. and we must I centionad rain Also, we must consid diffusions that is, the verticle trenport by motion in the atmosphere, This 4e also a factor wiich we heve had to look into, The purposes of the cresent study then, was to ctnderstand sea various factors that I described, and, in a sense, we have] perhaps lecked at this from a rathor academio viewpoint, feeling Donartment 9 * Energy. that the