CHAPTER 6 DURATION AND TIME DISTRIBUTION OF DOSES S$.) AVATLASIZC DATA In Chapter 2, the only existing field data on dose rates and to=« tal dose are sumeen The information dees not provide answers to two important questions: (1) what was the time for each island at which the fallout cloud arrived; 14.6., when did the radiation level on ©. each of the islands rise above the normal background and (2) how steeply and for how long did the radiation-level rise before it reached its. maximum valve and decayed away at ‘the rate determined by its own com="' position (discussed in Chapter 3}; 4.e., how heavy was the fallout at <2hue cl . any tine it was occurring and how long did it last? Since only the © [8° Ut tines of evacuation were direcily known, assumptions on both these quesiions were basic to an estimate of total dose, It would have been desirable to have had an instrument on at least one cf the islands capable of recording enough data to answer thesa questions, As it is, it was fortunate that there was even a lowlevel monitoring instrument in operation on Rongerik (Table 2.1), although its full scale capacity was soon exceeded by the rapidly increasing dose rate of the fallout, The tine at which the fallout began was at least quite definitely established on Rongerik and it coincided with the time at which the snow-like material was first seen, Fer the other istands, therefore, the tines at which similar mate- rial had been seen to commence falling could be taken as the beginning of the radiation exposure times, It only remained to determine what these tines had been, Questioning the inhabitants of the other islands resulted in a group of estimates of arrival time which were in fairly good agreement, though the manner of questioning sometimes appeared to influence the answers, However the tines estimated in this fashion were quite close to those resulting from other information; i.e., the wind velocities at the tine, the tine of beginning fallout on Kongerik, and the relative: distances of the other islands from Bikini, Only on Utirik was no actual observation of the fallout made; the estinate of arrival time there was made using only the tine of arrival on Kongerik and the wind-and—distance-factors, The values of fallout and evacuation tines used are sunnarized in Table 6.1,