Analysis of the gamma time-intensity recorder trace located at How gave the best evidence of the rate of arrival of fallout. Use of the differentinl fallout collector and the time-intensity recorder for determining the period of fallout was restricted to the lagoon and islands of Bikini Atoll thereby limiting the distance to 15 nauticel miles. The average arrivel time within the area was 0 + 28 min with cessation averaging O + 117 min resulting in an average period of 89 min. These data compare well with that observed at I 7/wher- the period was somewhat less than 2 hr. Residual fallout which war of such quantity thet it contributed Little to the overall field was found to deposit for a period of soverai hours after the deposition of the main bedy of materiel. The Bikini £toll islands along the axis of the fallout pattern experienced fallout over a longer period of time than did those islands leeated in a crosswise direction. 5.6.2 Shot No evidence was found of primary fallout at early times in the Bikini Logoon. Secondary fallout of maximum intensity of 40 mr/hr arrived at How Island 37.5 hr after Sh. 2, as shown by the gamma time- intensity recorder, ' Shot 506.3 No differertial fallout collectors were operative for Shot 3. The gamma time-intensity recorder at How Island indicated a time of arrival of 0 +¢ 38 min. Project 2,2 established an arrival time on Dog Island of approximately 0 + 20 min.2/ 56.4 Shot_6 Enivetok One differential fallour collector located at Alice Island, Atoll, received significant fallout amd indicated an arrival time of O + 35 min with the period of fallout teiny 65 min (Fig. C-18). £.7 RATE OF ARRIVAL OF FALLOUT AND INTEGRATED DOSE Of the two gamma icnization time-intensity recorders installed on Yoke and How Islands of S5ikini Atoll, only the one on How survived end recorded data from Shots 1, 2, an’ 3. These data give accurate information cn rate of arrival of fallout «1s well as time of arrival. 8.7.1 i - Rate of Arrival Table §.7 presants the time of arrival of fallout end time of yeak activity Sor Shots 1, 2, and 3. The time at which the activity peak- is not the tine of cessation of fallout. It is bert dascribed as the time at which the rate of decay is greater than the rate of buildup of fallout. 70