} | CRIR - 196 - | AERIAL SURVEY OF GROUND CONTAMINATION AT OPERATION IVY (WIr-617). Charles S. Brice, Jr., 29 May 1953. SECRET-RESTRICTED DATA a A procedure is described whereby air-ground correlation factors are determined, permitting evaluation of radioactive contamination on the ground from instrument readings in an airplane flying over the contaminated area, Ground intensities were obtained by multiplying the aerial readings by the air-ground correlation factor obtained during the survey. The reliability of the procedure depends upon the flight of the observing helicopter along a previously charted course at 4 constant speed (30 mi/hr), and at a constant height (25 ft) above the ground. Readings were taken by the helicopter crew at definite time intervals (5 sec) and compared with readings taken by ground personnel 3 ft above the ground, aaasee at locations corresponding to those of the aerial readings. During the first week after the surface detonation of a thermomuclear device, the average daily correlation factor (the ratio of the intensity at a point on the ground to the intensity in the helicopter at an altitude of 25 ft) remained about 2.8. By the end of the second week it had dropped to about 2.2. * . CRLR - 197 - FINAL REPORT ON CLOUD SAMPLING TECHNIQUES USING SNAP SAMPLERS (WT-617). (Operation Ivy) Michael J. Schumechyk, 3 June 1953. SECRET-RESTRICTED DATA The data presented here were derived from studies of the gas and particulate-matter samples collected from clouds produced by nuclear detonations in Project 5.45 of Operation IVY. Collection of these samples was made by snap samplers installed in F-84G aircraft, and by the methods described in CRLR-105. Analysis of the particulate samples collected after Mike shot (the detonation of a thermonuclear device) indicated that the total number Ne a oes of fissions that produced the sample was of the order of 1019 ¢o 1011. The following R factors (R factor: the counting rate ratio in a sample divided by the same ratio for thems fission of ye3 Po) were obtained, from bag particulate samples: Cel44/mo99, 0.1; Bali/Mo99, 1.37; Sr89/Mo99, 0.57; and from a filter particulate-sample: Cells/Mo99, 0.97. Activity readings obtained on the snap-sampler evacuation filters (used when transferring the gas sample from the collecting bags to the REST GY vA Pe ee