CHAPTER 1 INTRODUCTION 1.el OBJECTIVE The objective of the project was to document the characteristics of the close-in radioactive fallout resulting from the surface land or water detonation of high yield nuclear devices in order to provide informtion for the evaluation of (1) the immediate hazards associated with the residual contamination from such bursts, (2) the mechanism of particle formation and distribution, and (3) the characteristics and significance of the radioactive debris distributed by base surge phenomenon provided that a significant base surge is caused by surface water burstse To accomplish the cbjective, the following specific physical characteristics were documented where possible. ae Beta activity and the time at which it arrived. be. Beta decay. ce Maximum beta erergiese d. Gamma energy. @e The activity per unit weight or volume of liquid and solid fallout. f. The size distr: >5ution of radioactive particles and distribu- tion of activity within the sized particlese 1.2 MILITARY SIGNIFICANCE OF THIS INVESTIGATION Surface and sub-surface nuclear detonations result in the de=- position of radioactive debris (fallout) on the earth's surface. The degree to which fallout may influence military operations depends upon the magnitude of the significant radiation field and upon the ability to predict the extent and location of the field. The amount and activity of the fallout is primarily a fumction of weapon yield and conditions of detonation,!.9e, whether the detonation has taken place in the air, on the surface of land or water, or underneath the surface of land or water. This investigation seeks to extend the knowledge of such variations by studying the fallout results from high yield nuclear devicese The results from this project will aid in (1) determining the significance of fallout from surface detonations of high yield 15