CONTENTS (Continued) CHAPTER 4 4.1 4.2 4.3 4.4 4.5 Particle-size Distribution, Radioactive 4.4.1 Particle-size Distribution as a Function of Time 4.4.2 Particle-size Distribution as a Function of Distance Time of Arrival of Particulate . 4.5.1 Arrival of Fall-out . 4.5.2 Duration of Fall-out . 4.5.3 Distribution of Activity with Time . 48 Distribution of SecondaryFall-out Levels of Radioactivity Period of Secondary Fall-out Particle Size of Secondary Fall-out 48 48 48 48 METEOROLOGICAL CONSIDERATIONS AND FORECASTS OF FALL-OUT , . SUMMARY 54 54 54 55 55 Conclusions 7.1.1 Primary Fall-out Secondary Fall-out Recommendations 57 APPENDIX A EXPERIMENTAL PROCEDURE A.1 A.2 A.3 Analysis of the Total-collector Samples Analysis of the Gum-paper Samples . Analysis of the Differential Fall-out Samples A.5 A.6 Analysis of the Leached Activity . Radiochemical Analysis of Selected Samples A.4 A.7 Chemical Analysis of Fall-out Samples lon-exchange-collector Analysis 51 51 51 53 53 Theories of Fall-out Mechanism Primary Fall-out Secondary Fall-out . : The Effect of Vertical Mixing 7.1.2 7.2 33 35 35 35 39 41 41 41 41 41 41 47 47 47 SECONDARY FALL-OUT CHAPTER 7 7.1 33 Physical and Chemical Nature of the Fall-out 4.2.1 Physical Description of Particulate 4.2.2 Chemical Composition of the Particulate 4.2.3 Leaching of Activity . 4.2.4 Decay of Activity . Physical Distribution of Fall-out CHAPTER 6 6.1 6.2 6.3 6.4 PRIMARY FALL-OUT Gamma Field CHAPTER 5 §.1 5.2 5.3 5.4 Page . 57 57 57 58 58 58 58