EFFECTS OF IONIZING RADIATION 96 Japan, or if partial shelters are employed, the percentage of casualties from these sources would decrease and the percentage with radiation damage would increase. 6.22 Immediate Gamma and Neutron Radiations The radiation hazard is due essentially entirely to the immediate neutron and gamma radiation from the wenpon, and exposure to these radiations is only a matter of seconds in duration. Fallout is relatively of no significance.* Thus, there is no significant contamination of the skin and, therefore, no beta lesions of the skin. Likewise, there is no significant dangerof ingestionor inhalation of radionctive material, and hence, no “internal emitter” problem. Both the immediate gamma and neutron radiations are highly penetrating and will produce acute total body radiation injury in man. The ratio of neutron to gammaray contribution to the total effective dose at distances of biological significance varies with weapontype. With most commonshielding materials (earth, concrete), the relative neutron contribution to the total dose decreases with passage through the materials. 6.23, Dependence of Effects on Circumstances of Weapon Detonation The effects previously described were for a high air burst only. With surface, under- ground and underwater bursts of kiloton weapons, in addition to blast, heat, and immediate ionizing radiations, serious contamination from fallout can occur. Its extent would of course be less than with the “megaton” wenpon ; however, its potential seriousness can- not be ignored. *Sisnificunt levels of neutron-induced radioactivity may be present for a short time near ground zero. 6.3 6.31 Added Effects of Megaton Weapons Immediate Blast, Heat and Radiation Ef Wrrn Tie Mecaton Boer, the same pr lems encountered with earlier atomic we ons are also encountered, only magnified m: times. The aren of total destruction, instead one or two miles in dinmeter, may extend s eral times that far, depending upon the size the weapon. There are blast, heat and rac tion casualties as before, and the same proble of handling mass casualties on an unpre dented seale with minimal or no facilities | tain. In addition, the problem of extens fallout is likely to enter. 6.32 Phenomenology of Fallout Sientricant Farvout Rescurs only when fire ball of the bomb comes in contact with surface of the earth. With the high air bu radioactivity condenses only on solid parti from the bomb components itself, and on ¢ in the air. The particles are small, drawn high into the atmosphere and do settle to the eurth for periods of days or e months. By the time they reach the ear surface, the major part of their radioactr has been dissipated harmlessly in the atn phere and no significant hazard results. however, the weaponis detonated on the sur or close enough so that the fire ball touches surface, then large amounts of material drawn up into the bomb cloud. Many of particles thus formed are heavy enough to seend rapidly while still intensely radionet The result is 1 comparatively localized are: extreme radioactive contamination and aim larger area of some hazard, The fallout area consists, in effect, of a |: contaminated plane (except as modified buildings or other structures), emitting alj beta and penetrating gamma rays. It is