06 EFFECTS OF IONIZING RADIATION 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 weapon, and exposure to these radiations is only a matter of seconds in duration. Fallout is relatively of no signifieance.* Thus, there is no significant contamination of the skin and, therefore, no beta lesions of the skin. Likewise, there is no significant dangerof ingestion or inhalation of radioactive 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 etfects previously described were for a high air burst only. With surface, underground 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” weapon; however, its potential seriousness cannot be ignored. *Significant levels of neutron-induced radioactivity inay be present for a short time near ground zero. 6.3 6.31 Added Effects of Megaton Weapons Immediate Blast, Heat and Radiation Effects Wirn Tue Mecaton Bomrn, the same problems encountered with earlier atomic weapons are also encountered, only magnified many times. The aren of total destruction, instead of one or two miles in diameter, may extend several times that far, depending upon the size of the weapon. There are blast, heat and radiation casualties as before, and the same problems of handling mass casualties on an unprecedented scale with minimal or no facilities pertain. In addition, the problem of extensive fallout is likely to enter. 6.32 Phenomenology of Fallout SieniFicantr Fattout Rescvrs only whenthe fire ball of the bomb comes in contact with the surface of the earth. With the high air burst, “adioactivity condenses only on solid particles from the bomb components itself, and on dust in the air. The particles are small, are drawn high into the atmosphere and do not settle to the earth for periods of days or even months. By the time they reach the earth’s surface, the major part of their radioactivity has been dissipated harmlessly in the atmosphere and no significant hazard results. Tf, however, the weapon is detonated on the surface or close enough so that the fire ball touches the surface, then large amounts of material are drawn up into the bomb cloud. Many of the particles thus formed are heavy enough to descend rapidly while still intensely radioactive. The result is a comparatively localized area of extreme radioactive contamination and a much larger area of some hazard. The fallout area consists, in effect, of a large contaminated plane (except as modified by buildings or other structures), emitting alpha, beta and penetrating gamma rays. It is ap-