Initial Nuclear Radiation Nature of Nuclear Radiations

NEUTRONS AND GAMMA RAYS ries, namely, initial and residual \\\(§ 1.02). The line of demarcation is 8.01 As stated in Chapter I, one of somewhat arbitrary, but it may be taken the special features of a nuclear exploas about 1 minute after the explosion, sion is the emission of nuclear radiafor the reasons given in § 2.43. The tions. These radiations, which are quite initial nuclear radiation, with which the different from the thermal radiation dispresent chapter will be concerned, concussed in the preceding chapter, consist sequently refers to the radiation emitted of gamma rays, neutrons, beta particles, within I minute of the detonation. For and a small proportion of alpha partiunderground or underwater explosions, cles. Most of the neutrons and part of it is less meaningful to separate the the gamma rays are emitted in the fisinitial from the residual nuclear radiasion and fusion reactions, i.e., simultion \\\(§ 2.82, 2.100), although the distaneously with the explosion. The retinction may be made if desired. mainder of the gamma rays are 8.03 The ranges of alpha and beta produced in various secondary nuclear particles are comparatively short and processes, including decay of the fission they cannot reach the surface of the products. The beta particles are also earth from an air burst. Even when the emitted as the fission products decay. fireball touches the ground, the alpha Some of the alpha particles result from and beta particles are not very importhe normal radioactive decay of the uratanto The initial nuclear radiation may nium or plutonium which has escaped thus be regarded as consisting only of fission in the weapon, and others (hethe gamma rays and neutrons produced lium nuclei) are formed in fusion reacduring a period of 1 minute after the tions \\\(§ 1.69). nuclear explosion. Both of these nuclear 8.02 Because of the nature of the radiations, although different in characphenomena associated with a nuclear ter, can travel considerable distances explosion, either in the air or near the through the air. Further, both gamma surface, it is convenient, for practical rays and neutrons can produce harmful purposes, to consider the nuclear radiaeffects in livin.g organisms (see Chapter I tions as being divided into two categoXII). It is the highly injurious nature of