The penetrating power of nuclear radiations

Chapter 3 dealt with selected properties of ionising radiations emitted by radionuclides with emphasis on the properties of X and γ rays and this emphasis will continue in the present chapter.

Gamma rays are useful for applications because of their high penetrating power (Section 1.3.5). Other applications utilise the short or very short ranges in matter of α or β particles, e.g. for the manufacture of paper or plastic materials to be discussed in Section 7.3.2. The large majority of industrial applications require radiations that are capable of transmitting information to a detector after travelling through a few centimetres of a metal or equivalent thicknesses of other materials, which is most effectively done by sufficiently energetic γ rays, about 0.5 MeV or higher.

Electrically uncharged neutrons also have high penetrating powers, although they are strongly absorbed by some elements (Section 1.3.6). Being equal in mass to protons, their interactions with matter are subject to different rules than that of massless γ rays (Table 1.2) Additional information about neutrons will be given in Section 5.4.4 in preparation for the numerous important applications to follow in Section 7.4.

It is again emphasised that radionuclides and the emitted radiations should only be used if one is sufficiently familiar with their characteristics (see below). Familiarity is also required with methods for the preparation of radioactive sources, with the success or failure of a project often depending on how well this has been done.