Radioactivity

Figure 1.6, is unstable and decays by rearranging its nucleon numbers. This is achieved by releasing particles, changing a proton to a neutron or vice versa, or by absorbing nearby particles. The activity of an unstable, or radioactive isotope is the rate at which its nuclei decay, expressed in Becquerels (Bq) which correspond to one decay or disintegration per second. The activity of practical sources is generally represented in MBq (1 × 10⁶ disintegrations per second). The old unit of activity, the Curie (Ci) is commonly retained (1 Ci = 37 000 MBq). In the construction of practical radioactive sources, we are also interested in the amount of material that is needed to manufacture a source with a required activity, determined by the specific activity (MBq kg⁻¹).