ABSTRACT
The nuclei of most isotopes disintegrate spontaneously. This phenomenon is called radioactive decay. They eject energetic particles and sometimes, simultaneously, emit radiant energy. The whole of these phenomena is named radioactivity. Then, it is recalled that the detection and the measurement of radioactivity are grounded in three fundamental properties of the nuclear rays: photographic impression, ionization of encountered substances and excitation of their fluorescence spectra. Some emphasis is given to the ionization of gases and the Geiger-Müller counter and the scintillation counters. The analysis by radiochemical methods is investigated under three headings. They are 1) the direct radiometric determination, 2) the analysis by activation and 3) the analysis by isotopic dilution.
