[en] This work deals with the nuclear radiations. After having recalled some general notions of chemistry and physics (more particularly on chemical elements, molecules, atoms, photons, energy unities, restricted theory of relativity, structure of atoms, quantum mechanics, binding energy, protons, neutrons, isotopes and magic numbers), the author describes the different sources of radiations : radioactivity, nuclear radii, alpha beta and gamma radiations, cosmic radiations, X radiations, synchrotron radiations, nuclear reactions and reactors. The next parts are devoted to the properties, the penetration in matter and the detection of the different radiations previously evoked. Then is given the biological effects of nuclear radiations and the radiation protection measures taken in France. (O.L.). 16 refs., 43 figs., 5 tabs