Introduction to radioactive materials

摘要

Radioactivity is a part of nature. Everything is made of atoms. Radioactive atoms are unstable; that is, they have too much energy. When radioactive atoms spontaneously release their extra energy, they are said to decay. All radioactive atoms decay eventually, though they do not all decay at the same rate. After releasing all their excess energy, the atoms become stable and are no longer radioactive. The time required for decay depends upon the type of atom. When the nucleus of a radionuclide spontaneously gives up its extra energy, that energy is called ionizing radiation. Ionizing radiation may take the form of alpha particles, beta particles, or gamma rays.