see NUCLEAR SAFETY

(See also "RADIOACTIVITY") Commonly used to designate the branch of nuclear physics involved in protecting people from ionizing radiation. By extension, the term "radiation protection" encompasses any measure designed to protect personnel and public health from ionizing radiation and to ensure compliance with regulatory requirements.

(See also "RADIOACTIVITY") Electromagnetic waves (radio waves, light waves, ultraviolet rays, X-rays, cosmic radiation, etc.) from particles of matter (electrons, protons, neutrons) or particle clusters. The energy of the waves is proportional to wave frequency or particle speed. They affect irradiated objects by stripping electrons from atoms, leaving behind ionized (electrically charged) atoms, hence the generic term IONIZING RADIATION.

Period of time required for half of the atoms contained in a given quantity of radioactive substance to decay naturally, thereby decreasing the substance's radioactivity by half. Different radioelements have different radioactive half-lives, for example: - 110 minutes for argon 41, - 8 days for iodine 131, and - 4.5 billion years for uranium 238. No external physical activity can change the half-life of a radioelement.

Any radioactive substance. Only a small number of radioelements are naturally occurring: a few heavy elements (e.g. thorium, uranium, radium) and a few light elements (e.g. carbon 14, potassium 40). The others, numbering more than 1,500, are artificially created in the laboratory for medical applications or in nuclear reactors in the form of fission.