APPENDIX B GLOSSARY The following technical and organizational terms are used in this volume. ABSORBED DOSE The amount of energy absorbed per unit mass of irradiated material. Absorbed dose is measured in rads. AIR BURST The explosion of a nuclear weapon at such a height that the expanding fireball does not touch the earth’s surface. AIR SAMPLING for RADIOACTIVITY The process of collecting certain volumes of air to determine the level of radioactivity in the air. ALPHA PARTICLE A form of particulate radiation emitted from the nuclei of certain radioactive elements. An alpha particle is composed of two neutrons and two protons and is identical to the nucleus of a helium atom, having a double positive charge. An alpha particle cannot penetrate clothing or the outer layer of skin, so it is not a external exposure hazard. Such a particle is extremely hazardous, however, if exposure occurs internally. ATOM The smallest particle of an element that still retains the characteristics of that element. Every atom consists of a positively charged central nucleus, which carries nearly all the mass of the atom. The nucleus is generally composed of uncharged neutrons and positively charged protons. It is surrounded by electrons that carry a negative charge. ATOMIC ENERGY Energy released by various nuclear reactions, such as fission, fusion, or radioactive decay. Great amounts of energy are released during fission and fusion processes. It is this energy that makes nuclear weapons far more powerful than conventional explosives. Nuclear energy is another and a more appropriate label for this energy. BETA BURNS Skin lesions caused by deposition of beta-emitting fallout particles onto bare human skin. BETA PARTICLE A charged particle of very small mass emitted spontaneously from the nuclei of certain radioactive elements. Physically, the beta particle is identical to an electron moving at high speed. 203