DOSIMETER An instrument for measuring and recording the total accumulated dose of (or exposure to) ionizing radiation. Instruments worn or carried by individuals are called personnel dosimeters. DOSIMETRY The theories about and applications of the techniques involved in measuring and recording radiation doses and dose rates. Its practical application includes the use of various types of radiation detection instruments to measure radiation. EXPOSURE, X or A measure of the ionization produced by gamma (or X) rays in air. The exposure rate, exposure per unit of time, is commonly used to indicate the gamma radiation intensity of a source. The unit of exposure is the roentgen (R). FALLOUT The descent to the earth’s surface of particles contaminated with radioactive material as a result of a GAMMA RADIATION nuclear detonation. The term also applies to the contaminated particulate matter itself. FILE A The NTPR data base consisting of information extracted FILM BADGE A personnel dosimeter utilizing photographic film to FIREBALL The luminous sphere of hot gases that forms a few thousandths of a second after a nuclear detonation. FISSION The splitting of a heavy nucleus into two or more radioactive nuclei, accompanied by the release of a from telephone calls to the DNA toll-free lines and, from letters drafted by participants in the atmospheric nuclear weapons tests and in the postwar occupation of Hiroshima and Nagasaki. measure the radiation dose received by the wearer. The badge is usually clipped to an outer garment above waist level. The dose is calculated from the degree of film darkening that results from exposure to radiation. large amount of energy and generally one or more neutrons and one or more gammas. FUSION The formation of a heavier nucleus from two lighter nuclei, accompanied by the release of a large amount of energy. GAMMA RAYS A form of electromagnetic radiation emitted spontane- ously from the nuclei of certain radioactive elements, often in conjunction with the emisson of alpha or beta particles. Gamma rays also result from other nuclear reactions, such as fission and neutron capture. Gamma rays are identical to X-rays, except that they 205