DAUGHTER PRODUCTS	Isotopes that are formed by the radioactive decay of some other isotope. In the case of Radium-226, for example, there are ten successive daughter products ending in the stable isotope Lead-206.
DECAY CONSTANT	The fraction of the number of atoms of a radioactive nuclide which decay in unit time.
DECAY, RADIOACTIVE	Disintegration of the nucleus of an unstable nuclide by the spontaneous emission of charged particles and/or photons.
DECLARED PREGNANT WOMAN	A woman who has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception.
DECONTAMINATION	The reduction or removal of contaminating radioactive material from a structure, area, object, or person. Decontamination may be accomplished by (1) treating the surface to remove or decrease the contamination, (2) letting the material stand so that the radioactivity is decreased as a result of natural decay, and (3) covering the contamination to shield or attenuate the radiation emitted.
DEEP DOSE EQUIVALENT	Applies to external whole-body exposure and is the dose equivalent at a tissue depth of one centimeter (1,000 mg/cm squared).
DELAYED HEALTH EFFECTS	Radiation health effects which are manifested long after the relevant exposure. The vast majority are stochastic, meaning, the severity is independent of dose and the probability is assumed to be proportional to the dose, without threshold.
DEPARTMENT OF TRANSPORTATION (DOT)	A governmental agency responsible for promoting the safe transportation of hazardous materials by all modes to include land, air, waterways.
DEPLETED URANIUM	Uranium having a percentage of Uranium-235 smaller than the 0.7% found in natural uranium. It is obtained from spent (used) fuel elements or as a byproduct tails or residues from uranium isotope separation.
DERIVED AIR CONCENTRATION	The concentration of a given radionuclide in air which, if breathed by the reference man for a working year of 2,000 hours under conditions of light work (inhalation rate 1.2 cubic meters of air per hour), results in an intake of one ALI.
DETECTOR, RADIATION	Any device for converting radiant energy to a form more suitable for observation. An instrument used to determine the presence and sometimes the amount of radiation.
DOSE	A term that means absorbed dose, dose equivalent, effective dose equivalent, committed dose equivalent, committed effective dose equivalent, or total effective dose equivalent.
DOSE EQUIVALENT	The product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest. The units of dose equivalent are the rem in the conventional system and the sievert ( Sv ) in the System International.
DOSE RATE	The radiation dose delivered per unit of time. Measured, for example, in rem/hour.
DOSIMETER	A portable instrument for measuring and registering the total accumulated exposure to ionizing radiation.
DOSIMETRY	The theory and application of the principles and techiques involved in the measurement and recording of radiation doses. Its practical aspect is concerned with the use of various types of radiation instruments with which measurements are made, ie., film badge, thermoluminescent dosimeter, Geiger counter.