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Glossary
Committed dose equivalent The dose equivalent to organs or tissues that will be
received from an intake of radioactive material by an individual during the 50year period following the intake.
Contamination The deposition of radioactive material in any place where it is not
desired (units = dpm).
Controlled area Any area where access is controlled for the purpose of protecting
individuals from exposure to radiation and radioactive material. “Controlled
area” is synonymous with “restricted area.”
Curie (Ci) A unit of activity. One curie is that quantity of radioactive material that
decays at the rate of 3.7 × 10
10 decays per second.
Decay chain (Series) A series of isotopes resulting from the decay of a parent
nuclide and its subsequent radioactive daughters to an ultimate stable form.
Derived air concentration (DAC) The concentration of a given radionuclide in air,
which, if breathed without respiratory protection for a working year of 2,000 h
under conditions of light work, will give a radiation dose of 5 rem (50 mSv) to
the whole body.
Derived air concentration-hour (DAC-hour) The product of the concentration of
radioactive material in air, expressed as a fraction or multiple of the derived air
concentration for each radionuclide, and the time of exposure to that radionuclide
in hours. A person may receive up to 2000 DAC-hours of exposure annually.
Dose A generic term that refers to a person’s exposure to radiation.
Dose limits The permissible upper bounds of radiation doses established in accordance with regulations.
Dose meter An instrument designed to measure the dose rate of ionizing radiation—
usually displayed in mR/hr or mGy/hr.
Dose rate Absorbed dose delivered per unit time (mR/hr or mGy/hr).
Dosimeter An instrument used to detect and measure accumulated radiation
exposure.
Element A category of atoms having the same number of protons and the same
chemical properties.
External dose That portion of the dose equivalent received from any source of
radiation outside the body.
Extremity Hand, elbow, arm below the elbow, foot, knee, and leg below the knee.
Gray (Gy) The SI unit of absorbed dose. One gray is equal to 100 rad.
Half-life (radiological) The amount of time that is required for a radioactive
substance to lose ½ of its activity.
Half-value layer (HVL) The amount of material required to reduce the dose rate
from a radiation source by a factor of 2.
High-radiation area Any area, accessible to individuals, in which radiation levels
could result in an individual receiving in excess of 1 mSv (0.1 rem) in 1 h at 30 cm
from any source of radiation or from any surface that the radiation penetrates.
Incident Any unexpected event involving radiation or radioactivity with the potential for the spread of radioactive contamination, skin contamination, uptake of
radioactive materials, exposure to elevated radiation levels, loss of radioactive
material, and so forth.
Glossary
Committed dose equivalent The dose equivalent to organs or tissues that will be
received from an intake of radioactive material by an individual during the 50year period following the intake.
Contamination The deposition of radioactive material in any place where it is not
desired (units = dpm).
Controlled area Any area where access is controlled for the purpose of protecting
individuals from exposure to radiation and radioactive material. “Controlled
area” is synonymous with “restricted area.”
Curie (Ci) A unit of activity. One curie is that quantity of radioactive material that
decays at the rate of 3.7 × 10
10 decays per second.
Decay chain (Series) A series of isotopes resulting from the decay of a parent
nuclide and its subsequent radioactive daughters to an ultimate stable form.
Derived air concentration (DAC) The concentration of a given radionuclide in air,
which, if breathed without respiratory protection for a working year of 2,000 h
under conditions of light work, will give a radiation dose of 5 rem (50 mSv) to
the whole body.
Derived air concentration-hour (DAC-hour) The product of the concentration of
radioactive material in air, expressed as a fraction or multiple of the derived air
concentration for each radionuclide, and the time of exposure to that radionuclide
in hours. A person may receive up to 2000 DAC-hours of exposure annually.
Dose A generic term that refers to a person’s exposure to radiation.
Dose limits The permissible upper bounds of radiation doses established in accordance with regulations.
Dose meter An instrument designed to measure the dose rate of ionizing radiation—
usually displayed in mR/hr or mGy/hr.
Dose rate Absorbed dose delivered per unit time (mR/hr or mGy/hr).
Dosimeter An instrument used to detect and measure accumulated radiation
exposure.
Element A category of atoms having the same number of protons and the same
chemical properties.
External dose That portion of the dose equivalent received from any source of
radiation outside the body.
Extremity Hand, elbow, arm below the elbow, foot, knee, and leg below the knee.
Gray (Gy) The SI unit of absorbed dose. One gray is equal to 100 rad.
Half-life (radiological) The amount of time that is required for a radioactive
substance to lose ½ of its activity.
Half-value layer (HVL) The amount of material required to reduce the dose rate
from a radiation source by a factor of 2.
High-radiation area Any area, accessible to individuals, in which radiation levels
could result in an individual receiving in excess of 1 mSv (0.1 rem) in 1 h at 30 cm
from any source of radiation or from any surface that the radiation penetrates.
Incident Any unexpected event involving radiation or radioactivity with the potential for the spread of radioactive contamination, skin contamination, uptake of
radioactive materials, exposure to elevated radiation levels, loss of radioactive
material, and so forth.