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APPENDIX
B
Glossary
ABSORBED DOSE: The amount of of energy imparted by radiation to a unit
mass of absorbing material (100 ergs per gram), including tissue. The unit used
prior to the SI is the red; the SI unit is the gray (Gy).
ALPHA PARTICLE: A particle emitted spontaneously from the nuclei of some
radioactive elements. It is identical with a helium nucleus, having a mass of four
units and an electric charge of two positive units.
BACKSCATIER: The deflection of radiation by scattering processes through
angles greater than 90 degrees, with respect to the original direction of motion.
BETA PARTICLE: A charged particle of very small mass emitted spontaneously
from the nuclei of certain radioactive elements. Most (if not all) of the direct
fission products emit (negative) beta particles. Physically, the beta particle is
identical with an electron moving at high velocity.
BREMSSTRAHLUNG: Secondaly photon or x radiation produced by decelera-
tion of charged particles passing through matter.
COULOMB: The standard unit for electrical charge.
CURIE: A special unit of activity. One curie exactly equals 3.7 x 10~° nuclear
transitions per second.
203
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APPENDIX B
DEEP-DOSE EQUIVALENT: Dose equivalent from penetrating radiation to soft
tissue located at a depth of 10 mm in the body. Symbolized as Hp(10~. See also
ABSORBED DOSE and DOSE EQUIVALENT.
DENSITOMETER: An instrument utilizing a photocell to determine the degree
of darkening of developed photographic film.
DENSITY (PHOTOGRAPHIC)
OPI ICAL DENSITY (OD): The degree of darkening of photographic film.
D = log (lo/0, where Io is the incident light intensity and I is the transmitted
light intensity.
NET OPIICAL DENSITY (NOD): Optical density of a film corrected (re-
duced) by subtracting the optical density of an unexposed "control" film.
DOSE: As used in the general sense, dose denotes absorption of a quantity of
ionizing radiation. See ABSORBED DOSE,DOSE EQUIVALENT.
DOSE EQUIVALENT: A quantity used in radiation protection to normalize the
biological effectiveness of the absorption of different radiations. It is defined as
the product of the absorbed dose and certain modifying factors. The unit of dose
equivalent used prior to the SI is the rem. The SI unit is the Sievert (Sv). See also
DEEP-DOSE EQUIVALENT.
DOSIMETER: An instrument for measuring and registering the total accumu-
lated dose of (or exposure to) ionizing radiations. Instruments worn or earned by
individuals are called personnel dosimeters or Personal dosimeters.
. .
ELECTRON: A subatomic particle of very small mass, carrying a unit negative
or positive charge. Negative electrons, surrounding the nucleus, (i.e., orbital
electrons), are present in all uncharged atoms; their number is equal to the number
of positive charges (i.e., protons) in the particular nucleus. The tea electron,
where used alone, commonly refers to negative electrons. A positive electron is
usually called a positron.
ELECTRON VOLT: The energy imparted to an electron when it is moved
through a potential difference of 1 volt. It is equivalent to 1.6 x 10 -~2 erg. This is
a basic unit for expressing the energy of atomic and nuclear radiations.
ERYTHEMA: Abnormal redness of the skin due to capillary congestion (as in
inflammation).
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APPENDIX B
205
EXPOSURE: As used in the technical sense, exposure refers to a measure
expressed in roentgens of the ionization produced by gamma (or x) rays in air.
FALLOUT: The process or phenomenon of the descent to the earth's surface of
particles contaminated with radioactive material from the radioactive debris cloud.
FILM BADGE: It includes a pack of photographic film which measures radiation
exposure for personnel monitoring. The badge may contain one to three films of
differing sensitivities and filters to shield parts of the films from certain types of
radiation.
FISSION: The process whereby the nucleus of a particular heavy element splits
into (generally) two nuclei of lighter elements, with the release of substantial
amounts of energy. The most important fissionable materials are uranium 235
and plutonium 239; fission is caused by the absorption of neutrons.
FISSION PRODUCT: A nuclide, usually radioactive, formed by the fission
process.
GAMMA-RAY INTERACTIONS
.,
PHOTOELECTRIC ABSORPTION: The process whereby a gamma-ray (or
x-ray) photon, with energy somewhat greater than that of the binding energy of
an electron in an atom, transfers all its energy to the electron which is conse-
quently removed from the atom.
COMPION SCATlERING: An attenuation process observed for x or gamma
radiation in which an incident photon interacts with an orbital electron of an
atom to produce a recoil electron and a scattered photon of energy less that the
incident photon.
PAIR PRODUCTION: An absorption process for x and gamma radiation in
which the incident photon is annihilated in the vicinity of the nucleus of an
atom, with subsequent production of an electron and positron pair. This
reaction only occurs for incident photon energies exceeding 1.02 MeV.
GAMMA RAYS: Electromagnetic radiation (photons) originating in atomic
nuclei and accompanying many nuclear reactions (e.g., fission, radioactive decay,
and neutron capture). Physically, gamma rays are identical with x rays of high
energy, the only essential difference being that x rays do not originate in the
nucleus.
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APPENDIX B
GRAY: The SI unit of absorbed dose, abbreviated Gy. 1 Gy = 1 joule/kilogram =
100 red.
GROUND ZERO: The point on the earth's surface vertically below or above the
center of a burst of a nuclear (or atomic) weapon.
HALF-LWE: The time required for the activity of a given radioactive species to
decrease to half of its initial value due to radioactive decay.
M-HOUR: 'Dime zero" or the exact time of detonation to the minute, second, and
fraction of a second; as opposed to H + 1 which implies one hour after detonation
(unless indicated to be seconds or minutes).
INDUCED RADIOACTIVITY: Radioactivity produced in certain materials as a
result of nuclear reactions, particularly the capture of neutrons.
INITIAL NUCLEAR RADIATION: Nuclear radiation (essentially neutrons and
gamma rays) emitted during the first minute after a nuclear (or atomic) explosion.
INTEGRON: An ion chamber device used on cloud-sampling aircraft to provide
an immediate measure of gamma radiation present.
IONIZATION: The separation of a normally electrically neutral atom or mole-
cule into electrically charged components.
IONIZING RADIATION: Electromagnetic or particulate radiation capable of
producing charged particles through interactions with matter.
ISOTOPES: Forms of the same element having identical chemical properties but
differing in their atomic masses. Isotopes of a given element all have the same
number of protons in the nucleus but different numbers of neutrons. Some
isotopes of an element may be radioactive.
KILO-ELECTRON VOLT (or keV): An amount of energy equal to 1,000
electron volts.
MINIMUM DETECTABLE LEVEL: The minimum exposure that can be distin-
guished from zero.
MONITORING: Periodic or continuous determination of the amount of ionizing
radiation or radioactive contamination present in an occupied region.
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APPENDIX B
207
AREA MONITORING: Routine monitoring of the radiation level or contami-
nation of a particular area, building, room, or piece of equipment.
PERSONNEL MONITORING: Monitoring any part of an individual's body,
his breath, excretions, or any part of his clothing.
NEUTRON: A neutral particle (i.e., with no electrical charge) of approximately
unit atomic mass, present in all atomic nuclei, except those of ordinary (light)
hydrogen.
NOD: See DENSITY.
NUCLEAR RADIATION: Particulate and electromagnetic radiation emitted
from atomic nuclei in various nuclear processes. The important nuclear radia-
tions, from the weapons standpoint, are alpha and beta particles, x and gamma
rays, and neutrons.
NUCLEUS (OR ATOMIC NUCLEUS): The small, central, positively charged
region of an atom which carries essentially all the mass. Except for the nucleus of
ordinary (light) hydrogen, which is a single proton, all atomic nuclei contain both
protons and neutrons.
OD: See DENSITY.
PHOTON: A unit or "particle" of electromagnetic radiation, carrying a specific
quantum (particular level) energy.
PROTON: A particle of approximately unit atomic mass carrying a unit positive
charge; it is identical physically with the nucleus of the ordinary (light) hydrogen
atom.
QUALITY FACTOR: The factor by which absorbed doses are multiplied to
obtain (for radiation-protection purposes) a quantity that expresses - on a common
scale for all ionizing radiations - the biological effectiveness of the absorbed dose.
RAD: An older unit of absorbed dose of radiation; 1 red represents the absorption
of 100 ergs per gram of absorbing material, such as body tissue.
RADIOACTIVITY: The spontaneous emission of radiation, generally alpha or
beta particles, often accompanied by gamma rays, from unstable atoms.
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APPENDIX B
REM: The rem is a unit of dose equivalent, which is equal to the product of the
number of reds absorbed and the '~quality factor".
RESIDUAL RADIATION: Nuclear radiation, chiefly beta particles and gamma
rays, that persist for a time following a nuclear explosion. The radiation is emitted
mainly by the fission products and other bomb residues in the fallout, and to some
extent by earth and water constituents, and other materials in which radioactivity
has been induced by the capture of neutrons.
ROENTGEN: A unit of exposure to gamma (or x) radiation. It is defined
precisely as the quantity of gamma (or x) rays that will produce a total charge of
2.58 x 104 coulomb in 1 kilogram of dry air. An exposure of 1 roentgen is
approximately equivalent to an absorbed dose of 1 red in soft tissue.
SCA-~i~liRING: The diversion of radiation from its original path as a result of
interactions with atoms between the source of the radiations (e.g., a nuclear
explosion) and a point at some distance away. Scattered radiations are typically
changed in direction and of lower energy than the original radiation.
SERIES: A particular group of nuclear detonation tests, often referred to as
"Operation & Name".
SEVERT: The SI unit for dose equivalent, abbreviated Sv. 1 Sv = 100 rem.
SHELDING: Any material or obstruction which absorbs (or attenuates) radia-
tion and thus tends to protect personnel or materials from the effects of a nuclear
(or atomic) explosion.
SHOT: A nuclear detonation.
SI: Refers to Systems Internationale, an international system of units adopted in
1975.
X RAY: Ionizing electromagnetic radiation of extranuclear origin.
Representative terms from entire chapter:
gamma rays
