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of Nuclear related terms.
Possible
Household sources of radiation
[A] [B] [C]
[D] [E] [F] [G]
[H] [I] [L] [M]
[N] [P] [R] [S]
[T] [U] [V] [W]
[X] [Y]
For a complete listing of Nuclear related terms visit
Scientific
Digital Visions, Inc... this is a very comprehensive glossary with links to similar
terms. This is a very well done glossary.
A
Activity
The number of nuclear disintegration's occurring per unit of time in a quantity
of a radioactive substance. Activity is measured in Curies or Becquerels. Often
used loosely to mean radioactivity.
Alpha: Positively charged particles emitted from the nucleus of
an atom. Alpha particles are relatively large, and very heavy. Due to this
strong (+) charge and large mass, an alpha particle cannot penetrate far into
any material. A sheet of paper or an inch of air can usually stop most alpha
particles.
Alpha particle
A charged particle having a charge of 2 and a mass of 4 atomic mass units. It is
emitted in the decay of many heavy nuclei and is identical with the nucleus of a
helium atom, consisting of two protons and two neutrons.
Anti-particle
A particle having the opposite electric charge, but being otherwise identical
with, the normal particle.
Atom
An atom is the smallest particle of an element which has the chemical properties
of the element. An atom consists of a comparatively massive central nucleus of
protons and neutrons carrying a positive electric charge, around which electrons
move in orbits at relatively great distances away.
Atomic
Strictly, relating to the behavior and properties of entire atoms - nuclei and
orbital electrons. More usually a synonym for 'nuclear', as in 'atomic energy'.
Atomic Mass Unit (AMU)
One-twelfth of the mass of an atom of carbon 12. Approximately the mass of an
isolated proton or neutron.
Atomic Number (Z)
Of an element, the number of protons in the nuclei of its atoms. Its position in
the periodic table.
Atomic weight
The average mass of the atoms of an element at its natural isotopic abundance,
relative to that of the other atoms, taking carbon 12 as the basis. Roughly
equal to the number of protons and neutrons in its nucleus. See Mass number.
B 
Background Radiation
1. In discussing radiation levels and effects, it refers to the general
level of natural and man-made radiation's against which a particular added
radiation component has to be considered.
2. In discussing radiation measurement techniques, it may also include spurious
readings due to the 'noise' characteristic of the instrument and its power
supplies, and to the presence of local radioactive contamination etc.
Becquerel, Bq.
The unit of activity in the SI System. It is equivalent to 1 disintegration per
second or roughly 2.7 x 10-11 Curie.
Beta particle, 
An electron or positron emitted from a nucleus in certain types of radioactive
disintegration (beta decay).
Beta Particles: Negatively charged particles emitted from an
atom. Beta particles have a mass and charge equal to that of an electron. They
are very light particles (about 2,000 times less mass than a proton) and have a
charge of -1. Because of their light mass and single charge, beta particles can
penetrate more deeply than alpha particles. A few millimeters of aluminum will
stop most beta particles.
C
Cerenkov radiation
Light emitted when charged particles enter a transparent medium at a speed
greater than the speed of light in that medium. It is seen as a bluish glow
around strong radioactive sources, such as irradiated fuel elements stored under
water.
Counter
An instrument for counting pulses of radiation or the electronic pulses that it
causes, and displaying or recording them in digital form. See also Scaler,
Ratemeter.
CPM (counts per minute): The unit of measurement usually used
to measure alpha and beta radiation.
Critical organ
That part of the human body which is most liable to be damaged, either by a
stated radionuclide taken into the body, or by radiation from an external
source.
Curie, Ci
The unit of radioactivity, being the quantity of radioactive material of 1 gram
of radium-226. The curie has been superseded under the SI System by the
Becquerel (Bq), equal to 1 disintegration per second.
Cyclotron
An accelerator in which charged particles follow a spiral path in a magnetic
field and are accelerated by an oscillating electric field. See also
Synchrotron.
D
Dating, radioisotope
Determination of the age of an archaeological or geological specimen by
measuring its content of a radioactive isotope in relation to that of its
precursor or decay product or of its stable isotope. Applied particularly to
radiocarbon dating of archaeological specimens.
Daughter product
The nuclide immediately resulting from the radioactive decay of a parent or
precursor nuclide. If it is radioactive it will in due course become a parent
itself.
Decay, radioactive
The disintegration of a nucleus through emission or radioactivity. The decrease
of activity due to such disintegration.
Decay product
Synonym for daughter product.
Decommissioning
The final closing down and putting into a state of safety of a nuclear reactor
or other plant when it has come to the end of its useful life.
Delay Tank
A tank for the temporary storage of radioactive fluids while their activity
decays.
Delayed neutrons
Neutrons resulting from fission but emitted a measurable time (0.1 seconds or
so) after fission has taken place. They play an essential part in nuclear
reactor control.
Depleted uranium
Uranium with less than the natural content (0.71%) of U-235, e.g. the residue
from an isotope enrichment plant or from a nuclear fuel reprocessing plant.
Deuterium
The hydrogen isotope of mass 2, "heavy hydrogen". See Heavy water.
Disintegration
Any transformation of a nucleus, either spontaneous or by interaction with
radiation, in which particles or photons are emitted. Used in particular to mean
radioactive decay.
Dose, radiation
Generally, the quantity of radiation energy absorbed by a body. There are many
special definitions to cover different applications. See Rad, Rem, Roentgen,
etc.
Dose rate
The dose absorbed in unit time, e.g. rems per year, also used as the level of
intensity of radiation at a given point, e.g. millirads per hour.
Dosemeter, Dosimeter, Dose rate meter
An instrument which measures radiation doses or dose rates.
E
Electron
One of the stable elementary particles of which all matter consists. It carries
a single unit of negative charge equal to 1.6 x 10-19 Coulomb and has a mass of
9 x 10-31 kilograms. See Positron.
Electron volt
A unit in which energy is measured in the study of nuclear particles and their
interactions. It is equal to the change in energy of an electron crossing a
potential difference of 1 volt. Abbrev.: eV and multiples keV (103 eV) and MeV
(106 eV).
Energy, nuclear
The energy released when the particles constituting the nuclei of atoms undergo
rearrangement, especially through neutron-induced fission in uranium or
plutonium.
Energy containment time
In fusion research, the total energy of a confined plasma divided by the rate of
energy loss from it.
Excitation
The addition of energy to a system, e.g. a nucleus, transferring from its
"ground" state to an "excited" state.
F
Fast neutrons
Neutrons travelling with a speed close to that with which they were ejected from
the fissioning nucleus, typically about 20,000 km s-1. See Thermal neutrons.
Film badge
A small badge worn by people working in radiation areas containing a masked
piece of photographic film. The degree of darkening of the film on development
is a measure of the radiation dose received. See Thermoluminescence dosimeter.
Fission-counter
A detector consisting of a tube lined with fissile material or filled a fissile
gas which detects neutrons by the ionization produced in it by the fission
products.
Fission neutrons
Neutrons produced at the time of fission. See Delayed neutrons.
Fission products
The elements having nuclei of intermediate weight formed in the fission of
uranium or plutonium. Their nuclei have an excess of neutrons and most of them
are highly radioactive -emitters.
Fission spectrum
1. The energy distribution of prompt neutrons in fission of a specified nuclide.
2. The energy distribution of prompt gamma-radiation arising from the fission.
3. The range and abundance of nuclides formed from the fission.
Fission yield
The percentage of fission's that give rise to a particular nuclide.
Flask
A shielded container used to store or transport radioactive material,
especially used nuclear fuel.
Flux density
For a given point (especially in the core of a nuclear reactor), the number of
neutrons or other particles incident per second on an imaginary sphere centered
at that point, divided by the cross-sectional area (1 cm2) of that sphere. It is
identical with the product of the population density of the particles and their
average speed. Peak neutron fluxes in research reactors lie typically between
1010 n/cm2sec in GLEEP and 2.3 x 1014 n/cm2sec in DIDO and PLUTO.
G
Gamma Rays: Short wavelength electromagnetic radiation higher in
frequency and energy than visible and ultraviolet light. Gamma rays are emitted
from the nucleus of an atom. These high energy photons are much more penetrating
than alpha and beta particles.
Gamma-rays, 
Very short-wave electromagnetic radiation's of nuclear origin emitted during
transitions such as fission, radioactive disintegration and electron-position
annihilation. They have much in common with X-rays.
Geiger Müller counter
A simple and well-established form of radiation detector which produces
electrical pulses at a rate related to intensity of the radiation. Commonly
called a "Geiger Counter".
Gray, Gy
The SI unit of absorbed radiation dose, one joule per kilogram. 1 Gy = 100 rads.
H
Half-life
The characteristic time taken for the activity of a particular radioactive
substance to decay to half of its original value - that is, for half the atoms
present to disintegrate. Half-lives vary from less than a millionth of a second
to thousands of millions of years, depending on the stability of the nuclide
concerned.
Half-life, biological
The time required for the amount of a particular substance in the body to be
halved by biological processes when the rate of removal is approximately
exponential.
Health monitor
A person or instrument routinely employed in radiological protection monitoring
work.
Health Physics
The study and administration of radiological protection.
Heavy Water
Deuterium oxide, O2O. Water in which the hydrogen is replaced by "heavy
hydrogen" or deuterium. Because of the very low neutron absorption
cross-section of deuterium, heavy water makes an excellent moderator and is used
in e.g. CANDU (Canadian Deuterium Uranium Reactor) and SGHWR (Steam Generator
Heavy Water Reactor) nuclear reactors. It is present in ordinary water at part
in about 5000.
Hot Spot monitor
A portable radiation detector for health physics use, with the detector head on
a long probe so that the operator need not approach the radiation source
closely.
I
Ion
An atom that has lost or gained one or more orbital electrons, thus becoming
electrically charged.
Ionization: The process by which neutral atoms of molecules are divided
into pairs of oppositely charged particles known as ions.
Ionization Chamber
A device for measuring the intensity of ionizing radiation. The radiation
ionizes the gas in the chamber and the rate at which ions are collected (on
oppositely-charged electrodes) is measured as an electric current.
Ionizing Radiation
Radiation which removes orbital electrons from atoms, thus creating ion pairs.
Alpha and beta particles are more densely ionizing than gamma-rays or X-rays of
equivalent energy. Neutrons do not cause ionization directly.
Isotopes
Atoms of the same element having different atomic weights due to differences in
the number of neutrons in their nuclei. Isotopes have the same atomic number but
different mass numbers. (A useful working definition is "atoms that are the
same outside but different inside").
L
Label, radioactive
A relatively very small quantity of a radioactive substance added to a material
or object, the subsequent movements of which can then be studied by detecting
and measuring the radiation emitted from it.
Linear accelerator (LINAC)
An accelerator in which the accelerated particles move in a straight path.
Linear energy transfer (LET)
The rate at which a charged particle loses energy as it passes through matter.
It is high for alpha particles and low for electrons.
M
Magnetic confinement
In fusion research, the use of shaped magnetic fields to confine a plasma.
Mass defect
The difference between the mass of a nucleus and the sum of the masses of its
constituent nucleons. It is related to the binding energy of the nucleus by
Einstein's equation E=mc2.
Mass Number
The number of protons plus neutrons in the nucleus of an atom. See Isotopes.
Mass spectrometer
An analytical instrument in which accelerate positive ions of a material are
separated electromagnetically according to their charge to mass ratios.
Different species can be identified and accurate measurements made of their
relative concentrations.
Monitor
A person or an instrumental routinely employed on the measurement of some
quantity, particularly one that is of interest in the health physics field, e.g.
radiation levels.
N
National registry of radiation workers
Established by the National Radiological Protection Board in 1976. This is a
register of the health records of radiation workers.
Neutron
An elementary particle with mass of 1 atomic mass unit approximately the same as
that of the proton (approximately 1.67 x 10-27 kg). Together with protons,
neutrons form the nuclei of all atoms. Being neutral, a neutron can approach a
nucleus without being deflected by the positive electric field, so it can take
part in many types of nuclear interaction. In isolation neutrons are
radioactive, decaying with a half-life of about 12 minutes by beta emission into
a proton. See Nucleon.
Neutron generator
An accelerator designed or used for the production of neutrons, in particular by
a fusion reaction between accelerated deuterium ions and a tritium target which
produces neutrons with an energy of 14 MeV.
Neutron yield
The average numbers of fission neutrons emitted per fission. Usually per thermal
neutron absorbed in Uranium-235.
Nucleon
A proton or a neutron, the particles from which all atomic nuclei are composed.
Nucleus
The central part of an atom at which the positive electric charge, and nearly
all the mass, is concentrated and around which the orbital electrons revolve.
See Nucleon.
Nuclide
An individual species of atom characterized by its mass number, atomic number
and the energy state of its nucleus. See Isotopes, Radionuclide.
P
Positron
The anti-particle of an electron, having a positive charge instead of the more
usual negative charge. It is the only anti-particle of significance in the
context of nuclear power.
Pressure Vessel
A reactor containment vessel, usually made from thick steel or pre-stressed
concrete, capable of withstanding high internal pressure. Used in gas-cooled
reactors and light water reactors.
Proton
A stable elementary particle with a charge of 1.6 x 10-19 Coulomb and a mass of
1.67 x 10-27 kg (1 atomic mass unit). The proton forms the whole nucleus of
hydrogen atoms of mass number 1 and a part of all other nuclides. The number of
protons in a nucleus of any element is the atomic number (Z) of that element.
R
Rad
A unit of absorbed radiation dose, equivalent to 0.01 joules per kg. The unit is
being replaced by the SI unit, the Gray (Gy), equal to 100 rads. See Rntgen
and Rem.
Radiation
Electromagnetic waves especially (in the context of nuclear energy), X-ray and
gamma-rays, or streams of fast-moving particles (electrons, alpha-particles,
neutrons, protons), i.e. all the ways in which an atom gives off energy.
Radiation area
An area to which access is controlled because of a local radiation hazard.
Radiation chemistry
The study of influence of radiation on chemical properties and reactions, and
its applications. See Radiochemistry.
Radiation sickness
The acute non-stochastic effects caused by a large dose of radiation to the
whole body, such as might be received in a reactor accident or from a nuclear
weapon explosion or its fall-out. The symptoms and their outcome vary with dose
size, ranging from temporary nausea to death.
Radioactive chain, family, series
A radioactive decay chain.
Radioactive equilibrium
In a decay chain if the half-life of a daughter product is much shorter than
that of its parent, the daughter is continuously replaced by the decay of the
parent. So, unless it is separated out and measured independently, the daughter
appears to decay with the same half-life as the parent.
Radioactivity
The property possessed by some atomic nuclei of disintegrating spontaneously,
with loss of energy through emission of a charged particle and/or
gamma-radiation.
Radioactivity, induced
Radioactivity that has been induced in an otherwise inactive material, usually
by irradiation with neutrons.
Radioactivity, natural
The radioactivity of natural occurring materials, e.g. uranium, thorium, radium,
lead, potassium, carbon, hydrogen.
Radiobiology
The branch of science dealing with the interactions of radiation or radioactive
substances with biological systems.
Radiochemistry
That part of chemistry which deals with radioactive materials, including the
production of radionuclides etc. by processing irradiated or naturally occurring
radioactive materials. This is use of radioactivity in the investigation of
chemical problems. See also Radiation chemistry.
Radiography
A method of non-destructive testing in which a beam of penetrating radiation is
passed through the object under examination, where the dense parts absorb more
radiation. The resulting variations of radiation intensity can be recorded on
photographic film or as numbers in a computer. Medical diagnostic X-rays and
industrial gamma-radiography are the best-known examples. In neutron
radiography, a beam of thermal neutrons is used.
Radioisotope
Short for radioactive isotope.
Radiology
The branch of medicine specializing in the uses of ionizing radiation's for
medical diagnosis, and in studying their effects. See Radiobiology,
Radiotherapy.
Radiolysis
The decomposition of material by radiation, e.g. water into hydrogen and oxygen.
Radionuclide
Radioactive nuclide.
Radiotherapy
Treatment of disease by the use of ionizing radiation.
Radiotoxicity
A measure of the harmfulness of a radioactive substance to the body or to a
specified organ following its uptake by a given process.
Radon
A radioactive inert gaseous element of natural origin. It is estimated to cause
about one-third of the average radiation exposure in the UK.
Ratemeter
An instrument for detecting electrical pulses and displaying them in terms of
the average number of pulses arriving per unit time. Often used in conjunction
with radiation detectors. See also Counter.
Reactivity
(1) Of fuel, the ability to support a chain reaction.
(2) Of a reactor, a measure of the possible departure from the critical
condition, where the chain reaction is just self-sustaining (reactivity zero).
Added reactivity, e.g. by withdrawal of a control rod, will cause the reaction
to diverge with an increase in power output; conversely, removal of reactivity
will cause it to die down, e.g. as fuel burns up or as fission-product
"poisons" develop.
Reactivity = k-1 where k is the multiplication factor.
Rem
Roentgen equivalent man: the unit of effective radiation dose absorbed by
tissue, being the product of the dose in rads and the quality factor. The rem is
being replaced by the SI unit, the Sievert (Sv), equal to 100 rem.
Roentgen
A unit of exposure to radiation based on the capacity to cause ionization. It is
equal to 2.58 x 10-4 Coulomb per kg in air. Generally an exposure of 1 Roentgen
will result in an absorbed dose in tissue of about 1 Rad. See also Rem.
Roentgen (rent-gen): A basic unit of measurement of the
ionization produced in air by gamma or x-rays. One Roentgen (R) is exposure to
gamma or x-rays that will produce one electrostatic unit of charge in one cubic
centimeter of dry air. One thousand milliroentgen (1,000 mR)= 1R.
S
Safety rod
One of a set of additional reactor control rods used specifically for
emergency shut-down and for keeping the reactor in a safe condition during
maintenance etc.
Scaler
An instrument for counting electrical pulses and displaying their total in
digital form, often used in the measurement of radiation levels.
Scintillation Counter
A radiation detector in which the radiation's cause individual flashes of light
in a solid (or liquid) "scintillator" material. Their intensity is
related to the energy of the radiation. The flashes are amplified and measured
electrically and displayed or recorded digitally as individual
"counts".
Self-shielding
The shielding from external radiation's of the inner parts of a body or mass of
material by the absorption, in its outer, of some of the incoming radiation.
Semi-conductor detector
A radiation detector which uses the effect of radiation on the electrical
properties of semi-conducting material.
Sievert, Sv
The SI unit of radiation dose equivalent; the product of absorbed dose in grays
and the quality factor 1 Sv = 100 rem.
Sievert: A unit of dose equivalent. 1 Sv= 100 roentgens, 10 µSv/hr
= 1 milliroentgen/hr. (µSv
micro-Sievert, micro is one millionth, milli is one thousandth.)
Soft radiation
Radiation having little penetrating power.
Synchrotron
An accelerator in which charged particles follow a circular path in magnetic
field and are accelerated by synchronised electric pulses. See also Cyclotron.
T
Thermal fission
Fission induced by thermal neutrons.
Thermal neutrons
Neutrons in thermodynamic equilibrium (i.e. moving with the same mean kinetic
energy) with their surroundings. At room temperature their mean energy is about
0.025 eV and their speed about 2.2 km/sec. See also Fast neutrons.
Thermal reactor
A nuclear reactor in which the fission chain reaction is propagated mainly by
thermal neutrons, and which therefore contains a moderator.
Thermoluminescence dosimeter (TLD)
A type of personal dosimeter in which the radiation energy is stored and from
which it can be released by heating, in the form of light. The amount of light
emitted gives a measure of the radiation absorbed. See also Film Badge.
Thermonuclear reaction
A nuclear fusion reaction brought about by very high temperatures. For a net
energy gain from a deuterium-tritium plasma the temperature of the reacting
plasma must be about 100 million degrees C.
Thetatron
In fusion research a device for producing hot dense plasma. A large object
current is rapidly developed round a single turn of coil wound on a cylinder and
its magnetic field compresses the plasma towards the axis.
Tritium
The isotope of hydrogen having an atomic mass number of 3.
U
Unsealed source
Radioactive material that is not encapsulated or otherwise sealed, and which
forms a source of radiation. For example, radioactive material in use as a
"tracer".
V
Van de Graff generator
An electrostatic generator in which a high electrical potential is produced
by the accumulation of electric charge conveyed to an insulated conductor by a
continuously moving belt. The potential may be used for accelerating charged
particles.
W
Whole body monitors
An assembly of large scintillation detectors or proportional counters,
heavily shielded against background radiation, used to identify and measure the
total gamma-radiation emitted by the human body. This will include radiation
form normal constituents of the body, such as potassium and other minerals
(including fall-out from weapons tests) taken in with foodstuffs. All this forms
the back-ground against which the desired measurements must be made of the gamma
activity and/or X-rays, e.g. to radioactive materials inhaled or ingested
accidentally or as a result of working conditions.
X
Xenon effect
The rapid but temporary "poisoning" of a reactor by the build-up
of Xenon-135 from the radioactive decay of the fission product Iodine-135.
Xenon-135 is a strong absorber of neutrons and until it (and its parent) have
largely decayed away, reactor start-up can be difficult.
X-rays
Electromagnetic radiation's having wavelengths much shorter (i.e. energy
much higher) than those of visible light. X-rays with clearly defined energies
are produced by atomic orbital electron transitions, and are akin to gamma-rays
but usually of lower energy. X-rays produced by the interaction of high energy
electrons with matter have a continuous energy spectrum, and it is these that
are generally used in medical X-ray machines.
X-ray Fluorescence
An element may be identified and measured by the characteristic discrete X-rays
emitted when it is irradiated by radiation of a slightly higher energy. The
effect, due to transitions in the energy status of the orbital electrons, forms
the basis of a useful analytical technique.
Y
Yellow-cake
Concentrated crude uranium oxide, the form in which most uranium is shipped
from the mining areas to the fuel manufacturers.
Smoke Detectors: Some smoke detectors contain a sealed radioactive
isotope as part of the smoke sensing mechanism. There is no danger to the
individual if the container in sealed.
Camping Lantern Mantles: In recent years this has changed but
some lantern mantles are made with radioactive Thorium. Be especially careful
not to inhale or ingest the fine ash that is left when they are burned out.
Clocks, Watches, and Timers: Many old timepieces have dials painted
with radium to make them glow in the dark. Tritium is now commonly used to
obtain the same effect. Tritium is also radioactive but emits low energy
radiation which cannot penetrate the lens of the timepiece.
Jewelry: Some gold used to encapsulate radium and radon for medical
purposes was improperly reprocessed and entered the market as radioactive rings
and other types of gold jewelry. Some imported cloisonné being glazed with
uranium oxide exceeds U.S. limits.
Some gems are irradiated by an electron beam or in an accelerator to enhance
their color. Irradiated gems typically are held until there is no residual
activity remaining.
Rock Collections: Many natural formations contain radioactive
materials. Hobbyists who collect such things should vent the rooms in which
these items are stored and be careful to avoid inhaling the fine dust particles
from these samples.
Pottery: Some types of pottery are glazed with uranium oxide,
such as Fiesta ware. To the best of our knowledge, this process has been
discontinued, although some of these pieces are still in circulation.
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