A device that increases the momentum, and therefore the energy, of charged
particlessuch as electrons or protons.
Access Control System
Engineered and/or administrative systems that limit radiation dose to
personnel by managing and limiting entry to an area.
Activation (also Radioactivation)
The process of making a material radioactive by bombardment with neutrons,
protons, or high energy photons.
Activity (also Radioactivity)
The rate at which a source emits radiation. Activity is measured in terms of
the number of disintegrations that take place in some time period (eg.
disintegrations per second ). The special unit for activity is the curie.
One curie (Ci) is equal to 37 billion (3.7 x 1010)
disintegrations per second.
The absorption of a relatively large amount of radiation over a short period of time.
Acute Radiation Syndrome
The complex of symptoms brought about by excessive exposure to radiation. ARS is
the result of an acute dose; some early visible symptoms may include nausea, vomiting,
and fatigue, followed by a predictable progression of other deterministic effects
depending on the total dose.
Procedures and activities which involve human actions that are designed to minimize or
control personnel radiation exposure. Examples of administrative controls are
Radiation Work Permits, sweep procedures, and TOSPs.
As Low As Reasonably Achievable. Making every reasonable effort to maintain
exposures to radiation as far below the dose limits as is practical, taking into account
the state of technology and other societal and economic considerations, including the
benefit of the radiation producing activity.
A positively charged particle ejected spontaneously from the nuclei of some radioactive
atoms. It is identical to a helium nucleus - it contains two protons and two neutrons.
Assigned Radiation Monitor (ARM)
A person who has received training beyond the Radworker level in the use of radiation
protection instrumentation and administrative procedures for controlling exposure to
radiation and handling of radioactive material.
The process by which radiation is reduced in intensity when passing through some
material. It is the combination of absorption and scattering processes.
Atomic Number (Z number)
The number of protons in the nucleus of an atom.
Atomic Weight See mass number .
Radiation present in the environment to which all people are exposed. Background
radiation comes from natural radioactivity and radiation, and from manmade sources
such as global fallout and certain consumer products.
A flow of electromagnetic or particulate radiation that is either unidirectional by nature,
or has been collimated or restricted to a small solid angle.
The structure which houses the accelerator and experimental target areas. It is
interlocked during accelerator operation to prevent personnel access.
The vacuum chamber in which the beam travels (generally includes associated
components of beam transport, such as magnets, beam dumps, accelerating cavities,
An energetic electron which is emitted from the nucleus during beta decay.
Photon radiation (x-rays) produced by deceleration of charged particles as they pass
Controlled Area Radiation Monitor. A radiation detection system which is interlocked
to the Personnel Safety System and designed to turn off the electron beam if radiation
levels exceed pre-established set points.
An ion. A particle carrying a positive or negative electric charge.
The absorption of a relatively small amount of radiation over a long period of time.
A device which limits the size, shape, and direction of a radiation beam.
The sum of the individual doses received in a given period of time by a specific group
of people. See Person-rem .
The deposition of unwanted radioactive material (usually in an easily removable form)
on the surfaces of structures, areas, objects, or personnel.
Any area where access is controlled to ensure the radiological safety of personnel.
Controlled Areas contain radiological hazards which are identified by specific postings.
Personnel who work only in a Controlled Area are not expected to receive a dose in
excess of 100 mrem/yr. See Radiological Area.
The total dose received over a period of time.
Curie See Activity .
Daughter Product (progeny)
Nuclide (or isotope ) that is formed by the radioactive decay of some other nuclide. For
example, the radioactive isotope Cobalt-60 decays to the stable isotope Nickel-60. See
Nuclide and Isotope .
Declared Pregnant Worker
A woman who has voluntarily informed her employer, in writing, of her pregnancy and
the estimated date of conception, for the purpose of limiting her exposure to radiation.
Applies to the measurement of external, whole body radiation exposure - specifically, it
is the dose equivalent at a tissue depth of 1 cm. See Whole Body .
A material or device that is sensitive to radiation and can produce a response signal
suitable for measurement or analysis.
A biological effect which becomes more severe with an increase in dose. These effects
usually have thresholds or minimum values, below which the risk of experiencing the
effect is considered to be zero.
A generic term for the amount of radiation absorbed.
The product of absorbed dose (i.e. rads) in tissue and quality factor. Dose equivalent is
measured in units of rems. It is a description of the dose received by a person in terms
of biological effect, rather than strictly energy absorbed.
A device or instrument for measuring integrated (or cumulative) dose.
Radiation having no mass or charge. A traveling wave resulting from changing electric
and/or magnetic fields. See Photon .
An elementary particle with a unit negative charge and a mass 1/1837 that of a proton.
Electrons surround the positively charged nucleus and determine the chemical
properties of an atom.
Electron Volt (eV)
Unit of energy equivalent to the energy gained by an electron in passing through a
potential difference of one volt. It is used to quantify the energy or momentum
possessed by high energy particles or electromagnetic radiation. Typical ionizing
radiations are in the thousand (keV) or million (MeV) electron volt range
Equipment, structures, and devices which limit or prevent radiation exposure to
personnel with little or no human intervention. These controls may be passive (eg.
shielding) or active (eg. interlocks) in nature.
Term used generally to describe receiving radiation dose.
A measure of the ionization produced in air by x or gamma radiation. The unit for
exposure is the Roentgen (R). Whole body exposure to 1 R of x or gamma radiation
results in a dose equivalent of approximately 1 rem.
High energy, short wavelength electromagnetic radiation emitted from the nucleus.
Gamma radiation frequently accompanies beta, and alpha emission during radioactive
Genetic Effect (Heritable Effect)
An effect which occurs in a future generation of an exposed person.
High Radiation Area
Any area where a person could receive a whole body dose of 100 mrem in any one hour
up to 5000 mrem in any hour. For purposes of posting, an area where the whole body
dose rate is (or might be ) between 100 and 5000 mrem/hr. See whole body and whole
body dose rate .
Any automatic sensing device that causes a radiation producing device to shut off or
prevents access to the hazardous radiation beam while it is present.
Ion See charged particle .
Ionization The separation of orbital electrons from an atom.
Radiation which has enough energy to ionize the matter through which it passes.
One of two or more atoms of a given element having different numbers of neutrons.
Thus, carbon-12, carbon-13, and carbon-14 are isotopes of the element carbon. The
numbers 12, 13, and 14 denote the total number of protons and neutrons in the isotope.
See Nuclide .
Linear Accelerator (Linac)
A device used to accelerate charged particles in a straight line.
The total number of nucleons (protons and neutrons) in the nucleus of an atom.
An elementary particle with no electrical charge which has approximately the same
mass as a proton.
The small, central region of an atom consisting of protons and neutrons (nucleons).
The nucleus contains essentially all of the mass of the atom.
General term referring to all known isotopes, groups of isotopes, or a single isotope.
Operational Safety Procedure. An administrative control measure which describes
hazards present and what controls are in place to mitigate or minimize the hazards.
OSPs are used during routine operations. Generally associated with an operational
instruction rather than a purely safety-related procedure. See TOSP.
The cumulative dose received by a group of people. The person-rem total for a given
job and time period is the sum of all doses received by all persons involved in the work
for that period. See collective dose .
Personnel Safety System (PSS)
An active engineered control system comprised of interlocks, sensors, and other devices
which prevents personnel access to the beam enclosure and/or terminates accelerator
operation in the event that trip points are exceeded or interlocks are triggered.
A quantum (discrete packet) of electromagnetic energy. Gamma rays and x-rays are
examples of photons. It is customary to refer to photons that originate in the nucleus
(during radioactive decay) as gamma rays, and those which originate within the electron
field, such as bremsstrahlung photons, as X rays.
A positively charged beta particle.
Particulate or electromagnetic radiation resulting from the accelerator beam or
interaction of the beam with surrounding matter. Prompt radiation ceases immediately
after shut off of the beam.
Quality Factor (Q)
The modifying factor used to derive dose equivalent from absorbed dose. Quality
factor is based on the linear energy transfer (LET) of a particular type and energy of
radiation and is proportional to the relative biological effectiveness (RBE) of that
Radiation Absorbed Dose. The special unit of absorbed dose used to quantify the
amount of radiation energy absorbed per unit mass of any material. One rad is equal to
an absorbed dose of 100 ergs/gram or 0.01J/kg.
Any area where a person could receive a whole body dose of 5 mrem in any one hour
up to 100 mrem in an hour. For purposes of posting, an area where the whole body
dose rate is (or might be) between 5 and 100 mrem/hr. See whole body and whole body
dose rate .
A person who has received specific training and qualifications to make unescorted
accesses into the controlled area and perform work of a radiological nature.
Any material containing unstable atoms which decay with the release of ionizing
Radioactive Materials Area
An area in which radioactive materials are used, stored, or handled.
Any area requiring posting as a Radiation Area, High Radiation Area, Very High
Radiation Area, Contamination Area, High Contamintation Area, or Airborne
Radioactivity Area. Also used to describe Radiologically Controlled Area.
Radiologically Controlled Area - (RCA)
Any area where a person could receive a dose in excess of 100 mrem/yr. Also called
A radioactive isotope of an element which decays spontaneously, emitting radiation.
The special unit of any of the quantities expressed as dose equivalent. The unit used to
express the amount of biological harm done from chronic exposure to ionizing
radiation. The dose equivalent in rems is equal to the absorbed dose in rads multiplied
by the quality factor (Q). The dose, measured in rems is not a physical quantity due to
the application of the quality factor. It is therefore an expression of relative risk. See
quality factor .
Radiation resulting from the decay of activated material within the accelerator.
Residual radiation persists after beam shut off, and may contribute significantly to the
overall dose to radiation workers.
The special unit of exposure. That amount of gamma or x rays which produce ions
carrying one electrostatic unit of charge in one cubic centimeter of dry air. See
A device which is interlocked to the personnel safety system used to display the
accelerator machine state and visually warn of an unsafe condition. When armed,
pressing the red button on the box causes the PSS to remove beam or power permit.
Radiation Work Permit. An administrative control measure consisting of a set of
requirements for protective equipment, dosimetry, entry and stay time restrictions, and
work control measures used to limit personnel exposure during work in certain
Self Reading Pocket Dosimeter (SRPD)
Any type of dosimeter which allows the user to directly read the exposure from the
device. Examples of SRPDs are pocket ion chambers, neutron bubble dosimeters, and
digital electronic dosimeters.
Dose equivalent at a tissue depth of 0.007 cm. Shallow dose applies to the skin, not to
the whole body .
Sweep or Search
A physical search performed concurrent to establishing an interlocked state within the
beam enclosure prior to operating the accelerator.
An effect which occurs in an individual or population exposed (to radiation), as
opposed to effects which occur in future generations.
Health effects which occur randomly and for which the probability of the effect
occurring, rather than its severity, is assumed to be a linear function of dose without
threshold. Examples of stochastic effects are cancer incidence and heritable effects.
Thermoluminescent Dosimeter. TLDs are used as the primary means of recording
exposure to radiation. It may be "read" only by specialized processing equipment.
Temporary Operational Safety Procedure. An administrative control measure which
describes hazards present and what controls are in place to mitigate or minimize the
hazards. TOSPs are used during non-routine operations or temporary configurations of
equipment or systems such as special tests or commissioning activities.
Very High Radiation Area
An area where the dose rate exceeds 500 rad/hr a meter from the source. At Jefferson
Lab, a more conservative definition is used - an area where the whole body dose rate is
(or might be) above 5000 mrem/hr. See whole body and whole body dose rate.
The portion of the body consisting of the head, trunk and major blood forming organs
extending to the arms just below the elbow and the legs just below the knee. Whole
body dose occurs when any of these portions of the body receive a deep dose.
Whole Body Dose Rate
Radiation level measured at a point 30 cm (~ 1 foot) from the source of radiation or
from any surface through which radiation emanates.
X rays (also see photon )
Penetrating electromagnetic radiation (photons) with a wavelength much shorter than