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synonyms - Radioactive_contamination
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radioactive contamination (n.)
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[Domaine][Domaine][Domaine][Domaine][Domaine] - [Analogie][Domaine][Domaine][Analogie] radioactive contamination (n.)?
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The radiation warning symbol (trefoil).
Periodic table with elements colored according to the half-life of their most stable isotope.
  Elements which contain at least one stable isotope.
  Radioactive elements: the most stable isotope is very long-lived, with half-life of over four million years.
  Radioactive elements: the most stable isotope has half-life between 800 and 34.000 years.
  Radioactive elements: the most stable isotope has half-life between one day and 103 years.
  Highly radioactive elements: the most stable isotope has half-life between several minutes and one day.
  Extremely radioactive elements: the most stable isotope has half-life less than several minutes. Very little is known about these elements due to their extreme instability and radioactivity.
Radioactive contamination, also called radiological contamination, is
substances on surfaces, or within solids, liquids or gases (including the human body), where their presence is unintended or undesirable, or the process giving rise to their presence in such places. Also used less formally to refer to a quantity, namely the activity on a surface (or on a unit area of a surface).
As with other , radioactive contamination refers only to the presence of the unintended or undesired radioactivity, and gives no indication of the magnitude of hazard involved.
Cases of radioactive contamination include
in Colorado, the , the , and especially the case of the area around the
facility in Russia.
Radioactive contamination is typically the result of a spill or accident during the production or use of
(radioisotopes), an unstable nucleus which has excessive energy. Less typically,
is the distribution of radioactive contamination by a . The amount of radioactive material released in an accident is called the source term.
Contamination may occur from radioactive gases, liquids or particles. For example, if a radionuclide used in
is spilled (accidentally or, as in the case of the , through ignorance), the material could be spread by people as they walk around. Radioactive contamination may also be an inevitable result of certain processes, such as the release of radioactive
in . In cases that radioactive material cannot be contained, it may be diluted to safe concentrations. For a discussion of environmental contamination by
emitters please see .
Containment is what differentiates radioactive material from radioactive contamination. Contamination does not include residual
remaining at a site after the completion of . Therefore, radioactive material in sealed and designated containers is not properly referred to as contamination, although the units of measurement might be the same.
involves the measurement of radiation dose or radionuclide contamination for reasons related to the assessment or control of exposure to radiation or radioactive substances, and the interpretation of the results. The methodological and technical details of the design and operation of environmental radiation monitoring programmes and systems for different radionuclides, environmental media and types of facility are given in IAEA Safety Standards Series No. RS-G-1.8
and in IAEA Safety Reports Series No. 64.
Radioactive contamination may exist on surfaces or in volumes of material or air. In a , detection and measurement of radioactivity and contamination is often the job of a .
Surface contamination is usually expressed in units of radioactivity per unit of area. For , this is
(or Bq/m?). Other units such as
per 100 cm? or
per square
(1 dpm/cm? = 167 Bq/m?) may be used. Surface contamination may either be fixed or removable. In the case of fixed contamination, the radioactive material cannot by definition be spread, but it is still measurable.
In the natural world, there is always radiation being emitted from
as they decay. Not only is the entire world constantly bombarded by , but practically every living thing on earth contains
and most (including humans) contain some . These tiny levels of radioactivity pose little danger because the natural radioisotopes are diluted amongst stable isotopes. All of these sources of
form the natural . When, however, radioactive isotopes are concentrated in a particular place outside of a planned containment, we call that concentrated area contaminated. If radioactive contamination is acute (highly concentrated enough to pose a risk of radiation exposure), then we call that location a "hot spot."
Many instances of contamination arise from particles that have become airborne. Prior to the deposition of radionuclides on a surface, the air is contaminated, which poses an inhalation hazard.
The hazards to people and the environment from radioactive contamination depend on the nature of the radioactive contaminant, the level of contamination, and the extent of the spread of contamination. Low levels of radioactive contamination pose little risk, but can still be detected by radiation instrumentation. If a survey or map is made of a contaminated area, random sampling locations may be labeled with their activity in
on contact. Low levels may be reported in
In the case of low-level contamination by isotopes with a short half-life, the best course of action may be to simply allow the material to naturally . Longer-lived isotopes should be cleaned up and properly disposed of, because even a very low level of radiation can be life-threatening when in long exposure to it.
Facilities and physical locations that are deemed to be contaminated may be cordoned off by a
and labeled "Contaminated area." Persons coming near such an area would typically require
or anti-c's.
High levels of contamination may pose major risks to people and the environment. People can be exposed to potentially lethal radiation levels, both externally and internally, from the spread of contamination following an
(or a ) involving large quantities of radioactive material. The
to radioactive contamination are generally the same as those from an external radiation source not involving radioactive materials, such as
machines, and are dependent on the .
When radioactive contamination is being measured or mapped , any location that appears to be a
of radiation is likely to be heavily contaminated. A highly contaminated location is colloquially referred to as a "hot spot." On a map of a contaminated place, hot spots may be labeled with their "on contact" dose rate in mSv/hr. In a contaminated facility, hot spots may be marked with a sign, shielded with bags of , or cordoned off with warning tape containing the
in magenta on a yellow background.
The air can be contaminated with radioactive isotopes. Airborne radioisotopes pose a serious hazard to people who breathe the contaminated air. Respirators and air filters can help mitigate these dangers. Meters that sample the air may use a fan to draw in a metered amount of air across a special . The activity on the HEPA filter represents the cont therefore, the HEPA filter is checked for contamination using the same meters used to test for surface contamination.
The biological effects of internally deposited
depend greatly on the activity, the biodistribution, and the removal rates of the radionuclide, which in turn depends on its chemical form, the particle size, and route of entry. Effects may also depend on the chemical
of the deposited material, independent of its radioactivity. Some radionuclides may be generally distributed throughout the body and rapidly removed, as is the case with .
Some organs concentrate certain elements and hence radionuclide variants of those elements. This action may lead to much lower removal rates. For instance, the
gland takes up a large percentage of any
that enters the body. Large quantities of inhaled or ingested
may impair or destroy the thyroid, while other tissues are affected to a lesser extent. Radioactive iodine-131 it was a major component of the radiation released from the , leading to nine fatal cases of pediatric
and . On the other hand, radioactive iodine is used in the diagnosis and treatment of many diseases of the thyroid precisely because of the thyroid's selective uptake of iodine.
Radioactive contamination can enter the body through , , , or . For this reason, it is important to use
when working with radioactive materials. Radioactive contamination may also be ingested as the result of eating contaminated plants and animals or drinking contaminated water or milk from exposed animals. Following a major contamination incident, all potential pathways of internal exposure should be considered.
(1945) -- official US War Department film documenting damage to
(1952) -- documentary showing a Japanese school teacher who visits her hometown of Hiroshima 6 years after the bombing to find the horrors of radiation.
(1965) - banned television docudrama about a Soviet nuclear attack on Britain, not shown on TV until 1985
Hiroshima Nagasaki August 1945 (1970) -- documentary of
devastation.
(1982) -- documentary combines stock US government footage of
along with
films shown in public schools in the 1940s and 1950s about how citizens should respond to atomic attacks.
(1983) -- TV docudrama about the effects of a nuclear holocaust on the small-town residents in eastern .
(1988) -- documentary film about
atomic tests. Gruesome details and pictures of joking sailors being irradiated, and interview with an injured (irradiated) sailor.
Hiroshima: Out of the Ashes (1990) -- TV history and graphic depictions of the horror of .
(2002) -- TV documentary about Russia's disastrous first .
(2002) -- docudrama about the first of many disasters that befell the
(2006) -- documentary about the fate of the .
(2007) -- HBO documentary showing how many teenage Japanese are ignorant of what happened in 1945. Also includes some American atomic veterans.
for six more films about radioactive issues.
are collections of articles that can be downloaded or ordered in print.
(includes physicists' units of radiation exposure)
- Russian facility which has caused many deaths in the surrounding area
(disambiguation)
(disambiguation)
International Atomic Energy Agency (2007). . Vienna: IAEA.  . .
International Atomic Energy Agency (2005). . Vienna: IAEA. .
International Atomic Energy Agency (2010). . Vienna: IAEA. pp. 234.  . .
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Cookies help us deliver our services. By using our services, you agree to our use of cookies.USDA | OHSEC | Radiation Safety Division | Glossary
Office of Homeland Security & Emergency Coordination
Radiation Safety Division (RSD)
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Popular Topics
Radiation Safety Program
A1 is the activity limit of special form radioactive material
that can be packaged and shipped in a Type A package. DOT
establishes the A1 value for each radio-isotope. The values of the A1 quantity
arise through transport accident conditions with release of the sealed
source but no dispersal of its radioactive content.
A2 is the activity limit of normal form radioactive material
that can be packaged and shipped in a Type A package. DOT
establishes the A2 value for each radio-isotope. The values
of the A2 quantity arise through transport accident conditions with release
and dispersal of all of the radioactive content.
Accelerator Produced Radioactive Material
Radioactive material that has
been made radioactive through interactions in a cyclotron
or linear accelerator.
Activity is the rate of decay of radioactive material, observed
as the emission of radiation particles (alpha, beta, photon,
or neutron) from the atomic nucleus, indicating nuclear events.
Activity is measured in units of :
becquerel (bq),
curie (ci), and
disintegrations per minute (DPM).
Some conversions factors:
1 becquerel = 1 nuclear disintegration / second.
1 curie = 3.7 x 1010 becquerel.
1 giga-becquerel = 27 milli-curies
1 DPM = 60 becquerel
1 micro-curie = 2,220,000 DPM
Agreement States
An agreement state is a state that has entered into an
agreement with the Nuclear Regulatory Commission (NRC) giving
it authority to regulate radioactive material within its borders, except
for nuclear power plants and Federally controlled sites.
&As Low As is Reasonably Achievable&, a Health Physics philosophical
doctrine, to keep radiation doses lower than legal requirements.
Alpha radiation is a highly ionizing form of particle radiation
with a low penetration depth. Alpha particles (named after
and denoted by the first letter in the Greek alphabet, &) consist
of two protons and two neutrons bound together into a particle, identical
to a helium nucleus. Alpha particles are positively charged, and can be
deflected by a magnetic field. They can be stopped by a few centimeters
of air, a sheet of paper, or by the outer dead layer of skin. When isotopes
emitting alpha particle are ingested, they are far more dangerous than
their half-life or decay rate would suggest.
Analytic X-ray Equipment
Analytic x-ray equipment is used in laboratory
settings in research and industry, to make microscopic measurements
and examinations of chemical compounds and sample materials on an atomic
or nuclear scale. The intense beam of low-energy x-rays produced by analytical
x-ray equipment can cause serious injuries. The x-ray fluorescence
(spectroscopy) analyzer and the diffractometer are examples of analytic
equipment.
Annual Limit on Intake
The annual limit on intake is the limit that the
NRC places on the amount of radioactive material that a radiation
worker can take into their body over the course of a working year. These
values have been calculated for several radioisotopes and are listed in &
10 CFR 20 Appendix B Tables , Table 1 ALI values for occupational dose &
The ingestion of one ALI gives a dose of 5 rem. Regulations require that
the total external and internal radiation dose to a worker not exceed 5
rem in one year.
American National Standards Institute
Ash analysis
Ash residues remaining after radioactive waste has been incinerated
is analyzed to determine radioactive material content.
If radioactive materials are detected in the ash, the ash is treated as
radioactive waste. If no radioactive materials are detected, the ash
can be disposed of using normal ash disposal procedures.
Associate User
An associate user is a person listed on the Permit who is
authorized to work with radiation sources under the Permit
supervision. The Permit Holder must be the supervisor of the associate
users listed on the Permit.
Atomic Number
The protons in the nucleus and the orbiting electrons, hold
each other in balance, and are always equal in number.
This number is the atomic number. The atomic number identifies each element.
Each element has a name, which represents the atomic number.
The elements can be numerically organized in the Periodic Table. Because
the elements are number variations that fit into slots in this table, we
know that they have all been discovered, and that there will not be any
new ones, except perhaps, at the very end.
Background
Background radiation means radiation naturally
occurring radioactive material, and global
fallout as it exists in the environment from the testing
of nuclear explosive devices or from past nuclear accidents.
Baggage and Parcel Inspection Systems
X-ray equipment used at airport baggage
screening and security points. Security applications range
from screening baggage at airports to systems used to inspect
trucks entering the United States.
Becquerel (Bq)
A unit of activity.
1 becquerel = 1 nuclear disintegration / second.
1 curie = 3.7 x 1010 becquerel
1 giga-Becquerel = 27 milli-Curies
Beta radiation consists of particles of ionizing radiation
also known as beta particles or beta rays. Beta particles
(named after and denoted by the second letter in the Greek
alphabet, &)
are high-energy, high-speed electrons emitted by certain types of radioactive
nuclei such as potassium (K-40). Beta particles are negatively charged,
and can be deflected by a magnetic field. The production of beta particles
is termed beta decay. An unstable atomic nucleus with an excess of neutrons
may undergo beta decay, where a neutron is converted into a proton and
an electron. Although the beta particles given off by different radioactive
materials may vary in energy, most beta particles can be
stopped by a few millimeters of aluminum.
Bioassay (radiobioassay) means the determination of kinds,
quantities, and locations of radioactive material in the
human body, whether by direct measurement (in vivo counting)
or by analysis and evaluation of materials excreted or removed from the
human body.
Bone Densitometer
A densitometer is a diagnostic x-ray device that measures
bone mineral density. It is based on &dual-emission x-ray absorptiometry.& It
is also called a DXA scan, (previously known as a DEXA scan).
The patient is exposed to two x-ray beams of different energies. When soft
tissue absorption is subtracted out, the bone mineral density can be determined.
The DXA scan is typically used to diagnose and follow osteoporosis,
low bone density. It should not be confused with a bone scan, which diagnoses
disorders of the bones such as infections, fractures, or
tumors. A DXA scan radiation dose is approximately 50 milli-Rems, which
is less than the amount of radiation that one receives on a roundtrip flight
from California to New York.
Bremsstrahlung
&Braking radiation& is electromagnetic radiation, in the form of
x-rays, produced by the deceleration of a charged particle when
deflected by another charged particle, typically an electron
by an atomic nucleus. Bremsstrahlung has a continuous spectrum, which becomes
more intense and shifts toward higher frequencies when the energy of the
accelerated particles is increased. Bremsstrahlung is often used in the more
narrow sense to describe radiation from beta particles stopped in matter.
Bremsstrahlung radiation may be formed if dense material is used to shield
a high energy beta-emitter, such a lead shield for Phosphorus (P-32).
Byproduct Material
Byproduct material is material that has become radioactive
as a result of fission reactions in a nuclear reactor.
Byproduct material is regulated by the Nuclear Regulatory Commission or
Agreement States.
Cabinet X-ray Equipment
Cabinet x-ray equipment includes laboratory cabinet
equipment, and baggage and parcel inspection systems. This
type of equipment is typically regarded as low hazard.
Calibration Source
A calibration source is a contained source that is exempt
from NRC licensing consideration due to its low activity.
These sources are typically used to calibrate laboratory gamma or liquid
scintillation counters.
Chart of Nuclides
A chart of nuclides is a graph in which one axis represents
the number of neutrons and the other represents the number
of protons in an atomic nucleus. Points are plotted on the
graph where real nuclides are known to exist. This system of ordering nuclides
offers insight into the characteristics of isotopes.
Check Source
A check source is a contained source that is exempt from NRC licensing considerations due to its low activity.
This means that such sources will not be tracked on a Permit or other official radioactive inventory.
Check sources are typically used to monitor portable survey instrument performance.
Although not officially tracked, the control of all exempt check sources is required.
Therefore, such sources should not be casually given or thrown away.
When maintained for routine use, they should be securely locked in storage.
When they are no longer useful, they should be transferred to the manufacturer or a radioactive waste broker.
Code of Federal Regulations
Under DOT rules, class & 7 is the hazardous materials
classification for radioactive material.
Closeout Survey
A closeout survey is the final survey of a laboratory room
or space, listed on a unsealed isotope Permit before removing
the room from the Permit, and releasing it from Radiation
Safety Division surveillance, for unrestricted use.
Comprehensive Guidance and Requirements
The &Comprehensive Guidance
and Requirements& are the USDA
Radiation Safety Division&s official policy documents specifying
the Permit Holder obligations for each of the following rad-types:
unsealed isotopes, irradiators, nuclear gauges, ECDs, portable x-ray fluorescent
analyzers, and x-ray producing equipment. The RSD &Comprehensive
Guidance and Requirements& documents supersede the &Permit
Use Conditions.&
Contained Source
A contained source is a source containing radioactive
materials where the materials are enclosed or contained to
prevent dispersion. Examples of contained sources are plastic plates or
discs impregnated with radioisotopes, electron capture detector foils,
and sealed sources.
Contamination
The uncontrolled dispersal of radioactive material where
it is unwanted. The contamination potential is greater for
radioactive material that is dissolved in a liquid, broken into pieces,
or crushed into dust.
Controlled Area
An area where access to is limited or controlled by the
Permit Holder or location management for reasons of security.
Counts per minute. This is the unit of measurement of a counting
detector, before considerations of background, counting
efficiency, and geometry.
Curie (Ci)
A unit of activity. A Curie is defined as the activity in 1
pure gram of Radium (Ra-226)..
1 curie = 3.7 x 1010 Becquerel
1 giga-Becquerel = 27 milli-Curies
Radioactive decay, a process of spontaneous nuclear transformation
in the nucleus of an atom with the subsequent emission
of radiation, and change of an unstable nucleus into a more
stable isotope or a different element.
Decay-in-storage
Decay-in-storage is a method of handling radioactive material
that has a short half-life. Radioactive isotopes with a
half-life of 120 days or less may be disposed of as non-radioactive waste
after being held for decay for at least 10 half lives.
Declared Pregnant Worker
A woman who has voluntarily informed her employer,
in writing, of her pregnancy and the estimated date of conception
for purposes of radiation dose estimates.
Decommissioning Survey
A decommissioning survey certifies that all unsealed
radioactive material has been removed from a building and
that unsealed radioactive material is no longer being used in the building.
A decommissioning survey is conducted by inspectors from the Radiation
Safety Division, which involves the review of closeout survey records and
radioactive material disposal records, as well as visual inspections, meter
surveys, and on-site contamination surveys of the laboratories and storage
areas where unsealed radioactive material was used. The decommissioning
process verifies and documents that no evidence of any radioactive contamination
was found, nor that of any remaining radioactive material
or sources, and that all reference warning signs and labels regarding radioactive
material have been removed and disposed of. Decommissioning refers to unsealed
isotopes and to individual buildings and may not necessarily apply
to all work with radioactive material at a given location.
Diffractometer
A diffractometer is an instrument for analyzing the structure
of a material from the scattering pattern produced when
a beam of x-ray radiation interacts with it. This scattered pattern is
called diffraction. A diffractometer consists of an x-ray source and a
detector. X-ray diffraction yields the atomic structure of materials by
the scattering of x-rays through the electrons of the individual atoms
in the sample. X-ray scattering techniques can reveal information about
the crystallographic structure, chemical composition, and physical properties
of materials ranging from simple inorganic solids to complex compounds,
such as proteins. A diffractometer can also be used to identify unknown
substances, by comparing diffraction data against a database. These x-ray
systems are designed for use in a laboratory setting.
Radiation energy deposited in matter. Dose was originally defined
in units of rads. Dose is also now defined in units of
grays, which is an SI (metric) formulation.
1 gray is equal to a dose of 1 Joule / kilogram
1 gray = 100 rads
1 rad = 10 milli-grays
Dose Equivalent
Radiation energy deposited in human tissue, and normalized
for the sensitivity of the tissue to different types of
radiation. Often, when the normalizing factor is 1, the dose equivalent
is the same as dose. Dose equivalent was originally defined
in units of rem. Dose equivalent is also now defined in units
of sieverts, which is an SI (metric) formulation.
1 sievert is equal to a dose equivalent of 1 Joule / kilogram
1 sievert = 100 rem
1 rem = 10 milli-sievert
A device to determine dose from ionizing radiation.
Dosimetry is the study, measurement, method of measurement,
or instrument of measurement of radiation dose. Dosimetry
often refers to the personnel badge that people may wear
to measure and monitor their dose. It may also refer to the status of wearing
such a badge, dose history, or the records where dose history is maintained.
More specifically, radiation dosimetry is the calculation of the absorbed
dose in tissue resulting from exposure to ionizing radiation. Radiation
dose refers to the amount of energy deposited in matter and its biological
effect on living tissue, and should not be confused with activity measured
in units of curie or becquerel. Exposure to a radioactive source will give
a dose which depends on the activity, time of exposure, energy of the radiation
emitted, distance from the source, and shielding.
United States Department of Transportation
Disintegrations per minute. This is a unit of activity, derived
from detector measurements in CPM. Conversion of CPM to
DPM involves consideration of instrument counting efficiency,
background, and geometry.
60 DPM = 1 becquerel
1 micro-Curie = 2,220,000 DPM
The electron is a subatomic particle with a negative electric
charge and a mass that is far smaller than a proton or
a neutron. The electron revolves around the nucleus of an atom, in numbers
equal to the number of protons in the atomic nucleus, which
is also the atomic number. The interaction of electrons among atoms is
what forms chemical bonds. The disturbance of electrons in orbit around
a nucleus is what causes x-ray radiation. Low energy free electrons are
considered ions of charge. However, high-energy, high-speed electrons emitted
by certain types of radioactive nuclei such as potassium (K-40) are
called beta particles, or beta radiation.
Electron Capture Detector (ECD)
An electron capture detector (ECD) is
a device used in a gas chromatograph to detect trace amounts
of chemical compounds in a sample. Typically, it contains a 10 milli-curie
nickel (Ni-63) metal foil.
Chromatography is a set of laboratory techniques for the separation of
mixtures. A gas chromatograph is used in analytic chemistry for separating
and analyzing compounds that can be vaporized without decomposition. It
can measure the purity of a sample or separate the different components
of a sample, determining relative amounts. The ECD used in a gas chromatograph
detects electron-absorbing samples such as halogen compounds. A radioactive
beta emitter, nickel (Ni-63), is a component of an ECD. The beta particles
ionize a gas, which causes a background current to flow in the ECD circuitry.
If a sample absorbs some of the negative electron ions (a process called
ionizing electron capture) the current is reduced. The current fluctuation
therefore reveals the presence of the sample components.
Environmental Protection Agency (EPA)
The U.S. Environmental
Protection Agency (EPA) is an agency of the federal government
of the United States charged with protecting human health
and the environment, by writing and enforcing regulations
based on laws passed by Congress. It has the responsibility
of maintaining and enforcing national standards under a
variety of environmental laws, in consultation with state and local
governments. Within the EPA, there is an Office of Air
and Radiation.
A measurement of ionization in air, of x-ray radiation and
low to medium energy gamma radiation. Exposure cannot be
measured for other kinds of radiation. Units of exposure
are given in Roentgens. The concept of exposure is older
than dose, and is considered sci however,
it is still often used. The term exposure is sometimes used imprecisely
as a synonym for dose.
Field Study
A field study using unsealed isotopes involves selectively
distributing radioactive material in the environment. A
protocol for a special use field study must be reviewed and approved by
the RSC, as well as the Nuclear Regulatory Commission (NRC).
&Notice to Employees& consists
of questions and answers about the NRC and its responsibilities,
the employee&s
responsibilities, and instructions to employees as to how to
report safety concerns and violations of NRC rules. At locations
where radioactive material is stored or used, this form is
required to be prominently posted where employees can see it.
Food and Drug Administration
The Food and Drug Administration (FDA) is
an agency of the United States Department of Health and Human
Services, one of the federal executive departments. The FDA regulates food
safety, tobacco products, dietary supplements, prescription and over-the-counter
drugs, vaccines, biopharmaceuticals blood transfusions, medical
devices, electromagnetic radiation emitting devices, veterinary products,
and cosmetics.
Gamma radiation (named after and denoted by the third letter
in the Greek alphabet, &) is high energy electromagnetic radiation
released from an unstable nucleus, as it becomes more stable,
after the decaying nucleus has emitted either alpha or beta radiation.
This type of radiation is predicted from the electromagnetic theory of
radiation. However, such radiation has observed characteristics of particles,
like the other kinds of radiation, and is said to consist of photon particles,
having neither mass nor electric charge. These highly energetic
photons are deeply penetrating and difficult to stop. They can be attenuated
by thick layers of material, where stopping power of the
material depends mostly on its total mass.
Gamma Counter
Standard laboratory equipment that measures gamma radiation
emitted by a radionuclide. Samples are placed in vials, that
move along a track inside a shielded detector, set to measure
specific energy windows characteristic of the particular
isotope. Due to the heavy shielding of the detector, a gamma
counter often is not portable. In principle, the gamma counter is like
a scintillation detector except that a scintillation crystal such as sodium
idodide (NaI) surrounds the sample. The gamma rays interact with the crystal,
are absorbed, and produce light.
Geiger-Mueller detector
A tube t it consists of electrodes,
filled with a low-pressure inert gas and a halogen gas. The
walls of the tube form a cathode while the anode is a wire
passing up the center of the tube with a potential difference of several
hundred volts, but no current flowing. When ionizing radiation
passes through the tube, gas molecules are ionized. The tube's electrodes
accelerate the ions towards the cathode and the electrons towards the anode.
The ion pairs further ionize the gas, creating an avalanche
of charged particles. This results in a short, intense pulse
of current which &cascades& from
the negative electrode to the positive electrode and is
measured or counted. These current pulses are processed in
a count-rate meter that produces a readout on a scale, and an audible sound.
GM measurements do not relate easily to dose-rate. But GM detectors can
be calibrated for dose-rate, when working with specific, known
Metric prefix, meaning times 1,000,000,000 (billion)
The SI unit of absorbed dose. One gray is equal to an absorbed
dose of 1 Joule / kilogram or 100 rads.
The time it takes for ½ of a number of unstable atoms to
decay. Half-life is a physical property of radioactive isotopes,
and is different for each isotope. It can range from seconds to
billions of years. It cannot be calculated or predicted, but
can only be determined by empirical measurement.
HazMat Labels
Hazardous Materials labels are required by the DOT to be
placed on Type-A packages containing radioactive material,
intended for transport or shipment. Radioactive HazMat labels are white
or yellow diamond shaped labels that list radionuclide and activity, and
the package transport index.
Health Physicist
Radiation Safety Scientist
Human Use Study
A human use study involves the uptake of radioactive material
in a human subject. A human use protocol must first be
reviewed and approved by the US Food and Drug Administration (FDA) Radioactive
Drug Research Committee or other Institutional Review Board before it can
be submitted to the Radiation Safety Division. The human use application
must include an approval from the USDA Human Use Committee.
Incineration
Incineration is the disposal of radioactive waste through
incineration. An incineration program must be approved according
to the NRC guidance &Information
Required for Commission Approval of Treatment or disposal
by Incineration& dated
January 1, 1991. Incinerators must be approved as required
by Federal, state, and local authorities.
Ionization
The removal of electrons from atoms and molecules. This is
a process that can alter chemical properties and chemical
reactions.
Ionizing Radiation
A classification of radiation harmfulness according to
its ability to cause ionization. Radiation with sufficiently
high energy can ionize atoms, causing electrons to be
stripped (or 'knocked out') from an electron shell, which leaves
the atom with a net positive charge. Ionization disrupts chemical bonds,
which can damage cells and cellular DNA, as well as generating toxic chemicals
which interfere with cellular metabolism.
Irradiator
A device used to expose a wide range of samples to gamma radiation
for a variety of purposes. The source of the radiation
is typically a cobalt (Co-60) or cesium (Cs-137) sealed source.
The radioactive source is completely contained in lead shielding,
which is an integral part of the irradiator equipment. The
activity of the irradiator source can be in the thousands of Curies. Together
with the shielding, the irradiators can weigh thousands of pounds.
A weight variation of atoms of a single element resulting from
the different number of neutrons in atoms of the same element.
The element name together with the sum of its protons
and neutrons identifies the isotope, for example Carbon-14.
Isotopes may be radioactive or stable. However, the term isotope is often
used to indicate radioactive material.
Isotope Room
A room that appears on an unsealed isotope Permit, where unsealed
radioactive material may be used or stored, and which is
subject to required lab surveys, and which must be tracked
by the Radiation Safety Division until a final close-out
survey is done.
Metric prefix, meaning, times 1,000 (thousand)
Lab Survey
Evaluation of radiological conditions and potential hazards.
Surveys are required when it is reasonable to evaluate
a radiological hazard and when necessary to comply with the
regulations. Surveys are also used to plan work in areas
where radioactive material will be used.
Laboratory Cabinet X-ray Unit
A laboratory cabinet x-ray unit is a system
with an x-ray tube installed in a shielded enclosure intended
to contain the item being irradiated. The enclosure protects people from
the area of x-ray exposure. Shielding surrounds the volume exposed to x-rays
and the shielding is an inherent part of the system. Cabinet x-ray systems
are primarily used for industrial quality control inspections.
Large Animal
For purposes of unsealed isotope special use studies, a large
animal is a fully grown adult animal with a weight greater
than 10 kilo-grams (about 22 pounds).
A leak test is a test that consists of rubbing a source, or
the surfaces near a source, with filter paper to see if
any radioactive material is leaking from the source. In USDA, irradiators,
nuclear gauges, electron capture detectors, x-ray fluorescence
analyzers, and any other sealed source (except for very small sources,
which are exempt) are required to be leak tested every six months. The
Radiation Safety Division will provide the Permit Holder with a leak test
sheet and a leak test filter paper. The Permit Holder is expected to have
the leak test done and returned to RSD for evaluation and reporting results.
The document issued by the Nuclear Regulatory Commission authorizing
the U.S. Department of Agriculture to possess and use radioactive
materials at USDA facilities throughout the United States.
Limited Quantity
Under DOT rules, a limited quantity of radioactive material
means the quantity per package which is excepted from requirements
for Type-A packaging, labeling, marking (except for the
UN identification number), and shipping papers, provided that
the package surface
dose-rate does not exceed 0.5 milli-rem /
the packaging
bears the marking &Radioactive&;
the package does not contain
fissile material.
The limited quantity can be calculated for each isotope by dividing the
A1 values by 1,000 or by dividing the A2 values by 1,000 for solids, and
10,000 for liquids or gasses.
Liquid Scintillation Counter
A liquid scintillation counter is standard
laboratory equipment for measuring radiation from beta-emitting
nuclides. Samples are suspended in a &cocktail& containing a solvent, with
small amounts of other additives known as fluors, scintillants, or scintillators.
Beta particles emitted from the sample transfer energy to the fluors which
then emit light. In this way, each beta emission results
in a pulse of light. The samples are placed in small glass or plastic vials
that are loaded into the liquid scintillation counter. The counter has
photomultiplier tubes which detect the light pulses. Liquid scintillation
counters often contain an external standard reference that contains cesium
(Cs-137) or radium (Ra-226). These sealed sources are the responsibility
of the instrument's manufacturer when the instrument is surplused.
Location Radiation Protection Officer (LRPO)
An individual that has been
designated to provide advice and assistance regarding the
USDA Radiation Safety Program at a location. An LRPO must be
designated at locations that have more than one Permit Holder. However,
all locations are encouraged to designate an LRPO. There is an LRPO representative
on the Radiation Safety Committee.
Mass Number
The mass number is the sum of the protons and neutrons found
in the nucleus of an atom. An isotope is a weight variation
of an atom of a single element, and is identified by the
element name along with the mass number. The number of neutrons in the
nucleus of an isotope can be found by subtracting the atomic number (the
number of protons) from the mass number (the number of protons and neutrons).
Material License
The document issued by the Nuclear Regulatory Commission
authorizing the U.S. Department of Agriculture to possess
and use radioactive materials at USDA facilities throughout
the United States.
Metric prefix meaning, times1,000,000 (million)
Mega electron volt (1 million electron volts). This is a unit
of energy for particle or electromagnetic radiation. For
example, (cesium) Cs-137 emits gamma radiation of 0.662 MeV,
and (phosphorus) P-32 emits a 1.7 MeV Beta particle
Metric prefix meaning a millionth
Metric prefix meaning a thousandth
Minimum Detectable Activity (MDA)
The smallest amount of activity that can
be quantified for comparison with regulatory limits.
NaI detector
Sodium iodide detector
Metric prefix meaning a billionth
Naturally Occurring Radioactive Materials (NORM)
Radioactive materials
present in the earth's crust. This includes potassium (K-40),
Uranium, Thorium, and Radon.
National Council on Radiation Protection and Measurements
The neutron is a subatomic particle with no net electric charge
and a mass slightly larger than that of a proton. With
the exception of hydrogen, nuclei of atoms consist of protons and neutrons.
The number of protons in a nucleus is the atomic number and
defines the type of element the atom forms. The number of neutrons is the
neutron number and determines the isotope of an element. Neutron radiation
is a kind of ionizing radiation which consists of free neutrons.
Neutrons may be emitted from any number of different nuclear reactions.
Free neutrons readily pass through most material, but interact enough to
cause biological damage. Neutron radiation is considered
to be the most severe and dangerous radiation available. Neutrons can travel
great distances, but can be shielded by hydrogen rich material. The most
effective shielding materials are water, polyethylene, paraffin wax, or
concrete, where a considerable amount of water molecules are chemically
bound to the cement.
Nuclear Gauge
A nuclear gauge (also called a nuclear density gauge, a
soil moisture gauge, or a moisture density gauge) is a tool
used for civil construction that measures soil density or soil water content.
Nuclear gauges are also used for industrial, mining, and
scientific purposes. In USDA, nuclear gauges are used for building roads
and dams, and for collecting scientific data on soil water content in agricultural
and forestry settings. For measuring soil density, a radioactive
source emits gamma radiation into soil, and a sensor measures the radiation
that is reflected by the soil. The source of the gamma radiation is typically
a cesium (Cs-137) sealed source of about 8 to 10 milli-Curies.
For measuring water density, the radioactive source emits
neutrons and then measures the returning scattered neutrons. The source
of the neutron radiation is typically americium (Am-241) source, in combination
with the element beryllium, typically a source of about 40 to 50 milli-Curies.
Nuclear Regulatory Commission
The Nuclear Regulatory Commission (also called,
the NRC) is an independent agency of the US government. It
is the Federal regulator of radioactive material, established by the Energy
Reorganization Act of 1974, from the United States Atomic Energy Commission,
with headquarters located in Rockville, MD.
oversees agree
issues licenses in non-agreement
regulates all
issues licenses to Federal agencies
in all states.
Numerous special inspection teams, with many different specialties, routinely
conduct inspections at various licensee sites, including USDA sites
A nuclide is an atomic species characterized by the constitution
of its nucleus
Isotopes and elements are nuclides. Nuclides can be graphically
represented in a chart of nuclides.
Nuclear Regulatory Commission (NRC) consolidated guidance about
materials licenses, gives detailed information about what
information to include when applying for various kinds of
NRC licenses. These documents are also helpful in understanding compliance
issues with currently operating licenses.
Occupational Dose
The dose received by an individual in the course of employment
in which the individual's assigned duties involve exposure
to radiation.
Office of Homeland Security and Emergency Coordination (OHSEC)
the management office for the Radiation Safety Division.
It provides Departmental government-wide initiatives pertaining to physical
security, emergency programs, personnel and document security, continuity
of operations, and continuity of government. OHSEC also provides security
management of USDA's Headquarters facilities in the National Capital Region
and 24/7 operations center support to USDA national emergency response
and program operations. OHSEC also supports the USDA radiation safety program.
Permit (Radiation Source Permit)
The document issued by the Radiation
Safety Division authorizing a USDA employee to possess and
use radioactive materials or x-ray producing equipment at USDA locations.
Permit Holder
Any USDA employee whose training and experience have been
reviewed and approved by the Radiation Safety Division, who
is named on the Permit, and who uses or directly supervises
the use of radioactive material or x-ray producing equipment. Only
the Permit Holder and the associate users listed on the Permit
are authorized to acquire, possess, store, or use radioactive material
or x-ray producing equipment.
The existence of gamma and x-ray radiation was predicted from
the electromagnetic wave theory of radiation. However,
such radiation has observed characteristics of particles and is said to
consist of photon particles, having neither mass nor electric charge.
Metric prefix, meaning, trillionth
Portable X-Ray Fluorescence Analyzer (XFA)
X-ray fluorescence is the emission of characteristic &secondary& (or
fluorescent) x-rays from a material that has been excited by bombarding
with high-energy X-rays or gamma rays. The phenomenon is widely used for
elemental analysis and chemical analysis, particularly in the investigation
of metals, glass, ceramics and building materials, and for research in
geochemistry, forensic science and archaeology. Portable x-ray fluorescence
analyzers should not be confused with analytic laboratory x-ray equipment
where the target material being analyzed is usually bombarded by electronically
produced x-rays. Portable x-ray fluorescence analyzers may contain one
or more radioactive sources that bombard the target with gamma radiation.
An XFA may contain one or more of the following radioactive isotopes in
quantities up to 50 milli-Curies: Cadmium (Cd-109), Iron (Fe-55), Americium
Possession Limits
The possession limit for an unsealed isotope is the amount
of radioactive material listed on a Permit, that a Permit
Holder is allowed to possess in an active inventory.
The proton is a subatomic particle with a positive electric
charge and a mass slightly smaller than that of a neutron.
One or more protons are present in the nucleus of each
atom, along with neutrons. The number of protons in a nucleus is the atomic
number and defines the type of element the atom forms. Protons do not normally
exist free of an atomic structure, since free protons soon
pick up an electron and become neutral hydrogen, which may then react chemically.
The conventional unit of absorbed dose. One rad equals an absorbed
dose of 0.01 Joule / kilogram or 0.01 gray.
Radiation Area
Radiation area means an area, accessible to individuals, in
which radiation levels are greater than 5 milli-rem per
hour at one foot from the radiation source or from any surface that the
radiation penetrates.
Radiation Safety Committee (RSC)
The RSC is a policy making committee that meets quarterly,
in various places. It is required by the NRC license, and
represents USDA agencies using radioactive materials. The
RSC establishes policies and reviews program compliance.
Radiation Safety Division (RSD)
The Radiation Safety Division is the operational office of
the USDA radiation safety program. As a Department level
office, it interacts with agencies through Permits that it
issues to agency employees. The Radiation Safety Division works with agencies
in managing the Permit Holder&s program activities that involve the use of radioactive
material and x-ray equipment. The RSD periodically sends inspectors to
the Permit Holder locations. RSD also provides guidance and direction
regarding radiological emergency preparedness programs through the USDA
Office of Homeland Security and Emergency Coordination (OHSEC) and through
agency emergency response offices.
Radiation Source
A source of ionizing radiation, either from radioactive
materials or electronic x-ray equipment.
Radiation Source Permit (Permit)
The authorizing document issued by the
Radiation Safety Division to allow a USDA employee to possess
and use radioactive materials or x-ray producing equipment.
Radiation Worker
An individual who, in the course of employment, is assigned
duties in a restricted area involving exposure to radiation
or radioactive materials.
Radioactive Material License (see )
Radioactive Decay
A process of spontaneous nuclear transformation in the
nucleus of an atom with the subsequent emission of radiation,
and change of an unstable nucleus into a more stable isotope
or a different element.
Radioactive Material
Matter that emits radiation from the nucleus of its
atoms. (from byproduct material)
Radioactive Waste
Radioactive waste is what is left over from the use of radioactive
materials. During research and chemical analysis, test
tubes, bottles, tubing and process equipment come into contact with the
radioactive material. This material must be segregated as radioactive waste.
If laboratory animals are injected with radioactive material for research
purposes, the animal carcasses containing the radioactive
material become radioactive waste and must be handled appropriately. Other
examples of radioactive waste are contaminated protective clothing and
gloves, wiping rags, mops, filters, equipment, and tools. Small quantities
of radioactive chemicals which are left over from an experiment, or which
are no longer needed can also be classified as radioactive waste.
Radioactivity
The emission of radiation from the nucleus of atoms.
Radio-Isotope
Any radioactive material.
Radio-labeling
Radio-labeling is a technique for tracking the passage of a
sample of substance through a system. It is used in chemistry
and biochemistry to help understand chemical reactions and
interactions. A compound is &labeled& by
substituting a radioactive atom of the compound in place of a stable
atom of the same element. With this substitution in effect, the radioactive
atom will behave in the same way chemically as other like atoms in the
compound, and will not interfere with the reaction under investigation.
When these radioactive atoms are later detected in a different part of
the system, they are known to have come from the originally labeled substance.
A business term used in the Radiation Safety Division office
to designate different kinds of radiation sources. The
RSD rad-types are: unsealed isotopes, irradiators, nuclear
gauges, ECDs, portable x-ray fluorescent analyzers, and x-ray
producing equipment.
Radioactive material
The conventional unit of dose equivalent. One rem equals a
dose equivalent of 0.01 Joule / kilogram or 0.01 sieverts.
Responsible User
This is the USDA term, used in the past, for a &Permit Holder.& Other
organizations may use similar terms, such as &Principle Investigator.&
Restricted Area
An area, access to which is limited by the Permit Holder
or by location management for the purpose of protecting individuals
from undue risks from exposure to radiation and radioactive
materials.
RQ - Reportable Quantity
Abbreviated as RQ, the EPA has set transportation threshold activity limits for isotopes that, if exceeded, must be indicated at the end of the Proper Shipping Name, both on the paperwork, and on the exterior of the package.
The limit for americium (Am-241) is 10 milli-Curies.
Since a moisture density gauge may have an americium (Am-241) source greater than than 10 milli-Curies, the designation, RQ, must sometimes be shown.
Radiation Safety Management System, the RSD web-based database.
Radiation Safety Officer
Sealed Source
A contained source that has been constructed and tested to
pass specific accident conditions without the release of
radioactive material.
The French phrase, systeme internationale, which means, international
system of weights and measures, previously known as the
metric system.
Sievert (Sv)
The SI unit of the quantity expressed as dose equivalent. One
sievert equals a dose equivalent of 1 Joule / kilogram
or 100 rem.
Small Animal
For purposes of unsealed isotope general use, a small animal
is a fully grown adult animal with a weight not more than
10 kilo-grams (about 22 pounds).
Sodium Iodide detector
A common and useful scintillating material, with traces of
thallium, that is used as a detector to measures ionizing
radiation. The sensor, called a scintillator, consists of
a transparent crystal, that fluoresces when struck by ionizing
radiation. A photomultiplier tube measures the light from the
crystal. The photomultiplier tube is attached to an electronic amplifier
and other electronic equipment to count and quantify the amplitude of the
signals produced by the photomultiplier. When a charged particle strikes
the scintillator, a flash of light is produced. The association of a scintillator
and photomultiplier with the counter circuits forms the basis
of the scintillation counter apparatus.
Special Form
Special form radioactive material is either an indispersible
solid radioactive material or a sealed capsule containing
radioactive material.
Special Use Studies
Special use studies include:
Large Animal Use
Field Studies
For unsealed isotopes, a general research protocol is required for routine
program activities. Some protocols for special uses of unsealed isotopes
require the approval of the USDA Radiation Safely Committee (RSC) as well
as approval from other sources.
Metric prefix meaning, times 1,000,000,000,000 (trillion)
Thermoluminescent dosimeters
Transport Index
The radiation dose-rate in milli-Rem per hour measured at 1
meter from the Type-A package surface, rounded up to the
nearest tenth. The Ti appears on the HazMat Yellow-II or
Yellow-III label and on the on the Shipper&s Declaration
The three-bladed radiation warning symbol. It first appeared
at the University of California Radiation Laboratory in
Berkeley in 1946, improvised to represent activity radiating
from an atom. The color combination of magenta on yellow was
first used at Oak Ridge National Lab in 1948. By the late 50s, ANSI standards
and federal regulations had codified the version of the warning sign used
today. Present regulations also permit the use of black as a substitute
for magenta (a deep purple-red).
Type-A Package
Type A packaging is packaging that is designed to withstand
DOT specified water spray, drop, puncture, and crash tests.
A Type-A package is required for shipping radioactive materials
when the radioactivity inside the package does not exceed the A1 or A2
values. Type-A packaging, is specified to withstand normal transportation
conditions and minor accidents only.
UN numbers are four-digit numbers that identify hazardous
materials in the framework of international transport. In case of a
transportation accident involving hazardous material, the UN number
provides quick information to emergency responders. UN numbers are
assigned by the United Nations Committee of Experts on the Transport
of Dangerous Goods. They are published as part of their Recommendations
on the Transport of Dangerous Goods. These recommendations have been
adopted by the US Department of Transportation (DOT).
For a nuclear gauge, the UN number is UN3332. It should appear on the
carrying case and transportation papers as: UN3332, class & 7, Radioactive
Material, Type A package, special form.
For unsealed isotopes in normal form, shipped in excess of exempt quantities,
the UN number is UN2915, It should appear on the Type-A package and transportation
papers as: UN2915 class & 7, Radioactive Material, Type A package,
non special form
For unsealed isotopes in normal form, shipped in exempt limited quantities,
the UN number is UN2910. The package should me marked &radioactive
material,& but there is no requirement to list the UN number.
Unsealed Radioactive Materials
Radioactive materials that are in a liquid, powder or granular
form, and can be easily dispersed through routine laboratory
procedures. Unsealed radioactive material (also called isotopes)
refers to radioactive chemicals used in laboratory research
for their tagging, labeling, tracing, radiation, or decay properties.
Unsealed radioactive material is also variously referred to as (radio-)
isotopes, (radio-) nuclides, byproduct material, licensed material,
or activated material.
Unrestricted Area
An area, access to which is neither limited or controlled
by the Permit Holder or by location management.
Waste (see )
Waste broker
A company that is licensed to transfer radioactive waste to
licensed radioactive waste disposal or treatment facilities.
Waste stream
Waste with common properties managed in a similar manner is
called a waste stream. Radioactive waste should be segregated
into an appropriate waste streams for processing and disposal.
Some examples of waste streams are: decay-in-storage, sewer disposal, incineration,
waste broker transfer.
X-ray radiation is a form of high frequency electromagnetic
radiation, also characterized as high energy photon particles,
usually called, x-rays. X-rays are produced when electrons
undergo energy level transitions as they orbit the atomic nucleus. Since
an x-ray tube can induce this process, x-rays are regarded as electronically
produced radiation, which can be generated, controlled, and stopped according
to the electrical voltage applied to the x-ray tube.
X-ray Fluorescence Analyzer
X-ray fluorescence is the emission of characteristic &secondary& (or
fluorescent) x-rays from a material that has been excited by high-energy
x-rays or gamma rays. The phenomenon is used in an x-ray fluorescence (spectroscopy)
analyzer for chemical analysis, particularly in the investigation of metals,
glass, ceramics, and building materials, and for research in geochemistry,
forensic science, and archaeology. For laboratory equipment, the target
material being analyzed is usually bombarded by electronically produced
x-rays. This equipment should not be confused with portable x-ray fluorescent
analyzers, which contain radioactive sources.
X-ray Producing Equipment
X-ray radiation is a form of high frequency electromagnetic
radiation, also characterized as high energy photon particles,
usually called, x-rays. X-rays can be electronically produced
when an x-ray tube is turned on and electronically activated. Turning the
equipment off stops the production of x-rays. X-ray radiation is the same
kind of radiation as gamma radiation, but generated by a
different process and discovered and named under different circumstances.
The two types of radiation are now usually distinguished by their origin:
x-rays being electronically produced and emitted by electrons outside the
nucleus, while gamma rays are emitted by the nucleus as the result of radioactivity.
X-rays do not have anything to do with
therefore,
they are not regulated by the NRC. In USDA, x-ray producing equipment
includes a wide range of equipment types such as:
Diagnostic equipment
Laboratory Cabinet x-ray units
Fluorescence analyzer
Diffractometer
Baggage and parcel inspection systems
Bone Densitometers.
X-ray Tube
An x-ray tube is a vacuum tube that produces x-rays. They are
used in x-ray machines. The x-ray tube has a cathode, which
emits electrons into the glass-enclosed vacuum and an anode
to collect the electrons, thus establishing a flow of electrical current,
known as the beam, through the tube A high voltage power source, for example
30 to 150 kilovolts (kV), is connected across cathode and anode to accelerate
the electrons. Electrons from the cathode collide with the
anode material, usually tungsten, molybdenum, or copper, and accelerate
other electrons, ions and nuclei within the anode material. About 1% of
the energy generated is emitted, usually perpendicular to the path of the
electron beam, as x-rays. The rest of the energy is released as heat. The
x-ray spectrum depends on the anode material and the accelerating voltage.