A Card
The University's Master Card obtained through Buying and Contracting. Reminder - this cannot be used for purchasing radioactive materials.

Absorbed Dose
The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest. The conventional unit of absorbed dose is the rad; 1 rad = 100 ergs/g. The SI unit is the gray (Gy); 1 Gy = 1 Joule/Kg, or 100 rads. See also Dose, Absorbed.

Activated Metal
A metal that has been made radioactive through the process of activation. For the purpose of the University of Colorado, an activated metal is considered a sealed source and is usually a small metal disc. See also Activation.

The process of making a radionuclide by bombarding a stable element with neutrons, protons, or other nuclear radiation.

Time rate of nuclear transformations. The conventional unit of activity is the curie, Ci and the SI unit of activity is the becquerel, Bq. See also Radioactivity and Decay, Radioactive.

Acronym for "As Low As Reasonably Achievable." An approach to radiation protection which has the objective of attaining individual and collective doses as far below regulatory limits as is reasonably achievable. ALARA considers the state of technology, the economics of improvements in relation to the state of technology and benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and radioactive materials in the public interest.

Alpha Particle
A positively charged particle ejected spontaneously from the nuclei of some radioactive elements. It is identical to a helium nucleus that has a mass number of 4 and an electrostatic charge of +2. It has low penetrating power and a short range. The most energetic alpha particle will generally fail to penetrate the dead layers of cells covering the skin. Alphas are hazardous when an alpha-emitting radionuclide is inside the body.

Analytical X-ray
An x-ray producing device used to determine the elemental composition, or to examine the microstructure of materials using diffraction or fluorescence analysis. See also Medical X-ray and X-ray.

Annual Limit on Intake (ALI)
The derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. An ALI is the smaller value of intake of a given radionuclide in a year by the reference man that would result in a committed effective dose equivalent of 5 rem (0.05 Sv) or a committed dose equivalent of 50 rem (0.5 Sv) to any individual organ or tissue.

Area Survey
A survey using a portable radiation survey meter to determine the dose rate in a given area. Most radiation survey meters have scales of mR/hr or counts per minute (cpm). See also Contamination Survey.

The smallest particle of an element that cannot be divided or broken up by chemical means. It consists of a central core of protons and neutrons, called the nucleus. Electrons revolve in orbits in the region surrounding the nucleus.

Atomic Number
The number of positively charged protons in the nucleus of an atom.

The process by which the number of particles or photons entering a body of matter is reduced by absorption and scatter.

Audit, Laboratory
See Laboratory Audit.

Authorized User
An individual who uses radioactive materials and/or radiation unsupervised, or supervises their use and is issued a University of Colorado Radioactive Materials License. See also Principal Investigator and Licensee.


Background Radiation
from cosmic sources; naturally occurring radioactive Radiation materials, including radon and global fallout as it exists in the environment from the testing of nuclear explosive devices. It does not include radiation from source material, byproduct material, or special nuclear materials. The typically quoted average individual exposure from background radiation is 360 millirem per year.

Becquerel (Bq)
The unit of radioactive decay equal to 1 disintegration per second. 3.7 x 1010 Bq = 1 Curie.

Beta Particle
A charged particle emitted from a nucleus during radioactive decay, with a mass equal to 1/1837 that of a proton. A negatively charged beta particle is identical to an electron. A positively charged beta particle is called a positron. Large amounts of beta radiation may cause skin burns, and beta emitters are harmful if they enter the body. Beta particles may be stopped by thin sheets of plastic, wood, or metal.

The National Research Council's committee on the Biological Effects of Ionizing Radiations (BIER). Committee V published a report in 1990 titled, Health Effects of Exposure to Low Levels of Ionizing Radiation which suggested levels of risk associated with radiation exposure.

The determination of kinds, quantities or concentrations, and in some cases, the 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.

Biohazardous Waste
For the purposes of this handbook, waste material that has not been rendered non-infectious using bleach or other disinfectant. Reminder - Autoclaves are NOT PERMITTED for use with radioactive materials.

Biological Half-life
The time required for a biological system, such as that of a human, to eliminate, by natural processes, half of the amount of a substance (such as a radioactive material) that has entered it.

Biological Shield
A mass of absorbing material placed around a radioactive source to reduce the radiation to a level safe for humans.


The act or process of tuning an instrument by determining the deviation from a standard to ascertain the proper correction factors. Generally refers to radiation survey meters for the purposes of this handbook. Radiation survey meters are calibrated at least annually by Health Physics.

Acronym for the "Colorado Department of Public Health and Environment" which establishes and enforces the regulations relating to radiation and radioactive materials in the State of Colorado.

Computer-based Training
Radiation safety training offered by Health Physics at a computer workstation.

Container Contents Sheet
A sheet of paper near or attached to a waste container which describes the waste material inside the container. Each sheet must be completed in order for the container to be collected for disposal.

The deposition of unwanted radioactive material on the surfaces of structures, areas, objects, or personnel. It may also be airborne or internal (inside components or personnel).

A survey using a wipe smear and liquid scintillation counter (LSC) Survey or gamma counter to determine the radioactive contamination in a given area. Most LSCs and gamma counters provide results in counts per minute (cpm) which are converted to decays per minute (dpm) using the efficiency of the instrument. See also Area Survey.

Cosmic Radiation
Penetrating ionizing radiation, both particulate and electromagnetic, originating in outer space. Secondary cosmic rays, formed by interactions in the earth's atmosphere, account for approximately 45 to 50 millirem of the 360 millirem background radiation that an average individual receives in a year.

Curie (Ci)
The conventional unit used to describe the intensity of radioactivity in a sample of material. The curie is equal to 37 billion disintegrations per second, which is approximately the rate of decay of 1 gram of radium. A curie is also a quantity of any radionuclide that decays at a rate of 37 billion disintegrations per second. Named for Marie and Pierre Curie, who discovered radium in 1898.


Decay, Radioactive
The decrease in the amount of any radioactive material with the passage of time, due to the spontaneous emission from the atomic nuclei of either alpha or beta particles, often accompanied by gamma radiation. See also Activity and Radioactivity.

Declared Pregnant Woman
A woman who has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception. For the purposes of this handbook, informing the employer means informing Health Physics.

The reduction or removal of contaminating radioactive material from a structure, area, object, or person.

Door Label
A sticker or posting indicating the presence of radioactive materials, other hazard, or emergency information.

Door Sign
A notice indicating the presence of radioactive materials, other hazard, or emergency information.

The absorbed dose, given in rads or grays, that represents the energy absorbed from the radiation in a gram of any material. Furthermore, the biological dose or dose equivalent, given in rem or sieverts, is a measure of the biological damage to living tissue from the radiation exposure.

Dose, Absorbed
The amount of energy deposited in any substance by ionizing radiation per unit mass of the substance. It is expressed numerically in rads or grays. See also Absorbed Dose.

Dose Equivalent
A term used to express the amount of biologically effective radiation dose when modifying factors have been considered. The product of absorbed dose multiplied by a quality factor multiplied by a distribution factor. It is expressed numerically in reins or sieverts. If the dose is in rads, the dose equivalent is in rems. If the dose is in Gray, the dose equivalent is in sieverts

Dose Limit
A limitation on the legal amount of dose allowed during a given period, usually one year. The values are established in regulations and enforced by CDPHE. Dose limits vary depending upon the classification of the individual of concern, for example, a radiation worker, a member of the public, a minor, or an embryo/fetus.

A portable instrument for measuring and registering the total accumulated dose to ionizing radiation.

The theory and application of the principles and techniques involved in the measurement and recording of radiation doses.

Dose Rate
The radiation dose delivered per unit time. For example, rem per hour or millirem per hour. In practice, it may also be expressed as mR/hr.


Effective Dose
The sum over the tissues of the product of the dose equivalent in a Equivalent tissue, the weighting factor representing its proportion of the risk resulting from irradiation of tissue to the total risk when the whole body is irradiated uniformly.

Effective Half-life
The time required for the amount of a radioactive element deposited in a living organism to be diminished 50% as a result of the combined action of radioactive decay and biological elimination.

Electromagnetic Radiation
A traveling wave motion resulting from changing electric or magnetic fields. Familiar electromagnetic radiation range from x-rays (and gamma rays) of short wavelength, through the ultraviolet, visible, and infrared regions, to radar and radio waves of relatively long wavelength. All electromagnetic radiations travel in a vacuum with the velocity of light.

An elementary particle with a negative charge and a mass equal to 1/1837 of the proton. Electrons surround the positively charged nucleus and determine the chemical properties of the atom.

One of the 103+ known chemical substances that cannot be broken down further without changing its chemical properties. Some examples include: Hydrogen, Nitrogen, Gold, Lead, and Uranium.

Emergency Responder
For the purposes of this handbook, anyone responding to an emergency involving radioactive materials. These individuals may include EH&S, Police, and Fire personnel. Environmental Monitoring conducted to evaluate radioactive material and/or Monitoring radiation released to the environment to ensure compliance with applicable regulations. Monitoring may include area dosimetry, air samples, and water samples.

Environmental Sample
A sample taken to evaluate the radioactive material and/or radiation released to the environment to ensure compliance with applicable regulations. Examples may include area dosimeters, air samples, and water samples.

Equipment Survey
A contamination survey conducted to ensure that an instrument or piece of equipment is not contaminated prior to transfer and/or disposal.

Being exposed to radiation or to radioactive material. Also that amount of g or x-radiation that produces one electrostatic unit of charge in air at standard temperature and pressure. This concept applies only to electromagnetic radiation in air. External Radiation Exposure to ionizing radiation when the radiation source is located outside the body.

Extremity Dosimeter
An instrument used to measure and register the accumulated dose received by an extremity. Generally associated with radionuclides emitting high energy beta particles or gamma rays. See also Dosimeter, Fetal Dosimeter, Ring Badge, and Whole Body Dosimeter.

Extremity (-ies)
The hands, forearms, elbows, feet, knee, leg below the knee, and ankles. Permissible radiation exposures in these regions are generally greater than the whole body because they contain less blood forming organs and have smaller volumes for energy absorption.


Fetal Dosimeter
An instrument used to measure and register the accumulated dose received by an embryo/fetus. See also Declared Pregnant Woman, Dosimeter and Whole Body Dosimeter.

Film Badge
A pack of photographic film used for measurement of radiation exposure for personnel monitoring purposes. The badge may contain two or three films of differing sensitivities, and it may contain a filter that shields part of the film from certain types of radiation. See also Whole Body Dosimeter.

Freezer Frost
The frost created in a freezer that can be potentially contaminated with radioactive materials, especially tritium (H-3).


Gamma Ray
High-energy, short wavelength, electromagnetic radiation emitted from the nucleus. Gamma radiation frequently accompanies alpha and beta emissions and always accompanies fission. Gamma rays are very penetrating and are best stopped or shielded by dense materials, such as lead or uranium. Gamma rays are similar to X-rays.

Geiger-Mueller Counter
A radiation detection and measuring instrument. It consists of a gas-filled tube containing electrodes, between which there is an electrical voltage, but no current flowing. When ionizing radiation passes through the tube, a short, intense pulse of current passes from the negative electrode to the positive electrode and is measured or counted. The number of pulses per second measures the intensity of the radiation field. It was named for Hans Geiger and W. Mueller, who invented it in the 1920's. It is sometimes simply called a Geiger counter or a G-M Counter.

For the purposes of this handbook, anyone who handles or produces hazardous waste.

Generator Cabinet
A protective cabinet surrounding each x-ray generator which limits leakage radiation measured at a distance of 5 centimeters from its surface such that it is not capable of producing a dose in excess of 0.25 mrem (2.5 mSv) in one hour.

Genetic Effects
Those effects of radiation that may be transmitted to the progeny of exposed individuals.

Gray (Gy)
The System International (SI) unit of absorbed radiation dose equal to 1 Joule per Kilogram. 1 Gy = 100 rad.


The time in which one half of the atoms of a particular radioactive substance disintegrates into another nuclear form. Measured half-lives vary from millionths of a second to billions of years. Also called physical or radiological half-life.

Half-life, Biological
The time required for the body to eliminate one half of the material taken in by natural biological means.

Half-life, Effective
The time required for a radionuclide contained in a biological system, such as a human or an animal, to reduce its activity by one half as a combined result of radioactive decay and biological elimination.

Half-life Categories
The categories used by Health Physics to separate wastes for decay-in-storage prior to disposal. There are three categories, identified by the colors yellow, orange and green representing the half-lives less than 60 days, between 60 and 90 days, and greater than 90 days.

Health Physics
The science concerned with recognition, evaluation, and control of health hazards from ionizing radiation.

High Radiation Area
Any area with dose rates greater than 100 mrem in one hour at 30 cm from the source or from any surface through which the radiation penetrates. These areas must be posted as "high radiation area" and access into these areas is maintained under strict control.

A colloquial term meaning highly radioactive.

Hot Spot
The region in a radiation / contamination area in which the level of radiation / contamination is noticeably greater than in neighboring regions in the area.


A safety device used to prevent an operator from inadvertently placing any portion of their body in the direct beam of an x-ray device.

Internal Radiation
Nuclear radiation resulting from radioactive substances in the body. Some examples are Iodine-131 (found in the thyroid gland) and Strontium-90 and Plutonium-239 (found in bone).

See Radioactive Materials Inventory.

Inverse Square Law
A result of geometry, this law shows that the radiation intensity is inversely proportional to the square of the distance from the source. Therefore, if the distance is increased from 1 meter to 2 meters, the intensity will be only one fourth of the original intensity, 1/22.

The process of adding one or more electrons to, or removing one or more electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharges, or nuclear radiations can cause ionization.

Ionizing Radiation
Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions. Some examples are alpha, beta, gamma, X-ray, neutrons, and ultraviolet light. High doses of ionizing radiation may produce severe skin or tissue damage.

For the purposes of this handbook, a device containing a sealed source used for the irradiation of academic and commercial biological research samples.

Exposure to radiation.

One of two or more atoms with the same number of protons, but different numbers of neutrons in their nuclei. Thus Carbon-12, Carbon-13, and Carbon- 14 are isotopes of the element carbon, the numbers denoting the approximate atomic weights. Isotopes have very nearly the same chemical properties, but often different physical properties. For example, Carbon-12 and Carbon-13 are stable, but Carbon-14 is radioactive.




A sticker, sign, tape, or posting which provides identification or description. See also Door Label.

Laboratory Audit
An audit of a laboratory's procedures and use of radioactive materials under the University of Colorado Radioactive Materials License issued to a Principal Investigator. Usually conducted at least annually.

Laboratory Contact
An individual designated on the University of Colorado Radioactive Materials License who is the liaison between the laboratory and the Health Physics staff. This person usually receives mailings, exchanges dosimeters, and handles waste pick-up requests.

A device which produces an intense, coherent, directional beam of light by stimulating electronic or molecular transitions to lower energy levels. An acronym for Light Amplification by Stimulated Emission of Radiation.

Leak Test
A wipe smear test similar to a contamination survey which verifies the integrity of a sealed source. If the results of the survey indicate more than 0.005 mCi (185 Bq) of contamination, the sealed source is considered leaking, taken out of use, and either repaired or disposed of promptly.

A document authorizing an individual to use radioactive materials and/or radiation for specific purposes in specific locations. Officially referred to as the University of Colorado Radioactive Materials License. See also Authorized User, Licensee, and Principal Investigator.

An individual who uses radioactive materials and/or radiation unsupervised, or supervises their use and is issued a University of Colorado Radioactive Materials License. See also Authorized User and Principal Investigator.

The review process and paperwork necessary to obtain a University of Colorado Radioactive Materials License.

Liquid Scintillation Counter
Instrument used to measure radiation and/or contamination levels (LSC) by utilizing a liquid solution which fluoresces, or emits light, when interacting with radioactive material. LSCs are primarily used in association with beta emitters, however, they also are virtually 100% efficient for alpha particles and gamma rays.


Medical X-ray
A device used to irradiate human beings for the purpose of Device diagnosis or treatment. See also Analytical X-ray and X-ray.

A purchasing mechanism for items less than $1000. These are Purchase Order NOT permitted for purchasing radioactive materials or radiation producing machines.

One millionth of a rem. Abbreviated uCi.

Prefix indicating one thousandth of a unit. curie One thousandth of a curie. Abbreviated mCi. rad One thousandth of a rad. Abbreviated mrad. rem One thousandth of a rem. Abbreviated mrem. roentgen One thousandth of a Roentgen. Abbreviated mR. sievert One thousandth of a Sievert. Abbreviated mSv.

Mixed Waste
Waste that has both radioactive and chemical constituents. This waste must comply with regulations governing both hazards.

Periodic or continuous determination of the amount of ionizing radiation or radioactive contamination present in an occupied region, as a safety measure, for the purpose of health protection.


Natural Uranium
Uranium as found in nature. It contains 0.7% Uranium-235, 99.3 % of Uranium-238, and a trace of Uranium-234.

An uncharged elementary particle with a mass slightly greater than that of the proton, and found in the nucleus of every atom heavier than hydrogen.

Neutron Howitzer
A device that combines an alpha emitter with a target material to produce fast neutrons surrounded by a plastic water filled tank (howitzer) or other low-density moderating material which slows down the neutrons.

Non-Ionizing Radiation
Radiation not having enough energy to ionize atomic or molecular systems with a single event. Characterized by frequencies below the far ultraviolet region of the electromagnetic spectrum and includes ultraviolet (UV), visible light, infrared (IR), microwave, and other radio-frequency (RF)radiation. It is also found in the acoustic spectrum and includes sonic and ultrasonic radiation.

The small, central, positively charged region of an atom that carries essentially all of the mass. Except for the nucleus of ordinary hydrogen, which has a single proton, all atomic nuclei contain both protons and neutrons. The number of protons determines the total positive charge, or atomic number. This is the same for all the atomic nuclei of a given chemical element. The total number of neutrons and protons is called the mass number.

A general term referring to all known isotopes, both stable (279) and unstable (about 5,000), of the chemical elements.


An exposure to radiation which leads to a dose in excess of the regulatory limits.


Pancake Probe
A thin paddle-like probe used to detect high energy beta and gamma radiation. See also Geiger-Mueller Counter.

Personnel Monitoring
The use of survey meters to determine the amount of radioactive contamination on an individual, or the use of dosimetry to determine an individual's radiation dose.

A quantum (or packet) of energy emitted in the form of electromagnetic radiation. Gamma rays and X-rays are examples of photons.

Pick-up Request
See Radioactive Waste Pick-up Request Form.

A container (usually lead or plastic) used to ship or store radioactive materials. The thick walls protect the person handling the container from radiation. Large containers are commonly called casks. (The word may have originated from the use of "pig iron" in the early days of handling radioactive materials.)

Plated Source
Generally considered a sealed source for the purposes of this handbook. A source which has radioactive material bound to its surface by electroplating. The material cannot be removed from the surface under normal conditions.

An opening on an x-ray device which allows the primary beam to pass out of the device to irradiate an object of interest. Sometimes used to mount a camera or other analytical device.

Particle equal in mass, but opposite in charge, to the electron (a positive electron).

Principal Investigator
An individual who uses radioactive materials and/or radiation unsupervised, or supervises their use and is issued a University of Colorado Radioactive Materials License. See also Authorized User and Licensee.

An elementary nuclear particle with a positive electric charge located in the nucleus of an atom.

A plutonium and beryllium source which, when combined, creates a source of neutrons. See Neutron Howitzer.

Purchase Request
A form used to request a purchase and designate a shipping address. Normally available in each department, these forms are approved by Health Physics for purchasing radioactive materials and radiation producing machines. If used without a Standing Purchase Order, they must be signed by Health Physics.


Quality Factor
The factor by which the absorbed dose (rad) is to be multiplied to obtain a quantity that expresses, on a common scale for all ionizing radiation, the biological damage (rem) to exposed persons. It is used because some types of radiation, such as alpha particles, are more biologically damaging than other types.


Acronym for Radiation Absorbed Dose, the basic unit of absorbed dose of radiation. A dose of one rad means the absorption of 100 ergs (a small but measurable amount of energy) per gram of absorbing tissue.

Radiation, Nuclear
Particles (alpha, beta, neutrons) or photons (gamma) emitted from the nucleus of an unstable radioactive atom as a result of radioactive decay.

Radiation Area
Any area with radiation levels greater than 5 mrem in one hour at 30 cm from the source or from any surface through which the radiation penetrates.

Radiation Producing Machines
Machines designed to produce radiation, usually x-rays, when operating.

Radiation Safety Committee (RSC)
The on-site regulatory agency for the University's Radioactive Materials License. This committee has the authority to establish policies and procedures, provide enforcement sanctions, and restrict the use of radioactive materials and/or radiation. The RSC issues, amends, and terminates laboratory licenses, which authorize the specific activities associated with radioactive materials and/or radiation. It is composed of faculty and staff members representing numerous departments and levels of experience with radioactive materials and radiation, as well as a representative from Administration.

Radiation Safety Handbook
Essentially, a user's guide for the University of Colorado's laboratory licensees that includes topics such as the safe use of radioactive materials and radiation, licensing, and waste disposal. This document becomes regulation through the Radiation Safety Committee (RSC) and the State of Colorado. Amendments are reviewed and approved by the RSC.

Radiation Safety Officer
An individual approved by the State of Colorado who has the knowledge, responsibility, and authority to apply appropriate radiation protection regulations. The University of Colorado must have an RSO in order to have its Radioactive Materials License.

Radiation Safety Orientation
The basic radiation safety course offered by Health Physics to fulfill the training requirements of the University's License.

Radiation Safety Survey Log
A logbook of contamination survey results for each laboratory. This log may also contain room diagrams and results of area surveys. It should be kept in a central location for review during laboratory audits and inspections by Federal, State, or local agencies.

Radiation Shielding
Reduction of radiation by interposing a shield of absorbing material between any radioactive source and a person, work area, or radiation-sensitive device.

Radiation Sickness (Syndrome)
The complex of symptoms characterizing the disease known as radiation injury, resulting from excessive exposure to the whole body (or large part) to ionizing radiation. The earliest of these symptoms are nausea, fatigue, vomiting, and diarrhea, which may be followed by loss of hair (epilation), hemorrhage, inflammation of the mouth and throat, and general loss of energy. In severe cases, where radiation exposure has been relatively large, death may occur within two to four weeks. Those who survive 6 weeks after the receipt of a single large dose of radiation generally may be expected to recover.

Radiation Source
Usually a manmade sealed source of radiation used in teletherapy (a form of radiation therapy), radiography, as a power source for batteries, or in various types of instruments and industrial gauges. Machines such as accelerators and natural radionuclides may be considered sources.

Radiation Source Housing
The material surrounding the x-ray tube that restricts physical proximity and radiation released from the radiation producing machine.

Radiation Standards
Exposure standards, permissible concentrations, rules for safe handling, regulations for transportation, regulations for industrial control of radiation, and control of radioactive material by legislative means.

Radiation Warning Symbol
An officially prescribed symbol (a magenta or black trefoil) on a yellow background that must be displayed where certain quantities of radioactive materials are present or where certain doses of radiation could be received.

Exhibiting radioactivity or pertaining to radioactivity.

Radioactive Materials
Any solid, liquid, or gas which emits radiation spontaneously. Sometimes abbreviated as RAM.

Radioactive Materials Inventory
A list of radionuclides in a laboratory. The inventory includes the date of receipt, an unique identification number, the radionuclide, and the activity. Reminder - try to keep this list updated at all times. Health Physics updates each laboratory's inventory on a quarterly basis.

Radioactive Waste Pick-Up Request
A form used to request a radioactive waste pick-up. It summarizes for each container, the container type(s), volume, radionuclide(s), total activity, constituents, pH, and location. This form is used to properly manifest the waste for transportation and to ensure appropriate replacement containers are issued.

Radioactive Waste
Unwanted radioactive material or items that are contaminated with radioactive material.

The spontaneous emission of radiation, generally alpha or beta particles, often accompanied by gamma rays, from the nucleus of an unstable atom. See also Activity and Decay, Radioactive.

The making of a shadow image on photographic film by the action of ionizing radiation.

An unstable form of an element that decays or disintegrates spontaneously, emitting radiation. Approximately 5000 natural and artificial radioisotopes have been identified. See also radionuclide.

The branch of medicine dealing with the diagnostic and therapeutic application of radiant energy, including X-rays and radioisotopes.

An unstable form of an element that decays or disintegrates spontaneously, emitting radiation. Approximately 5000 natural and artificial radioisotopes have been identified. See also radioisotope.

The relative susceptibility of cells, tissues, organs, organisms, or other substances to the injurious action of radiation.

Reference Man
A hypothetical individual whose characteristics are often used to estimate radiation dose. Reference Man is assumed to be 20-30 years of age, 170 cm in height, weighing 70 Kg; and living in a moderate climate. Reference Man is a Caucasian and is Western European or North American in habitat and custom.

Relative Risk
The ratio of risk from radiation in an irradiated population to the risk in a comparable non-irradiated population.

The special unit of dose equivalent. The dose equivalent equals the absorbed dose multiplied by the quality factor.

Restricted Materials
Items that should be segregated from each other and include (Waste) sharps, lead pigs, liquids, solids, scintillation vials,

Ring Badge
See Extremity Dosimeter.

An unit of exposure to ionizing radiation. It is the amount of gamma or X-rays required to produce ions resulting in a charge of 0.00258 coulombs/kilogram of air under standard conditions. Named after Wilhelm Roentgen, German scientist who discovered X-rays in 1895.


Safety Devices
When used in conjunction with x-ray devices, these may be interlocks, physical barriers, or other engineering controls.

Scattered Radiation
Radiation that, during its passage through a substance, has been changed in direction. It may also have been modified by a decrease in energy. It is one form of secondary radiation.

Sealed Source
Radioactive material that is permanently bonded or fixed in a capsule or matrix designed to prevent release and dispersal of the radioactive material under the most severe conditions which are likely to be encountered in normal use and handling.

Sealed Source Inventory
A list of sealed sources in a laboratory. The inventory includes the date of receipt, an unique identification number, the radionuclide, and the activity.

Sealed Source Sign-out Log
A record of source use including the date when it is removed from storage, the date it is returned to storage, and the location in which it is being used. Generally found on or near the storage location.

Secondary Radiation
Radiation originating as the result of absorption of other radiation in matter. It may be either electromagnetic or particulate in nature.

Any material or obstruction that absorbs radiation and thus tends to protect personnel or materials from the effects of ionizing radiation.

An automatic closure device on x-ray machines that cannot be opened unless a collimator or coupling has been connected to the port. Sievert (Sv) The System International (SD unit of dose equivalent equal to 1 Joule per Kilogram. 1 Sv = 100 rem.

An unintentional release or spread of radioactive materials.

Standing Purchase Order
A form/system used to request multiple purchases from the same supplier. Normally available in each department, these forms are approved by Health Physics for purchasing radioactive materials and radiation producing machines for a period of one year. They are established through the office of Buying and Contracting.

Storage Cabinet
A cabinet used to hold radioactive materials not in use in a laboratory. Generally used for sealed sources of radioactive material.

Storage Freezer
A freezer used to hold radioactive materials not in use in a laboratory. Generally used for unsealed radioactive sources.

Storage Refrigerator
A refrigerator used to hold radioactive materials not in use in a laboratory. Generally used for unsealed radioactive sources.

Support Staff
University of Colorado staff members, AHEC personnel, and others involved in service functions relation to administration of laboratories using radioactive materials. Custodians and facilities management trades people are examples of support staff.

A study to find the radiation or contamination level of specific objects or locations within an area of interest, or to locate regions of higher-than-average intensity, i.e., hot spots.

Survey Meter
Any portable radiation detection instrument especially adapted for inspecting an area to establish the existence and amount of radioactive material present


Terrestrial Radiation
The portion of natural radiation (background) that is emitted by naturally occurring radioactive materials in the earth.

Thermoluminescent Dosimeter (TLD)
A device used to measure radiation by measuring the amount of visible light emitted from a crystal in the detector when exposed to radiation. See also Extremity Dosimeter.

Thin-end Window
A small cylinder-like probe used to detect high energy beta and Probe gamma radiation. See also Geiger-Mueller Counter.

A radioactive isotope of hydrogen (3H, one proton, two neutrons). Because it is chemically identical to natural hydrogen, tritium can easily be taken into the body by any ingestion path. It decays by beta emission. It has a radioactive half-life of about 12.5 years.


Electromagnetic radiation of wavelength between the shortest visible violet and low energy X-rays.

Unstable Isotope
A radioisotope. Unsealed Radioactive materials which do not meet the definition of sealed Radionuclide sources. Generally, these are in liquid form in laboratories.

Uranium (U)
A radioactive element with the atomic number 92 and as found in natural ores, an atomic weight of approximately 238. The two principle natural isotopes are U-235 (0.7% of natural Uranium) and U-238 (99.3% of natural Uranium). See also Natural Uranium.

An analysis and evaluation of urine used to determine kinds, quantities or concentrations, and in some cases, the locations of radioactive material in the human body. A form of bioassay used for individuals working with large amounts of tritium.


Very High Radiation Area
An area in which radiation levels exceed 500 rads in one hour at 1 meter from the source or from any surface that the radiation penetrates.


Warning Device(s)
Lights, sounds, signs, or barriers which indicate an existing hazard.

Waste, Radioactive
Solid, liquid, and gaseous materials from nuclear operations that are radioactive or become radioactive and for which there is no further use. Wastes are generally classified as high level (having radioactivity concentrations of hundreds of thousands of curies per gallon or foot), low level (in the range of 1 microcurie per gallon or foot), or intermediate level (between these extremes).

Waste Container
For the purposes of this handbook, containers used to hold waste items. These are color coded for half-life categories and are specific to the type of waste generated. See also Container Contents Sheet and Radioactive Waste Pick-up Request Form.

For the purposes of external dose, head, trunk including male gonads, arms above the elbow, or legs above the knee.

Whole-Body Counter
A device used to identify and measure the radioactive material in the body (body burden) of human beings and animals. It uses heavy shielding to keep out background radiation and ultrasensitive radiation detectors and electronic counting equipment.

Whole-Body Dosimeter
An instrument used to measure and register the accumulated dose received by the whole body. See also Dosimeter and Extremity Dosimeter.

Whole-Body Exposure
An exposure of the body to radiation, in which the entire body, rather than an isolated part, is irradiated. Where a radioisotope is uniformly distributed throughout the body tissues, rather than being concentrated in certain parts, the irradiation can be considered as whole-body exposure.

Wipe Sample
A sample made to determine the presence of removable (a.k.a. Wipe Smear, radioactive contamination on a surface. It is done by wiping, with Swipe, etc.) slight pressure, a piece of soft filter paper over a representative type of surface area.


Penetrating electromagnetic radiation (photon) having a wavelength that is much shorter than that of visible light. These rays are usually produced by excitation of the electron field around certain nuclei. In nuclear reactions, it is customary to refer to photons originating in the nucleus as gamma rays, and to those originating in the electron field of the atom as X-rays. These rays are sometimes called roentgen rays after their discoverer, W.K. Roentgen. See also Analytical X-ray and Medical X-ray.



Table of Contents

X-ray Machines Appendices