Weapons of Mass Destruction (WMD)

Activity

The number of nuclear transformations occurring in a given quantity of material per unit time. See Curie; Radioactivity.

Administrative limit

A limit imposed administratively on the quantity of a radionuclide permitted in a building or part of a building.

AIRDOS

A computer code endorsed by the EPA for predicting radiological doses to members of the public due to airborne releases of radioactive material. It accounts for inhalation, external exposure to direct radiation, and food ingestion pathways.

Alpha, alpha particle

A heavy particle consisting of two neutrons and two protons and thus having a charge of +2; the nucleus of a helium-4 atom.

Americium

An artificial radioactive element of atomic number 95. Am-241 is produced by the beta decay of Pu-241.

Atmospheric dispersion, dilution

The greater the spread downwind of airborne material, the greater the spread and the smaller the concentration along the hotline.

Atmospheric stability

The tendency of the atmosphere to slow the rise of a contaminant plume; the more stable the atmosphere, the smaller the cloud rise and the greater the concentration of the contaminant along the hotline.

Background radiation

Radiation arising from radioactive material other than that directly under consideration. Background radiation due to cosmic rays and natural radioactivity is always present. There may also be external background radiation from the presence of radioactive substances in building material itself and internal radiation from natural radioactive substances such as potassium-40 in the body.

Best estimate

An estimate made with the numerical inputs that are believed to be representative of the real situation, not biased conservatively.

Beta particle

Charged particle emitted from the nucleus of an atom, with a mass and charge equal in magnitude to that of the electron.

Bounding

An accident is bounding if no reasonably foreseeable, equally probable accident can be found with greater consequences. A bounding envelope consists of a set of individual bounding accidents that cover the range of probabilities and possible consequences.

Carcinogen

A substance that directly or indirectly causes cancer.

CHARM™

A Gaussian puff model for atmospheric dispersion of gases.

Collective (effective) dose equivalent

The sum of the doses to all exposed groups of people times the number of individuals receiving each dose. For example, if 20 persons receive a dose of 5 rem, 10 a dose of 10 rem, and 5 a dose of 20 rem, the collective dose is (20 x 5) + (10 x 10) + (5 x 20) = 100 + 100 + 100 = 300 person-rem.

Committed dose

The time integral of the dose equivalent rate for a specified time period.

Committed Effective Dose Equivalent (CEDE)

"The sum of the committed dose equivalents to various tissues in the body, each multiplied by its weighting factor. It does not include contributions from external dose. Committed dose equivalent is expressed in units of rem (or sievert)" (DOE Order 5480.11, section 8e(8).

Conservative

Having consequences that are greater than the most likely consequences; using assumptions that tend to overestimate consequences, that err on the safe side.

Criticality

The state of a mass of fissionable material when it is sustaining a chain reaction.

Curie (Ci)

A special unit of activity. One curie equals 37 billion nuclear transformations per second.

Default parameters

Inputs to a computer code that are supplied by the code if the operator fails to supply them.

Depletion of the plume

Removal of contaminants from the plume by rain or deposition on the ground.

Design basis accident

A postulated abnormal event that is used to establish the performance requirements of structures, systems, and components necessary to maintain a safe shutdown condition indefinitely, so that the general public and operating staff are not exposed to hazards in excess of appropriate guidelines.

Deterministic

With results determined by input assumptions and data, but without the probability of occurrence.

Dose

A general term denoting the quantity of radiation or energy absorbed. For special purposes, it must be appropriately qualified.

Dose equivalent

"The product of absorbed dose in rads (or gray) in tissue, a quality factor, and other modifying factors. Dose equivalent is expressed in units of rem (or sievert)" (DOE Order 5480.11, section 83(2)). The relative biological effectiveness of different kinds of radiation is expressed in the quality factor. (Note: The International Commission on Radiological Protection (ICRP) now uses the term radiation weighting factor to replace the term quality factor.)

Effective Dose Equivalent (EDE)

The dose equivalent from irradiation of an organ or part of the whole body that bears the same risk of cancer as uniform irradiation of the whole body. "The sum over specified tissues of the products of the dose equivalent in a tissue and the weighting factor for that tissue. The effective dose equivalent is expressed in units of rem (or sievert)" (DOE Order 5480.11, section 8e(5)). (Note: The International Commission on Radiological Protection (ICRP) decided in ICRP Publication 60 to use the term effective dose to replace the term effective dose equivalent.)

Enriched uranium

Uranium enriched in the fissile nuclide U-235.

Explosives

See High explosives.

Exponential notation

A means of expressing large or small numbers in powers of ten. For instance, 4.3 × 106 = 4,300,000 and 4.3 × 10-5 = 0.000043. This relationship is also sometimes expressed in the form 4.3E+6 = 4,300,000 and 4.3E-5 = 0.000043.

Exposure assessment

The determination of the magnitude, frequency, duration, and route of exposure.

Fission

The splitting of a heavy atomic nucleus into two nuclei of lighter elements, accompanied by the release of energy and generally one or more neutrons. Fission can occur spontaneously or be induced by neutron bombardment.

Fuel-grade plutonium

Plutonium-239 with enough admixture of other plutonium isotopes (such as plutonium-240) that it cannot be used in weapons although it can be used in reactors.

g notation

Accelerations measured relative to the acceleration of gravity at the earth's surface. Thus, 0.1g = 3.2 ft/sec2 or 98.3 cm/sec2.

Gamma spectroscopy

Analysis of the radionuclides in a sample by measurement of the intensities of the various gammas given off.

Gaussian plume

A plume of contaminants is said to be Gaussian when the contaminant concentrations are greatest at the center line and decrease to either side as exp[-(x/s)2/2], where x is the distance from the center line and s is the distance to the point where the concentration is down to 37 percent of the centerline concentration. See Standard deviation.

Glovebox

A sealed box in which workers, while remaining outside and using gloves attached to and passing through openings in the box, can safely handle and work with radioactive materials, other hazardous materials, and nonhazardous air-sensitive compounds.

Hazardous waste

Any solid, semisolid, liquid, or gaseous waste that is ignitable, corrosive, toxic, or reactive as defined by RCRA and identified or listed in 40 C.F.R. part 261.

HEPA filter (High Efficiency Particulate Air)

Filter material that captures entrained particles from an air stream, usually with efficiencies in the range of 99.95 percent and above for particle sizes of 0.3 micron. Filter material is usually a paper or fiber sheet that is pleated to increase its surface area.

High explosives

Chemically energetic materials with the potential to react explosively; nuclear explosives are not included.

Immediately-Dangerous-to-Life-or-Health (IDLH)

Immediately dangerous to life or health concentrations (IDLHs) represent the maximum concentration from which, in the event of respirator failure, one could escape within 30 minutes without a respirator and without experiencing any escape-impairing (e.g., severe eye irritation) or irreversible health effects.

Internal exposure

Radiation exposure from sources inside the body: from materials ingested, inhaled, or (in the case of tritium) absorbed through the skin.

Low specific activity

"'Low Specific Activity material (LSA)' means any of the following":

"(1) Uranium or thorium ores and physical or chemical concentrates of those ores.

"(2) Unirradiated natural or depleted uranium or unirradiated natural thorium.

"(3) Tritium oxide in aqueous solutions provided the concentration does not exceed 5.0 millicuries per milliliter.

"(4) Material in which the radioactivity is essentially uniformly distributed and in which the estimated average concentration of contents does not exceed:

"(i) 0.0001 millicurie per gram of radionuclides for which the A2 quantity* is not more than .05 curie;

"(ii) 0.005 millicurie per gram of radionuclides for which the A2 quantity* is more than .05 curie, but not more than 1 curie; or

"(iii) 0.3 millicurie per gram of radionuclides for which the A2 quantity* is more than 1 curie.

"(5) Objects of nonradioactive materials externally contaminated with radioactive material, provided that the radioactive material is not readily dispersible and the surface contamination, when averaged over an area of 1 square meter, does not exceed 0.0001 millicurie (220,000 disintegrations per minute) per square centimeter of radionuclides for which the A2 quantity* is not more than .05 curie, or 0.001 millicurie (2,200,000 disintegrations per minute) per square centimeter for other radionuclides" (49 C.F.R. section 173.403(n)).

* "'A2 quantities' are the maximum activities of radioactive material permitted in the package being transported. These quantities are listed in 49 C.F.R. 173.435; they depend on the isotopes included."

Maximum credible accident

An accident that has the greatest offsite consequence from hazardous material release and that has a frequency of occurrence greater than 10-6 per year, when credit for mitigation is allowed. Such an accident is one of the set of reasonably foreseeable accidents.

Misfire

Failure of an explosive to detonate (completely) when the firing signal is given. Also called a hang-fire.

Mixed fission products

The ensemble of fission products resulting from the fission of a heavy element such as uranium. See Fission.

Mixed waste

Radioactive waste also containing RCRA-designated hazardous constituents.

mrem, millirem

1/1000 rem.

Natural uranium

Uranium as it occurs in nature. The natural substance is 99.28 percent uranium-238, 0.72 percent uranium-235, and 0.0055 percent uranium-234. Only the uranium-235 isotope is fissionable by slow neutrons.

Overpressure

In a blast wave, the pressure above ambient. The pressure in the wave rises sharply to the peak overpressure, then falls more slowly to and below ambient.

Packaging

In the NRC regulations governing the transportation of radioactive materials (10 C.F.R. part 71), the term "packaging" is used to mean the shipping container together with its radioactive contents.

Permissible Exposure

Limit (PEL)

Occupational exposure limits enforced by OSHA. May be for short term or 8-hour duration exposure.

Person-rem

A unit of collective dose.

Plutonium

An artificial, fissile metal of atomic number 94.

Plutonium-239-equivalent activity

A radioactive hazard index factor that relates the radiotoxicity of transuranic nuclides to that of plutonium-239.

Population exposure

The collective radiation dose received by a population group. See Collective dose equivalent.

Probabilistic

With results taking into account the probability of occurrence. Probabilistic calculations sometimes combine the results of several deterministic calculations, weighting their results by their probabilities. See Deterministic.

Prompt radiation

Gamma or neutron radiation emitted during the fission process is said to be prompt (within microseconds) or delayed (as much as seconds).

Protective (Preventive)

Action Guide

FDA-recommended levels of radiation exposure above which actions should be taken to prevent or reduce the radioactive contamination of human food or animal feeds.

Radiation source

In context, a small sealed source of ionizing radiation. Sealed sources are generally used to supply a material that has a known radiation intensity or a specific type of radiation and are not easily dispersed or altered chemically under normal use.

Radioactive material

Any material having a specific activity greater than 0.002 microcuries per gram, as defined by 49 C.F.R. part 173.4-3(y).

Radioactive waste

Material that contains radionuclides regulated under the Atomic Energy Act of 1954, as amended, and is of negligible economic value given the cost of recovery.

Radioactivity

The properties that certain nuclides have of spontaneously emitting particles, gamma radiation, or x radiation.

RADTRAN

An NRC-approved code for estimating the radiological impacts of transportation of radioactive materials.

Reasonably foreseeable

An accident whose impacts "have catastrophic accident consequences, even if their probability of occurrence is low, provided that the analysis of the impacts is supported by credible scientific evidence, is not based on pure conjecture, and is within the rule of reason" (10 C.F.R. part 1502.22(b)(4)).

Release fraction

The fraction of the amount of a substance present that is released in an accident.

Rem

The special unit of dose equivalent that expresses the effective dose calculated for all radiation on a common scale. It is the absorbed dose in rads multiplied by certain modifying factors (e.g., the quality factor). The equivalent SI unit is the sievert, abbreviated Sv; 1 Sv = 100 rem.

Resuspension

The process by which material deposited on the ground is again made airborne, such as by wind or vehicle disturbance.

Satellite waste accumulation area

The initial point of waste accumulation at waste-generating facilities. Waste is held here for later transfer to the waste management organization.

Scenario

A particular chain of hypothetical circumstances that could, in principle, release radioactivity or hazardous chemicals from a storage and handling site, or during a transportation accident.

Sealed source

In context, a small source of ionizing radiation. Sealed sources are generally used to supply a material that has a known radiation intensity or a specific type of radiation and are not easily dispersed or altered chemically under normal use.

Source term

In a calculation of contaminant dispersion, the amount of that contaminant assumed available to be dispersed.

Standard deviation

A description used in statistical theory for the average variation of a random quantity. The root-mean-square deviation from an average value.

Threshold Limit Values/Time-Weighted Average (TLV/TWA)

Guidelines or recommendations that refer to airborne concentrations of potentially hazardous substances. A time weighted average TLV is an average for a normal 8-hour workday or 40-hour workweek, to which all workers may be repeatedly exposed, day after day, without adverse effect.

Transuranic (TRU) waste

Waste containing 100 nCi/g or more of alpha-emitting isotopes of elements above uranium in the periodic table with half-lives of over 20 years.

Tritiated water

Water in which one of the hydrogen atoms has been replaced by a tritium atom; sometimes shown as HTO.

Tritium

A radioactive isotope of the element hydrogen, with two neutrons and one proton in its nucleus. Common symbols for the isotope are H3 and T.

TRU

See Transuranic waste.

TRUPACT-II

The package designed to transport contact-handled transuranic waste to the WIPP site. (TRUPACT = Transuranic Package Transporter)

Type A packaging

"A packaging designed to retain the integrity of containment and shielding . . . under normal conditions of transport as demonstrated by" a water spray test, a free-drop test, a compression test, and a penetration test (40 C.F.R. parts 173.403(gg), 173.465).

Type B packaging

An NRC-certified container that must be used for the transport of transuranic waste containing more than 20 curies of plutonium per package. Type B packaging must be able to withstand both normal and accident conditions without releasing its radioactive contents. These containers are tested under severe, hypothetical-accident conditions that demonstrate resistance to impact, puncture, fire, and submersion in water (49 C.F.R. part 173).

Uranium

See Natural uranium.

Waste Isolation Pilot

Plant (WIPP)

A facility in southeastern New Mexico being developed as the disposal site for transuranic and transuranic mixed waste, not yet approved for operation.

Work station waste management unit

See Satellite waste accumulation area.