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99Tc is a radioisotope with a half-life of 211,000 years releasing beta particles as it decays. 
Technetium-99 is a man-made radioisotope that is a by-product of the fissioning of nuclear fuel rods and was introduced to the PGDP enrichment process through spent nuclear fuel rods from the U.S. Department of Energy (DOE) Savannah River nuclear facility.  Processing of recycled uranium from nuclear reactors was conducted during 1953-1964 and 1969-1976.  During these recycling periods, PGDP received 100,000 tons of recycled uranium containing an estimated 661,000 grams of 99Tc.  
For more information, see

Air stripping

The process of bubbling air through water to remove volatile organic compounds from the water.


Administrative Order on Consent
A consent order is governed by federal and state laws and issued by administrative agencies.  An AOC is a voluntary agreement worked out between two or more parties to a dispute.  An AOC carries the same weight as a court order.
Administrative Orders on Consent (AOCs) and other administrative agreements issued by EPA, which are consensual, negotiated agreements pursuant to sections 104, 106(a), 107, and 122 of CERCLA, that obligate parties to perform response activity (e.g., removal, remedial investigation, feasibility study, remedial design) and/or reimburse EPA for costs incurred under Superfund.
For a list of the EPA's AOCs in Region 4, visit


Alternate Concentration Limits
Default concentration levels are established through conservative scientific assumptions but Facility owners/operators may apply for ACLs if they can prove that the ACLs will not pose a substantial present or potential hazard to human health or the environment.
For more information, download the EPA's Alternate Concentration Limits/Groundwater Cleanup Levels guide.


Atomic Energy Commission
Established after World War II by Congress to foster and control the peace time development of atomic science and technology.  The agency was abolished by the Energy Reorganization Act of 1974, which assigned its functions to two new agencies: the Energy Research and Development Administration and the Nuclear Regulatory Commission.


Agreement in Principle
An agreement which clarifies the major terms of an agreement, laying out the groundwork to make a contract.

Alpha particle

A positively charged particle emitted from the nucleus of an atom having the same charge and mass as that of a helium nucleus (two protons and two neutrons).


A geologic formation, group of formations, or part of a formation capable of yielding a significant amount of groundwater to wells or springs.


A geologic unit that inhibits the flow of water.


To take up or absorb.


Smallest particle of an element capable of entering into a chemical reaction.

Beta particle

A negatively charged particle emitted from the nucleus of an atom. It has a mass and charge equal to those of an electron.



Paducah Citizens Advisory Board


Kentucky Cabinet for Human Resources


Kentucky Cabinet for Health Services


Comprehensive Environmental Response, Compensation, and Liability Act,
commonly known as Superfund, was enacted by Congress on December 11, 1980.  This law created a tax on the chemical and petroleum industries and provided broad Federal authority to respond directly to releases or threatened releases of hazardous substances that may endanger public health or the environment.
CERCLA was amended by the Superfund Amendments and Reauthorization Act (SARA) on October 17, 1986.

CERCLA-reportable release

A release to the environment that exceeds reportable quantities as defined by the Comprehensive Environmental Response, Compensation, and Liability Act.

Chain-of-custody form

A form that documents sample collection, transport, analysis, and disposal.


Formal shutdown of a hazardous waste management facility under Resource Conservation and Recovery Act requirements.


Fulfillment of applicable requirements of a plan or schedule ordered or approved by government authority.


The amount of a substance contained in a unit volume or mass of a sample.


A measure of a material’s capacity to convey an electric current. For water, this property is related to the total concentration of the ionized substances in water and the temperature at which the measurement is made.


The point at which two or more streams meet; the point where a tributary joins the main stream.

Contained landfill

A solid waste site or facility that accepts disposal of solid waste. The technical requirements for contained landfills are found in 401 KAR 47:080, 48:050, and 48:070 to 48:090.


Deposition of unwanted material on the surfaces of structures, areas, objects, or personnel.


A unit of radioactivity, measures the amount of radioactivity of a material and describes the rate at which a radioactive substance is decaying through alpha, beta, and/or gama radiation.  One curie is defined as 3.7 x 1010 (37 billion) disintegrations per second. Several fractions and multiples of the curie are used commonly:

  • • kilocurie (kCi)—103 Ci, one thousand curies; 3.7 x 1013 disintegrations per second.
  • • millicurie (mCi)—10-3 Ci, one-thousandth of a curie; 3.7 x 107 disintegrations per second.
  • • microcurie (μCi)—10-6 Ci, one-millionth of a curie; 3.7 x 104 disintegrations per second.
  • • picocurie (pCi)—10-12 Ci, one-trillionth of a curie; 3.7 x 10-2 disintegrations per second.



The process when a gas transforms into solid. Also know as deposition. The reverse of deposition is sublimation.

D & D

Decontamination and Decommissioning


nuclear disintegration
A spontaneous nuclear transformation (radioactivity) characterized by the emission of energy and/or mass from the nucleus of an atom.


Department of Energy (DOE) Material Storage Areas
Areas established for storage of unused material and equipment at indoor and outdoor onsite locations.


U.S. Department of Defense


U.S. Department of Energy


Depleted Uranium Hexafluoride


Drinking Water Standards
Federal primary drinking water standards, both proposed and final, as set forth by the EPA in 40 CFR § 141 and 40 CFR § 143.



A liquid or gaseous waste discharge to the environment.

Effluent monitoring

The collection and analysis of samples or measurements of liquid and gaseous effluents for purposes of characterizing and quantifying the release of contaminants, assessing radiation exposures to members of the public, and demonstrating compliance with applicable standards.


Uranium Enrichment is the process used to increase in the percentage of the fissile isotope U-235.


U.S. Environmental Protection Agency



The population of animals in a given area, environment, formation, or time span.


Federal Facilities Agreement
When a site is listed on the NPL and becomes a Superfund site, federal law requires that responsible state and federal agencies enter into a
Federal Facilities Agreement (FFA). The FFA outlines the roles and responsibilities of the responsible agencies for the investigation and implementation of corrective measures at the facility and integrates state and federal cleanup requirements into an effective and comprehensive process.


Federal Facilities Oversight Unit


The population of plants in a given area, environment, formation, or time span.


A mappable unit of consolidated or unconsolidated geologic material of a characteristic lithology or assemblage of lithologies.


Gamma ray

High-energy, short-wavelength electromagnetic radiation emitted from the nucleus of an excited atom. Gamma rays are identical to X-rays except for the source of the emission.

Grab sample

A sample collected instantaneously with a glass or plastic bottle placed below the water surface to collect surface-water samples (also called dip samples).


unconfined groundwater
Water that is in direct contact with the atmosphere through open spaces in permeable material.



radiological half-life
The time required for half of a given number of atoms of a specific radionuclide to decay.  Each nuclide has a unique half-life.


Highly Enriched Uranium
Enriched uranium containing at least 90% U-235; used in bomb manufacture, research and naval reactors.

High-level waste

High-level radioactive waste or HLW means:

  • (1) Irradiated reactor fuel,
  • (2) liquid wastes resulting from the operation of the first cycle solvent extraction system, or equivalent, and the concentrated wastes from subsequent extraction cycles, or equivalent, in a facility for reprocessing irradiated reactor fuel
  • (3) solids into which such liquid wastes have been converted.


Hydraulic aspects of site geology.


The science dealing with the properties, distribution, and circulation of natural water systems.


In situ

In its original place; field measurements taken without removing the sample from its origin; remediation performed while groundwater remains below the surface.


An atom or compound that carries an electrical charge. irradiation—Exposure to radiation.


Forms of an element having the same number of protons but differing numbers of neutrons in the nuclei.

  • long-lived isotope
    A radionuclide that decays at such a slow rate that a quantity of it will exist for an extended period (half-life is greater than three years).
  • short-lived isotope
    A radionuclide that decays so rapidly that a given quantity is transformed almost completely into decay products within a short period (half-life is two days or less).



Kentucky Department of Fish and Wildlife Resources


Kentucky Division of Waste Management


Kentucky Research Consortium for Energy & the Environment


Kentucky Water Resources Research Institute


LATA Environmental Services of Kentucky, LLC
The PGDP primary cleanup contractor for the DOE.


Low Enriched Uranium
The proportion of U-235 in reactor fuel is 3 to 5 percent; used as reactor fuel.



Maxey Flats Nuclear Disposal Site

Minimum detectable concentration

The smallest amount or concentration of a radionuclide that can be distinguished in a sample by a given measurement system at a preselected counting time and at a given confidence level.


Memorandum of Agreement


Process whereby the quantity and quality of factors that can affect the environment or human health are measured periodically to regulate and control potential impacts.


A measure of X-ray or gamma radiation. The unit is one-thousandth of a roentgen.


The dose equivalent that is one-thousandth of a rem.

Natural radiation

Radiation from cosmic and other naturally occurring radionuclide (such as radon) sources in the environment.


An atom specified by its atomic weight, atomic number, and energy state. A radionuclide is a radioactive nuclide.


NPL National Priorities List,
list of the known releases or threatened releases of hazardous substances, pollutants, or contaminants throughout the United States and its territories. The NPL is intended primarily to guide the EPA in determining which sites warrant further investigation.  The NPL is part of the Superfund program, a U.S. environmental policy established by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and regulated by the Resource Conservation and Recovery Act (RCRA).
See for current list status.


Natural Resources & Environmental Protection Cabinet



The point of conveyance (e.g., drain or pipe) of wastewater or other effluents into a ditch, pond, or river.


Polychlorinated biphenyl
Any chemical substance that is limited to the biphenyl molecule and that has been chlorinated to varying degrees.


Programmatic Environmental Impact Statement
A document that describes the impacts on the environment as a result of a proposed action. It also describes impacts of alternatives, as well as plans to mitigate the impacts. And it evaluates the environmental impacts of broad agency actions, such as the development of programs or the setting of national policies.


Paducah Gaseous Diffusion Plant
A uranium enrichment plant located in Western Kentucky which uses the gaseous diffusion process; uranium hexafluoride is heated to a gas and passed repeatedly through porous barriers to separate U235 and U238 isotopes.


Quality factor

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


Radiation Absorbed Dose
The rad is a basic unit of absorbed radiation dose. (This is being replaced by the "gray," which is equivalent to 100 rad.)


The spontaneous emission of radiation, generally alpha or beta particles or gamma rays, from the nucleus of an unstable isotope.


Radioactive isotopes.


An unstable nuclide capable of spontaneous transformation into other nuclides by changing its nuclear configuration or energy level. This transformation is accompanied by the emission of photons or particles.


Radiation Control Branch
Cabinet for Health and Family Services Radiation Control Branch, now the Radiation Health Branch


Resource Conservation Recovery Act
RCRA gives EPA the authority to control hazardous waste from the "cradle-to-grave."  This includes the generation, transportation, treatment, storage, and disposal of hazardous waste.  RCRA also set forth a framework for the management of non-hazardous solid wastes.  The 1986 amendments to RCRA enabled EPA to address environmental problems that could result from underground tanks storing petroleum and other hazardous substances.


Record of Decision
The Record of Decision (ROD) is a public document that explains which cleanup alternatives will be used to clean up a Superfund site.
Search for RODs in EPA's Record of Decision System
  A ROD contains:

  • • site history
  • • site description
  • • site characteristics
  • • community participation
  • • enforcement activities
  • • past and present activities
  • • contaminated media
  • • the contaminants present
  • • scope and role of response action
  • • the remedy selected for cleanup


Any discharge to the environment. Environment is broadly defined as any water, land, or ambient air.


The unit of dose equivalent (absorbed dose in Rads multiplied by the radiation Quality Factor).  Dose equivalent is frequently reported in units of milliRem(mRem).

  • mRem    milliRem
    The dose equivalent that is one-thousandth of a Rem.


The environmental cleanup and restoration of a contaminated site.

RFI Program

RCRA Facility Investigation Program
EPA-regulated investigation of a solid waste management unit with regard to its potential impact on the environment.


A unit of exposure from X-rays or gamma rays. One roentgen equals 2.58 x 104 coulombs per kilogram of air.

  • mR    milliRoentgen
    A measure of X-ray or gamma radiation. The unit is one-thousandth of a roentgen.



The SI (International System of Units) unit of dose equivalent; 1 Sv = 100 Rem.


A suspension of solid particles (sludge) in water.


A point or object from which radiation or contamination emanates.

Specific conductance

The ability of water to conduct electricity; this ability varies in proportion to the amount of ionized minerals in the water.


Not radioactive or not easily decomposed or otherwise modified chemically.


Beds, layers, or zones of rocks.


The substance, base, surface, or medium in which an organism lives and grows.

Surface water

All water on the surface of the earth, as distinguished from groundwater.

Suspended solids

Mixture of fine, non-settling particles of any solid within a liquid or gas.



A solvent used to remove grease from metal parts, but it is also an ingredient in adhesives, paint removers, typewriter correction fluids, and spot removers. Drinking or breathing high levels of trichloroethylene may cause nervous system effects, liver and lung damage, abnormal heartbeat, coma, and possibly death.
For more information download the Center for Disease Control, Agency for Toxic Substances and Disease Registry Factsheet about TCE. 
The DOE has banned the use of TCE at the Paducah plant in 1993.

Terrestrial radiation

Ionizing radiation emitted from radioactive materials, primarily 40K, thorium, and uranium, in the earth’s soils. Terrestrial radiation contributes to natural background radiation.


Thermoluminescent dosimeter
A device used to measure external gamma radiation.


Total Maximum Daily Load

Total activity

The total quantity of radioactive decay particles that are emitted from a sample.

Total solids

The sum of total dissolved solids and suspended solids.

Total suspended particulates

Refers to the concentration of particulates in suspension in the air irrespective of the nature, source, or size of the particulates.


Transuranic element
An element above uranium in the Periodic Table, that is, with an atomic number greater than 92. All 11 TRUs are produced artificially and are radioactive. They are neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium.

Troughing system

A collection and containment system designed to collect leaks of oil that have been contaminated with PCBs.


A measure of the concentration of sediment or suspended particles in solution.



Uranium Hexafluoride


In the direction of increasing hydrostatic head.


United States Enrichment Corporation, Inc.
Established by Congress through the Energy Policy Act of 1992, USESC was originally formed as a government corporation to manage PGDP operations.  USEC became a publically traded company and continued as a DOE contractor.  The USEC took over all operations in 1999.

Vadose zone

Soil zone located above the water table.


Volatile organic compound
Any organic compound that has a low boiling point and readily volatilizes into air (e.g., trichloroethane, tetrachloroethene, and trichloroethene). VOCs include a variety of chemicals and concentrations, the adverse health effects vary.



The region draining into a river, river system, or body of water.


A lowland area, such as a marsh or swamp, inundated or saturated by surface or groundwater sufficiently to support hydrophytic vegetation typically adapted to life in saturated soils.


Western Kentucky Wildlife Management Area
Area surrounding the PGDP leased and managed by the Kentucky Department of Fish Á Wildlife Resources (KDFWR) for recreational purposes.
For additional information download a KDFWR map of the area.