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ABACC
Brazilian-Argentine Agency for Accounting and Control of Nuclear Materials.

Acid rain
Rain (or snow) that contains an abnormal amount of acid resulting from high atmospheric concentrations of carbon, sulfur, or nitrogen oxides. Acid rain is often attributed to burning of fossil fuels.

Actinide
Element with atomic number of 90 through 103; includes uranium and plutonium.

Activation analysis
Form of scientific investigation where the chemical makeup of different materials is figured out by bombarding them with neutrons or other types of radiation. This produces radioactive atoms that give off specific types of radiation, and this radiation reveals what types of elements (qualitative) and what quantity are in the samples.

AESJ
Atomic Energy Society of Japan.

ALARA
(As Low As Reasonably Achievable) is a safety principle designed to minimize radiation doses and releases of radioactive materials. More than merely best practice, ALARA is predicated on legal dose limits for regulatory compliance, and is a requirement for all radiation safety programs.

Alpha particle
Positively charged particle emitted in radioactive decay of unstable atoms. An alpha is made up of two neutrons and two protons (a helium atom nucleus) and is thus heavier and slower moving than other decay emissions. Alpha particles can be stopped quite easily. They cannot penetrate a piece of paper or the dead outer layer of our skin.

ANS
American Nuclear Society.

Atom
Basic component of matter. An atom is the smallest part of an element having all the chemical properties of that element. An atom consists of a nucleus (that contains protons and neutrons) and surrounding electrons.

Atoms for peace
An initiative signed by President Eisenhower in 1954 to allow the peaceful uses of atomic energy to be available to other nations.

Background radiation
Radiation arising from natural sources always present in the environment, including solar and cosmic radiation from outer space and naturally radioactive elements in the atmosphere, the ground, building materials, and the human body.

Backup safety system
Safety system that will go into operation if the first-line safety system fails.

Baffles
Tiles inside the cooling tower of a nuclear power plant that slow the rate of water flow and provide area for cooling.

Becquerel (Bq)
Measure of the rate of decay of a radioactive substance. One Bq is 1 disintegration per second. The human body has thousands of disintegrations from the presence of potassium-40.

Beta particle
Negatively charged particle (an electron) emitted in radioactive decay of unstable atoms. A beta moves faster than an alpha and can be stopped by a thin piece of aluminum or a short span of air.

Biomass
Organic substances that can be turned into energy producing fuel, such as trees, plants, other flora, and organic wastes.

Biosphere
Portion of the earth's surface and atmosphere that supports life.

Boiling water reactor (BWR)
Nuclear reactor in which water, used as both coolant and moderator, boils in the reactor core. The steam from the boiling water is used to turn the turbine-generator.

Boron
Nonmetallic element that occurs in borax and other compounds. Boron is used in nuclear power plants to control the rate of nuclear fission. Its atomic number is 5 and its atomic weight is 10.811. Its symbol is B.

Breeder reactor
Nuclear fission reactor that makes more usable new fuel (plutonium-239) than it consumes.

British thermal unit (Btu)
Quantity of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

BSP
Basic Safety Principles of INSAG.

BWR
Boiling Water Reactor.

Cadmium
Soft, bluish-white metallic element resembling tin, used in control rods in nuclear reactors. Its atomic number is 48 and its atomic weight is 112.411. Its symbol is Cd.

CANDU
(Canadian heavy water reactor).

Canister
A corrosion-resistant container used to enclose high-level nuclear waste during long-term storage.

Carbon dating
Method used to discover the age of old objects by determining the amount of radioactive carbon-14 present.

Carbon dioxide
Common gas molecule consisting of one carbon atom and two oxygen atoms made by burning carbon substances such as fossil fuels or by metabolism in the body.

Carcinogen
Chemical substance or type of energy that can cause cancer in the human body.

CAT scanner
Medical instrument that combines X-ray machines with computers in order to provide color television images of internal organs. CAT is an abbreviation for Computerized Axial Tomography.

Ceramic
Material from which pottery, earthenware, or porcelain is made. Uranium fuel is made into a ceramic at a fuel fabrication plant.

Chain reaction
Continuing series of nuclear fission events that take place within the fuel of a nuclear reactor. Neutrons produced by a split nucleus collide with and split other nuclei causing a chain of fission events.

Chemical energy
Energy released when the chemical makeup of materials changes. The energy in coal is released when the coal is burned leaving sulfur dioxide, carbon dioxide, ash, etc.

Chemical reaction
Reaction that occurs between the electrons of atoms; the reaction does not change the element itself.

Chlorofluorocarbon (CFC)
Gas containing carbon and fluorine in various combinations. CFCs are generally volatile and are alleged to decrease the earth's protective ozone layer.

Cladding
Metallic tube that encases nuclear reactor fuel.

CNS
Canadian Nuclear Society.

Cold fusion
Combining (fusing), at essentially room temperature, the nuclei of two light atoms into a heavier nucleus. This has never yet been attained and most scientists believe it is impossible.

Condenser
Equipment that cools steam and turns it back into water.

Conservation
Protection or preservation.

Construction costs
Money required to build a power plant.

Construction permit
Permission granted by law to build something.

Containment
A heavy structure completely surrounding a nuclear reactor to prevent radioactivity from getting into the atmosphere in the event of a major accident.

Containment building
Structure made of steel-reinforced concrete that houses a nuclear reactor. "Containment" is designed to prevent the escape of radioactive materials into the environment.

Contamination
Act of making a substance impure, radioactive, or unclean.

Control rods
Devices that can be raised and lowered in the reactor core to absorb neutrons and regulate the chain reaction. The speed of the chain reaction is controlled by control rods.

Control room
The area in a nuclear power plant where the plant operators work. The equipment in the control room tells operators what is happening in the reactor and other parts of the plant.

Conversion plant
Plant where mined uranium is converted to a gas and purified.

Coolant
Gas or liquid used in a nuclear reactor to remove the heat generated by the fission process.

Coolant/moderator
Substance used to cool the reactor and to slow neutrons. In most nuclear power plants, water is used for cooling to keep the reactor from getting too hot and to slow down neutrons so they are more likely to cause uranium-235 to fission.

Cooling tower
Structure in a nuclear power plant used to remove heat from cooling water from the condenser. The cooling tower prevents thermal pollution of lakes and rivers.

Core
The center fuel region of a nuclear reactor.

Core meltdown
The process of a changing geometry in a nuclear reactor core should melting occur as a result of losing the coolant.

Corrosion
Deterioration of material, usually a metal, that results from reaction with its environment.

Cosmic rays
Naturally occurring powerful radiation that exists in outer space (radiation coming from the cosmos). Many cosmic rays are absorbed by the atmosphere; some of these rays reach the earth's surface.

Criticality
Condition in which a chain reaction involving neutrons and fuel is self-sustaining.

Curie (Ci)
Unit of measure of the rate of decay of a radioactive material. One Curie is the radioactive intensity of one gram of radium--37 billion disintegrations per second.

Decay chain
Process that certain elements pass through to become stable.

Decommissioning
Closing a nuclear power plant after it has operated about 40 years.

Deuterium
Isotope of hydrogen whose nucleus contains one neutron and one proton and is about twice as heavy as the nucleus of normal hydrogen. Hydrogen has only a single proton. Deuterium is often referred to as heavy hydrogen. Deuterium is fuel used in fusion.

DFR
Demonstration Fast Reactor, Japan.

Dose
Amount of radiation or energy absorbed (often measured in mrem).

Efficient
Something done or produced with the least amount of wasted energy.

EFR
European Fast Reactor.

Electrical energy
Form of energy produced by the flow of electrons, usually through a wire.

Electricity
Energy in the form of moving electrons.

Electromagnetic wave
Wave that comes from the action of electric and magnetic forces and moves at the speed of light.

Electron
One of three basic particles in an atom. The electron has a negative electrical charge, orbits the atom nucleus, and has very little mass compared to the nucleus.

Electron volt
Unit equal to the energy of one electron moving through a potential difference of one volt.

Electroscope
Instrument that measures small electrical charges and shows whether they are positive or negative.

Element, chemical
Atom that has a unique number of protons in its nucleus. Oxygen is an element with eight protons in the nucleus. There are more than 100 elemental substances that cannot be chemically separated into other elements. All matter is composed of one or more chemical elements. As of 2000, 109 elements have been assigned a name.

Energy
Ability to do work. Energy is found in forms such as mechanical, chemical, electrical, nuclear, heat, and light.

Energy conversion
Process of changing one form of energy into another.

Energy crisis
When the supply of an energy source (such as oil) is limited and prices go up dramatically.

Engineers
People trained to plan, design, build, and operate machines, bridges, roads, and other types of construction or equipment.

ENS
European Nuclear Society.

Environmental
Having to do with our surroundings.

Environmentalist
Person who studies our surroundings and the effects that certain conditions have on the surroundings.

EPA
Environmental Protection Agency, a federal agency chartered to focus on environmental protection activities in the United States.

Fast reactor
Nuclear reactor that employs fast (high speed) neutrons to sustain the fission process. Such reactors require the coolant to be a liquid metal (such as sodium) or a gas (such as helium) to prevent the energetic neutrons generated during the fission process from being slowed down.

FBR
Fast Breeder Reactor.

Fertile
Material that becomes fissile upon absorbing a neutron.

Film badge
Piece of film worn by workers in order to see if they have been exposed to radiation.

Fissile
Material that will fission, i.e. split into two or more lighter materials, upon absorbing a neutron.

Fission
Process of splitting the nucleus of a heavy atom into two or more lighter atoms when the heavy atom absorbs a neutron. Fission also releases a large amount of energy and two or more neutrons. When the heavy atoms are numerous and close enough, the new neutrons split more atoms and sustain a chain reaction.

Fission products
The atoms that remain when uranium is split in a nuclear reactor. Fission products are usually radioactive.

Fossil fuel
Natural, burnable, carbon based substance resulting from millions of years of biological decay of ancient plant and animal matter. Coal, oil, and natural gas are common examples.

FSU
Former Soviet Union.

Fuel
Material that can be converted into useful energy (see nuclear fuel for the specific application to nuclear energy).

Fuel assembly
Structure that often has 240 fuel rods containing uranium dioxide pellets. Fuel for a nuclear power plant is loaded in the reactor core in fuel assemblies.

Fuel cost
Expense to get fuel ready to use in a power plant, e.g. mining plus processing, transportation, storage.

Fuel cycle
All the steps required to supply, use, and process fuel for nuclear reactors. Includes mining that starts the front end of the cycle, and disposal of nuclear wastes that ends the back end of the cycle.

Fuel fabrication plant
Factory where uranium fuel is made into uranium dioxide ceramic.

Fuel pellet
Cylinder shape into which nuclear fuel is formed for use in a reactor. A fuel pellet is about the size of your fingertip.

Fuel rods
11 to 15-foot-long tube containing fuel pellets.

Fusion
Combining (fusing) the nuclei of two light atoms into one heavier nucleus (a process that releases an enormous amount of energy; more energy than from fission). This requires a very high temperature, as in our sun.

Gamma radiation
High energy, high speed, and short wavelength electromagnetic radiation emitted by the radioactive decay of an unstable atom. Gamma radiation is highly penetrating and can be stopped by high density materials such as lead. X-rays are a form of gamma rays.

Gamma ray
See "Gamma radiation."

Gas cooled reactor
See "High Temperature Gas-Cooled Reactor."

Gaseous diffusion plant
A facility where uranium hexafluoride gas is processed to increase its percentage of uranium-235 from about 0.7 percent to 3-4 percent.

Geiger counter
An electronic instrument for detecting and measuring radiation and radioactive substances.

Generator
A machine that makes electricity. A generator uses mechanical energy to spin a shaft that turns a coil of wire in the presence of a magnetic field. When this happens, an electric current is produced. The generator shaft may be turned by a high-pressure steam turbine (as in a nuclear or fossil plant), water turbine (as in a hydroelectric plant), or wind blades, for examples.

Geologic repository
A burial ground deep beneath the earth's surface designed for the long-term safe storage of high level nuclear waste.

Geothermal energy
Energy from heat inside the earth.

Graphite
A pure form of carbon used as a moderator in some nuclear reactors.

Greenhouse effect
The heating of the earth's atmosphere due to the presence of certain gases (e.g. carbon dioxide) that trap solar energy.

GRS
GRS is Germany's central scientific-technical expert organization for all issues related to nuclear safety and nuclear waste management.

Habitat
Place where a plant or animal naturally grows or lives.

Half-life
Time for a radioactive substance to lose half of its activity due to radioactive decay. At the end of one half-life, 50% of the original radioactive material has decayed.

Hearings
Meetings where all points of view are presented.

Heavy water
Water in which the hydrogen atoms contain one neutron in their nucleus in addition to the characteristic proton.

Helium
Very light, colorless, odorless gas used as a coolant in some nuclear reactors. Its atomic number is 2 and its atomic weight is 4.0026. Its symbol is He.

High level waste (HLW)
Highly radioactive solid material that results from chemical reprocessing of spent fuel from a nuclear fission reactor. HLW consists mainly of fission products, but also trace amounts of uranium and plutonium, plus other transuranic elements. NOTE: This definition could change with time as new uses of HLW become recognized and commercially employed (e.g. medical and industrial applications, use of the large amount of energy that remains in used fuel).

High-temperature gas-cooled reactor (HTGR)
Nuclear reactor cooled with helium.

Hormesis
Term describing biologically beneficial effects of low level radiation.

Hydroelectric
Process for producing electricity by utilizing the potential energy of water behind river dams to turn electrical generators.

Hydropower
Electric energy produced when the force of falling or moving water is used to spin a generator.

IAEA
International Atomic Energy Agency, an agency created in 1954 within the United Nations to create and apply international safeguards consistent with promoting the peaceful uses of atomic energy while simultaneously preventing new nations from making nuclear weapons. The IAEA has issued internationally agreed radiation protection standards based on the recommendations of the ICRP.

ICRP
The International Commission on Radiological Protection: An independent group of experts from a wide range of scientific disciplines which has published recommendations for protection against ionizing radiation for more than half a century.

IFR
Integral Fast Reactor, a fail-safe version of the liquid metal cooled fast reactor (LMR) based on an integral (or closed) fuel cycle at the plant site. A key feature of this concept, developed by the Argonne National Laboratory, is that the plutonium never occurs in a pure form. This provides potentially attractive nuclear proliferation resistant characteristics. IFR is designed as either a small or large plant to produce low-cost electricity. The metallic fuel uses long-life fuel elements with proven burn-ups more than twice that of conventional nuclear fuel.

ILO
An international organization that has issued internationally agreed radiation protection standards based on the recommendations of the ICRP.

Indirect observation
Scientific investigation to study things that cannot be directly sensed. This is often done by observing the interaction and effects that things have with and on their environment.

INEA
International Nuclear Energy Academy.

INFCE
International Nuclear Fuel Cycle Evaluation, late 1970s.

INLA
International Nuclear Law Association.

INSAG
International Nuclear Safety Advisory Group, IAEA.

INSC
International Nuclear Societies Council.

Ion
Atom, or group of atoms, that carries a positive or negative electrical charge as a result of having gained or lost one or more electrons.

Ionization
The process in which a charged portion of a molecule (usually an electron) is given enough energy to break away from the atom. This process results in the formation of two charged particles or ions: the molecule with a net positive charge, and the free electron with a negative charge.

Ionizing radiation
Radiation that has enough energy to remove an electron from a struck atom, thus leaving positively charged particles (ions) behind. High enough doses of ionizing radiation can cause cellular damage.

IPSN
(The French nuclear safety agency).

Isotope
Atom of the same element but with a different mass number. Isotopes contain the same number of protons in their nucleus (hence, the same chemical properties), but different numbers of neutrons, e.g. isotopes of carbon are C-12, C-13, and C-14.

Kilowatt-hour (kwh)
Energy unit defined as 1,000 watts of electricity for one hour (equivalent to 3,413 Btu).

Kinetic energy
Energy from motion.

KNS
Korean Nuclear Society.

Labeling
Attaching radioisotopes to a substance so that the substance can be followed closely.

License
Permission given by law.

Linear hypotheses
Assumption that any radiation causes biological damage according to a straight-line graph of adverse health effects versus dose.

Liquid metal fast breeder reactor (LMFBR)
Nuclear reactor that uses a liquid metal, such as sodium, to transfer heat from the reactor to a steam generator. A breeder reactor makes more fuel than it uses by converting uranium-238 to plutonium-239.

LLE
Loss-of-Life-Expectancy, the average amount by which one's life is shortened by a particular risk.

LMR
Liquid Metal-cooled Reactor, a nuclear reactor in which the heat is removed by a liquid metal coolant (usually sodium). Since the highly energetic neutrons created during the fission process are not slowed down very much by this relatively heavy coolant, the neutrons remain at a fairly high speed. Hence, the LMR is often called a fast reactor.

LNSG
London Nuclear Suppliers Group, deals with import and export restrictions on nuclear-related equipment.

Low level waste (LLW)
Waste from nuclear processes containing very low amounts of radioactivity, requiring essentially no shielding or heat removal.

LWR
Light Water Reactor.

Mass
Amount of matter a body contains.

Mechanical energy
Energy made or run by machine.

MHTGR
Modular High Temperature Gas Reactor, a nuclear reactor in which the heat is removed by a gas (usually helium). This reactor operates at higher coolant temperatures than other systems because the coolant is already in a gaseous form (negating concerns of coolant boiling).

Mill tailings
Crushed rock left after uranium has been removed from uranium ore.

millirem
Unit of radiation dosage equal to one-thousandth of a rem. The average American receives about 360 millirems per year from all sources.

Moderator
Substance that slows down neutrons so they are more likely to cause fission.

Molecule
Smallest unit into which a substance can be divided and still keep all its characteristics.

Monitor
Device used for checking and listening.

MOX
Mixed plutonium and uranium oxide, fuel.

mrem
Millirem, common unit of radiation dose defined as one-thousandth of a rem. An average American receives about 360 mrem of radiation in a year. Other units are also used to measure radiation.

MRS
Monitored Retrievable Storage, facility in which spent nuclear fuel can be stored and monitored on a temporary basis.

Natural uranium
Uranium as mined (containing 0.7% U-235 and 99.3% U-238).

NEA
Nuclear Energy Agency, an entity of OECD. NEA contributes in the areas of nuclear safety, radioactive waste management, radiation protection, nuclear law, nuclear development, and nuclear science.

NEI
Nuclear Energy Institute, the Washington DC voice of the nuclear industry.

NEST
Nuclear Energy Society Taipei, China.

Neutron
One of three basic particles in all atoms except hydrogen. Neutrons are located in the atom nucleus, are electrically neutral, and each has mass about equal to a proton.

Nitrogen dioxide
Gas molecule consisting of one nitrogen atom and two oxygen atoms that is a combustion by-product of burning fossil fuels. The combustion temperature is high enough to oxidize atmospheric nitrogen.

Nonproliferation
Policy to discourage (and even prevent) non-nuclear weapons nations from acquiring nuclear bombs.

Nonrenewable
Not able to be replaced. Fossil fuels are nonrenewable energy sources.

NPT
Nuclear Proliferation Treaty, international treaty ratified in 1970 in which signatory nations agreed to submit to international safeguards (administered by the IAEA) to prevent the spread of nuclear weapons.

NRC
Nuclear Regulatory Commission, U.S. agency chartered to develop and administer rules for regulating commercial nuclear applications (including nuclear power plants, medical and industrial uses).

NRDC
Natural Resources Defense Council, private organization developed to champion "environmental" causes.

Nuclear chain reaction
Nuclear reaction that takes place in the nucleus of an atom and changes the atom into one or two entirely different elements. A chain reaction stimulates its own repetition.

Nuclear energy
Energy, usually in the form of heat or electricity, produced by the process of nuclear fission within a nuclear reactor. The coolant that removes the heat from the nuclear reactor is normally used to boil water, and the resultant steam drives steam turbines that rotate electrical generators. Nuclear energy is also produced when two nuclei fuse.

Nuclear engineer
Person who plans, designs, and operates a nuclear power plant or other nuclear facility.

Nuclear fission
Process of dividing or splitting the nucleus of an atom.

Nuclear fuel
Fissionable material that can be "burned" (fissioned) in a nuclear reactor (e.g. uranium-235).

Nuclear proliferation
Process of new nations, not currently having nuclear bombs, acquiring nuclear warheads.

Nuclear waste
Waste produced within the nuclear enterprise. This includes nuclear power plants, hospitals and medical laboratories, and numerous industrial users of nuclear products. See HLW, LLW, and TRU for definitions of specific types of nuclear waste.

Nuclei
The plural form of nucleus.

Nucleus
The central part of an atom that contains protons and neutrons. The number of protons uniquely defines the chemical element.

Nuclides
General term used to describe the full range of elements and their family of isotopes.

ODAP
Overseas Development Aid Program, Japan.

OECD
Organization for Economic Cooperation and Development. A regional organization that has issued internationally agreed radiation protection standards based on the recommendations of the ICRP. (See NEA)

Once-through
Fuel cycle in which spent (used) fuel is not reprocessed.

Operating cost
Expense to keep a power plant running after it has been built, e.g. workers' salaries, repair, plant upkeep.

Operating license
Permission given by law to operate something, e.g. a nuclear power plant.

Orbit
Path an electron takes around the nucleus of an atom.

Ozone
An atmospheric gas consisting of three atoms of oxygen in the molecule.

P-T
Partitioning-Transmutation. This refers to a process whereby spent nuclear fuel is chemically partitioned (i.e., separated into its constituent parts) and then converted (transmuted) into stable elements or isotopes by neutron bombardment.

Partitioning
The process of chemically separating spent nuclear fuel into its constituent parts (nuclides). It is akin to separating our household trash into baskets of glass, wood, paper, etc.

Periodic table
A chart containing all the nuclides, i.e., all elements and their family of isotopes. Older charts showed only the elements.

Photosynthesis
Process by which a green plant makes its food using energy from the Sun.

Physicist
Scientist who studies and works with matter, energy, and motion.

Pitchblende
Ore from which uranium and radium are obtained.

Plasma
A gas so hot that all electrons are stripped away from the atoms. As such, the gas has a positive charge and can be confined in a magnetic field. High-temperature plasma is used in controlled fusion experiments.

Plutonium-239
Radioactive element used to produce nuclear energy. It has an atomic number of 94, an atomic weight of 244, and is thus a relatively heavy element. Plutonium-239 is formed by neutron absorption in uranium-238, and like uranium, has two principal isotopes that are fissile. Its symbol is Pu.

PNC
Pacific Nuclear Council.

Pollution
Contamination of the environment.

Potential energy
Capability to produce energy. Coal has potential energy; when it is burned, it gives off heat and light energy.

Power plant
Facility that produces electricity.

Pressure vessel
Extremely strong steel container that surrounds the core of a nuclear reactor.

Pressurized water reactor (PWR)
Nuclear reactor in which water is kept under pressure in a vessel to prevent boiling. Steam is made in a second vessel.

Primary energy source
Energy source used directly to produce heat, light, or motion. Primary energy sources are fossil fuels, geothermal, nuclear, solar, and tidal.

Primary system
The enclosed coolant system within a nuclear reactor in which heat is directly removed from the fuel elements.

Proton
One of three basic particles in an atom. Protons are located in the atom nucleus, have a positive electrical charge, and each has mass about equal to a neutron.

PWR
Pressurized Water Reactor.

Quad
A measure of energy equivalent to a quadrillion (a million times a million times one thousand, or 1015) British thermal units (Btu).

Quark
An elementary particle and a fundamental constituent (“building block”) of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei.

rad
Basic unit of absorbed dose of ionizing radiation.

Radiant energy
Solar energy which strikes the ground or air and becomes heat.

Radiation
Particles and electromagnetic rays (waves) emitted from the center of an atom during radioactive disintegration.

Radiation dose
Radiation received during a time interval.

Radioactive
Giving off energy in the form of particles and rays by the disintegration of atomic nuclei.

Radioactive decay
Spontaneous change of an atom into a different atom or a different state of the same atom.

Radioactive isotope
Element that emits ionizing radiation when it decays. Radioactive isotopes are commonly used in science, industry, and medicine.

Radioactivity
Spontaneous emission of radiation from the unstable nucleus of an atom.

Radiography
Use of ionizing radiation to produce shadow images on a photographic film. Some of the gamma or X-rays pass through an item being evaluated while others are partially or completely absorbed by more opaque parts of the item and cast a shadow on the photographic film.

Radioisotope
Element that emits ionizing radiation when it decays. Radioactive isotopes are commonly used in science, industry, and medicine.

Radionuclide
Any species of an atom that is radioactive. A generic word used to replace radioisotope, which is limited to one element.

Radiotoxicity
The toxicity to human cells caused by absorption of high doses of radioactive substances. Many chemicals are toxic or poisons at high doses.

Radium
Radioactive metallic element, discovered by Pierre and Madame Curie in 1898, with an atomic number of 88 and atomic weight of 226. Its symbol is Ra.

Radon
Heavy, natural, radioactive gas formed by the radioactive decay of radium, a decay product of uranium. Its atomic number is 86 and its atomic weight is 222. Its symbol is Rn.

RCA
Regional Cooperative Agreement for research, development, and training; sponsored by IAEA.

Reactor
Part of a nuclear power plant where neutrons produce a fission chain reaction.

Reclamation
Restoration to a useful condition.

Recycling
A term made popular in the environmental movement to reuse materials that otherwise would be discarded as waste. Within the nuclear industry, it is a synonym for reprocessing spent (used) fuel.

Regulate
Change or adjust to agree with a standard or rule.

Regulation
Maintenance of standards of performance through rules.

rem
(Roentgen equivalent man), a unit used in radiation protection to measure the amount of damage to human tissue from a dose of ionizing radiation. An average American receives about 0.360 rems of radiation per year.

Renewable
Able to be replaced. The Sun's energy is a renewable energy source.

Repository
Storage facility for high-level nuclear waste.

Reprocessing
The mechanical and chemical processing of spent nuclear fuel to separate useable products (i.e., uranium and plutonium) from waste material (i.e., fission products). As time progresses, much of what is currently defined as "waste" will likely find commercial applications.

Risk assessment
Science of studying the amount of risk associated with doing something.

Roentgen
Unit of exposure to ionizing radiation.

Rubidium
Soft, silver-white, metallic element. Its atomic number is 37 and its atomic weight is 85.47. Its symbol is Rb.

Safety system
Procedure and equipment designed to keep accidents from happening or to provide corrective action.

Scintillation counter
Detector that measures the amount of ionizing radiation in materials. Used in medical and nuclear research and in looking for a radioactive material.

Secondary energy source
Sources of energy produced by a primary energy source. Electricity, a secondary source, can be made by burning fossil fuel, a primary source.

Secondary system
The enclosed coolant system within a nuclear power plant in which heat is transferred from the primary system to the steam generators. Not all nuclear power plants require a secondary system.

Service
Performance of work paid by someone else. When a person sells his or her work, it is called a service. Doctors, teachers, waiters, and mechanics are paid for services.

Shielding
Material used to protect people or living things from ionizing radiation. Lead can shield from gamma rays.

Shipping cask
A container that provides appropriate shielding and structural rigidity for the transportation of radioactive material.

Sievert
Unit that measures the effect of radiation on the body. "Sievert" replaces the old unit "REM" (Radiation Equivalent Man), a calculated number based on dose and the body organ (e.g. a dose on your eye would give a different number from the same dose on the liver). 1 REM = 10 milliSieverts (mSv).

Sodium
Soft, silver-white, metallic element used in liquid state as coolant in some nuclear reactors. The atomic number of Sodium is 11, its atomic weight is 22.99, and its symbol is Na.

Solar energy
Energy derived from our sun. Strictly speaking, direct solar radiation, hydroelectric, wind, and even biomass and fossil energy are all forms of solar energy since none would be present without the existence of the sun. However, for this glossary, only direct solar radiation is denoted by this term.

Spent (used) fuel
Nuclear fuel elements removed from a nuclear reactor after they have been used to produce power. Spent fuel has great potential for use as a fuel after reprocessing; thus "used fuel" is a more accurate term.

Spent (used) fuel casks
Shipping containers for spent (used) fuel.

Spent (used) fuel pool
A pool of water near the reactor where used fuel from a nuclear power plant is immersed for safe storage.

Steam-Generator
Equipment using heat in a power plant to produce steam to turn turbines.

Sulfur dioxide
A gas molecule consisting of one sulfur atom and two oxygen atoms produced as a by-product of burning fossil fuels that contain sulfur impurities.

Sustainable development
A term used to connote ways humanity must learn to use and develop its resources in order to sustain a high quality of life on the planet Earth for periods well into the future.

Technical Specifications (Tech Specs)
Document that records the mandated specific limits on equipment conditions and on the state of systems that a nuclear plant must maintain to keep operating safely and in accordance with NRC requirements. The Tech Specs define the limiting conditions for plant operation; these conditions ensure that the plant does not get into a situation where it poses an undue risk.

Thermal energy
Energy in the form of heat.

Thermal reactors
Nuclear reactors that employ slow ("thermal") neutrons to sustain the fission process. Water is commonly used in such reactors for a coolant since the hydrogen contained in water is very effective in slowing down the highly energetic neutrons generated during fission.

Thorium
Radioactive element with an atomic number of 90 and an atomic weight of 232. Its symbol is Th.

Time, distance, shielding
The three most important factors for limiting exposure to radiation.

Toxicity
A measure of significant biological damage done by the absorption of a foreign substance. Many toxic materials, including radiation, are not toxic at low levels.

TPPNM
Treaty on Physical Protection of Nuclear Materials.

Transmutation
The process of changing one isotope into another using nuclear reactions.

Transuranics (TRU)
Nuclides with an atomic number greater than uranium (i.e., greater than 92). The principal transuranics are neptunium (No. 93), plutonium (No. 94), and americium (No. 95).

Tritium
Radioactive isotope of hydrogen with two neutrons and one proton in the nucleus. Tritium is manmade and heavier than deuterium. Tritium is used in industrial thickness gauges and as a label in chemical and biological experiments.

TRU
Transuranic element (actinide).

Turbine
Wheel with many blades that is spun when steam pushes the blades. A turbine converts heat energy into mechanical energy.

UNSCEAR
United Nations Scientific Committee on the Effects of Atomic Radiation.

Unstable isotope
Isotope that is likely to change.

Uranium
The heaviest element normally found in nature. The fissile isotope uranium-235 is the principal nuclear fuel material used in today's nuclear power reactors. Uranium is a hard, shiny, metallic radioactive element. Its atomic number is 92, its atomic weight is 238, and its symbol is U.

Uranium carbide
Fuel used in high-temperature gas-cooled reactors.

Uranium dioxide
Chemical form of uranium when it is made into fuel pellets.

Uranium enrichment
Process that increases the percentage of uranium-235 isotopes in uranium fuel from 0.7 percent to 3-4 percent.

Uranium hexafluoride
Gaseous form of uranium made from yellowcake and fluoride. The gas is made and purified at a conversion plant and shipped to a gaseous diffusion plant for enrichment.

Uranium milling
Process of removing uranium from uranium ore. Milling produces a substance called yellowcake.

Utility
Company that provides a public service or product such as electricity, water, or telephone.

Vitrification
The process of placing nuclear high-level waste (HLW) into a glass form for long-term disposal.

WANO
World Association of Nuclear Operators.

WEC
World Energy Council.

X-rays
Electromagnetic radiation with more energy than visual light, usually produced by an x-ray machine. Physically, x-rays and gamma rays are similar.

Yellowcake
Yellow powder that is mostly uranium. Yellowcake is produced by pouring crushed uranium ore into an acid that dissolves uranium. The acid is drained from the crushed ore and dried, leaving a yellow powder called yellowcake.

Last updated May 27, 2014, 3:59pm CDT.

 
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