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α
A symbol for alpha particle.

α decay
A synonym for alpha decay.

α particle
A synonym for alpha particle.

A
A symbol for mass number.

absorb
particles: To take up kinetic energy of a particle. To combine a particle with an atom, a nucleus, or another particle.

electromagnetic radiation: To take up the energy of electromagnetic radiation. The interaction can cause the disappearance of the photon as in the photoelectric effect, and it can cause the production of a secondary photon with a lower energy as in the Compton effect.

Synonym: capture.
Related to photoelectric effect.
Related to Compton scattering.


absorbed dose
The amount of energy of an ionizing radiation absorbed per unit mass of material. The standard unit for absorbed dose is the gray.

Symbol: D.
Synonym: imparted specific energy.
Related to collective dose.
Related to committed dose equivalent.
Related to committed effective dose equivalent.
Related to dose.
Related to dose equivalent.
Related to effective dose equivalent.
Related to gray.
Related to integral absorbed dose.
Related to total effective dose equivalent.


absorber rod
A synonym for control rod.

absorption
nuclear reactions and particulate radiation

   (1) The process of taking up kinetic energy of a particle.

   (2) The process of combining a particle with an atom, a nucleus, or another particle.

   (3) The decrease of the number of particles in a beam as it passes through matter.

electromagnetic radiation

   (1) The process of transferring the energy of electromagnetic radiation to matter.

   (2) The decrease of the number of photons in a beam as it passes through matter.

Related to Compton scattering.
Related to photoelectric effect.


absorption cross section
A synonym for capture cross section.

abvolt
A unit of electric potential defined as exactly 1×10-8 V.

Related to statvolt.
Related to volt.


Ac
A symbol for actinium.

accelerator
A device that uses electrostatic or electromagnetic fields to increase the kinetic energy of a particle.

Related to cyclotron. Related to linear accelerator.

access hatch
An airtight door system that preserves the pressure integrity of a reactor containment while allowing access to personnel and equipment.

AcEm
(obsolete term)
A symbol for actinium emanation.


A chain
A synonym for isobar.

actinides
(1) Elements with atomic numbers 90 through 103 (Z=90-103), the elements that follow actinium in the periodic chart. The set of actinides includes the following elements: 90 thorium (Th); 91 protactinium (Pa); 92 uranium (U); 93 neptunium (Np); 94 plutonium (Pu); 95 americium (Am); 96 curium (Cm); 97 berkelium (Bk); 98 californium (Cf); 99 einsteinium (Es); 100 fermium (Fm); 101 mendelevium (Md); 102 nobelium (No); 103 lawrencium (Lr).

(2) (obsolete)  The set of elements now known as actinides that are in an oxidation state of 3+.

Synonym: actinide series.
Related to americium.
Related to berkelium.
Related to californium.
Related to curium.
Related to einsteinium.
Related to fermium.
Related to lawrencium.
Related to mendelevium.
Related to neptunium.
Related to nobelium.
Related to periodic table.
Related to plutonium.
Related to protactinium.
Related to thorium.
Related to uranium.


actinide series
Synonym for actinides.

actinium
A chemical element with atomic number 89. Actinium was discovered in 1899 by André-Louis Debierne who analyzed the pitchblende residues from the pioneering experiments of Marie and Pierre Curie. Friedrich Giesel found actinium in 1902 although he was unaware of the work by Debierne (Giesel proposed the name emanium for this element). The name actinium is derived from aktis, the Greek word for beam.

Symbol: Ac.
Synonym: emanium.


actinium emanation
(obsolete term)

The nuclide 219Rn.

Symbol: AcEm.

actinium decay series
The nuclides fed in the radioactive decay of 235U including all daughters through stable 207Pb. Also known as the (4n+3) series because each member of the series has a mass equivalent to (4n+3), where n is an integer.

Synonym: actinium series.
Related to thorium decay series.
Related to uranium decay series.


actinium series
A synonym for actinium decay series.

activation
Of or pertaining to the process of inducing radioactivity by bombarding a nuclide with radiation.

activation analysis
Use of radioactivity produced by nuclear bombardment for chemical analysis.

activation product
A nuclide formed through the process of activation.

active fuel length
The length of fuel within a fuel element.

Acronym: AFL.

activity
(1) (Colloquial) Radioactivity; the dose rate of a sample.

(2) The rate of decay of a population of radioactive nuclides. Activity can also refer to the emission rate of a radiation from a sample, useful for samples with nuclides that emit multiple radiations per disintegration. The activity of a sample is given by -λN when it contains one dominant nuclide that has a single half life. In this expression, λ is the decay constant and N is the number of atoms of that particular nuclide. N is more specifically defined as the number of nuclei in a particular nuclear state, a definition that accounts for systems in which a particular nuclide can exist in a number of isomeric states and the ground state. When the total activity is defined by a two or more radioactive nuclides or isomers, it is given by the expression -λ1N1 + λ2N2 + ... λnNn, where the terms define the decay constant and number of atoms for each isomer and nuclide.

(3) (10CFR20) The rate of disintegration (transformation) or decay of radioactive material. The units for activity are further defined as the curie (Ci) and the becquerel (Bq).

Synonym: decay rate.
Synonym: disintegration rate.


acute dose
The amount of a substance that produces an acute exposure to a biological system. For radiation it is the amount of energy deposited in the biological system or a specific tissue or component of that system.

Related to acute radiation dose.

acute exposure
A short, intense exposure to a microorganism, radiation or a toxic substance severe enough that the recovery of the biological system cannot readily occur. Acute exposures generally last less than one day.

Related to acute dose. Related to chronic exposure.

AEC
A synonym for Atomic Energy Commission.

AF
An acronym for auxiliary feedwater.

AFL
An acronym for active fuel length.

after heat
Heat produced by the decay of radioactive materials in a reactor that has been shut down.

Related to decay heat.

AFW
An acronym for auxiliary feedwater.

Ag
A symbol for silver.

agreement state
A State of the U.S. that has entered into an agreement with the Nuclear Regulatory Commission under the Atomic Energy Act of 1954 (68 Stat 919), subsection 274b, allowing that State to regulate the use of by-product radioactive materials within its borders.

Acronym: AS.
Related to nonagreement state.


air sampling
The process of collecting samples of air to measure the concentration of chemicals, radionuclides, gross radioactivity, or particulates.

Al
A symbol for aluminum.

ALARA
An acronym for as low as reasonably achievable.

ALI
An acronym for annual limit on intake.

alkali metals
The set of chemical elements that form group IA in the periodic chart. The elements making up the alkali metals include lithium (Li, Z=3), sodium (Na, Z=11), potassium (K, Z=19), rubidium (Rb, Z=37), cesium (Cs, Z=55), and francium (Fr, Z=87).

Related to cesium.
Related to francium.
Related to lithium.
Related to periodic table.
Related to potassium.
Related to rubidium.
Related to sodium.


alkaline earth metals
The set of chemical elements that form group IIA in the periodic chart. The elements making up the alkaline earth metals beryllium (Be, Z=2), magnesium (Mg, Z=12), calcium (Ca, Z=20), strontium (Sr, Z=38), barium (Ba, Z=56), and radium (Ra, Z=88).

Related to barium.
Related to beryllium.
Related to calcium.
Related to magnesium.
Related to periodic table.
Related to radium.
Related to strontium.


alpha
A synonym for alpha particle.

alpha decay
Radioactive disintegration by emission of an alpha particle.

Synonym: α decay
Synonym: alpha change
Synonym: alpha disintegration
Synonym: alpha emission
Synonym: alpha particle decay
Synonym: alpha transformation
Synonym: alpha transition
Related to alpha particle.
Related to beta decay.
Related to electron capture decay.
Related to spontaneous fission.


alpha particle
A 4He nucleus, a helium isotope that contains two protons and two neutrons. The term alpha is reserved for 4He nuclei emitted during radioactive decay or as an ejectile in a nuclear reaction. The name alpha was coined by Rutherford in 1897.

Reference: E. Rutherford. Phil. Mag. 7, 109 (1897).
Symbol: α.
Symbol: 4He2+.
Synonym: α particle.
Synonym: alpha.
Synonym: alpha radiation.
Synonym: alpha ray.
Related to alpha decay.
Related to beta particle.
Related to gamma ray.
Related to positron.


alpha particle decay
A synonym for alpha decay.

aluminum
A chemical element with atomic number 13. Aluminum was first prepared in impure form in 1825 by Hans Christian Oersted. The name aluminum is derived from alumen, the Latin word alum, which is a common aluminum-containing mineral that has been used since ancient times.

Symbol: Al


Am
A symbol for americium.

ambient dose equivalent
A synonym for equivalent dose.

American Nuclear Society
The American Nuclear Society is a not-for-profit, international, scientific and educational organization. It was established by a group of individuals who recognized the need to unify the professional activities within the diverse fields of nuclear science and technology. December 11, 1954, marks the Society's historic beginning at the National Academy of Sciences in Washington, D.C. ANS has since developed a multifarious membership composed of approximately 11,000 engineers, scientists, administrators, and educators representing 1,600 plus corporations, educational institutions, and government agencies. It is governed by three officers and a board of directors elected by the membership.

The American Nuclear Society mission is to serve its members in their efforts to develop and safely apply nuclear science and technology for public benefit through knowledge exchange, professional development, and enhanced public understanding.

Acronym: ANS.
Web Site: ANS


americium
A chemical element with atomic number 95. Americium was discovered in 1944 by Glenn Seaborg, Albert Ghiorso and colleagues at the Wartime Metallurgical Laboratory, University of Chicago. The name americium was derived from the word America.

Symbol: Am.

anion
A negatively charged ion.

Synonym: negative ion.
Related to cation.
Related to ion.


annihilate
To combine a particle with its antiparticle, converting matter into electromagnetic radiation. An electron and a positron, for example, annihilate to form two gamma rays each with an energy equivalent to the rest mass of the electron (511 keV).

annihilation
The spontaneous process where a particle and its antiparticle annihilate, producing electromagnetic radiation.

Related to free annihilation.
Related to pick-off annihilation.
Related to singlet state annihilation.
Related to triplet state annihilation.


annual dose limit
The maximum dose that may be received in a calendar year.

annual limit on intake
The derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. It 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 rems (0.05 Sv) or a committed dose equivalent of 50 rems (0.5 Sv) to any individual organ or tissue.

Acronym: ALI.
Related to derived air concentration.


anode ray
A synonym for cation.
Related to cathode ray.


ANS
Acronym for American Nuclear Society.

antimony
A chemical element with atomic number 51. Antimony has been recognized in compounds from antiquity, and as a metal since the 17th century. The name antimony is derived from anti and monos, Greek for metal not found alone.

Symbol: Sb.
Synonym: stibium.
Related to metalloids.


Ar
A symbol for argon.

argentum
A synonym for silver.

argon
A chemical element with atomic number 18. Argon was discovered in 1894 by Lord Rayleigh and Sir William Ramsay. The name argon is derived from argos, Greek for no reaction.

Symbol: Ar.
Symbol: (obsolete) A.
Related to noble gases.


arsenic
A chemical element with atomic number 33. Arsenic has an unknown date of discovery. Magnus obtained it in 1250, and in 1649 Schroeder published two methods for preparing aresenic. The name arsenic is derived from arsenikos, Greek for male.

Symbol: As.
Related to metalloids.


As
A symbol for arsenic.

AS
An acronym for agreement state.

as low as reasonably achievable
A goal for reducing radiation doses to levels far below the dose limits, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed materials in the public interest.

Acronym: ALARA.
References: 10CFR20, 10CFR30, 10CFR70, 10CFR72.


astatine
A chemical element with atomic number 85. Astatine was discovered in 1940 by Emilio Segré and colleagues at the University of California, Berkeley. Astatine was produced by irradiating 200Bi with alpha particles. The name astatine is derived from astatos, Greek for unstable.

Symbol: At.
Related to halogens.


At
A symbol for astatine.

atom
The smallest particle of a chemical element. An atom consists of a small, dense nucleus surrounded by a cloud of electrons. The nucleus contains protons and neutrons that account for much of the atomic mass. Chemical properties are defined largely by the number of protons in the nucleus. An atom is said to be ionized when the number of electrons is not equivalent to the number of protons; the resulting electrical charge is the number of protons minus the number of electrons.

Related to exotic atom.
Related to ion.


atom disintegration
A synonym for radioactive decay.

atomic disintegration
A synonym for radioactive decay.

atomic energy
A synonym for nuclear energy.

Atomic Energy Commission
A Federal agency created in 1946 to manage the development, use, and control of nuclear energy for military and civilian applications. It was abolished in 1974 by the Energy Reorganization Act and replaced by the Energy Research and Development Administration and the Nuclear Regulatory Commission. The Energy Research and Development Administration is now part of the Department of Energy.

Acronym: AEC.

atomic fission
A synonym for fission.

atomic fusion
A synonym for nuclear fusion.

atomic mass number
A synonym for mass number.

atomic nucleus
The central part of an atom that contains protons and neutrons and which accounts for much of the atomic mass.

Synonym: nucleus.

atomic number
The number of protons in a nucleus. Each atomic number represents a chemical element that has an assigned name and symbol. A nuclide with 20 protons is an isotope of calcium and is represented by the symbol Ca.

Symbol: Z.
Synonym: Moseley number.
Synonym: proton number.
Related to mass number.
Related to neutron number.


atomic pile
A synonym for pile.

atomic power
A synonym for nuclear power.

attenuate
To reduce or diminish. Particle and photon beam intensities are attenuated by scattering the radiation out of a beam, by converting the radiation to another form (e.g., converting a photon through pair production into an electron-positron pair), or by a molecule, atom or nucleus absorbing the radiation.

attenuation
Of or pertaining to the process of attenuating radiation.

attenuation coefficient
The rate at which the intensity of a radiation decreases or is absorbed in matter. If μ is the attenuation coefficient, and I0 is the initial intensity of the radiation, then the intensity at some absorber thickness d is given by I = I0 e-μd.

Symbol: μ.
Synonym: attenuation constant.
Related to attenuation factor.


attenuation constant
A synonym for attenuation coefficient.

attenuation factor
The degree to which a beam of radiation has been attenuated. It is equal to I/I0 or e-μx, where I0 is the intensity of the unattenuated beam, I is the intensity of the beam after passing through an absorber with a thickness of x and an attenuation coefficient μ.

Related to attenuation coefficient.

Au
A symbol for gold.

ausonium
(obsolete term)
A synonym for lanthanum.


auxiliary building
A building at a nuclear power plant, typically adjacent to the reactor containment structure, that houses the reactor auxiliary and safety systems, such as the radioactive waste system, the chemical and volume control systems, and the emergency cooling system.

auxiliary feedwater
A backup water supply for a nuclear power plant. It is used to supply water to steam generators during reactor startup and shutdown, and during accident conditions to remove decay heat from the reactor.

Acronym: AF.
Acronym: AFW.
Synonym: emergency feedwater
 
 
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