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(1) A symbol for neutron.
(2) A symbol for nano.

(1) A symbol for neutron number.
(2) A symbol for nitrogen.

A symbol for sodium.

A unit prefix equivalent to 10-9.

Symbol: n.

A unit of radioactivity equivalent to 1.0x10-9 curies. The becquerel has replaced the curie as a unit of radioactivity.

Symbol: nCi.
Related to becquerel.
Related to curie.
Related to megacurie.
Related to microcurie.
Related to millicurie.
Related to picocurie.

An acronym for naturally occurring or accelerator-produced radioactive materials.

A synonym for sodium.

natural background radiation
Ionizing radiation produced by cosmic rays, the interaction of cosmic rays with matter, and from the decay of non-anthropogenic radioactive materials.

natural radiation
A synonym for natural background radiation.

natural source
A sample containing natural, long-lived radioactive nuclides and any radioactive daughters.

natural thorium
Thorium with the naturally occurring distribution of thorium isotopes (essentially 100 weight percent 232Th).

Reference: 10CFR part 71.

natural uranium
Uranium whose constituent isotopes have an isotopic abundance equivalent to that found in nature. The naturally-occurring isotopic abundance for 235U is approximately 0.711% and for 238U it is approximately 99.289%.

Reference: 10CFR71.
Related to depleted uranium.
Related to enriched uranium.

A synonym for niobium.

A symbol for nanocurie.

A symbol for neodymium.

A symbol for neon.

negative ion
A synonym for anion.

negative thermion
A synonym for electron.

(obsolete term)

An early proposed name for the electron. It was proposed by the Cosmic Ray Commission of the International Union of Physics at their annual meeting in October 1947.

A synonym for electron.

(obsolete term)

(1) A synonym for electron.
(2) A synonym for beta particle.

Related to positron.

A chemical element with atomic number 60. Neodymium was discovered in 1885 by Carl Auer von Welsbach in samples of didymium. The name neodymium is derived from neos and didymos, Greek for new and twins.

Symbol: Nd.
Related to cerium earths.
Related to lanthanides.
Related to rare earths.

A chemical element with atomic number 10. Neon was discovered in 1898 by Alexander Ramsay and Morris William Travers in the residue of an experiment on a sample of hydrogen. The name neon is derived from neos, Greek for new.

Symbol: Ne.
Related to noble gases.

A chemical element with atomic number 93. Neptunium was discovered in 1940 by Philip Hauge Abelson and Edwin McMillan who irradiated <sup>238</sup>U with neutrons. It was the first man-made transuranic element. Neptunium was named after the planet Neptune.

Symbol: Np.

A basic constituent of the atomic nucleus. The neutron is a fundamental particle, has a mass of 1.008664904 ± 0.000000014 atomic mass units (939.56563 ± 0.00028 MeV). Free, unbound neutrons are produced in fission and in some radioactive decay processes (especially beta decay). A free neutron is unstable, having a half life of 614.6±1.3 s and decaying by β- decay. The neutron is a hadron that is composed of three quarks, udd, and it has a spin-parity of 1/2+ and a magnetic moment of -1.91304275±0.00000045.

Symbol: n.
Related to Bragg neutron.
Related to neutron.
Related to proton.

neutron absorption
A synonym for neutron capture.

neutron absorption cross section
A synonym for neutron absorption cross section.

neutron activation
The process of inducing radioactivity in a sample using the neutron capture reaction.

neutron activation analysis
A method of elemental analysis which uses radiations from neutron-induced radioactivity.

Acronym: NAA.
Synonym: radioactivation analysis.

neutron capture
Absorption of a neutron by an atomic nucleus. A measure of the probability that a material will capture a neutron is given by the neutron capture cross section, which depends on the energy of a neutron and on the composition of the material.

Synonym: neutron absorption.
Related to induced radioactivity.
Related to neutron capture cross section.

neutron-capture cross section
The probability that a neutron passing near a nuclide will be captured or absorbed.

Symbol: σc.
Related to cross section.

neutron chain reaction
A chain reaction that is propagated by neutrons. Neutrons emitted by nuclei in a material are capable of inducing reactions which lead to the production of additional neutrons, thereby sustaining the reaction chain.

Related to chain reaction.
Related to fission.

neutron cycle
A synonym for neutron generation.

neutron generation
A population of neutrons produced during one link in the fission chain reaction. Neutrons in one generation that are successfully moderated and that induce further fission reactions produce a new generation of neutrons.

Synonym: neutron cycle.
Related to chain reaction.
Related to fission.

neutron leakage
Neutrons that escape the moderator of a reactor or a neutron source without undergoing capture by the fissile material or other material in the system.

neutron moderator
A substance used to reduce the energy of neutrons through inelastic scattering. Good moderators have a large scattering cross section and a small absorption cross section. Graphite, water, and heavy water are examples of good neutron moderators.

Synonym: moderator.
Related to capture cross section.
Related to cross section.
Related to scattering cross section.

neutron number
The number of neutrons in a nucleus. It is equivalent to the number of nucleons minus the atomic number or N = (A-Z).

Symbol: N.
Related to atomic number.
Related to mass number.

neutron poison
A synonym for fission poison.

neutron reflector
(1) Material containing elements with a high neutron scattering cross section that is used to reflect neutrons back into a neutron source, thereby increasing the neutron flux inside the source. Beryllium is a common element in reflectors because it has an ultra-high scattering cross section and a very low capture cross section.

(2) A device containing elements with a high neutron scattering cross section that is used to reflect neutrons back into the reactor core, thereby increasing the reactor reactivity and thus the energy output of the reactor.

Synonym: tamper.
Related to neutron capture cross section.
Related to scattering cross section.
Related to reactivity.

neutron separation energy
The energy required to remove one neutron from a nucleus.

Symbol: Sn.
Synonym: neutron binding energy.
Related to binding energy.
Related to nuclear binding energy.
Related to proton separation energy.
Related to separation energy.

An acronym for neutron flux.

An acronym for noble gas.

A symbol for nickel.

A chemical element with atomic number 28. Nickel was discovered in 1751 by Axel Fredrik Cronstedt in the mineral niccolite. The name nickel is derived from the German for Satan.

Symbol: Ni.
Related to transition metals.

(obsolete term)

A synonym for bohrium.

Symbol: Ns.

A chemical element with atomic number 41. Niobium was discovered in 1801 by Charles Hatchett who named it columbium. In 1950, it was renamed niobium by the International Union of Pure and Applied Chemistry. The name niobium was named after the mythological creature Niobe, daughter of Tantalus.

Symbol: Nb.
Synonym: columbium.
Related to transition metals.

(obsolete term)
A synonym for technetium.

(obsolete term)

Symbol: Nt.
A synonym for radon.

A chemical element with atomic number 7. Nitrogen was independently discovered in 1772 by Daniel Rutherford, Jospeh Priestly, Karl Wilhelm Scheele, and Henry Cavendish, but Rutherford is usually credited for its discovery. The name nitrogen is derived from nitrum, Latin for soda producing.

Symbol: N.

A symbol for nobelium.

A chemical element with atomic number 102. Nobelium was discovered in 1957 by Albert Ghiorso, Glenn Seaborg, and associates at the University of California at Berkeley. Nobelium was named after Alfred Nobel who discovered dynamite.

Symbol: No.
Related to actinides.

noble gases
The set of chemical elements that form group VIIIA in the periodic chart. Noble gases have a closed shell of electrons and are thus chemically relatively inert. The elements making up the noble gases include helium (He, Z=2), neon (Ne, Z=10), argon (Ar, Z=18), krypton (Kr, Z=36), xenon (Xe, Z=54), and radon (Rn, Z=86).

Acronym: NG.
Synonym: inert gases.
Synonym: rare gases.
Related to argon.
Related to helium.
Related to krypton.
Related to neon.
Related to periodic table.
Related to radon.
Related to xenon.

non-agreement state
A State that has not entered into an agreement with the Nuclear Regulatory Commission under the Atomic Energy Act of 1954 (68 Stat 919), subsection 274b, to allow that State to regulate the use of by-product radioactive materials within its boarders.

Related to agreement state.

nonionizing radiation
Electromagnetic or particulate radiation that lacks sufficient energy to remove electrons from the outer shells of atoms.

Related to electromagnetic radiation.
Related to gamma ray.
Related to infrared radiation.
Related to ionizing radiation.
Related to particulate radiation.
Related to radiation.
Related to x-ray.

nonstochastic effects
Health effects, the severity of which varies with the dose and for which a threshold is believed to exist. Radiation-induced cataract formation is an example of a nonstochastic effect.

Reference: 10CFR20.
Synonym: deterministic effects.
Related to stochastic effects.

An acronym for naturally-occurring radioactive material.

A symbol for neptunium.

An acronym for nuclear power.

An acronym for nuclear power plant.

An acronym for nonpower reactor.

Acronym for Nuclear Regulatory Commission.

A symbol for nielsbohrium.

(1) An acronym for nuclear steam supply system.
(2) An acronym for nuclear steam system supplier.

A symbol for niton.

nuclear binding energy
A synonym for binding energy.

nuclear breeder
A synonym for breeder reactor.

nuclear disintegration
A synonym for radioactive decay.

nuclear disintegration energy
A synonym for decay Q-value.

nuclear energy
Energy released by radioactive decay, through a nuclear reaction, or in the course of nuclear fission.

A synonym for nuclear power.
Synonym: atomic energy.
Synonym: (obsolete) tomic energy.

nuclear facility
A facility for producing, processing, using, storing, or handling special nuclear material. This includes irradiated material that is of national security significance.

nuclear fission
A synonym for fission.

nuclear force
The strong force between nucleons. Nuclear forces are short-ranged and charge independent and they do not include electromagnetic forces.

nuclear fuel
Fissile material used in a reactor.

Synonym: fuel.

nuclear fusion
The process of forming a heavier nucleus from two lighter ones.

Synonym: atomic fusion.
Synonym: fusion.
Related to fission.
Related to thermonuclear.

nuclear heat of formation
A synonym for binding energy.

nuclear incident
An unexpected event involving a nuclear weapon, facility, or component, resulting in any of the following, but not constituting a nuclear weapon(s) accident: (1) an increase in the possibility of explosion or radioactive contamination; (2) errors committed in the assembly, testing, loading, or transportation of equipment, and/or the malfunctioning of equipment and materiel which could lead to an unintentional operation of all or part of the weapon arming and/or firing sequence, or which could lead to a substantial change in yield, or increased dud probability; and (3) any act of God, unfavorable environment, or condition resulting in damage to the weapon, facility, or component.

nuclear material
(1) Any source material or any special nuclear material. This definition is similar to that for Radioactive Material but 10CFR part 75 does not specifically include by-product material.

(2) The following nuclides, chemical elements, and materials: 2H, 3H, 6Li, 233U, 237Np, 252Cf, 238-242Pu and 239-241Pu [sic.]; americium, berkelium, curium, and thorium; depleted uranium, normal uranium, and enriched uranium. [DOE Order 5633.3B]

(3) A collective term for materials subject to the provisions of DOE Order 5660.1B.

Related to radioactive material.

nuclear power
Electric power generated using nuclear reactors.

Acronym: NP.
Synonym: atomic power.

nuclear power plant
Any device that converts nuclear energy into electrical power. Many nuclear power plants use the energy from fission to produce steam (directly or indirectly) to drive a turboelectric generator thereby generating electricity.

Acronym: NPP.
Related to nuclear reactor.

nuclear radiation
Particulate and electromagnetic radiation emitted from atomic nuclei in various nuclear processes. The important nuclear radiations, from the weapon standpoint, are alpha and beta particles, gamma rays, and neutrons. All nuclear radiations are ionizing radiations, but the reverse is not true; x-rays for example, are included among ionizing radiations, but they are not nuclear radiations since they do not originate from atomic nuclei.

nuclear reaction
A reaction involving an atomic nucleus. It is usually initiated by bombarding a target nucleus with a radiation, called a projectile. The interaction of the radiation with the nucleus may cause the emission of other radiations, called ejectiles. In the reaction 14N + n → 14C + p, the target nucleus is 14N, the neutron is the projectile, and the proton is the ejectile. This reaction can also be written as 14N(n,p)14C.

Related to chemical reaction.
Related to reaction.

nuclear reactor
(1) A device that produces a sustained, controlled fission chain reaction.

(2) A device in which a sustained fission reaction can be maintained. The core is made of a fissile material such as uranium enriched in the isotope 235U. It is usually surrounded by water which moderates neutrons and removes heat from the core.

Synonym: reactor.
Related to nuclear power plant.
Related to research reactor.

Nuclear Regulatory Commission
The U.S. Nuclear Regulatory Commission (NRC) is an independent agency established by the Energy Reorganization Act of 1974 to regulate civilian use of nuclear materials. NRC is headed by a five-member Commission.

The NRC's mission is to regulate the Nation's civilian use of byproduct, source, and special nuclear materials to ensure adequate protection of public health and safety, to promote the common defense and security, and to protect the environment.

The NRC's regulatory mission covers three main areas: (1) Reactors - Commercial reactors for generating electric power and nonpower reactors used for research, testing, and training; (2) Materials - Uses of nuclear materials in medical, industrial, and academic settings and facilities that produce nuclear fuel; (3) Waste - Transportation, storage, and disposal of nuclear materials and waste, and decommissioning of nuclear facilities from service.

Acronym: NRC.
Web Site: NRC

nuclear safety
Aspects of safety that encompass activities and systems that present the potential for (1) uncontrolled releases of fission products or other radioactive materials to the environment or (2) for inadvertent criticality.

Reference: DOE Order G450.

nuclear spallation
A synonym for spallation.

nuclear waste
A synonym for radioactive waste.

Plural of nucleus. A population of one or more nuclides, either specified or left unspecified.

A proton or a neutron. the nuclides 3H and 3He both have three nucleons.

Related to neutron.
Related to proton.

nucleon number
A synonym for mass number.

A synonym for atomic nucleus.

An atom or a collection of atoms whose nuclei have a specified number of protons and neutrons. Isotope is often (incorrectly) used for the term nuclide. The term nuclide was originally proposed by T.P. Kohman in 1947.

Related to isobar.
Related to isomer.
Related to isotone.
Related to isotope.

nuclide chart
A synonym for chart of nuclides.
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