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