The amount of energy absorbed per unit mass, expressed in gray (Gy)

As Low As Reasonably Achievable

A decay mode in which the nucleus emits an alpha particle

A particle consisting of two protons and two neutrons, which is emitted from a nucleus in alpha decay

The smallest particle of a chemical element that can exist

A unit of mass used to express atomic and molecular weights, equal to 1/12 of the mass of a carbon-12 atom

The number of protons in a certain nuclide

The gradual loss in intensity of radiation as it passes through a medium

A coefficient used to express how easily particles or radiation can penetrate a material

A unit of area most commonly used to express nuclear cross sections

A decay mode in which the nucleus emits an electron and an antineutrino after converting a neutron to a proton

A decay mode in which the nucleus emits a positron and a neutrino after converting a proton to a neutron

A type of reactor in which steam is generated inside the primary loop to drive a turbine directly

A type of electromagnetic radiation (photon) produced when a charged particle is decelerated by another charged particle

A measure of the amount of fissile material used in a reactor expressed in gigawatt-day/tonne (GWd/t)

A physical property of matter that causes it to experience a force in an electromagnetic field

A graph containing all known nuclides

The layer of material separating the nuclear fuel from the coolant

The temporary combination of an incident particle and the target nucleus after a collision

The decrease of the energy of a photon, as a result of the inelastic scattering of this photon with an electron

Rods of neutron absorbing material that can be inserted into the reactor to control the fission rate

The material used to extract heat from the nuclear fuel

The energy barrier due to electrostatic interaction that two particles need to overcome so they can get close enough to undergo a nuclear reaction

A chemical bond, which involves the sharing of electron pairs between atoms

A neutron emitted by one of the fission products after a nuclear fission event

Health effects for which a threshold is believed to exist and which vary in severity with the dose

The calculation and assessment of the radiation dose received by the human body

The tissue-weighted sum of the equivalent doses for all tissues and organs in the human body

The ratio between neutron production and neutron losses (absorption and leakage)

A particle that is emitted during a reaction

An elementary particle with a negative charge, which orbits the nucleus of an atom

A decay mode in which the nucleus absorbs an electron from its shells and emits a neutrino after converting a proton to a neutron

A species of atoms having the same number of protons in their nuclei

A reaction in which the system absorbs energy from its surroundings

The process used to increase the concentration of a fissile isotope

A neutron with a kinetic energy higher than 0.2 eV, but lower than 1 MeV

The dose absorbed by a certain tissue, summed over all types of radiation, expressed in sievert (Sv)

A reaction in which the system releases energy to its surroundings

A nuclear reactor that creates more fissile material than it consumes

The ratio of the total number of fission neutrons and the number of fission neutrons from thermal fission alone

A neutron with a kinetic energy of 1 MeV or higher

The probability that a fast neutron will not leak out of the reactor

A neutron that is a product of a fission reaction

The nuclides that result from a fission reaction

A type of reaction in which a nucleus splits into smaller parts

The smallest unit of nuclear fuel in a typical reactor

A long cylindrical tube of cladding material filled with fuel pellets

A photon emitted spontaneously by a nucleus

The unit used to express the absorbed dose

The time required for half of an initial amount of radioactive material to decay

The effective multiplication factor of an infinitely large reactor (no leakage possible)

The number of ionizations per unit path length caused by ionizing radiation

Radiation consisting of particles or electromagnetic waves with sufficient energy to cause ionization in the medium through which it travels

All nuclides with a certain mass number, but a different atomic number

A decay mode in which a nucleus in an excited metastable state emits a gamma ray

All nuclides with a certain neutron number, but a different atomic number

All nuclides with a certain atomic number, but a different neutron number

A group of reactor types that use regular water as the coolant and neutron moderator

The probability that a particle will undergo a reaction with another particle or nucleus in a certain volume

The difference between the mass of a composite particle and the sum of the masses of its parts

The number of neutrons and protons in a certain nuclide

The average distance travelled before a particle undergoes an interaction

The probability that a particle will undergo a reaction with a single other particle or nucleus

An elementary particle that interacts only through the weak force and gravity

A subatomic particle with no charge and a mass of approximately 1 atomic mass unit

A nuclear reaction in which a nucleus and one or more neutrons collide and merge to form a heavier nucleus

The number of neutrons crossing some unit area in a certain direction per unit time

The number of neutrons per unit volume

The path length covered by neutrons per unit volume per unit time, calculated by multiplying the neutron density and the neutron velocity

The process of slowing fast neutrons down to thermal energies

The number of neutrons in a certain nuclide

A material (nuclide) with a large absorption cross section for neutrons

The ratio of the number of fast fission neutrons produced by thermal fission and the number of thermal neutrons absorbed in the fuel

The energy required to disassemble the nucleus into its component parts

A reaction in which a nucleus splits into two smaller parts

A reaction in which two or more nuclei merge to form one or more different nuclei.

A process in which two nuclei, or a nucleus and a subatomic particle collide to produce one or more nuclides that are different from the nuclide(s) that began the process

One of the particles of a nucleus; either a neutron or a proton

The dense region at the center of an atom, consisting of neutrons and protons

An approach to solving the neutron transport equation by assuming all neutrons have the same energy, and therefore velocity

The process in which a high energy photon is converted into an electron and a positron

The average number of particles per unit volume

The complete transfer of energy from a photon to an electron, which is more than the electron binding energy of the material

An elementary particle, which is the quantum of electromagnetic radiation

An elementary particle, which is the antiparticle of the electron

A type of reactor in which the primary loop is under such high pressure that the water remains liquid

A neutron emitted immediately by a nuclear fission event

A subatomic particle with a positive charge and a mass of approximately 1 atomic mass unit

The amount of energy released by a certain reaction

A device that measures exposure to ionizing radiation

A dimensionless factor used to obtain the equivalent dose based on the type of radiation absorbed

A process in which an unstable nucleus releases energy by emitting radiation

The relative susceptibility of cells, tissues, organs, and organisms to the harmful effect of ionizing radiation

A measure of the deviation from a critical condition

The metal vessel containing the reactor core and coolant

The fraction of fission neutrons that manage to slow down from fast to thermal energies without being absorbed

The unit used to express the equivalent dose

A neutron with a kinetic energy similar to that of atoms in its environment (less than 0.2 eV)

A decay mode in which the nucleus splits into two parts

Health effects which occur by chance (e.g. cancer, genetic effects)

The density a material would have if no porosity was present

The probability that a thermal neutron will not leak out of the reactor

The probability that a neutron that gets absorbed does so in the fuel

A relative measure of the risk of stochastic effects that might result from irradiation of a specific tissue