ENERGY & SECURITY No.
Glossary of Selected Terms
Other terms can be found in IEER's
- BREEDER REACTOR
- A reactor that is designed to produce more fissile material than it consumes. Most breeder
reactors use fast neutrons for sustaining the nuclear chain reaction, and are therefore called "fast
breeders." A fast reactor that does not produce more fissile materials than it consumes is called a
"fast neutron reactor."
- The amount of energy that has been generated from a unit of nuclear fuel; usually measured
in megawatt-days thermal per metric tons of initial heavy metal (MWdth/MTIHM).
- A negatively-charged elementary particle.
- FERTILE MATERIAL
- Material that is not fissile, but which can be converted into a fissile material. Uranium-238
and thorium-232 are the principal fertile materials.
- FISSILE MATERIAL
- Material whose nucleus can be fissioned when it absorbs a low-energy (ideally zero energy)
neutron. Fissile materials can sustain nuclear chain reactions.
- FISSIONABLE MATERIAL
- Material that can undergo nuclear fission when bombarded by a high-energy neutron. Most
fissionable materials that are not fissile cannot sustain chain reactions.
- The amount of time it takes half of a given quantity of a radioactive element to decay.
- A variant of an element that has the same number of protons but a different number of
neutrons in the nucleus. Isotopes of elements have the same atomic numbers, but different mass
- A material used in a nuclear reactor to slow down the fast neutrons emitted in the process of
- A neutral elementary particle that occurs in the nuclei of elements (except ordinary
hydrogen). Free neutrons decay into a proton, an electron and an anti-neutrino. A neutron is
about 1,838 times heavier than an electron.
- NUCLEAR FISSION
- The splitting of a nucleus of a heavy element into two lighter nuclei, generally accompanied
by the release of one or more neutrons and energy.
- An elementary particle with a positive charge equal to that of an electron, but which is
about 1,836 times heavier than an electron.
- REACTOR CORE
- The core of a reactor, consisting of the fuel, moderator (in the case of thermal reactors), and
- The separation of irradiated nuclear fuel into uranium, plutonium, and fission products.
- THERMAL REACTOR
- A reactor that uses thermal (or slow) neutrons to sustain the chain reaction.
- The process of making glass. In the context of plutonium and nuclear waste management, it
means the mixing of a material with molten glass in order to render it immobile, safe for storage,
and not easily usable for weapons.
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Last updated: February, 1997