Glossary of terms used on this site
A
| Term | Definition |
|---|---|
| Absorbed dose |
Quantity of energy imparted by ionising radiation to unit mass of matter such as tissue. Unit gray, symbol Gy. 1 Gy = 1 joule per kilogram. |
| Actinides |
A group of 15 elements with atomic number from that of actinium (89) to lawrencium (103) inclusive. All are radioactive. Group includes uranium, plutonium, americium, and curium. |
| Activity |
Attribute of an amount of a radionuclide. Describes the rate at which transformations occur in it. Unit becquerel, symbol Bq. 1 Bq = 1 transformation per second. |
| Advanced gas cooled reactor |
A development of the Magnox reactor, using enriched uranium oxide fuel in stainless steel cladding. |
| AGR |
Advanced gas cooled reactor. |
| Alpha particle |
A particle consisting of two protons plus two neutrons. Emitted by a radionuclide. |
| Atom |
The smallest portion of an element that can combine chemically with other atoms. |
| Atomic bomb |
See nuclear weapon. |
| Atomic mass |
The mass of an isotope of an element expressed in atomic mass units, which are defined as one-twelfth of the mass of an atom of carbon-12. |
| Atomic number |
The number of protons in the nucleus of an atom. Symbol Z. |