Encyclopedia
Radionuclide
A radionuclide is any radioactive atom with a given mass number and atomic number, and for isomeric atoms — also with a specific defined energy state of the atomic nucleus. Radionuclides (and non-radioactive nuclides) of a given chemical element are referred to as its isotopes.
Source: "RULES FOR ENSURING SANITARY-HYGIENIC REGIME DURING CONSTRUCTION AND OPERATION OF ENERGY OBJECTS IN AREAS WITH RADIOACTIVE CONTAMINATION"
(approved by the Ministry of Energy of the Russian Federation on 20.11.96)