Meaning of RADIOACTIVITY in English
[noun] [U] - the quality that some atoms have of producing energy, which might be harmful even in very small amountsBecquerel was one of the first scientists to study radioactivity.Radioactivity is also used to refer to the energy produced by atoms.A spokesperson said that there was no danger of a leak/escape of radioactivity from the nuclear power station.There is concern about the amount of radioactivity being released into the environment.
Cambridge English vocab. Кембриджский английский словарь. 2012