Radioactive elements will breakdown and yield energetic gamma rays and x-rays and particles. After enough time has elapsed (usually ten half-lives) the material has decayed to a point were a radiation survey meter cannot distinguish between it and natural background radiation levels.
STORAGE-IN-DECAY
Meaning of STORAGE-IN-DECAY in English
Environmental engineering English vocabulary. Английский словарь экологического инжиниринга. 2012