radioactive emission(The release of radioactive substances into the environment deriving from nuclear installations and from mining, purification and enrichment operations of radioactive elements)
radioactive pollutant(A substance undergoing spontaneous decay or disintegration of atomic nuclei and giving off radiant energy in the form of particles or waves, often associated with an explosion of a nuclear weapon or an accidental release from a nuclear power plant, holding facility or transporting container)
radioactive substance(Any substance that contains one or more radionuclides of which the activity or the concentration cannot be disregarded as far as radiation protection is concerned)
radioactive tracer(A radioactive isotope which, when injected into a biological or physical system, can be traced by radiation detection devices, permitting determination of the distribution or location of the substance to which it is attached)