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 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 decontamination(The removal of radioactive contamination which is deposited on surfaces or may have spread throughout a work area. Personnel decontamination is also included. Decontamination methods follow two broad avenues of attack, mechanical and chemical)