FALLOUT	Radioactive debris from a nuclear detonation which is airborne or has been deposited on the earth
FILM BADGE	A packet of photographic film used for the approximate measurement of radiation exposure for personnel monitoring purposes. The badge may contain two or more films of differing sensitivity and may contain filters which shield parts of the film from certain types of radiation.
FISSION	The splitting of a nucleus into at least two (2) other nuclei and the release of a relatively large amount of energy. Two or three neutrons are usually released during this type of transformation.
FLUOROSCOPE	A fluorescent screen used for indirect visualization of internal organs in the body or internal structures in apparatus or in masses of material.
FUSION	The act of coalescing two or more atomic nuclei.