A banana equivalent dose (BED) is a concept occasionally used by nuclear power proponents to place in scale the dangers of radiation by comparing exposures to the radiation generated by a common banana. Bananas are high in potassium, and naturally radioactive, due to the isotope potassium-40 they contain. One BED is the radiation exposure received by eating a single banana.
Bananas are radioactive enough to cause false alarms on radiation sensors used to detect possible illegal smuggling of nuclear material at US ports. After the Three Mile Island nuclear accident, the Nuclear Regulatory Commission detected radioactive iodine in local milk at levels of 20 picocuries/liter, a dose much less than one would receive from ingesting a single banana."