Fresh Plaza: Bananas are a natural source of radioactive isotopes. True, there's not much in one banana. But enough, according to Nuclear Threat Initiative - a security-minded think tank - for a few bananas to trigger radiation sensors used at US ports to
detect smuggled nuclear material. The standard measure of the biological effect of radiation is the sievert. One sievert is a heck of a big dose, but one tenth of a millionth of a sievert, or 0.1 micro sieverts, is roughly the dose from eating one banana. So we can use one banana as our basic unit and convert other radiation exposures to so many bananas. The data for the table comes from
here.
Source: bbc.co.uk , Source: Fresh Plaza