Editing Nuclear fallout (section)

===Half-life===
A [[half life]] is the time it takes the radiation emitted by a specific substance to decay to half the initial value. A large amount of short-lived isotopes such as <sup>97</sup>Zr are present in bomb fallout. This isotope and other short-lived isotopes are constantly generated in a power reactor, but because the [[critical mass|criticality]] occurs over a long length of time, the majority of these short lived isotopes decay before they can be released.