Nuclear Energy and Nuclear Disasters. (Nucl Phys) The total energy released in a nuclear explosion. It is usually expressed in equivalent tons of TNT (the quantity of TNT required to produce a corresponding amount of energy). Cf: Fission Yield. See: TNT Equivalent. Note: Low Yield is generally considered to be less than 20 kilotons; intermediate yield from 200 kilotons to 1 megaton. There is no standar dized term to cover yields from 1 megaton upward