 The result was the fission of about 1 kilogram ( 2 @.@ 2 lb ) of the 6 @.@ 19 kilograms ( 13 @.@ 6 lb ) of plutonium in the pit , i.e. of about 17 % of the fissile material present . 1 gram ( 0 @.@ 035 oz ) of matter in the bomb is converted into the active energy of heat and radiation , releasing the energy equivalent to the detonation of 21 kilotons of TNT or 88 terajoules . 
