E = mc2
where E is energy released in Joules.
m is actual mass converted into energy in kg.
c is velocity of light (3 x 108 m/s)
There are three common nuclear reactions that change nuclear energy into thermal energy (radioactive decay, fission and fusion). At the present day’s just fission method that make sizable quantity of thermal energy is used.
Fissions can be cause with neutrons, which being electrically neutral, strikes the positively charged nucleus at low, sensible and high speeds. Neutrons bombardment results in continued reactions as two or three neutrons are generally released for each one absorbed in fission.
The instant products of fission reactions, for example Xc140 and Sr94 are call as fission remains. They are their molder products are call fission products. After lots of fission reactions, energy is released. Complete fission of 1 gm of U235 nucleus produces 0.948 MW per day.