The nuclear reactions involves the nuclei of the atoms, large amount of energy will be involved and some of the mass is converted into energy.
Explanation
Nuclear reactions are reactions which leads to change in the nuclei of the atoms.
The nuclear reaction occur between the nuclei of two atoms or between nuclei and other particles of two atoms.
The product formed will be different from the reactants.
The difference in the mass of the products and reactants are generally converted into energy.
In some nuclear reactions like nuclear fusion reaction, large amount of energy is required to collide the nuclei of two heavy elements to undergo nuclear chain reaction.