the splitting of a heavy nucleus,with release of neutrons and liberation of energy, division of a heavy nucleus into two or, rarely, more parts with masses of equal order of magnitude, usually accompanied by the emission of neutrons, gamma rays and, rarely, small charged nuclear frag, lõhustumine - aatomituuma muundumine kaheks (harvemini enamaks) ligikaudu võrdse massiga kildtuumaks. Raske tuuma lõhustumisel vabaneb energiat ja kiirgub mitu neutronit, mis võivad tekitada ahelreakt