Development of study concerning the nuclear fission of actinoid nuclide

The study of nuclear fission is reviewed. At first, the phenomena of nuclear fission are explained. There are some spontaneous fissile nuclear isomers, and the study of these isomers made clear the shape of the potential fission barrier. The height of the barrier was estimated from excitation function, and excitation energy and fission probability. The deformation of nuclear shape results in the reduction of the barrier height. The models of nuclear fission are presented. One of adiabatic models is the liquid drop model. There is also the calculation considering one-particle shell model. As for non-adiabatic models, there are the statistical model and the diabatic model. Various experiments concerning the typical characteristics of nuclear fission process have been done. Observed characteristic features are the total kinetic energy of fission fragments, the relation between mass division ratio and total energy, the relation between angular momentum and total energy, mass distribution, mass yield, the fine structure of mass distribution, charge dispersion and charge distribution, the odd-even dependence of fission yield, the average number of emitted neutrons, the relation between the mass of fission fragments and neutron yield, photon emission, and the isomer ratio of fission fragments. (Kato, T.)