Calculating the (n, xn) and (n, xnf) reaction cross sections on fissionable nuclei

The cross sections of (n, 2n) and (n, 3n) fission reactions on the U-238 nuclei are calculated in the framework of a statistic theory and the exciton model of pre-equilibrium particle emission. The dependence of the density parameter of nuclear levels in a model of Fermi-gas on the nucleus excitation energy and shell correction is taken into account. A good qualitative description of experimental data is obtained. The conclusion as made on the possibility of their good qualitative description in the framework of the approach by way of an optimum choice of calculation parameters