A number of neutronics of JNIR big uranium target are simulated towards the planning of experimental investigations aimed to the transmutation of radioactive waste. Integral data of the neutron yield and energy spectra are given for several homogeneous spallation targets which are planned to be used as insertions in uranium blanket. Combined spallation targets are also of interest, because it can help to obtain an optimal neutron energy spectrum for effective burning of long-lived fission products and minor-actinides. For this purpose, uranium-beryllium dual insertion was also considered and described in this work.