In the work the development materials of an industrial technique definition of fission materials concentration in radioactive waste are resulted. The active analysis lays on the basis of a technique. Researched samples were irradiated with flows of neutrons received on the basis of the electron linear accelerator. Experiment was carried out on ELE - 300 NSC KIPT using neutron - making target made of Pb (5 cm in diameter and 4 cm in thickness). At an electron beam energy of 20 МeV and an average current of 1 mА such a target can produce a total neutron flux of about 2x10¹⁰s⁻¹. The achieved sensitivity by definition of concentration ²³⁵U is at the level 10⁶ g/g.