Neutron pumping of active medium formed by gadolinium isotopes Gd¹⁵⁵ and Gd¹⁵⁶ pair

The possibility of accumulation of excess energy in the active medium formed by the gadolinium isotopes Gd-155 and Gd-156 possible due to the formation and accumulation of Gd-156m nuclei in the isomeric state during radiation capture of neutrons by the nuclei of a stable isotope with a lower mass is shown. A numerical simulation of the dynamics of the energy levels population of Gd-156 nuclei at repetitively-pulsed pumping of the active medium formed by isotope-modified gadolinium oxide was carried out. The calculation for various combinations of neutron duty cycle of pulses, flux density, and neutron energy spectrum in pulses was performed. It was established that combinations of these parameters, which provide the possibility of inverting the population of the excitation levels of Gd-156 isotope nuclei were largely determined by the energy neutron flux spectrum in pulses.