Neutron economy of transmutation of tru in thermal and fast neutron fields

Neutron economy of the transmutation of TRU was examined in well thermalized, thermal and fast neutron fields. Burn-up chains of²³⁷Np,²⁴¹Am and²⁴³Am, which are the main TRU nuclides in the high level waste, were calculated in the flux region from 10¹⁴to 10¹⁷n/cm²-s. Numbers of neutrons absorbed and produced of each chain were calculated using JENDL-3. The net number of neutron produced n_net, which was obtained by the difference of the two numbers, largely varied with the neutron fields, the nuclides and the flux levels. The n_netvalue in the fast neutron field was positive (0.0-1.0) for²³⁷Np,²⁴¹Am,²⁴³Am and TRU with the nuclide composition in the high-level waste generated by the conventional PWR. The transmutation of TRU by fission can be performed with producing neutrons in the fast neutron field. On the other hand, the n_netvalue was negative for the well thermalized and thermal neutron fields. For TRU in the high-level waste, the values in those fields were ‒1.0 at 10¹⁴n/cm²∙s and 0.0 at 10¹⁶n/cm²∙s In the high flux region of 10¹⁶n/cm²-s, TRU in the high-level waste can be transmuted by fission without consuming additional neutrons. In the flux region about 10¹⁴n/cm²∙s, the transmutation of TRU in the high-level waste by fission requires about one neutron.