Nuclear burning wave in fast reactor with mixed Th-U fuel

The possibility of creating a self-sustained regime of a running nuclear burning wave in the critical fast reactor with the mixed Th-U fuel is demonstrated. The calculations were performed in the deterministic approach based on solving the non-stationary multi-group diffusion equation of neutron transport together with the set of equations of the fuel component burn-up and the nuclear kinetics of precursor nuclei of delayed neutrons. The presence of the constructional material Fe and the coolant (the Pb–Bi eutectic) in the reactor composition is taken into account. The calculation results of the space-time evolution of neutron flux and fuel component concentrations are presented for different values of the Th-U ratio in the fuel. The calculations show the remarkable stability of the nuclear burning wave regime against neutron flux distortions in the reactor, which is a result of the negative feedback on reactivity inherent to this regime. This is one of the most important features of the reactor of this type, which ensures its intrinsic safety.

► Deterministic approach for nuclear burning wave (NBW) phenomenon study is developed.
► Existence of NBW regime in fast reactor (FR) with mixed Th-U fuel is proved.
► Remarkable stability of NBW regime in FR is demonstrated.
► Negative feedback on reactivity ensures intrinsic safety of FR working in NBW regime.