Neutronics analysis of Americium-based fuel for long-life core

Feasibility study on the ultra long-life lithium (Li) cooled fast reactor loaded with conventional LWR-grade Am has been performed. Americium-241 has a potential to reduce the initial excess reactivity because it has relatively high capture cross section to be effectively converted to 238Pu, a fissile nuclide in fast neutron spectrum. For the better neutron economy, 7Li enrichment in coolant, nitride fuel with 15N enrichment, and lead–bismuth (Pb–Bi) reflector were selected and parametrically analyzed to find the optimal condition of criticality achievement with Am-based fuel. In the case of single region homogeneous core with only Am nitride fuel, it was found the condition of criticality sustained more than 100 years operation though the core has a large gradient of flux level distribution. The flattening of geometrical neutron flux distribution were also studied by adjustment of the fuel composition of Am and fissile material in dual region core. With these mechanisms, the change of burn-up reactivity was within 3% and ultra long-life core with over 100-year-life and less than 1.5 radial peaking factor could be achieved simultaneously throughout the operation. Safety parameters such as Doppler and void coefficient are also improved by dual region core. This mechanism of ultra long-life core is expected to be applied to future nuclear reactor concepts such as a space nuclear reactor.

► Feasibility study on the ultra long-life reactor loaded with Am has been performed.
► In Am nitride fuel, it was found the criticality sustained more than 100 years.
► The flattening of geometrical neutron flux distribution were also studied.
► The change of burn-up reactivity was within 3% during irradiation time.