Monte Carlo modeling of spallation targets containing uranium and americium

Abstract

Neutron production and transport in spallation targets made of uranium and americium are studied with a Geant4-based code MCADS (Monte Carlo model for Accelerator Driven Systems). A good agreement of MCADS results with experimental data on neutron- and proton-induced reactions on ${}^{241}$Am and ${}^{243}$Am nuclei allows to use this model for simulations with extended Am targets. It was demonstrated that MCADS model can be used for calculating the values of critical mass for ${}^{233,235}$U, ${}^{237}$Np, ${}^{239}$Pu and ${}^{241}$Am. Several geometry options and material compositions (U, U+Am, Am, Am${}_2$O${}_3$) are considered for spallation targets to be used in Accelerator Driven Systems. All considered options operate as deep subcritical targets having neutron multiplication factor of $k\sim 0.5$. It is found that more than 4 kg of Am can be burned in one spallation target during the first year of operation.