Neutronic Investigation of Fissionable Spallation Targets in Accelerator Driven Systems

Spallation process is the most important neutron generation method in industry, medicine, etc. This process in the subcritical reactor core is also another technique. In this research, we study the neutronic behavior of the spallation targets consisting of U-238 and Th-232 materials, by MCNPX code. The parameters under study comprise the spallation neutron yield, deposition energy, target geometry; angular spectrum of the neutron output, gas rate and residual mass spectrum. The results show that geometry has the greatest impact on the neutron output spectrum, but not on the residual mass spectrum. Numbers of neutrons per energy unit are stable at higher energies of 1 GeV, then the changes in neutron generation rate are reduced. Furthermore, hydrogen which is the principal factor in swelling of spallation target, consists of about %88 of gas production.