The accelerator driven system is an innovative reactor which is being
considered as a dedicated high-level waste burner. The function of the
spallation target in accelerator driven system is to convert the incident
high-energy particle beam to low-energy neutrons. One of the quantities of
most interest for practical purposes is the number of neutrons produced per
proton in a spallation target. However, this vital value depends not only on
the material, but on the size of the target as well, due to the internuclear
cascade. The MCNPX 2.4 code can be used for spallation target computation.
Some benchmark results have been compared with MCNPX 2.4 simulations to
verify the code's potential for calculating various parameters of an
accelerator driven system target. Using the computation method, neutron
interaction processes such as loss, capture and (n, xn) into a spallation
target have been studied for W, Ta, Pb, Bi, and LBE spallation targets in
different target dimensions. With relative errors less than 10%, the
numerical simulation provided by the MCNPX code agrees qualitatively with
other simulation results previously carried out, qualifying it for spallation
calculations. Among the studied targets, W and Ta targets resulted in a
higher neutron spallation yield using lesser target dimensions. Pb, Bi, and
LBE spallation targets behave similarly regarding the accessible leaked
neutron yield on the outer surface of the spallation target. By use of a
thicker target, LBE can compete with both W and Ta targets regarding the
neutron yield parameter.