Neutron yields from proton-induced spallation reactions in thick targets of lead

Total neutron yield, integrated over the neutron energy and emission angle, is calculated for spallation reactions in lead at proton energies between 0.4 and 2 GeV. The computations were made with the LAHET/MCNP code package using the intranuclear-cascade-evaporation model of Bertini. The dependence of the integral neutron yield on the target dimensions is investigated and the contribution from the (n, xn) interactions of neutrons of energy < 100 MeV is evaluated. For 1.6 GeV protons, the integral neutron yield from a 100 cm diameter, 100 cm long Pb target is calculated to be in the range of 46 to 57 np, depending on the level density parameter used in the evaporation model.