Shielding calculations for a 100 MeV 30 mA proton beam

The Study and Production of Exotic Species (SPES) project employs a 100 MeV, 30 mA proton beam that strikes a primary target. The resulting high-energy neutron flux impinges on a secondary target of depleted uranium to produce, through fission, beams of short-lived, neutron-rich nuclei. This paper deals with some of the preliminary shielding calculations for the bunker. Monte Carlo is employed with MCNPX and, because of the deep penetrations involved, the in-house variance reduction optimiser, the direct statistical approach. The calculations exhibited a number of typical features that are addressed and discussed.