Radioprotection and shielding aspects of the nTOF spallation source

The neutron Time of Flight (nTOF) facility at CERN is a high flux neutron source obtained by the spallation of 20 GeV/c protons onto a solid lead target. The first experimental measurements performed in April 2001 have revealed an important neutron background, 50 to 100 times higher than expected, along with some secondary effects such as air activation, with a strong presence of Be-7 and Ar-41. In a subsequent study this neutron background was accounted to the strong presence of charged particles and especially negative muons, resulting from the interaction of the high-energy proton beam with the lead target. The present paper reports the study and solutions to the radioprotection and shielding aspects related to the nTOF spallation source.