From the early days, accelerator shielding and radiation protection in general have been influenced by the increasing knowledge of the health effects of ionizing radiation, which has progressively decreased the dose rates allowed in occupied areas. At the same time the tools available for estimating shielding have benefited from increasing computing power. Nonetheless, the simplified models of the early days are often still useful for a first estimate before going into complex and detailed Monte Carlo simulations.

This paper provides a brief historical overview of accelerator shielding. As the subject is vast, it is restricted to a review of the various phases of accelerator shielding studies at CERN. CERN is a good example as its accelerators and the related shielding problems span 50 yr of history and cover all major aspects that can be encountered in accelerator radiation protection: various types of accelerators with a wide range of beam intensities producing many varieties of accelerated and secondary particles with energies from MeV to TeV.