Preliminary Shielding Assessment of EURISOL Postaccelerator

Abstract

The purpose of this safety study, carried out within the EURISOL Design Study, was to characterize the radiation environment and design the appropriate shielding of the new-generation radioactive ion beam postaccelerator. Both variants of linac layouts—without stripper (L#1) and with stripper (L#2)—were analyzed using the ¹³²Sn²⁵⁺ radioactive beam of unprecedented intensity, namely, up to ~10¹³ particles/s, as reference for simulations. In this work two scenarios were analyzed: (a) an accidental full beam loss during 1 s every day and (b) continuous beam loss of 10^–4 m^–1, representing normal operation conditions. Representative loss positions along the accelerator at variable energies of 21, 45.5, 76, 115, and 150 MeVu^–1 were investigated. The lost ions were assumed to strike a stopping copper target. Dedicated simulations were performed by means of the PHITS code. The induced radioactivity in the accelerator components, concrete walls, and air inside the tunnel were estimated using the DCHAIN-SP-2001 code based on an external neutron source and spallation products derived from PHITS. Ambient dose equivalent rates due to the residual radiation were calculated with the MCNPX code using photon sources resulting from DCHAIN. The effect of implanted radioactive ions at low energies in the accelerator structure was also assessed.