EURISOL-DS multi-MW target unit: Neutronics performance and shielding assessment, dose rate and material activation calculations for the MAFF configuration

One of the objectives of the EURISOL (EURopean Isotope Separation On-Line Radioactive Ion Beam) Design Study consisted of providing a safe and reliable facility layout and design for the following operational parameters and characteristics: (a) a 4 MW proton beam of 1 GeV energy impinging on a mercury target (the converter); (b) high neutron fluxes (similar to 3 x 10(16) neutrons/s) generated by spallation reactions of the protons impinging in the converter and (c) fission rate on fissile U-235 targets in excess of 10(15) fissions/s. In this work, the state-of-the-art Monte Carlo codes MCNPX (Pelowitz, 2005) and FLUKA (Vlachoudis, 2009; Ferrari et al., 2008) were used to characterize the neutronics performance and to perform the shielding assessment (Herrera-Martinez and Kadi, 2006; Cornell, 2003) of the EURISOLTarget Unit and to provide estimations of dose rate and activation of different components, in view of the radiation safety assessment of the facility. Dosimetry and activation calculations were performed for the different components, regions and systems of the Target Unit. The detailed description of the geometry and constituent materials were implemented and the time evolution of the dose rate and activity for the different components was performed, both during operation and after shutdown of the proton beam. The results obtained indicate that the very high activation of the structural materials in some components will require a detailed study and comparison of the behavior of different materials, namely their remaining activity several years after beam shutdown. The very high dose rates assessed in the computational studies performed and reported in this work, also impose stringent requirements in the radiological protection and radiation safety issues associated to the operation and maintenance of the EURISOL facility. (C) 2010 Elsevier Ltd. All rights reserved.