Shielding and activation studies for the design of the MYRRHA proton beamline

Accelerator-driven systems require the use of high energy Mega-Watt proton beams, in combination with a nuclear reactor core operating in sub-critical mode. Between the challenges in the design, key points are the radiation shielding and the minimization of the induced activation.
This study has been done to optimize the design of the MYRRHA facility at SCK•CEN in Mol (Belgium), where a 600 MeV, 4 mA proton beam will be produced and transported through a linear accelerator up to a LBE spallation target, located inside the core of a 100 MW, LBE cooled reactor. To assess the shielding of the proton accelerator, as well as to fix the activation problems that heavily influence the design, an extensive simulation study has been performed with the FLUKA Monte Carlo code. FLUKA has the unique feature to perform via a full Monte Carlo method the transport of both the prompt and the residual radiation, allowing in addition modifications in the geometry and material characterization from the prompt to the residual radiation analysis. The optimization of the elements devoted to the partial or total beam absorption (collimators, beam dump) is also presented: it will be shown how a suitable material configuration will improve the accessibility and the long-term treatment of the irradiated elements