XT-ADS: Neutronics, Shielding, and Radiation Damage Calculations

This work is related to the design of the core of the eXperimental demonstration of the technological feasibility of Transmutation in an Accelerator-Driven System (XT-ADS) facility in the framework of the EUROpean Research Programme for the TRANSmutation of High Level Nuclear Waste in an Accelerator Driven System (EUROTRANS) project. The design specifications for the proton accelerator of the XT-ADS are 600 MeV and up to 3.5 mA for the beam energy and current, respectively. The proton beam impinges on a liquid target consisting of a lead-bismuth-eutectic mixture. The state-of-the-art Monte Carlo code MCNPX was used to assess the neutronics performance and shielding properties of the system. The nuclear data-processing system NJOY 99 was also used. The work consisted of the optimization of the core configuration (geometry, number, and location of the fuel and absorber assemblies) and the appropriate fuel composition in order to reduce radiation damage (namely, the displacement per atom values) on the core barrel and top grid plate, while maintaining the high neutron fluxes (10¹⁵ ncm^-2s^-1) and the k_eff of the system of [approximately]0.95.

The assessment of the core configuration and fuel composition was performed, resulting from the interplay among parameters such as the desired high neutron fluxes, the k_eff value wanted for safety and core performance reasons, the as-low-as-possible radiation damage of the core barrel and top grid plate, and the fuel composition, among others.