At the start-up of the FP5 project PDS-XADS, the main initial specifications for the accelerator system (e.g. beam energy, beam intensity, beam profile, their stability and the accelerator availability and reliability) have been defined by Working Package 1 (WP1), ‘Global Coherence', in connection with the other WPs of the project. From this, WP3 (‘The Accelerator') has assessed the main requirements and the corresponding technical answers. A reference solution, based on a linear superconducting accelerator with its associated doubly achromatic beam line has been worked out to some detail. For high reliability, the proposed design is intrinsically fault tolerant, relying on highly modular ‘de-rated' components associated with a fast digital feedback system. The proposed solution also appears to be robust in terms of operational aspects like maintenance and radioprotection. A programme for the remaining R&D required has been elaborated and is proposed within the FP6 project EUROTRANS.