A possible issue to the nuclear waste problem is the transmutation of the long‐lived radiotoxic components of the spent fuel. The development of subcritical systems with an external neutron source, provided by a high‐energy proton beam impinging onto a spallation target are of special interest in this context. This paper describes the accelerator for such an Accelerator Driven System (ADS), studied within the European PDS‐XADS programme. © 2004 American Institute of Physics