R&D activities and construction plans related to high power proton accelerators are being considered in various countries to promote basic and applied sciences. Both accelerator scientists and reactor physicists gathered at an NEA workshop to discuss the reliability of the accelerator; spallation target design characteristics; safety and operational characteristics of a sub-critical system driven by a spallation source; and test facilities. These proceedings contain all the technical papers presented at the workshop, as well as summaries of the discussions held during each technical session.