Fundamental studies of the radiation process for wastewater treatment, its analogues and differences to other advanced oxidation technologies and of combined processes are presented in the report. Possible fields of application, technical solutions and economic factors concerning engineering and other applications are addressed. Developments concerning accelerator design, engineering and construction as well as other features of radiation sources are reviewed. Further discussions include the design of under-beam systems. Such progress and developments are critical for further applications. A reduction in cost and an improvement of technical reliability are expected; in particular high power accelerators are needed for environmental applications. The book points out that such applications should be carefully revised in accordance with the existing regulations and state of the art knowledge. The results of the discussions summarized in the publication may serve as the basis for the preparation of guidelines and feasibility studies for full-scale process implementation. Public awareness and technology acceptance are additional factors to be considered for further dissemination; therefore this publication is a valuable source providing necessary information for engineers, environmentalists and decision makers.