This work offers a comparative economic study of the development and commercialisation of the LWR technology and an analysis of the thermoelectromechanical and nuclear equipment industry, with special reference to France, Germany and Italy. It takes the view that a nuclear power plant cannot be analysed as a technical good independent of the relevant technological environment and industrial structure. The chief contribution of the study lies in combining the analysis of a technology and the reasons underlying its selection and the grounds for success or failure of national technology paths, with investigation of the relation between the technology and structure and organisation of the industry. Major emphasis is laid on the evolutionary nature of nuclear technological change, and its incremental rather than radical innovation path, dictated by criteria of technological-industrial continuity. The study thus focuses on the interplay between technology, market structure and state intervention, and the effects of these factors on national nuclear systems and international trade. The work is divided into three separate but interrelated parts. The first is concerned with economic aspects of technological change and, in particular, the role, instruments and extent of state intervention in the industrial economy and technology policy. Part II is devoted to the development and co •• ercialisation of LWRs. The approach adopted combines historical and economic analysis. An account is provided of the early stages of growth of the US nuclear industry and its establishment on the world market. The growth paths of the main European industries are examined with emphasis on the transition from independent technologies, to US licensees, to the successful autonomous implementation of the LWR, and the problems encountered by further nuclear expansion. Rere - as in Part III which provides a more detailed analysis of the development and present situation of the Italian nuclear system - stress is laid on the institutional frameworks in promoting innovation and technical change, and in providing adequate export support.