Preliminary design of a gas-cooled accelerator driven system demonstrator

The practicality on an industrial scale of partitioning and transmutation through Accelerator Driven System (ADS) for reducing the amount of long life radio-nuclides has to be evaluated. It was recognised that the most efficient way, in terms of cost and planning, to conclusively assess the potential and the feasibility of a full scale industrial programme on ADS was to design and operate an ADS Demonstration Facility (DF). After a description of the spallation mechanisms, the justification of the interest of ADS is provided. The paper then focuses on ADS DF features (the sub-critical reactor and interfaces with the accelerator) including the process for the selection of design options. The main ADS DF characteristics, defined within a joint working group (CEA/CNRS/FRAMATOME), are described and justified. Then, general conceptual principles for the design of an ADS DF are provided, including the reasons for the selection of the gas for the cooling medium. A description of ADS DF basic options is provided and the gas cooled DF currently under study by FRAMATOME and CEA is presented, including the spallation target, the sub-critical core and the primary cooling system. For each of these sub-systems, interfaces with the accelerator part and adjacent sub-systems are highlighted and main issues which call for research and development support are identified. (authors)