A key experiment in the roadmap for accelerator-driven systems is the demonstration of the feasibility, licensibility and reliable operation of a high-power spallation target. The MEGAwatt PIlot Experiment (MEGAPIE) was initiated in 1999 in order to design and build a liquid lead-bismuth spallation target, then to operate it at the Swiss spallation neutron facility SINQ at Paul Scherrer Institute (PSI) . The project is supported by an international group of research institutions.

An accelerator-driven system (ADS) for transmutation of nuclear waste typically requires a 600 MeV-1 GeV accelerator delivering a proton flux of a few mAs for demonstrators, and of a few tens of mAs for large industrial systems. This paper briefly describes the reference solution adopted for such a machine, based on a reliability-oriented linear superconducting accelerator, and focuses on the status of the R&D presently ongoing on some prototypical accelerator components. This work is performed within the 6th Framework Programme EC project “EUROTRANS”.

The Spallation Neutron Source accelerator complex includes a superconducting RF linac that accelerates a proton beam from 186 MeV to 1 000 MeV, at a design power level of 1.5 MW. It includes 81 independently powered cavities. One of the advantages of the many independently powered cavities is rapid fault recovery in the event of a problem with a single cavity or any of its subsystems. We have developed a system to automatically calculate the new downstream cavity phase set-points, in the event of an upstream cavity failure (or any change in its setting). The system requires an initial setting of each cavity using a beam measurement, and uses a model to predict changes in cavity arrival times due to cavity failures. It has been successfully tested with up to 20 simultaneous changes in cavity amplitude and phase set-points, and is used regularly. The principles behind the scheme and results will be presented.

The WEBEXPIR (Windowless target Electron Beam EXPerimental IRradiation) programme was set up as part of the MYRRHA/XT-ADS R&D efforts on the spallation target design, in order to answer different questions concerning the interaction of a proton beam with a liquid lead-bismuth eutectic (LBE) free surface. An experiment was conceived at the IBA TT-1000 Rhodotron, a 7-MeV electron accelerator which produces beam currents of up to 100 mA. Due to the small penetration depth of the 7-MeV electron beam and the high beam currents available, the TT-1000 allows to imitate the high power deposition at the MYRRHA/XT-ADS LBE free surface. The main goals of the experiment were to assess possible free surface distortion or shockwave effects under nominal conditions and during sudden beam on/off transient situations, as well as possible enhanced evaporation. The geometry and the LBE flow characteristics in the WEBEXPIR set-up were made as representative as possible of the actual situation in the MYRRHA/XT-ADS spallation target. Irradiation experiments were carried out at beam currents of up to 10 mA, corresponding to 40 times the nominal beam current necessary to reproduce the MYRRHA/XT-ADS conditions. As a preliminary general conclusion, it can be stated that the WEBEXPIR free surface flow was not disturbed by the interaction with the electron beam and that vacuum conditions stayed well within the design specifications.

Within the EUROTRANS integrated project, the domain DESIGN has the task to provide the pre-design of a European Facility for Industrial Transmutation (EFIT) able to demonstrate the feasibility aspect of the nuclear waste transmutation/burning in an ADS at industrial scale. The helium-cooled EFIT is one of the solutions studied for this purpose. The present paper summarises the work carried out during the first two years of the project. The approach followed to design the plant is presented first. The plant characteristics (proton beam characteristics, core power, inlet/outlet temperatures, etc.) are then discussed and the He-EFIT core is described as well as the spallation module design.

The GUINEVERE project is a European project in the framework of FP6 IP-EUROTRANS. The IP-EUROTRANS project aims at addressing the main issues for ADS development in the framework of partitioning and transmutation for nuclear waste volume and radiotoxicity reduction. The GUINEVERE project is carried out in the context of Domain 2 of IP-EUROTRANS, ECATS, devoted to specific experiments for the coupling of an accelerator, a target and a subcritical core. These experiments should provide an answer to the questions of on-line reactivity monitoring, subcriticality determination and operational procedures (loading, start-up, shutdown, etc.) in an ADS by 2009-2010. The GUINEVERE project will make use of the VENUS reactor, serving as a lead fast critical facility, coupled to a continuous beam accelerator. In order to achieve this goal, the VENUS facility has to be adapted and a modified GENEPI-C accelerator has to be designed and constructed. During the years 2007 and 2008, the VENUS facility will be modified in order to allow the experimental programme to start in 2009. The paper describes the main achievements with regard to the modifications for the VENUS facility.