Progress review of accelerator-driven system at Kyoto University Critical Assembly

The Kyoto University Research Reactor Institute is going ahead with a research project on the accelerator-driven system (ADS) using the fixed field alternating gradient (FFAG) accelerator. The goal of the research project is to demonstrate the basic feasibility of ADS as an energy amplifier system using the Kyoto University Critical Assembly (KUCA) coupled with the FFAG accelerator. A series of basic ADS experiments on nuclear reactor physics has been carried out using a solid-moderated and reflected core (A-core) with 14 MeV pulsed neutrons generated by deuterium-tritium reactions. Static and kinetic experiments have been conducted for examination of the neutronic characteristics in the subcritical systems: reaction rate distribution and neutron spectrum using the foil activation method; subcriticality using several methods; neutron decay constant and neutron multiplication using the optical fibre detection systems. In the new ADS experiments using the FFAG accelerator (protons: 100 MeV energy; 5 pA intensity), the high-energy neutrons generated at a tungsten target were successfully injected into the KUCA A-core in March 2009. In March 2010, thorium-loaded ADS experiments (100 MeV energy; 30 pA intensity) were carried out to conduct a feasibility study on neutron multiplication by thorium fission reactions generated by the high-energy neutrons. In the future, on the basis of the experiments conducted in the past at KUCA relating to the minor actinides (MA) of 237Np and 241Am, ADS experiments with 150 MeV protons are planned to be carried out to investigate the MA characteristics through their reaction rate analyses, and to examine the feasibility of ADS with MA in high-energy neutron spectrum combined with several fuels (highly-enriched uranium, natural uranium and thorium) and reflectors (polyethylene, aluminium, graphite and beryllium). (authors)