Accelerator-driven nuclear reactor

Quite neat: accelerator-driven nuclear reactor!: http://www.world-nuclear-news.org/WR_First_for_accelerator_driven_nuclear_reactor_1101121.html "The term supercritical means the number of fissions is increasing, while subcritical means it is decreasing and will therefore dwindle to nothing.
Guinevere is designed to be subcritical if it were not for an accelerator system that sends a constant stream of protons to a target that emits neutrons to trigger fission."