Application of Accelerators for Nuclear Systems: Accelerator Driven System (ADS)

High energy protons liberate copious neutrons from heavy element targets though spallation reactions. These neutrons can be used for breeding fresh fissile materials from bulk fertile isotopes occurring in nature; e.g. from 238U; and 232Th. However it is economical to utilize streams of spallation neutrons to trigger fission chains in sub-critical reactor core and utilizing bred fissile material in-situ rather than extracting it and re-injecting as thought earlier. Such a sub-critical reactor is deterministically free from power excursion accidents in this mode of operation. This feature is beneficial when utilizing fuels which have nuclear properties leading to higher risks of prompt criticality - such as minor actinides-rich fuel (Np, Am and Cm etc.) in fast reactors. ADS would require developing new technologies, main among which being superconducting RF linear accelerator and heavy liquid molten metal -lead or lead-bismuth eutectic (LBE) as target-coolant. An Indian roadmap and current activities under ADS programme are elaborated in this paper.