Accelerator driven sub-critical systems with enhanced neutron multiplication

Utilisation of thorium, by way of the U-Th cycle, is of particular interest to the Indian Nuclear Power Programme because of large thorium deposits and limited Uranium reserves. Several schemes, such as fast and advanced heavy water reactors, leading to thorium utilisation, are under study at this centre. The present paper discusses a scheme for evolving a practical accelerator driven sub-critical U-Th system with increased neutron multiplication and consequentually a reduced requirement of the accelerator current. It is shown that the requirement of the accelerator current is considerably reduced if a sub-critical assembly with a given K eff is composed of two partially coupled regions.