Thorium utilization in existing and advanced reactor types

A comparative study of the capability of some of the existing power reactor designs to produce fissile material that is vital for sustenance of fission nuclear power is made. The fissile conversion rate is less in reactors using enriched fuel compared to the natural uranium fueled ones. Even in fast reactors the net fissile breeding is feasible only due to blanket regions. A case is made for reconfiguring the existing reactor designs to accommodate internal blankets or exclusive fissile breeding zones. For maximizing the net fissile accumulation it is suggested to use suitably large volume/mass of fertile breeding zones and extend the fuel cycle duration to as long as 2 or 3 years. The burnup reactivity swing of such modified core designs can be as little as ±5 mk over 2 to 3 full power years, thus obviating the need for large excess reactivity control through either burnable absorbers like boron, Gd or control absorbers. The safety characteristics of the new core designs improve with minimal reactivity changes due to temperature, Xe, Sm, burnup and voiding.