Potential use of thorium through fusion breeders in the Indian context

The Indian Nuclear Programme is based on a three stage strategy: the first stage of about 10 GWe comprises of natural uranium fuelled Pressurised Heavy Water Reactors (PHWRs); the second stage would consist of Liquid Metal Cooled Fast Breeder Reactors (LMFBRs) to be fuelled with plutonium generated in the first stage PHWRs and the third stage is envisaged to be based on advanced converters/breeders operating on the Th/U-233 cycle. It has generally been assumed that the initial inventory of U-233 for the third stage reactors would be generated in the blankets of LMFBRs containing thorium. But the success of this strategy depends crucially on the attainment of LMFBR doubling times as short as 14 years. The progress registered in recent years in the magnetic confinement of fusion plasmas has opened up the prospects of developing Fusion Breeders for the direct conversion of fertile 232Th into fissile 233U using the 14 MeV neutron released in the (D-T) fusion reaction. A detailed study of the dependence of the 233U production characteristics as well as energy cost of fissile fuel production of such systems on parameters such as plasma energy gain Q, blanket neutron multiplication has been carried out. The growth rate dynamics of the symbiotic combination of 233U generating fusion breeders with PHWRs operating on the Th/U-233 cycle in the so called near-breeder regime has been examined. 95% of the energy generated by PHWRs operating with Th/233U fuel would arise from thorium consumption rather than fission of the initially loaded 233U. A few sub-engineering breakeven fusion breeders producing U-233 at an energy cost well under 200 MeV per atom are adequate to give the requisite nuclear capacity growth rates in conjunction with such near breeder PHWRs. This corresponds to only a 5% diversion of the grid electrical power for the operation of such fusion breeders. In summary the symbiotic combination of a few fusion breeders with a number of PHWRs gives fresh hopes for the early exploitation of thorium in India. (author). 13 refs., 1 tab