Towards an intrinsically safe and economic thorium breeder reactor

Thorium does not have intrinsic fissile content unlike uranium. 232Th has nearly three times thermal absorption cross section compared to 238U and hence requires much larger externally fed fissile content compared to uranium based fuel. These factors give a permanent economic competitive edge to uranium. Thus thorium is not inducted in any significant measure in present day power reactors, despite the fact that thorium is three times more abundant in the earth’s crust than uranium. Uranium reserves vary from country to country and there is also difficulty in having equitable distribution of uranium. Thus when 235U would get exhausted, perhaps much sooner in countries having limited uranium reserve, there will be a need to switch over from the today’s open fuel cycle programme based on 235U feed to closed fuel cycle based on Pu feed. At that stage thorium and (depleted) uranium would become equal candidates to form the fertile base. All economic considerations would have to be readdressed. The size and growth of the nuclear power programme based on closed fuel cycle would be dependent on maximizing the fissile conversion rate in those reactors. In this paper we reemphasize the principles and the details of the thermal reactor concept ‘A Thorium Breeder Reactor’ (ATBR), in which the use of PuO2 seeded thoria fuel is found to give excellent core characteristics like two years cycle length with nearly zero control maneuvers, fairly high seed output to input ratio and intrinsically safe reactivity coefficients [Jagannathan V, Ganesan S, Karthikeyan R. Sensitivity studies for a thorium breeder reactor design with the nuclear data libraries of WIMS library update project. In: Proceedings of the international conference on emerging nuclear energy systems ICENES-2000, September 25–28, 2000, Petten, The Netherlands].