Weapon-Grade Plutonium Production Potential in the Indian Prototype Fast Breeder Reactor

India is building a 500 MWe Prototype Fast Breeder Reactor (PFBR) that is sched- uled to be operational by 2010. India has refused to accept international safeguards on this facility, raising concerns that the plutonium produced in its uranium blankets might be used to make nuclear weapons. Based on neutronics calculations for a detailed three-dimensional model of the reactor, we estimate that up to 140 kg of weapon-grade plutonium could be produced with the PFBR each year. We show how modest amounts of India's large stockpile of separated reactor-grade plutonium from its unsafeguarded spent heavy-water reactor fuel could serve as makeup fuel to allow such diversion of the weapon-grade plutonium from the PFBR blankets. We describe and assess the most plausible refueling strategies for producing weapon-grade plutonium in this way.