of years using its large reserve of thorium, a top scientist said.

"The rate at which we can grow in installed capacity is dependent on the availability of uranium as it is used in pressurised heavy water reactors (PHWR)

and the spent fuel from these reactors has plutonium which is used in the fast breeder reactor (FBR)," Dr Srikumar Banerjee, Director, Bhabha Atomic Research

Centre, said.

Thorium itself is not a fuel, it is only a fertile material. It can be converted into Uranium-233 using excess neutrons available from the fast reactors.

Thorium fuelled reactors cannot give high breeding ratio like that in fast reactors fuelled by plutonium, Banerjee said.

"That is why we cannot grow with thorium but once we establish a large capacity with fast breeders we can sustain that capacity with thorium for several

centuries," he said.

Uranium is used in PHWR and the spent fuel from them has plutonium, which is used in the breeder reactor. India is building a 500 Prototype FBR in Tamil

Nadu. The third-stage of the nuclear power programme envisioned by Homi Bhabha can be a reality only if an inventory of Uranium-233 is generated from thorium.

The implementation of this scheme can, therefore, occur only in stages, he said.

"Our immediate effort is to increase the capacity by setting up more nuclear power stations using uranium as fuel.

The plutonium from spent fuel will provide plutonium for the growth of our FBR programme, which in turn, will allow building the inventory of Uranium-233

from thorium at a faster rate.

Country's Fast Breeder Test Reactor (FBTR) has been operating with record fuel burn up for over two decades.

"We are now building a 500 MW prototype fast breeder reactor at Kalpakkam in Tamil Nadu and it is expected to be ready by 2010. India is also planning for

two more FBRs at Kalpakkam and two others in some other location by 2020," he said.

"If we can get adequate uranium for increasing the capacity of nuclear power production at a faster rate, we will be able to accelerate the pace of our

second stage growth and initiate the third stage at an earlier date," Banerjee said.

The growth of nuclear power generation capacity with fast reactors will be significantly determined by the doubling time.

Explaining the concept of doubling time, Banerjee said, a fast breeder reactor consumes plutonium but at the same time produces more plutonium than what

it consumes. Not only can it generate its own fuel but also it builds an inventory to support a new fast breeder reactor.

The time period in which one reactor can produce enough fuel necessary for meeting the demand for a second reactor is known as the doubling time. There

is an urgent need for decreasing this doubling time by development of new type of fast reactor fuel.

Research efforts are under way both in BARC and IGCAR to achieve this goal.

"As mentioned earlier, thorium based reactor does not allow a growth in the installed capacity but with the induction of Accelerator Driven Sub-critical