New Delhi, Nov. 22: India has extracted 30,000 tonnes of thorium concentrate to prepare for the third stage of the nuclear power programme, the minister of state in the Prime Minister’s Office, Prithviraj Chavan, told the Rajya Sabha today.

Nuclear scientists expect the thorium-based third stage to begin only around 2030. Thorium by itself is not a nuclear fuel but has to be converted into uranium-233 fuel. This is done by adding blankets of thorium in India’s second-stage reactors.

India has vast reserves of thorium but modest amounts of uranium. Scientists at the Indira Gandhi Centre for Atomic Research, Kalpakkam, have said the conversion of thorium into uranium-233 fuel would depend on the rate of growth of the second-stage, fast-breeder reactors.

A 500MW fast-breeder reactor is under construction and is expected to become operational in about four years. When a fast-breeder reactor begins operations, it can use about 30 tonnes of thorium for conversion, a scientist said.

The actual amount of thorium available for conversion from the 30,000 tonnes of thorium concentrate would depend on the level of concentration, the scientist added.

A 1 per cent concentration would mean 300 tonnes while a 10 per cent concentration would mean 3,000 tonnes of thorium available for conversion.

Chavan also outlined other steps the atomic energy department had taken over the past several years in preparation for the third-stage programme.

These include setting up a research reactor — Kamini — that has demonstrated the use of uranium-233 fuel obtained from converted thorium, and design work on an advanced heavy-water reactor that uses thorium-based fuel.

India has also developed technologies to reprocess irradiated thorium and for fabrication of uranium-233 based fuel for the third-stage nuclear reactors, Chavan said.