Mumbai: The construction of the prototype fast breeder reactor (PFBR) at Kalpakkam, in Tamil Nadu, crossed an important milestone on Tuesday with the installation of its massive safety vessel, a critical component of the reactor.

The vessel, made of special stainless steel, is 13.5 metres in diameter, 13.5 metres in height and 43 metres in circumference, and weighs 160 tonnes. It was also the most difficult component to install.

The vessel, fabricated  by Larsen & Toubro, meets world-class specifications and has given a boost to the country's fast breeder reactor capabilities, according to Prabhat Kumar, project director of PFBR.

Atomic Energy Commission chairman Anil Kakodkar and Nuclear Power Corporation chairman and managing director S K Jain were also present at the occasion.

The PFBR, which will generate 500 MW of electricity, will use plutonium-uranium oxide as fuel and liquid sodium as coolant.

The safety vessel will prevent the liquid sodium in the main vessel from coming in contact with the reactor vault. The main vessel will be placed inside the safety vessel.

Kakodkar described the event as ''the most important milestone in the history of India's fast breeder reactor (FBR) programme.''

NPC chief called it ''the beginning of the march towards reaching maturity in building breeder reactors.''

The PFBR project, started in 2003, will be built at a cost of Rs3,500 crore and attain criticality in September 2010.

Meanwhile, moves are on to meet uranium requirements for the country's nuclear reactors. Trial production of yellow-cake from natural uranium at the new processing mill at Turamdih in Jharkhand is under way. When the mill stabilised, it would double the production of yellow-cake, for fabrication into reactor fuel rods.

Work is also in full swing at Tummlapalle, in Kadapa district of Andhra Pradesh, to start excavation for natural uranium.

Another uranium mine will come up at Gogi in Karnataka. Lambapur in Andhra Pradesh had a huge reserve of uranium but mining there had become embroiled in legislation.

In Meghalaya and at Lambapur, the Uranium Corporation of India Limited was trying to convince the local stakeholders about the environmental safety of uranium mines, Jain said.