India's fast breeder reactor gets critical component

"The 65-tonne inner vessel has been successfully installed and bolted precisely inside the main vessel. The process started at 6 a.m. Friday and got over around 2 a.m. Saturday without any scratch to any of the components," Prabhat Kumar, project director at Bhavini, told IANS.

With the meteorological department forecasting a clear sky Friday, Bhavini officials decided to lower the 11-metre tall conical shaped inner vessel into the already erected main vessel.

The inner vessel, which would support reactor components like pumps and heat exchangers, was ready for installation for nearly a week but cloudy weather deterred the officials to proceed further.

The sodium-cooled PFBR designed by the Indira Gandhi Centre for Atomic Research (IGCAR) has three vessels -- a safety vessel, a main vessel and an inner vessel. A breeder reactor is one that breeds more material for a nuclear fission reaction than it consumes.

Outer-most is the stainless steel safety vessel (200 tonnes, 13 metres in diameter and 13 metres in depth) which was lowered into the reactor vault in June 2008.

The main vessel - 12.9 metres in diameter and 12.94 metres in height, weighing 206 tonnes - was lowered into the safety vessel December 2009.

The project achieved its third milestone in May this year when another critical component, thermal baffle, a cylindrical safety vessel weighing 60 tonnes, measuring 12 metres in diameter and more than six metres in height, was lowered into the main vessel.

The inner vessel installation process consists of opening and closing the reactor vault cover (now temporary), lifting the heavy component by a crane, lowering it into the main vessel at a precise position and bolting it properly.

"Precision is the major challenge in this operation though tonnage-wise inner vessel is much lighter than the other two vessels that were erected earlier," Kumar said.

But the process wasn't entirely smooth. "One of the hydraulic systems in a jack used to lift the inner vessel was found to be malfunctioning. It had to be replaced immediately," Kumar said.

The PFBR is expected to start operations next September. After erecting the inner vessel, the top opening will be covered with a component called 'roof slab' and the main vessel will be welded to it.

Other reactor components will be inserted into the main vessel through the opening in the roof slab.

Kumar is confident that 95 percent of the reactor components would be received by the end of this year.