The main vessel of the 500 MW Prototype Fast Breeder Reactor that is being constructed at Kalpakkam will be installed anytime during the second half of September, according to Dr. Baldev Raj, Director of the Indira Gandhi Centre for Atomic Research (IGCAR).
The main vessel will house some of the main components of the reactor, like the grid plate (on which the subassemblies containing the fuel will be placed), core support structure, and the primary pipes that will bring the coolant to the grid plate.
Fast breeder reactors have three vessels — the innermost is the inner vessel where the sodium coolant is present, followed by the main vessel and finally the safety vessel. The safety vessel is the outermost vessel. The safety vessel is to contain the sodium coolant in case of any leak in the main vessel.
The main vessel is about 13 metres in diameter, 13 metres in height and about 25 mm in thickness. The small thickness is sufficient because it has to only bear the weight of the coolant (1150 tonnes) and other structures (about 700 tonnes). Also, the pressure inside the main vessel will be low.
This is because the fast breeder reactor uses liquid sodium as a coolant. Sodium becomes liquid at about 100 degree C, and being a metal, the heat transfer property is very good.
Robots for checking
The PFBR reactor is designed to have a gap of 30 cm between the main vessel and safety vessel. “This gap is required for checking the health of the main and safety vessels,” said Dr. Raj.
Highly mechanised robots will be used to check the vessels for any signs of a crack in the vessels through which the sodium can leak. The robots will not be a permanent part of the reactor but will be lowered as and when required. “These must be one of the high tech robots developed in the country,” he said.
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