Heat treatment done of reactor vessel for unit 5 of India’s Kudankulam nuclear plant

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The final heat treatment of the reactor vessel for unit 5 of the Kudankulam nuclear power project (KNPP) in India has been completed at a plant in Russia, the Russian state atomic energy corporation Rosatom announced earlier this week. 

Rosatom is the equipment supplier and technical consultant for the KNPP being operated by the state-run Nuclear Power Corporation of India Ltd (NPCIL). The KNPP units 1 and 2 of 1,000 MW capacity each are already commercially connected to the grid.  Rosatom is similarly collaborating in the construction of four more units at Kudankulam – 3, 4, 5 and 6 – of 1,000 MW capacity each.     

A Rosatom statement said that after welding the finishing weld and carrying out inspections of the unit 5 reactor vessel weighing 320 tons, it was moved to a gas furnace. The equipment was in the furnace for four days at a temperature of 650 degrees Celsius for 8-10 hours. 

“Heat treatment of the reactor vessel is necessary to relieve the stress of welds and obtain the required mechanical properties of the metal. Afterwards, the item was moved to machining for the manufacture of 54 threaded holes for the studs of the main joint for the reactor vessel”, the statement said.  

The reactor is a safety item of the first class It is a vertical cylindrical vessel with an elliptical bottom and is hermetically sealed from above by a top head. The active zone and internals are located inside the vessel.  

Earlier this month, Rosatom said that the welding of the steam generator heads for the fifth unit had been completed. The welding work was also carried out at the Volgodonsk plant of Atommash which is a subsidiary of Atomenergomash, the machine building division of Rosatom.