Welding work in progress on unit 5 reactor of India’s Kudankulam nuclear plant

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Russian state atomic energy corporation Rosatom’s machine building division Atomenergomash has started welding the upper semi-vessel of the VVER-1000 type nuclear reactor for unit 5 of the Kudankulam nuclear power plant (NPP) under construction in India, Rosatom said in a statement.  

The Kudankulam Nuclear Power Plant (KNPP) in India’s Tamil Nadu state is being built by the state-run Nuclear Power Corporation of India Ltd (NPCIL) with the assistance of Rosatom, who are the equipment suppliers and technical consultants for the KNPP consisting of six units. 

“After vertical assembly of two shells and flange, the 170-tonne upper semi-vessel was moved by crane to the turner and then to the welding station, where specialists started welding of two circumferential welds. Welding is performed under heating at a temperature of 150-300 degrees for 22 days”, the statement said.  

“After the operation is completed, weld areas of the semi-vessel will be heated to 300 degrees. Then the semi-vessel is transferred to a heat treatment furnace to obtain the required mechanical properties of the metal. The heating and holding process takes place at a maximum temperature of 620 degrees for three days”, it added.  

The reactor is a vertical cylindrical vessel with an elliptical bottom, inside of which the core and internals are located. The top of the reactor is hermetically sealed with a cover. The upper part of the vessel contains nozzles for supplying and removal of the coolant, as well as nozzles for emergency supply of the coolant when the circuit is depressurized. 

The first concrete was poured into the foundation plate of the reactor building for the fifth unit of the KNPP on June 29, 2021, which marked the official commencement of the third phase of construction consisting of units 5 and 6. Phase 2 of the KNPP construction involving units 3 and 4, also to be equipped with the Russian-made VVER-1000 reactors of 1,000 MW capacity each, are currently at an advanced stage. 

The KNPP units 1 and 2, similarly equipped with VVER-1000 type reactors of 1,000 MW capacity each, have been connected to the grid in 2013 and 2016, respectively. As per an intergovernmental agreement, Rosatom will also help construct 6 more units in India at another location. 

The Kudankulam NPP units meet the latest International Atomic Energy Agency (IAEA) safety requirements and the VVER-1000 reactors are equipped with state-of-the-art safety features.