Main coolant pipeline welding completed at unit 3 of India’s Kudankulam nuclear plant

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The welding of the main coolant pipeline has been completed earlier this month at the under-construction third unit of the Kudankulam nuclear power plant (KNPP) located in India’s Tamil Nadu state. 

According to a statement by the Russian state atomic energy corporation Rosatom, the welding of the main coolant pipeline at unit 3 began in December 2022. 

The main coolant pipeline combines the main equipment of the primary circuit, including the reactor, the steam generators, and the reactor coolant pumps. Considering high requirements for quality and operational conditions, the main coolant pipeline welding is one of the most complicated and important stages of civil and erection works at the power unit. 

“It is the reactor coolant pipeline that carries the water heated in the reactor into the steam generators from which the generated steam goes into the turbine steam path, and the turbine generator generates electricity,” the statement said. 

The main coolant pipeline has a total length of about 140 metres (m), the thickness of the pipe walls is 70 millimetres (mm), and the total length of 28 welded joints is more than 87 m.  

“Its design service life in a tough environment (with pressure 160 atm., temperature 3,500С) is 60 years,” the statement said. 

“During the welding of the main coolant pipeline which began in December 2022, a technology proposed by the Russian party was used, which made it possible for the Nuclear Power Corporation of India Ltd (NPCIL) to reduce the operation time from 270 to 219 days,” it added. 

On completion of the main coolant pipeline welding, the work of flushing with the open reactor and the hydraulic tests and circulation flushing of the primary circuit will start.  

Rosatom is the equipment supplier and technical consultant for the KNPP, India’s largest nuclear plant operated by India’s state-run NPCIL. Its units 1 and 2 of 1,000 MW capacity each, started commercial operations in 2014 and 2016, respectively. The construction is underway of four more units at Kudankulam – 3, 4, 5 and 6 – also of 1,000 MW capacity each.  

Rosatom said last month that the “core catcher”, which is an essential part of the nuclear plant’s safety system ensuring prevention of radiation leakage into the environment in case a severe accident causes destruction of the reactor vessel, had been installed in the KNPP fifth unit.