India’s second indigenously built 700 MW reactor at Kakrapar attains criticality


India’s second fully indigenously built 700 MW pressurised heavy water reactor (PHWR) – the unit 4 at the Kakrapar Atomic Power Project (KAPP) in Gujarat state – attained criticality, or the start of controlled fission chain reaction, on December 17, 2023, according to the operator state-run Nuclear Power Corporation of India Ltd (NPCIL). 

The initial loading of nuclear fuel in the fourth unit at Kakrapar had been undertaken in late October 2023.  

The country’s only other indigenously built 700 MW reactor, the KAPP unit 3, began commercial operations in September 2023, following its connection to the grid in January 2021. 

“The criticality was achieved after meeting all the stipulations of the Atomic Energy Regulatory Board (AERB), which had issued clearance after a rigorous review of safety of the plant systems,” the Department of Atomic Energy (DAE) said in a statement.  

The unit will now undergo further testing, while its power level is gradually increased in steps until the unit is operating at full power, the statement added.  

KAPP-4 is the second in the series of sixteen indigenously made PHWRs of 700 MW each being set up in the country. 

The NPCIL has three operational nuclear power units at Kakrapar – two 220 MW units and one 700 MW unit.  

The former Atomic Energy Commission (AEC) Chairman, Anil Kakodkar, had earlier described Kakrapar unit 3 as a “true example of indigenous technology”. 

“The success of this 700 MW unit comes on the back of India’s nuclear programme that has earlier put on stream indigenously designed reactors with capacities of up to 540 MW,” he had said.    

Kakrapar 1 and 2 – both Indian-designed PHWRs of 220 MW each – entered commercial operation in 1993 and 1995, respectively.    

Two more 700 MW PHWRs are currently under construction at the Rajasthan Atomic Power Plant.    

According to the NPCIL Chairman B.C. Pathak, the achievement of criticality of KAPP-4, within six months of the commercial operation of Unit-3 was a significant achievement. 

“Together with the smooth operation of KAPP-3, it demonstrates the strength of NPCIL in all facets of nuclear power, namely, design, construction, commissioning and operation,” he said.  

“With the successful and stable operation of KAPP-3, the capability of NPCIL in setting up of indigenous reactors of PHWR technology of this size is validated and paves the path for early completion of the remaining 14 reactors, beginning with Units 7 and 8 of the Rajasthan Atomic Power Project at Rawatbhata in Rajasthan,” NPCIL said in a statement.  

“The indigenous 700 MW PHWRs are designed, constructed, commissioned and operated by NPCIL, with the supply of equipment and execution of contracts by Indian industry,” it added.  

The Indian government has earlier approved the fleet mode construction of ten PHWRs, each of 700 MW capacity, at a total estimated cost of $16.3 billion. The fleet mode of construction of multiple units ensures standardisation, lower costs and speeds up the setting up of nuclear power plants in the country.   

Besides, construction is underway of four more Russian supplied units of 1,000 MW capacity each at India’s largest nuclear power plant at Kudankulam in Tamil Nadu state. The units 1 and 2 at Kudankulam, also of 1,000 MW each, started commercial operations in 2014 and 2016, respectively   

India currently has 23 reactors in operation with a total capacity of around 7,500 MW.