Criticality is one of the final stages in the start-up process. Going critical means the beginning of a controlled chain reaction as the first neutrons were spotted by sensors in the reactor core. The criticality in the reactor is maintained for an average of 12 days. This period is enough for the station’s experts to obtain the neutron data from the reactor core to verify whether the operating parameters comply with the design and the reactor control and protection systems function properly.

Earlier Russia participated in the construction of two VVER-1000 reactors at Kudankulam with a total capacity of 2,000 MW. In the spring of 2014, Russia and India signed a framework agreement to build the third and fourth units at Kudankulam. Construction documents were signed in December of the same year. Russian companies are already fulfilling Rosatom’s order for the equipment to be installed at the new units.

For instance, Izhorskiye Zavody signed a contract in June to manufacture a VVER-1000 reactor vessel for Kudankulam Unit 4, including reactor internals, a vessel head, a bottom support ring, core sealing components, witness specimens and vessel head alignment fixtures.

Currently, the plant is manufacturing equipment for Kudankulam Unit 3, including a reactor vessel with internals, a vessel head, a pressurizer and a main circulation circuit. The contract was signed in August 2015.

In the meantime, Russia hold talks over the third phase of the Indian nuclear station construction project. This issue is expected to be discussed by Russia’s President Vladimir Putin and India’s Prime Minister Narendra Modi during the forthcoming meeting in Tashkent. “The parties will touch upon crucial aspects of mutual relations, particularly those pertaining to energy cooperation,” said Presidential Assistant Yuri Ushakov at a press conference. “Russia helps India carry out a major nuclear construction project. Preparations are being made for the next phase of the construction project. This is what they will discuss.”