Chennai, Dec 17 : India's atomic power plant operator, the Nuclear Power Corporation of India Ltd (NPCIL) said its second 700 MW unit at Kakrapar Atomic Power Project (KAPP) in Gujarat attained criticality ' start of controlled fission chain reaction- at 1.17 a.m. on Sunday. This will be the fourth atomic power unit for the NPCIL at Kakrapar. The NPCIL has three operational nuclear power plants at Kakrapar ' two 220 MW units and one 700 MW unit. The first 700 MW unit began commercial operations on August 30, 2023 and the two units at Kakrapar are part of the NPCIL's indigenously designed and built 16 pressurised heavy water reactors (PHWR) being set up in the country. "The criticality was achieved after meeting all the stipulations of the Atomic Energy Regulatory Board (AERB), which had issued learance after a rigorous review of safety of the plant systems," the operator said. According to NPCIL Chairman and Managing Director B.C.Pathak, the achievement of criticality of KAPP-4, within six months of commercial operation of Unit-3 was a significant achievement. Together with the smooth operation of KAPP-3, it demonstrated the strength of NPCIL in all facets of nuclear power viz. design, construction, commissioning and operation. After the first criticality, several experiments/ tests will be conducted in KAPP-4 and the power level raised in steps, in line with the clearances of the AERB, ultimately culminating in operation of the unit at full power. In October, the NPCIL began the fuel loading process for the second 700 MW unit. These indigenous PHWRs have advanced safety features and are among the safest reactors in the world. While these reactors have been designed, constructed, commissioned and operated by NPCIL, the supply of equipment and execution of contracts have been by Indian industries/companies, and thus the true reflection of the spirit of AtmaNirbhar Bharat, the NPCIL said. Two more 700 MW PHWRs are coming up at the Rajasthan Atomic Power Station (RAPS) in addition to the existing four units of 220 MW, one 200 MW, and one 100 MW units. The NPCIL presently operates 23 reactors with a total capacity of 7,480 MW and has nine units (including KAPP-4) with a capacity of 7,500 MW under construction. In addition, 10 more reactors with a total capacity of 7,000 MW are in pre-project activities. These are expected to be completed progressively by 2031-32, the NPCIL said. /IANS