Second 1000 MWe Unit at Kudankulam goes Critical Published: July 2016 New Delhi. Second nuclear power reactor unit of 1000 MWe capacity at Kudankulam in Tamil Nadu has achieved criticality, a statement from the government in this regard said July 10. This is the second 1,000 MW pressurised water reactor to go critical in the country. The first unit at Kudankulam went critical in July 2013. The unit will start commercial generation in four to six months time. Prior to that, tests have to be conducted and then the unit will be connected to the Southern power grid. The approach towards criticality started on Friday with the gradual removal of the control rods. Once the second unit at Kudankulam starts power generation to its full capacity, the total atomic power capacity in Tamil Nadu would go up to 2,440 MW.