Angra 1 and Angra 2 were reconnected to the grid on 11 November, after a blackout a day earlier triggered a shutdown.
On 10 November the transmission lines that supply the power plant were disconnected as a result of the blackout occurred in several Brazilian states and Paraguay.
With the lack of external power, the emergency diesel generators were fired power plants to operate automatically given the security systems of units. The pumps that cool the nuclear reactor system were turned off and cooling was done through natural circulation.
Local media reports suggest that the power failure occurred after a storm knocked out two transmission lines at the Itaipu dam, with a third line overloading. The dam is the world's second biggest hydroelectric producer after China’s Three Gorges, and it supplies 20% of Brazil's electricity