Unit 1 of Romania's Cernavodă nuclear power plant was reconnected to the national grid on Friday after more than three months offline due to critically low Danube River levels.

The 706 MW reactor began injecting power into the grid on Friday afternoon. Output rose from 42 MW at 16:27 to 227 MW by 20:15. That represented 3.66 percent of national production. Nuclearelectrica, the state operator, said specialists confirmed minimum safety conditions were met on 4 November.

The shutdown began on 28 July. Prolonged drought had reduced the Danube's level and available cooling water. Unit 2 was disconnected on 13 August for the same reason. The plant was completely offline from that date. Together the two reactors normally supply about 20 percent of Romania's electricity.

During the outage, authorities restarted coal-fired units at Rovinari and Paroșeni. They offered consumers compensation for reducing peak demand. They authorized grid operator Transelectrica to limit supply to industrial customers.

Reconnection does not mean immediate full output. The reactor's power will be increased in stages, with tests at each level. It is expected to reach normal operating regime later on Saturday around 19:00.

Unit 2 cannot be restarted yet. Unit 1 requires large volumes of cooling water, which lowers the level in the plant's intake basin. The Danube level at Cernavodă stood at minus 219 centimeters on Friday, five centimeters higher than Thursday. Forecasts predict a rise to minus 187 centimeters over the next seven days.

Energy expert Cosmin Gabriel Păcuraru said the plant's vulnerability to drought was known for over two decades. The Danube stood at minus 194 centimeters when Unit 1 shut down on 28 July. It fell to minus 234 centimeters by 13 August. Similar low-water episodes occurred in 2003 and 2012. Solutions discussed included deepening the navigation channel and the entrance to the Danube-Black Sea Canal. These investments were not made.

During the summer, authorities attempted to raise water levels. They used dredging, blasting a rock formation on the riverbed, and sinking loaded barges.

Nuclearelectrica general manager Mihai Gioară called the start of Unit 1's start-up maneuvers "an important step, awaited by the company, authorities and public alike." He said the reconnection was important for energy security and system stability. He said the company was working with authorities on solutions to reduce the effects of similar hydrological situations.

Energy Minister Dumitru Chisăliță had estimated on 27 October that a realistic timeframe for restarting a reactor was about two weeks. He put the date around 15 November.