Cernavodă Unit 1 nuclear reactor set to reconnect to grid on Friday, 6 November

Start-up procedures under way

Nuclearelectrica told the Bucharest Stock Exchange on Wednesday, 4 November, that it had begun start-up manoeuvres for Unit 1 of the Cernavodă plant once the minimum conditions for a safe restart were in place. The company described reactor start-up as a complex operation carried out under strict procedures and nuclear security requirements. Resynchronisation with the national energy system is estimated for Friday, 6 November 2026. Unit 1 has an installed capacity of about 700 MW, and Libertatea describes it as the largest individual energy facility in Romania.

“Starting Unit 1's start-up manoeuvres, once the minimum conditions for a fully safe start are met, is an important step.”

Synchronisation and ramp-up schedule

Libertatea gives the grid connection as Friday afternoon, from 11:00, while a Transelectrica timetable reported by adevarul.ro puts the synchronisation at 13:00 on the same day. After synchronisation, power will be raised in stages, with the reactor held at set load levels for fixed periods so that technical parameters can be checked before it runs at full output. The reactor is expected to reach maximum power around 19:00 on Saturday, 7 November. From that point Unit 1 is due to enter normal commercial operation and deliver its full output to the transmission network.

Why the reactors are offline

Both units were taken offline because the Danube's flow dropped so far that safe operation of the plant was threatened. Unit 1 was shut down on 28 July, although Libertatea gives 27 July, and Unit 2 was disconnected from the grid on 13 August, when the whole plant went offline. Nuclearelectrica said at the end of October that both reactors were held in safe shutdown and that the water level in the pump intake basin had risen, though the general rise of the Danube upstream of Cernavodă had not yet followed. A restart requires the level to hold for several days and keep trending upward. Prime Minister Luca Niculescu said the plant could return within days if the recent rain keeps lifting the river flow.

“I hope we will have good news in a few days.”

Speaking to TVR, Niculescu said it was raining, that the flow was starting to improve, and that the restart date would depend on how the river behaves.

Unit 2 and grid pressure

Unit 2 can only restart after a sustained rise in the Danube, because Unit 1's operation draws large volumes of water for cooling and lowers the level in the intake basin. Once that condition is met, Unit 2 will be synchronised to the national grid afterwards. Energy Minister Dumitru Chisăliță said on 27 October that about two weeks was a realistic timeframe for a Cernavodă reactor to restart, which put the date around 15 November. Meanwhile the government has extended until 30 November the special measures that let Transelectrica limit consumption by large industrial users or halt electricity exports if supply security is at risk. Documents behind that extension indicated that peak demand in November could reach 8,500 MW, and could go higher in much colder spells.

Next steps for the operator

Nuclearelectrica says it is working with the competent authorities and partners on short-, medium- and long-term solutions to raise the availability of its installations and reduce the effects of any similar event. Gioară thanked the plant's specialists, who carried out professional and responsible work to keep the units in safe condition throughout the shutdown. He said the company will continue the measures it has already started in case such circumstances recur. Both the company and the prime minister tie the restart to river levels in the coming days, so the timetable depends on whether the current rise in the Danube holds.