Unit 1 of Romania’s Cernavodă Nuclear Power Plant has been reconnected to the national grid, starting its gradual return to full operation after a severe three-month shutdown caused by drought and a drop in the level of the Danube.
Following the initiation of startup procedures on 4 November, the unit was reconnected to the grid and began supplying power. As of 7 November, Transelectrica data showed the reactor was gradually ramping up its output to hit its full capacity of approximately 700 MWe.
Reconnecting unit 1 requires large volumes of cooling water, which temporarily drops the level in the plant’s intake basin. Consequently, unit 2 cannot be restarted until the Danube experiences a more sustained and significant rise in water levels.
The prolonged outage has dealt a significant blow to Romania’s energy grid, as the two reactors normally generate roughly 20% of the country’s electricity. Unit 1 was forced offline on 28 July, followed by unit 2 on 13 August.
To try and prevent the shutdown, Romanian authorities resorted to extraordinary measures over the summer, including using naval forces for a controlled blast of the Pârjoaia rock formation and planning to submerge barges to redirect more river water toward the plant’s cooling systems. However, water levels remained too low for safe operation until recent autumn rainfall.
To mitigate the resulting power shortage, Romania had to increase its reliance on coal-fired plants, hydropower, and expensive electricity imports, prompting the government to extend a state of alert over energy security into November.
Plant owner/operator Nuclearelectrica has emphasised that the reconnection process must follow the station’s nuclear safety procedures. Grid synchronisation requires the generator’s electrical operating conditions to be coordinated with those of the connected network.
Cernavodă exports electricity through Romania’s high-voltage transmission infrastructure, which is operated by Transelectrica. Returning unit 1 to service would restore a major source of generation, although its initial output following reconnection will depend on the operating sequence and any technical restrictions applied during the restart.
The extended interruption has prompted Nuclearelectrica to examine measures that could reduce the impact of similar conditions in future. The company is working with relevant authorities and technical partners on short-, medium- and long-term options intended to improve the availability of its generating installations during periods of restricted water supply.
The operator is separately progressing preparations for the long-term refurbishment of unit 1, a programme intended to extend the reactor’s operating life. That investment project is distinct from the current restart operation.
