Cernavodă Unit 2 completed a controlled shutdown on 13 August after the Danube fell to 182 centimetres, below the 185-centimetre operating mark [E3]. Unit 1 was already offline, so the disconnection left Romania’s only nuclear plant with both reactors shut [E3]. The two units represent 1,300 MWe of operable nuclear capacity and normally generate about one-fifth of Romanian electricity [E4]. The immediate grid problem was therefore concrete: the last reactor had left the system, while the replacement mix had to absorb the full plant outage [E3][E4].
Cernavodă’s water constraint sits upstream of the megawatts [E2]. The operator’s force-majeure filing says the drought pushed river flow and level below values needed to ensure process-water and cooling-water supply under nuclear-safety conditions [E2]. The earlier Unit 2 notice tied the shutdown decision to river levels, hydrological forecasts and operating parameters [E1]. That sequence describes a controlled operating response, not evidence of a loss-of-coolant accident; the unit was taken down while safety margins remained the governing constraint [E1][E3].
Romanian authorities had already tried to buy water margin with civil works: blasting a rock obstruction, dredging the riverbed and sinking four rock-filled barges to redirect flow [E3]. The intervention reportedly raised water around Unit 2 by about four centimetres, and the ministry said on 9 August that this bought at least nine more days of operation [E3]. By the morning of 12 August, the river was reported at 182 centimetres against the 185-centimetre mark required for normal operation [E3]. Four centimetres had become nine days on the generation ledger, and then the ledger ran out [E3].
Low water had also moved from plant operations into contract administration before Unit 2 shut. Force-majeure certificates were issued on 10 August for electricity supply contracts after Unit 1’s outage left Nuclearelectrica unable to fully meet obligations from its own production [E2]. The certificates allocate contractual consequences during the hydrological event, leaving replacement procurement to the power system [E2]. Once Unit 2 disconnected, all 1,300 MWe of the country’s operable nuclear capacity was unavailable at Cernavodă [E3][E4].
That power system stayed balanced through the disconnection [E3]. Officials said available domestic production, imports, hydro, wind and reserve capacity could cover the deficit, while the ministry’s public assurance was that supply would be fully covered by alternatives and imports [E3][E5]. The record contains no final megawatt-by-megawatt replacement ledger and no settled price for the substitution [E3][E5]. The measurable shortage is clear at the plant, 1,300 MWe unavailable; the shares supplied by imports, wind, hydro and reserves remain unquantified here [E3][E4][E5].
The counter-case starts with the shutdown itself. Nuclearelectrica said keeping both units safely shut had no impact on nuclear-safety parameters, personnel, the environment or the population [E3]. The energy ministry said the national system remained stable and activity proceeded normally after Unit 2’s disconnection [E3]. No widespread blackout is established by this record; the documented outcome at cutoff is a hydrological constraint handled through planned shutdown procedures while the grid remained supplied [E3][E5].
Restart is now an operator decision tied to the river [E3]. Cernavodă specialists said they would decide when to restart as Danube forecasts evolve, with nuclear-safety margins taking priority [E3]. The force-majeure notice leaves contractual disruption open for as long as the event and its consequences prevent fulfillment of obligations [E2]. Forecasts move expectations; the next settlement artifact is Nuclearelectrica’s restart decision [E3]. Until that decision, 185 centimetres is the operating mark, 182 centimetres crossed it, and 1,300 MWe waits on water [E3][E4].