Romania invokes power emergency over Danube losses

Romania has declared a nationwide power emergency for August after record-low Danube levels reduced nuclear and hydroelectric generation while summer demand remained elevated. The government is financing emergency water works, arranging additional imports, and attempting to keep the second unit at Nuclearelectrica’s Cernavodă nuclear station in service after the other reactor was shut down.

The two CANDU units at Cernavodă normally provide a substantial block of low-carbon electricity to the Romanian system. Both depend on water from the Danube-Black Sea Canal for cooling, so exceptionally low river levels have become an immediate operating constraint rather than a distant environmental concern. Prime Minister Ilie Bolojan said the emergency would run throughout August because the reduction in generation could not be treated as a short, isolated outage.

One reactor has already been taken offline. To support the remaining unit, authorities are funding work to redirect water from another canal and maintain the cooling-water supply. The intervention is an engineering response to a narrow hydraulic margin: without sufficient intake flow, the plant cannot reject heat reliably, and continued operation would conflict with the conservative safety requirements applied to nuclear generation.

Hydropower output has also fallen as river and reservoir conditions deteriorated. That simultaneous loss is particularly difficult because hydroelectric plants usually provide both bulk energy and flexible response. When nuclear output falls, hydropower would normally be one of the resources used to cover ramps and peaks; when both are constrained by the same drought, the system loses firm energy and operational flexibility at the same time.

Romania expects peak import requirements of up to 1.7GW against daily demand of roughly 7GW. Discussions have included neighbouring Ukraine, Greece, and Bulgaria, although regional conditions mean those supplies cannot be assumed to be unlimited or cheap. Hungary is shutting the Paks nuclear plant because of its own Danube cooling-water restrictions, while hot weather is affecting thermal and renewable output elsewhere in Europe.

The transmission system must manage larger cross-border flows while preserving domestic security margins. Imports can compensate for lost generation if sufficient interconnector capacity and regional supply are available, but they expose Romania to prices and operating conditions outside its control. Neighbouring systems may also be managing heat-related demand and reduced hydroelectric output.

Demand management may become necessary if imports and remaining generation cannot cover evening peaks. Cooling demand rises when solar output is declining, and low hydropower availability removes a resource that can respond quickly. Gas-fired generation can contribute, but fuel availability, operating cost, and plant efficiency during extreme heat affect how much capacity can be dispatched economically and reliably.

The emergency exposes the common dependence of different generation technologies on water. Nuclear stations require cooling, hydroelectric plants require flow and reservoir levels, and many thermal plants lose efficiency as ambient temperatures rise. A diversified nameplate mix can still experience correlated outages when weather affects several technologies through the same physical resource.

Water security becomes power system planning

Romania’s immediate measures are intended to sustain the remaining nuclear unit and procure replacement electricity. The same low-water conditions can constrain hydroelectric output and nuclear cooling at once, extending the engineering problem beyond August. Cooling-water systems, canal operations, intake design, and drought-management rules are now part of electricity security planning.

The Cernavodă site is central to Romania’s longer-term nuclear plans, including life-extension work and proposed additional capacity. Future nuclear investment will require cooling arrangements that remain effective during low river flows and high water temperatures, alongside reliable transmission-system integration. Emergency canal works can protect current operations, but future projects will be judged against more severe combinations of low flow, high water temperature, and high electrical demand.

Additional storage, demand response, and flexible generation can reduce the system impact of major plant outages, although none removes the need for dependable cooling water. Strengthening interconnectors may widen the pool of available electricity, but neighbouring countries can face the same drought. Regional coordination and domestic flexible resources are both required when shared environmental conditions tighten several national systems simultaneously.

Romania entered August with one reactor offline, hydropower constrained, and the remaining nuclear unit dependent on an urgent water-transfer intervention. Future planning must account for how much capacity remains operable during low Danube flows, not merely the installed megawatts listed in project documents.