Southeast Europe’s August heatwave revealed a less familiar risk for nuclear generation: the dependence of large thermal plants on river conditions.
At Slovenia’s Krško nuclear power plant, reactor output was reduced to 80% during Aug. 5-6 because low Sava River flows and elevated temperatures made it harder to remain within environmental limits governing cooling-water discharge.
The operator said it was the first substantial reduction caused by such conditions since 2003.
Romania faced a larger interruption.
Nuclearelectrica began a controlled shutdown of Cernavoda Unit 2 on Aug. 13 because of the continuing decline in Danube water levels.
The events matter because nuclear generation is generally treated as one of the region’s most dependable low-carbon sources.
Unlike wind and solar, its fuel input is not weather-dependent.
Cooling conditions, however, can become weather-sensitive.
A prolonged heatwave can therefore affect nuclear output even when the reactor itself is technically available.
This will matter increasingly as SEE countries plan new nuclear capacity.
Hungary is developing Paks II.
Romania is pursuing additional Cernavoda capacity and SMR development.
Bulgaria continues to assess new nuclear options.
Serbia has reopened the longer-term discussion around nuclear generation.
Projects designed to operate for 60 years or more will need to be assessed against future hydrological and temperature conditions rather than only historical river data.
Cooling-system design therefore becomes a material engineering and investment consideration.
Alternative cooling technologies can reduce water dependence, but they can also increase capital costs or reduce plant efficiency under certain conditions.
For existing stations, climate resilience may become a larger part of life-extension expenditure.
August does not undermine the case for nuclear power in SEE.
It does show that investors should treat nuclear availability as an engineering variable rather than an absolute constant.
