The Krško nuclear power plant in Slovenia has lifted generation to around 90% of capacity after cooler weather and improved conditions in the Sava river. The increase follows an earlier heat-related production cut. Output had previously been reduced to around 80% during extreme temperatures and exceptionally weak river flows.
Krško began gradually increasing production from the evening of 14 August. The change came after operational constraints eased as river conditions improved.
Sava temperature limits under Krško environmental permit
Krško’s environmental permit requires the average daily temperature of the Sava downstream of the Brezice hydropower plant to stay below 28C. The permit also allows the plant to raise river temperature by no more than 3C. During the recent heatwave, maintaining these limits became increasingly difficult.
During the period of reduced generation, Krško increased the use of cooling towers and other cooling equipment. Water withdrawals from the Sava were cut from around 25 cubic metres/second to approximately 8.5 cubic metres/second.
The reactor does not use river water in direct contact with the nuclear system. Instead, Sava water is used in the tertiary cooling circuit to remove heat from the condenser. Plant output remains partly dependent on river temperatures, water levels and weather conditions.
Regional power market impact of lower summer output
Operational restrictions tied to river conditions have market significance across the region. Krško provides electricity equivalent to around 20% of annual Slovenian consumption and 16% of Croatian demand. Reduced production therefore increases reliance on alternative generation or wholesale-market purchases.
This is particularly relevant for Croatia, where HEP has indicated that shortages can be covered through domestic generation and imported electricity.
Krško’s summer operating pattern highlights how nuclear availability can interact with climate-related hydrological constraints. The same interaction is expected to matter more for regional power pricing during future heatwaves.
