The Krško nuclear power plant has increased generation to around 90% of capacity after cooler weather and improved conditions in the Sava river allowed the reactor to recover part of an earlier heat-related production cut.
Output had been reduced to around 80% following extreme temperatures and exceptionally weak river flows.
The reactor began gradually increasing production from the evening of 14 August.
Krško’s environmental permit requires the average daily temperature of the Sava downstream of the Brezice hydropower plant to remain below 28C. The plant is also permitted to raise river temperature by no more than 3C.
These limits became increasingly difficult to maintain during the recent heatwave.
While generation was reduced, Krško increased the use of cooling towers and other cooling equipment, cutting water withdrawals from the Sava 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. Sava water is employed in the tertiary cooling circuit to remove heat from the condenser.
Plant output will continue to depend partly on river temperatures, water levels and weather conditions.
The operational restrictions have regional market significance because Krško provides electricity equivalent to around 20% of annual Slovenian consumption and 16% of Croatian demand.
Reduced production therefore raises the requirement for alternative generation or wholesale-market purchases, particularly in Croatia, where HEP has indicated that shortages can be covered through domestic generation and imported electricity.
Krško’s summer operating pattern increasingly demonstrates the interaction between nuclear availability and climate-related hydrological constraints — a factor likely to become more important in regional power pricing during future heatwaves.
