Czech Temelín nuclear power plant disconnects Unit 2; engineers to repair seal in non-nuclear section

The Temelín nuclear power plant unexpectedly disconnected its second unit from the transmission grid this morning. Energy workers need to repair a seal in the generator’s internal cooling circuit. The issue is in the non-nuclear part of the plant. It is an operational matter and has no impact on the surrounding area or customers. The work should take no more than a few days. It is not possible to replace the cooler while the unit is operating at full capacity, ČEZ head of nuclear communications Petr Šuleř told reporters today. It is Temelín’s first unplanned outage since 2019, Šuleř confirmed in response to a question from the Czech News Agency (ČTK).

Plant management decided to gradually reduce output and disconnect the second unit from the transmission grid. „The sensor may be faulty, but we suspect a leak is more likely,“ Šuleř told ČTK. Inspecting and potentially replacing one of the coolers is not possible while the unit is operating at full capacity. The work will not affect the primary circuit or the first unit, which is operating at 100 percent. The temporary disconnection of the unit will not affect customers; ČEZ will provide replacement power from other energy sources.

The turbine-generator units at Temelín are the largest in the Czech Republic. Each unit has one high-pressure and three low-pressure turbine sections, directly connected to an electric generator with a maximum output of 1125 megawatts. „They convert thermal energy into electricity and, through so-called extractions, supply steam to heat exchangers,“ Šuleř said. The reliability of the Temelín power plant has been 99.5 percent in recent years, which is well above average compared with other energy sources, he added.

Temelín is the country’s largest electricity producer, covering about a fifth of domestic consumption. Last year it generated 16.1 terawatt-hours (TWh) of electricity, and so far this year it has generated 3.04 TWh.