A selection of unplanned outages at the Czech Temelín nuclear power plant since 2014

A selection of problems at the Temelín nuclear power plant in recent years (the plant disconnects Unit 2 for several days; energy workers plan to modify a turbine that was vibrating excessively):

7 February 2014 – Temelín disconnected the turbogenerator in Unit 2 from the power grid. The reason was repairs to the electric heater of the pressurizer. The unplanned outage lasted two weeks.

10 July 2014 – Temelín stopped supplying electricity. Unit 2 was disconnected because of a pump failure, while Unit 1 was offline for a planned refuelling outage. The plant was out of operation until 17 July.

13 November 2014 – Energy workers shut down Unit 2 to carry out repairs to one of the two electric feed pumps (auxiliary equipment in the plant’s non-nuclear section, used mainly when shutting down and starting up a unit). The repairs took a week.

June 2015 – The planned outage of Unit 2, which began on 18 April, was extended by about a month. Its restart after refuelling and modernisation was delayed mainly by an internal leak in one of the steam generators. The unit began supplying electricity on 31 July.

12 August 2015 – Less than two weeks later, technicians disconnected Unit 2 because of a fault in the generator cooling system in the plant’s non-nuclear section. The unplanned outage lasted a week.

3 September 2015 – A week after resuming operation following a planned outage, Unit 1 was disconnected because of a fault in a check valve on piping in the plant’s non-nuclear section. Repairs took ten days.

11 September 2015 – Energy workers shut down Unit 2 again, this time because of increased vibration in the turbogenerator in the plant’s non-nuclear section. The 11-day unplanned outage was required to modify the edges of the oil seals on the bearing pedestals.

December 2015 – During inspections of welds at the Dukovany nuclear power plant, documentation at Temelín was also checked. Temelín’s management announced that, unlike at Dukovany, it contained no errors that would require the units to be shut down.

8 September 2016 – After less than a day of operation following a planned outage, Temelín stopped electricity production in Unit 2. The reason was work on the turbine and in the non-nuclear section of the steam generator. The unit resumed operation in mid-October.

7 September 2018 – During the cleaning of cooling water at Temelín, a small amount of weakly radioactive water was accidentally transferred to a different tank than the one intended. Everything remained within the closed system, and the incident did not affect electricity generation, safety, employees or the environment, Temelín spokesperson Marek Sviták told the Czech News Agency (ČTK).

11 November 2019 – The plant unexpectedly disconnected Unit 1. The cause was turbine vibration resulting from fluctuations in outdoor temperatures. The outage lasted just under two days.

24 December 2019 – The Temelín nuclear power plant disconnected Unit 1 from the grid for repairs to part of the electric generator, in the plant’s non-nuclear section. The need for repairs became apparent during the previous power change. The outage ended on 3 January 2020.

24 June 2021 – Temelín shut down Unit 2 because of storm damage. Transmission towers belonging to ČEPS, the company responsible for operating the transmission system, had fallen. The shutdown brought forward the unit’s planned two-month outage by a week. The unit resumed electricity production in late August after refuelling.

31 January 2024 – The Temelín nuclear power plant unexpectedly disconnected Unit 2 from the transmission grid. Energy workers had to repair a seal in the generator’s internal cooling circuit in the plant’s non-nuclear section. The unit returned to operation after five days.

17 March 2024 – The plant disconnected Unit 1 from the grid to repair a valve in one of the three service water systems. The outage lasted just under four days, and Unit 1 began supplying electricity again on 21 March.

17 July 2024 – The Temelín nuclear power plant unexpectedly disconnected Unit 1 from the grid in the morning, with the reactor operating at reduced power. The disconnection was prompted by an inspection and repair of a valve controlling water circulating between the condensers and cooling towers in the plant’s non-nuclear section. The unit returned to full power the following day.

30 July 2024 – Temelín unexpectedly disconnected Unit 2 for several hours because of turbine vibration.

2 August 2024 – The plant disconnected Unit 2 for several days. During the planned outage, energy workers will modify the turbine to stabilise its vibration.