Temelín's first unit back at full power after Wednesday water-valve repair

The first unit of the Temelín Nuclear Power Plant is operating at 100 percent. It reached full power shortly before midnight, ČEZ nuclear power plant spokesperson Petr Šuleř told the Czech News Agency (ČTK) today. Both Temelín units are currently supplying electricity to the grid without restrictions.

Energy company staff unexpectedly disconnected the first reactor unit from the transmission grid on Wednesday morning and reduced its output. The unit was disconnected so a water valve could be inspected and repaired. The valve controls water circulation between the condensers and cooling towers in the non-nuclear part of the plant. Staff gradually increased the reactor's output to 50 percent and reconnected it to the grid in the evening.

ČTK was alerted to the outage on Wednesday by Pavel Vlček of the Environmental Protection Civic Initiative. The State Office for Nuclear Safety reported on the situation on its website.

Temelín's first unit was offline for a planned two-month outage in the spring. Energy company staff replaced 48 of the reactor's 163 fuel assemblies, inspected the safety systems, turbine and generator, and carried out 66 investment projects. The outage began on 5 April and ended on 11 June.

The first unit was last unexpectedly shut down in March this year. The reason was a repair to a valve in one of the three technical water systems, which took just under four days.

The second unit at the Temelín plant was also unexpectedly shut down this year. It stopped supplying electricity on 31 January for repairs to a seal in the generator's internal cooling circuit and was reconnected to the grid on 5 February. The second unit was unexpectedly shut down again on 20 June.

Since the start of the year, the Temelín Nuclear Power Plant, the country's largest electricity producer, has generated 8.2 terawatt-hours of electricity.